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class="vector-toc-text"> 4.2 Current estimates </div> </a> <ul id="toc-Current_estimates-sublist" class="vector-toc-list"> <li id="toc-Rate_of_star_creation_in_this_Galaxy,_R∗" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Rate_of_star_creation_in_this_Galaxy,_R∗"> <div class="vector-toc-text"> 4.2.1 Rate of star creation in this Galaxy, R∗ </div> </a> <ul id="toc-Rate_of_star_creation_in_this_Galaxy,_R∗-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Fraction_of_those_stars_that_have_planets,_fp" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Fraction_of_those_stars_that_have_planets,_fp"> <div class="vector-toc-text"> 4.2.2 Fraction of those stars that have planets, fp </div> </a> <ul id="toc-Fraction_of_those_stars_that_have_planets,_fp-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Average_number_of_planets_that_might_support_life_per_star_that_has_planets,_ne" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Average_number_of_planets_that_might_support_life_per_star_that_has_planets,_ne"> <div class="vector-toc-text"> 4.2.3 Average number of planets that might support life per star that has planets, ne </div> </a> <ul id="toc-Average_number_of_planets_that_might_support_life_per_star_that_has_planets,_ne-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Fraction_of_the_above_that_actually_go_on_to_develop_life,_fl" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Fraction_of_the_above_that_actually_go_on_to_develop_life,_fl"> <div class="vector-toc-text"> 4.2.4 Fraction of the above that actually go on to develop life, fl </div> </a> <ul id="toc-Fraction_of_the_above_that_actually_go_on_to_develop_life,_fl-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Fraction_of_the_above_that_develops_intelligent_life,_fi" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Fraction_of_the_above_that_develops_intelligent_life,_fi"> <div class="vector-toc-text"> 4.2.5 Fraction of the above that develops intelligent life, fi </div> </a> <ul id="toc-Fraction_of_the_above_that_develops_intelligent_life,_fi-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Fraction_of_the_above_revealing_their_existence_via_signal_release_into_space,_fc" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Fraction_of_the_above_revealing_their_existence_via_signal_release_into_space,_fc"> <div class="vector-toc-text"> 4.2.6 Fraction of the above revealing their existence via signal release into space, fc </div> </a> <ul id="toc-Fraction_of_the_above_revealing_their_existence_via_signal_release_into_space,_fc-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Lifetime_of_such_a_civilization_wherein_it_communicates_its_signals_into_space,_L" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Lifetime_of_such_a_civilization_wherein_it_communicates_its_signals_into_space,_L"> <div class="vector-toc-text"> 4.2.7 Lifetime of such a civilization wherein it communicates its signals into space, L </div> </a> <ul id="toc-Lifetime_of_such_a_civilization_wherein_it_communicates_its_signals_into_space,_L-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Range_of_results" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Range_of_results"> <div class="vector-toc-text"> 4.3 Range of results </div> </a> <ul id="toc-Range_of_results-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Possible_former_technological_civilizations" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Possible_former_technological_civilizations"> <div class="vector-toc-text"> 4.4 Possible former technological civilizations </div> </a> <ul id="toc-Possible_former_technological_civilizations-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Modifications" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Modifications"> <div class="vector-toc-text"> 5 Modifications </div> </a> <ul id="toc-Modifications-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Criticism" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Criticism"> <div class="vector-toc-text"> 6 Criticism </div> </a> <button aria-controls="toc-Criticism-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> Toggle Criticism subsection </button> <ul id="toc-Criticism-sublist" class="vector-toc-list"> <li id="toc-Fermi_paradox" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Fermi_paradox"> <div class="vector-toc-text"> 6.1 Fermi paradox </div> </a> <ul id="toc-Fermi_paradox-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-In_fiction_and_popular_culture" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#In_fiction_and_popular_culture"> <div class="vector-toc-text"> 7 In fiction and popular culture </div> </a> <ul id="toc-In_fiction_and_popular_culture-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> 8 See also </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Notes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Notes"> <div class="vector-toc-text"> 9 Notes </div> </a> <ul id="toc-Notes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> 10 References </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> 11 Further reading </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> 12 External links </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" > Toggle the table of contents </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading">Drake equation</h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 53 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-53" aria-hidden="true" > 53 languages </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%85%D8%B9%D8%A7%D8%AF%D9%84%D8%A9_%D8%AF%D8%B1%D9%8A%D9%83" title="معادلة دريك – Arabic" lang="ar" hreflang="ar" data-title="معادلة دريك" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target">العربية</a></li><li class="interlanguage-link interwiki-an mw-list-item"><a href="https://an.wikipedia.org/wiki/Ecuaci%C3%B3n_de_Drake" title="Ecuación de Drake – Aragonese" lang="an" hreflang="an" data-title="Ecuación de Drake" data-language-autonym="Aragonés" data-language-local-name="Aragonese" class="interlanguage-link-target">Aragonés</a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Dreyk_t%C9%99nliyi" title="Dreyk tənliyi – Azerbaijani" lang="az" hreflang="az" data-title="Dreyk tənliyi" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target">Azərbaycanca</a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%A1%E0%A7%8D%E0%A6%B0%E0%A7%87%E0%A6%95%E0%A7%87%E0%A6%B0_%E0%A6%B8%E0%A7%82%E0%A6%A4%E0%A7%8D%E0%A6%B0" title="ড্রেকের সূত্র – Bangla" lang="bn" hreflang="bn" data-title="ড্রেকের সূত্র" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target">বাংলা</a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%A3%D1%80%D0%B0%D1%9E%D0%BD%D0%B5%D0%BD%D0%BD%D0%B5_%D0%94%D1%80%D1%8D%D0%B9%D0%BA%D0%B0" title="Ураўненне Дрэйка – Belarusian" lang="be" hreflang="be" data-title="Ураўненне Дрэйка" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target">Беларуская</a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%A3%D1%80%D0%B0%D0%B2%D0%BD%D0%B5%D0%BD%D0%B8%D0%B5_%D0%BD%D0%B0_%D0%94%D1%80%D0%B5%D0%B9%D0%BA" title="Уравнение на Дрейк – Bulgarian" lang="bg" hreflang="bg" data-title="Уравнение на Дрейк" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target">Български</a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Drakeova_jedna%C4%8Dina" title="Drakeova jednačina – Bosnian" lang="bs" hreflang="bs" data-title="Drakeova jednačina" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target">Bosanski</a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Equaci%C3%B3_de_Drake" title="Equació de Drake – Catalan" lang="ca" hreflang="ca" data-title="Equació de Drake" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target">Català</a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Drakeova_rovnice" title="Drakeova rovnice – Czech" lang="cs" hreflang="cs" data-title="Drakeova rovnice" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target">Čeština</a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Drakes_ligning" title="Drakes ligning – Danish" lang="da" hreflang="da" data-title="Drakes ligning" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target">Dansk</a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Drake-Gleichung" title="Drake-Gleichung – German" lang="de" hreflang="de" data-title="Drake-Gleichung" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target">Deutsch</a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%95%CE%BE%CE%AF%CF%83%CF%89%CF%83%CE%B7_%CF%84%CE%BF%CF%85_%CE%9D%CF%84%CF%81%CE%AD%CE%B7%CE%BA" title="Εξίσωση του Ντρέηκ – Greek" lang="el" hreflang="el" data-title="Εξίσωση του Ντρέηκ" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target">Ελληνικά</a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Ecuaci%C3%B3n_de_Drake" title="Ecuación de Drake – Spanish" lang="es" hreflang="es" data-title="Ecuación de Drake" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target">Español</a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Formulo_de_Drake" title="Formulo de Drake – Esperanto" lang="eo" hreflang="eo" data-title="Formulo de Drake" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target">Esperanto</a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Drakeren_ekuazioa" title="Drakeren ekuazioa – Basque" lang="eu" hreflang="eu" data-title="Drakeren ekuazioa" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target">Euskara</a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%85%D8%B9%D8%A7%D8%AF%D9%84%D9%87_%D8%AF%D8%B1%DB%8C%DA%A9" title="معادله دریک – Persian" lang="fa" hreflang="fa" data-title="معادله دریک" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target">فارسی</a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/%C3%89quation_de_Drake" title="Équation de Drake – French" lang="fr" hreflang="fr" data-title="Équation de Drake" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target">Français</a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/Cothrom%C3%B3id_Drake" title="Cothromóid Drake – Irish" lang="ga" hreflang="ga" data-title="Cothromóid Drake" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target">Gaeilge</a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EB%93%9C%EB%A0%88%EC%9D%B4%ED%81%AC_%EB%B0%A9%EC%A0%95%EC%8B%9D" title="드레이크 방정식 – Korean" lang="ko" hreflang="ko" data-title="드레이크 방정식" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target">한국어</a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Drakeova_jednad%C5%BEba" title="Drakeova jednadžba – Croatian" lang="hr" hreflang="hr" data-title="Drakeova jednadžba" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target">Hrvatski</a></li><li class="interlanguage-link interwiki-ig mw-list-item"><a href="https://ig.wikipedia.org/wiki/Usoro_Drake" title="Usoro Drake – Igbo" lang="ig" hreflang="ig" data-title="Usoro Drake" data-language-autonym="Igbo" data-language-local-name="Igbo" class="interlanguage-link-target">Igbo</a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Persamaan_Drake" title="Persamaan Drake – Indonesian" lang="id" hreflang="id" data-title="Persamaan Drake" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target">Bahasa Indonesia</a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Equazione_di_Drake" title="Equazione di Drake – Italian" lang="it" hreflang="it" data-title="Equazione di Drake" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target">Italiano</a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%A0%D7%95%D7%A1%D7%97%D7%AA_%D7%93%D7%A8%D7%99%D7%99%D7%A7" title="נוסחת דרייק – Hebrew" lang="he" hreflang="he" data-title="נוסחת דרייק" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target">עברית</a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%94%D1%80%D0%B5%D0%B9%D0%BA_%D1%82%D0%B5%D2%A3%D0%B4%D0%B5%D1%83%D1%96" title="Дрейк теңдеуі – Kazakh" lang="kk" hreflang="kk" data-title="Дрейк теңдеуі" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target">Қазақша</a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Dreiko_lygtis" title="Dreiko lygtis – Lithuanian" lang="lt" hreflang="lt" data-title="Dreiko lygtis" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target">Lietuvių</a></li><li class="interlanguage-link interwiki-lfn mw-list-item"><a href="https://lfn.wikipedia.org/wiki/Formula_de_Drake" title="Formula de Drake – Lingua Franca Nova" lang="lfn" hreflang="lfn" data-title="Formula de Drake" data-language-autonym="Lingua Franca Nova" data-language-local-name="Lingua Franca Nova" class="interlanguage-link-target">Lingua Franca Nova</a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Drake-formula" title="Drake-formula – Hungarian" lang="hu" hreflang="hu" data-title="Drake-formula" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target">Magyar</a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%A1%E0%B5%8D%E0%B4%B0%E0%B5%87%E0%B4%95%E0%B5%8D%E0%B4%95%E0%B5%8D_%E0%B4%B8%E0%B4%AE%E0%B4%B5%E0%B4%BE%E0%B4%95%E0%B5%8D%E0%B4%AF%E0%B4%82" title="ഡ്രേക്ക് സമവാക്യം – Malayalam" lang="ml" hreflang="ml" data-title="ഡ്രേക്ക് സമവാക്യം" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target">മലയാളം</a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Vergelijking_van_Drake" title="Vergelijking van Drake – Dutch" lang="nl" hreflang="nl" data-title="Vergelijking van Drake" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target">Nederlands</a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E3%83%89%E3%83%AC%E3%82%A4%E3%82%AF%E3%81%AE%E6%96%B9%E7%A8%8B%E5%BC%8F" title="ドレイクの方程式 – Japanese" lang="ja" hreflang="ja" data-title="ドレイクの方程式" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target">日本語</a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Drakes_ligning" title="Drakes ligning – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Drakes ligning" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target">Norsk bokmål</a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Drake-likninga" title="Drake-likninga – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Drake-likninga" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target">Norsk nynorsk</a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Equacion_de_Drake" title="Equacion de Drake – Occitan" lang="oc" hreflang="oc" data-title="Equacion de Drake" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target">Occitan</a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/R%C3%B3wnanie_Drake%E2%80%99a" title="Równanie Drake’a – Polish" lang="pl" hreflang="pl" data-title="Równanie Drake’a" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target">Polski</a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Equa%C3%A7%C3%A3o_de_Drake" title="Equação de Drake – Portuguese" lang="pt" hreflang="pt" data-title="Equação de Drake" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target">Português</a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Ecua%C8%9Bia_lui_Drake" title="Ecuația lui Drake – Romanian" lang="ro" hreflang="ro" data-title="Ecuația lui Drake" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target">Română</a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%A3%D1%80%D0%B0%D0%B2%D0%BD%D0%B5%D0%BD%D0%B8%D0%B5_%D0%94%D1%80%D0%B5%D0%B9%D0%BA%D0%B0" title="Уравнение Дрейка – Russian" lang="ru" hreflang="ru" data-title="Уравнение Дрейка" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target">Русский</a></li><li class="interlanguage-link interwiki-sq mw-list-item"><a href="https://sq.wikipedia.org/wiki/Ekuacioni_Drejk" title="Ekuacioni Drejk – Albanian" lang="sq" hreflang="sq" data-title="Ekuacioni Drejk" 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data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">This article is about Frank Drake's equation. For other uses, see <a href="/wiki/Drake_equation_(disambiguation)" class="mw-disambig" title="Drake equation (disambiguation)">Drake equation (disambiguation)</a>.</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Dr._Frank_Drake.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/69/Dr._Frank_Drake.jpg/200px-Dr._Frank_Drake.jpg" decoding="async" width="200" height="224" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/69/Dr._Frank_Drake.jpg/300px-Dr._Frank_Drake.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/69/Dr._Frank_Drake.jpg/400px-Dr._Frank_Drake.jpg 2x" data-file-width="646" data-file-height="724" /></a><figcaption><a href="/wiki/Frank_Drake" title="Frank Drake">Frank Drake</a></figcaption></figure> The Drake equation is a <a href="/wiki/Probability_theory" title="Probability theory">probabilistic argument</a> used to estimate the number of active, communicative <a href="/wiki/Extraterrestrial_life" title="Extraterrestrial life">extraterrestrial civilizations</a> in the <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a> <a href="/wiki/Galaxy" title="Galaxy">Galaxy</a>.<a href="#cite_note-Drake_1961-1">[1]</a><a href="#cite_note-Burchell-2">[2]</a><a href="#cite_note-3">[3]</a> The equation was formulated in 1961 by <a href="/wiki/Frank_Drake" title="Frank Drake">Frank Drake</a>, not for purposes of quantifying the number of civilizations, but as a way to stimulate scientific dialogue at the first scientific meeting on the <a href="/wiki/Search_for_extraterrestrial_intelligence" title="Search for extraterrestrial intelligence">search for extraterrestrial intelligence</a> (SETI).<a href="#cite_note-December_2002-4">[4]</a><a href="#cite_note-5">[5]</a> The equation summarizes the main concepts which scientists must contemplate when considering the question of other radio-communicative life.<a href="#cite_note-December_2002-4">[4]</a> It is more properly thought of as an approximation than as a serious attempt to determine a precise number. Criticism related to the Drake equation focuses not on the equation itself, but on the fact that the estimated values for several of its factors are highly conjectural, the combined multiplicative effect being that the uncertainty associated with any derived value is so large that the equation cannot be used to draw firm conclusions. <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Equation">Equation</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=1" title="Edit section: Equation">edit</a>]</div> The Drake equation is:<a href="#cite_note-Drake_1961-1">[1]</a> <math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle N=R_{*}\cdot f_{\mathrm {p} }\cdot n_{\mathrm {e} }\cdot f_{\mathrm {l} }\cdot f_{\mathrm {i} }\cdot f_{\mathrm {c} }\cdot L}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>N</mi> <mo>=</mo> <msub> <mi>R</mi> <mrow class="MJX-TeXAtom-ORD"> <mo>∗</mo> </mrow> </msub> <mo>⋅</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">p</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>n</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">e</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">l</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">i</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">c</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <mi>L</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle N=R_{*}\cdot f_{\mathrm {p} }\cdot n_{\mathrm {e} }\cdot f_{\mathrm {l} }\cdot f_{\mathrm {i} }\cdot f_{\mathrm {c} }\cdot L}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/08459525b4c05af9b9e1748406e26ad869d9462d" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:30.039ex; height:2.843ex;" alt="{\displaystyle N=R_{*}\cdot f_{\mathrm {p} }\cdot n_{\mathrm {e} }\cdot f_{\mathrm {l} }\cdot f_{\mathrm {i} }\cdot f_{\mathrm {c} }\cdot L}"> where <ul><li>N = the number of <a href="/wiki/Civilization" title="Civilization">civilizations</a> in the Milky Way galaxy with which communication might be possible (i.e. which are on the current past <a href="/wiki/Light_cone" title="Light cone">light cone</a>);</li></ul> and <ul><li>R∗ = the average rate of <a href="/wiki/Star_formation" title="Star formation">star formation</a> in <a href="/wiki/Milky_Way" title="Milky Way">our Galaxy</a>.</li> <li>fp = the fraction of those stars that have <a href="/wiki/Planet" title="Planet">planets</a>.</li> <li>ne = the average number of planets that can potentially support <a href="/wiki/Life" title="Life">life</a> per star that has planets.</li> <li>fl = the fraction of planets that could support life that actually develop life at some point.</li> <li>fi = the fraction of planets with life that go on to develop <a href="/wiki/Intelligence" title="Intelligence">intelligent</a> life (civilizations).</li> <li>fc = the fraction of civilizations that develop a technology that releases <a href="/wiki/Technosignature" title="Technosignature">detectable signs of their existence into space</a>.</li> <li>L = the length of time for which such civilizations release detectable signals into space.<a href="#cite_note-NOVA-6">[6]</a><a href="#cite_note-SETI-Drake-Equation-7">[7]</a></li></ul> This form of the equation first appeared in Drake's 1965 paper.<a href="#cite_note-8">[8]</a><a href="#cite_note-9">[9]</a> <div class="mw-heading mw-heading2"><h2 id="History">History</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=2" title="Edit section: History">edit</a>]</div> In September 1959, physicists <a href="/wiki/Giuseppe_Cocconi" title="Giuseppe Cocconi">Giuseppe Cocconi</a> and <a href="/wiki/Philip_Morrison" title="Philip Morrison">Philip Morrison</a> published an article in the journal <a href="/wiki/Nature_(journal)" title="Nature (journal)">Nature</a> with the provocative title "Searching for Interstellar Communications".<a href="#cite_note-Cocconi_1959-10">[10]</a><a href="#cite_note-history-11">[11]</a> Cocconi and Morrison argued that <a href="/wiki/Radio_telescope" title="Radio telescope">radio telescopes</a> had become sensitive enough to pick up transmissions that might be broadcast into space by civilizations orbiting other stars. Such messages, they suggested, might be transmitted at a <a href="/wiki/Wavelength" title="Wavelength">wavelength</a> of 21 cm (1,420.4 <a href="/wiki/Megahertz" class="mw-redirect" title="Megahertz">MHz</a>). This is the wavelength of radio emission by neutral <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a>, the most common element in the universe, and they reasoned that other intelligences might see this as a logical landmark in the <a href="/wiki/Radio_spectrum" title="Radio spectrum">radio spectrum</a>. Two months later, Harvard University astronomy professor <a href="/wiki/Harlow_Shapley" title="Harlow Shapley">Harlow Shapley</a> speculated on the number of inhabited planets in the universe, saying "The universe has 10 million, million, million suns (10 followed by 18 zeros) similar to our own. One in a million has planets around it. Only one in a million million has the right combination of chemicals, temperature, water, days and nights to support planetary life as we know it. This calculation arrives at the estimated figure of 100 million worlds where life has been forged by evolution."<a href="#cite_note-SydneyMorningHerald-12">[12]</a> Seven months after Cocconi and Morrison published their article, Drake began <a href="/wiki/Search_for_extraterrestrial_intelligence" title="Search for extraterrestrial intelligence">searching for extraterrestrial intelligence</a> in an experiment called <a href="/wiki/Project_Ozma" title="Project Ozma">Project Ozma</a>. It was the first systematic search for signals from communicative extraterrestrial civilizations. Using the 85 ft (26 m) dish of the <a href="/wiki/Green_Bank_Observatory" title="Green Bank Observatory">National Radio Astronomy Observatory, Green Bank</a> in <a href="/wiki/Green_Bank,_West_Virginia" title="Green Bank, West Virginia">Green Bank, West Virginia</a>, Drake monitored two nearby Sun-like stars: <a href="/wiki/Epsilon_Eridani" title="Epsilon Eridani">Epsilon Eridani</a> and <a href="/wiki/Tau_Ceti" title="Tau Ceti">Tau Ceti</a>, slowly scanning frequencies close to the 21 cm wavelength for six hours per day from April to July 1960.<a href="#cite_note-history-11">[11]</a> The project was well designed, inexpensive, and simple by today's standards. It detected no signals. Soon thereafter, Drake hosted the first search for extraterrestrial intelligence conference on detecting their radio signals. The meeting was held at the Green Bank facility in 1961. The equation that bears Drake's name arose out of his preparations for the meeting.<a href="#cite_note-Astrobiology_Magazine-13">[13]</a> <style data-mw-deduplicate="TemplateStyles:r1244412712">.mw-parser-output .templatequote{overflow:hidden;margin:1em 0;padding:0 32px}.mw-parser-output .templatequotecite{line-height:1.5em;text-align:left;margin-top:0}@media(min-width:500px){.mw-parser-output .templatequotecite{padding-left:1.6em}}</style><blockquote class="templatequote">As I planned the meeting, I realized a few day[s] ahead of time we needed an agenda. And so I wrote down all the things you needed to know to predict how hard it's going to be to detect extraterrestrial life. And looking at them it became pretty evident that if you multiplied all these together, you got a number, N, which is the number of detectable civilizations in our galaxy. This was aimed at the radio search, and not to search for primordial or primitive life forms.<div class="templatequotecite">— <cite>Frank Drake</cite></div></blockquote> The ten attendees were conference organizer J. Peter Pearman, Frank Drake, <a href="/wiki/Philip_Morrison" title="Philip Morrison">Philip Morrison</a>, businessman and radio amateur Dana Atchley, chemist <a href="/wiki/Melvin_Calvin" title="Melvin Calvin">Melvin Calvin</a>, astronomer <a href="/wiki/Su-Shu_Huang" title="Su-Shu Huang">Su-Shu Huang</a>, neuroscientist <a href="/wiki/John_C._Lilly" title="John C. Lilly">John C. Lilly</a>, inventor <a href="/wiki/Barney_Oliver" class="mw-redirect" title="Barney Oliver">Barney Oliver</a>, astronomer <a href="/wiki/Carl_Sagan" title="Carl Sagan">Carl Sagan</a>, and radio-astronomer <a href="/wiki/Otto_Struve" title="Otto Struve">Otto Struve</a>.<a href="#cite_note-Wende-14">[14]</a> These participants called themselves "The Order of the Dolphin" (because of Lilly's work on <a href="/wiki/Dolphin_communication" class="mw-redirect" title="Dolphin communication">dolphin communication</a>), and commemorated their first meeting with a plaque at the observatory hall.<a href="#cite_note-15">[15]</a><a href="#cite_note-16">[16]</a> <div class="mw-heading mw-heading2"><h2 id="Usefulness">Usefulness</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=3" title="Edit section: Usefulness">edit</a>]</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:C_G-K_-_DSC_0421.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0c/C_G-K_-_DSC_0421.jpg/200px-C_G-K_-_DSC_0421.jpg" decoding="async" width="200" height="245" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0c/C_G-K_-_DSC_0421.jpg/300px-C_G-K_-_DSC_0421.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0c/C_G-K_-_DSC_0421.jpg/400px-C_G-K_-_DSC_0421.jpg 2x" data-file-width="408" data-file-height="500" /></a><figcaption>The <a href="/wiki/Allen_Telescope_Array" title="Allen Telescope Array">Allen Telescope Array</a> for SETI</figcaption></figure> The Drake equation results in a summary of the factors affecting the likelihood that we might detect radio-communication from intelligent extraterrestrial life.<a href="#cite_note-Burchell-2">[2]</a><a href="#cite_note-NOVA-6">[6]</a><a href="#cite_note-17">[17]</a> The last three parameters, fi, fc, and L, are not known and are very difficult to estimate, with values ranging over many orders of magnitude (see <a href="#Criticism">§ Criticism</a>). Therefore, the usefulness of the Drake equation is not in the solving, but rather in the contemplation of all the various concepts which scientists must incorporate when considering the question of life elsewhere,<a href="#cite_note-Burchell-2">[2]</a><a href="#cite_note-December_2002-4">[4]</a> and gives the question of life elsewhere a basis for <a href="/wiki/Scientific_method" title="Scientific method">scientific analysis</a>. The equation has helped draw attention to some particular scientific problems related to life in the universe, for example <a href="/wiki/Abiogenesis" title="Abiogenesis">abiogenesis</a>, the development of <a href="/wiki/Multi-cellular_life" class="mw-redirect" title="Multi-cellular life">multi-cellular life</a>, and the development of <a href="/wiki/Intelligence" title="Intelligence">intelligence</a> itself.<a href="#cite_note-18">[18]</a> Within the limits of existing human technology, any practical search for distant intelligent life must necessarily be a search for some manifestation of a distant technology. After about 50 years, the Drake equation is still of seminal importance because it is a 'road map' of what we need to learn in order to solve this fundamental existential question.<a href="#cite_note-Burchell-2">[2]</a> It also formed the backbone of <a href="/wiki/Astrobiology" title="Astrobiology">astrobiology</a> as a science; although speculation is entertained to give context, astrobiology concerns itself primarily with <a href="/wiki/Hypotheses" class="mw-redirect" title="Hypotheses">hypotheses</a> that fit firmly into existing <a href="/wiki/Theory#Science" title="Theory">scientific theories</a>. Some 50 years of SETI have failed to find anything, even though radio telescopes, receiver techniques, and computational abilities have improved significantly since the early 1960s. SETI efforts since 1961 have conclusively ruled out widespread alien emissions near the 21 cm wavelength of the <a href="/wiki/Hydrogen_frequencies" class="mw-redirect" title="Hydrogen frequencies">hydrogen frequency</a>.<a href="#cite_note-19">[19]</a> <div class="mw-heading mw-heading2"><h2 id="Estimates">Estimates</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=4" title="Edit section: Estimates">edit</a>]</div> <div class="mw-heading mw-heading3"><h3 id="Original_estimates">Original estimates</h3>[<a href="/w/index.php?title=Drake_equation&action=edit&section=5" title="Edit section: Original estimates">edit</a>]</div> There is considerable disagreement on the values of these parameters, but the 'educated guesses' used by Drake and his colleagues in 1961 were:<a href="#cite_note-Drake_1961-1">[1]</a><a href="#cite_note-20">[20]</a><a href="#cite_note-21">[21]</a> <ul><li>R∗ = 1 yr−1 (1 star formed per year, on the average over the life of the galaxy; this was regarded as conservative)</li> <li>fp = 0.2 to 0.5 (one fifth to one half of all stars formed will have planets)</li> <li>ne = 1 to 5 (stars with planets will have between 1 and 5 planets capable of developing life)</li> <li>fl = 1 (100% of these planets will develop life)</li> <li>fi = 1 (100% of which will develop intelligent life)</li> <li>fc = 0.1 to 0.2 (10–20% of which will be able to communicate)</li> <li>L = somewhere between 1000 and 100,000,000 years</li></ul> Inserting the above minimum numbers into the equation gives a minimum N of 20 (see: <a href="#Range_of_results">Range of results</a>). Inserting the maximum numbers gives a maximum of 50,000,000. Drake states that given the uncertainties, the original meeting concluded that N ≈ L, and there were probably between 1000 and 100,000,000 planets with civilizations in the <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a> Galaxy. <div class="mw-heading mw-heading3"><h3 id="Current_estimates">Current estimates</h3>[<a href="/w/index.php?title=Drake_equation&action=edit&section=6" title="Edit section: Current estimates">edit</a>]</div> This section discusses and attempts to list the best current estimates for the parameters of the Drake equation. <div class="mw-heading mw-heading4"><h4 id="Rate_of_star_creation_in_this_Galaxy,_R∗">Rate of star creation in this Galaxy, R∗</h4>[<a href="/w/index.php?title=Drake_equation&action=edit&section=7" title="Edit section: Rate of star creation in this Galaxy, R∗">edit</a>]</div> Calculations in 2010, from <a href="/wiki/NASA" title="NASA">NASA</a> and the <a href="/wiki/European_Space_Agency" title="European Space Agency">European Space Agency</a> indicate that the rate of star formation in this Galaxy is about 0.68–1.45 <a href="/wiki/Solar_mass" title="Solar mass"><var>M</var>☉</a> of material per year.<a href="#cite_note-Robitaille-22">[22]</a><a href="#cite_note-The_Drake_Equation-23">[23]</a> To get the number of stars per year, we divide this by the <a href="/wiki/Initial_mass_function" title="Initial mass function">initial mass function</a> (IMF) for stars, where the average new star's mass is about 0.5 <var>M</var>☉.<a href="#cite_note-24">[24]</a> This gives a star formation rate of about 1.5–3 stars per year. <div class="mw-heading mw-heading4"><h4 id="Fraction_of_those_stars_that_have_planets,_fp">Fraction of those stars that have planets, fp</h4>[<a href="/w/index.php?title=Drake_equation&action=edit&section=8" title="Edit section: Fraction of those stars that have planets, fp">edit</a>]</div> Analysis of <a href="/wiki/Gravitational_microlensing" title="Gravitational microlensing">microlensing</a> surveys, in 2012, has found that fp may approach 1—that is, stars are orbited by planets as a rule, rather than the exception; and that there are one or more bound planets per Milky Way star.<a href="#cite_note-bbc.co.uk-25">[25]</a><a href="#cite_note-Nature-20120111-26">[26]</a> <div class="mw-heading mw-heading4"><h4 id="Average_number_of_planets_that_might_support_life_per_star_that_has_planets,_ne">Average number of planets that might support life per star that has planets, ne</h4>[<a href="/w/index.php?title=Drake_equation&action=edit&section=9" title="Edit section: Average number of planets that might support life per star that has planets, ne">edit</a>]</div> In November 2013, astronomers reported, based on <a href="/wiki/Kepler_space_telescope" title="Kepler space telescope">Kepler space telescope</a> data, that there could be as many as 40 billion <a href="/wiki/Terrestrial_planet" title="Terrestrial planet">Earth-sized</a> <a href="/wiki/Extrasolar_planets" class="mw-redirect" title="Extrasolar planets">planets</a> orbiting in the <a href="/wiki/Habitable_zone" title="Habitable zone">habitable zones</a> of <a href="/wiki/Sun-like" class="mw-redirect" title="Sun-like">sun-like stars</a> and <a href="/wiki/Red_dwarf_stars" class="mw-redirect" title="Red dwarf stars">red dwarf stars</a> within the <a href="/wiki/Milky_Way_Galaxy" class="mw-redirect" title="Milky Way Galaxy">Milky Way Galaxy</a>.<a href="#cite_note-NYT-20131104-27">[27]</a><a href="#cite_note-PNAS-20131031-28">[28]</a> 11 billion of these estimated planets may be orbiting sun-like stars.<a href="#cite_note-LATimes-20131104-29">[29]</a> Since there are about 100 billion stars in the galaxy, this implies fp · ne is roughly 0.4. The nearest planet in the habitable zone is <a href="/wiki/Proxima_Centauri_b" title="Proxima Centauri b">Proxima Centauri b</a>, which is as close as about 4.2 light-years away. The consensus at the Green Bank meeting was that ne had a minimum value between 3 and 5. Dutch science journalist <a href="/wiki/Govert_Schilling" title="Govert Schilling">Govert Schilling</a> has opined that this is optimistic.<a href="#cite_note-schilling2011-30">[30]</a> Even if planets are in the <a href="/wiki/Habitable_zone" title="Habitable zone">habitable zone</a>, the number of planets with the right proportion of elements is difficult to estimate.<a href="#cite_note-Trimble-31">[31]</a> Brad Gibson, Yeshe Fenner, and Charley Lineweaver determined that about 10% of <a href="/wiki/Star_system" title="Star system">star systems</a> in the Milky Way Galaxy are hospitable to life, by having heavy elements, being far from <a href="/wiki/Supernova" title="Supernova">supernovae</a> and being stable for a sufficient time.<a href="#cite_note-32">[32]</a> The discovery of numerous <a href="/wiki/Gas_giant" title="Gas giant">gas giants</a> in close orbit with their stars has introduced doubt that life-supporting planets commonly survive the formation of their stellar systems. So-called <a href="/wiki/Hot_Jupiter" title="Hot Jupiter">hot Jupiters</a> may migrate from distant orbits to near orbits, in the process disrupting the orbits of habitable planets. On the other hand, the variety of <a href="/wiki/Star_system" title="Star system">star systems</a> that might have habitable zones is not just limited to solar-type stars and Earth-sized planets. It is now estimated that even tidally locked planets close to <a href="/wiki/Red_dwarf" title="Red dwarf">red dwarf</a> stars <a href="/wiki/Habitability_of_red_dwarf_systems" title="Habitability of red dwarf systems">might have habitable zones</a>,<a href="#cite_note-33">[33]</a> although the flaring behavior of these stars might speak against this.<a href="#cite_note-34">[34]</a> The possibility of life on <a href="/wiki/Natural_satellite" title="Natural satellite">moons</a> of gas giants (such as <a href="/wiki/Jupiter" title="Jupiter">Jupiter</a>'s moon <a href="/wiki/Europa_(moon)" title="Europa (moon)">Europa</a>, or <a href="/wiki/Saturn" title="Saturn">Saturn</a>'s moons <a href="/wiki/Titan_(moon)" title="Titan (moon)">Titan</a> and <a href="/wiki/Enceladus" title="Enceladus">Enceladus</a>) adds further uncertainty to this figure.<a href="#cite_note-35">[35]</a> The authors of the <a href="/wiki/Rare_Earth_hypothesis" title="Rare Earth hypothesis">rare Earth hypothesis</a> propose a number of additional constraints on habitability for planets, including being in galactic zones with suitably low radiation, high star metallicity, and low enough density to avoid excessive asteroid bombardment. They also propose that it is necessary to have a planetary system with large gas giants which provide bombardment protection without a <a href="/wiki/Hot_Jupiter" title="Hot Jupiter">hot Jupiter</a>; and a planet with <a href="/wiki/Plate_tectonic" class="mw-redirect" title="Plate tectonic">plate tectonics</a>, a large moon that creates tidal pools, and moderate <a href="/wiki/Axial_tilt" title="Axial tilt">axial tilt</a> to generate seasonal variation.<a href="#cite_note-RareEarth-36">[36]</a> <div class="mw-heading mw-heading4"><h4 id="Fraction_of_the_above_that_actually_go_on_to_develop_life,_fl">Fraction of the above that actually go on to develop life, fl</h4>[<a href="/w/index.php?title=Drake_equation&action=edit&section=10" title="Edit section: Fraction of the above that actually go on to develop life, fl">edit</a>]</div> Geological evidence from the Earth suggests that fl may be high; life on Earth appears to have begun around the same time as favorable conditions arose, suggesting that <a href="/wiki/Abiogenesis" title="Abiogenesis">abiogenesis</a> may be relatively common once conditions are right. However, this evidence only looks at the Earth (a single model planet), and contains <a href="/wiki/Anthropic_bias" class="mw-redirect" title="Anthropic bias">anthropic bias</a>, as the planet of study was not chosen randomly, but by the living organisms that already inhabit it (ourselves). From a classical <a href="/wiki/Hypothesis_testing" class="mw-redirect" title="Hypothesis testing">hypothesis testing</a> standpoint, without assuming that the underlying distribution of fl is the same for all planets in the Milky Way, there are zero <a href="/wiki/Degrees_of_freedom_(statistics)" title="Degrees of freedom (statistics)">degrees of freedom</a>, permitting no valid estimates to be made. If life (or evidence of past life) were to be found on <a href="/wiki/Life_on_Mars" title="Life on Mars">Mars</a>, <a href="/wiki/Europa_(moon)" title="Europa (moon)">Europa</a>, <a href="/wiki/Enceladus" title="Enceladus">Enceladus</a> or <a href="/wiki/Titan_(moon)" title="Titan (moon)">Titan</a> that developed independently from life on Earth it would imply a value for fl close to 1. While this would raise the number of degrees of freedom from zero to one, there would remain a great deal of uncertainty on any estimate due to the small sample size, and the chance they are not really independent. Countering this argument is that there is no evidence for abiogenesis occurring more than once on the Earth—that is, all terrestrial life stems from a common origin. If abiogenesis were more common it would be speculated to have occurred more than once on the Earth. Scientists have searched for this by looking for <a href="/wiki/Bacteria" title="Bacteria">bacteria</a> that are unrelated to other life on Earth, but none have been found yet.<a href="#cite_note-37">[37]</a> It is also possible that life arose more than once, but that other branches were out-competed, or died in mass extinctions, or were lost in other ways. Biochemists <a href="/wiki/Francis_Crick" title="Francis Crick">Francis Crick</a> and <a href="/wiki/Leslie_Orgel" title="Leslie Orgel">Leslie Orgel</a> laid special emphasis on this uncertainty: "At the moment we have no means at all of knowing" whether we are "likely to be alone in the galaxy (Universe)" or whether "the galaxy may be pullulating with life of many different forms."<a href="#cite_note-38">[38]</a> As an alternative to abiogenesis on Earth, they proposed the hypothesis of <a href="/wiki/Directed_panspermia" title="Directed panspermia">directed panspermia</a>, which states that Earth life began with "microorganisms sent here deliberately by a technological society on another planet, by means of a special long-range unmanned spaceship". In 2020, a paper by scholars at the <a href="/wiki/University_of_Nottingham" title="University of Nottingham">University of Nottingham</a> proposed an "Astrobiological Copernican" principle, based on the <a href="/wiki/Principle_of_Mediocrity" class="mw-redirect" title="Principle of Mediocrity">Principle of Mediocrity</a>, and speculated that "intelligent life would form on other [Earth-like] planets like it has on Earth, so within a few billion years life would automatically form as a natural part of evolution". In the authors' framework, fl, fi, and fc are all set to a probability of 1 (certainty). Their resultant calculation concludes there are more than thirty current technological civilizations in the galaxy (disregarding error bars).<a href="#cite_note-39">[39]</a><a href="#cite_note-40">[40]</a> <div class="mw-heading mw-heading4"><h4 id="Fraction_of_the_above_that_develops_intelligent_life,_fi">Fraction of the above that develops intelligent life, fi</h4>[<a href="/w/index.php?title=Drake_equation&action=edit&section=11" title="Edit section: Fraction of the above that develops intelligent life, fi">edit</a>]</div> This value remains particularly controversial. Those who favor a low value, such as the biologist <a href="/wiki/Ernst_Mayr" title="Ernst Mayr">Ernst Mayr</a>, point out that of the billions of species that have existed on Earth, only one has become intelligent and from this, infer a tiny value for fi.<a href="#cite_note-Ernst_Mayr_on_SETI-41">[41]</a> Likewise, the Rare Earth hypothesis, notwithstanding their low value for ne above, also think a low value for fi dominates the analysis.<a href="#cite_note-42">[42]</a> Those who favor higher values note the generally increasing complexity of life over time, concluding that the appearance of intelligence is almost inevitable,<a href="#cite_note-acampbell.ukfsn.org-43">[43]</a><a href="#cite_note-44">[44]</a> implying an fi approaching 1. Skeptics point out that the large spread of values in this factor and others make all estimates unreliable. (See <a href="#Criticism">Criticism</a>). In addition, while it appears that life developed soon after the formation of Earth, the <a href="/wiki/Cambrian_explosion" title="Cambrian explosion">Cambrian explosion</a>, in which a large variety of multicellular life forms came into being, occurred a considerable amount of time after the formation of Earth, which suggests the possibility that special conditions were necessary. Some scenarios such as the <a href="/wiki/Snowball_Earth" title="Snowball Earth">snowball Earth</a> or research into <a href="/wiki/Extinction_events" class="mw-redirect" title="Extinction events">extinction events</a> have raised the possibility that life on Earth is relatively fragile. Research on any past <a href="/wiki/Life_on_Mars" title="Life on Mars">life on Mars</a> is relevant since a discovery that life did form on Mars but ceased to exist might raise the estimate of fl but would indicate that in half the known cases, intelligent life did not develop. Estimates of fi have been affected by discoveries that the Solar System's orbit is circular in the galaxy, at such a distance that it remains out of the spiral arms for tens of millions of years (evading radiation from <a href="/wiki/Nova" title="Nova">novae</a>). Also, Earth's large moon may aid the evolution of life by <a href="/wiki/Rare_Earth_hypothesis#A_large_moon" title="Rare Earth hypothesis">stabilizing the planet's axis of rotation</a>. There has been quantitative work to begin to define <math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle f_{\mathrm {l} }\cdot f_{\mathrm {i} }}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">l</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">i</mi> </mrow> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f_{\mathrm {l} }\cdot f_{\mathrm {i} }}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/9192cceab490934e6cc4c0de48434dcaa5a876f9" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:5.337ex; height:2.509ex;" alt="{\displaystyle f_{\mathrm {l} }\cdot f_{\mathrm {i} }}">. One example is a Bayesian analysis published in 2020. In the conclusion, the author cautions that this study applies to Earth's conditions. In Bayesian terms, the study favors the formation of intelligence on a planet with identical conditions to Earth but does not do so with high confidence.<a href="#cite_note-Kipping2020-45">[45]</a><a href="#cite_note-ColumbiaPR-46">[46]</a> Planetary scientist <a href="/wiki/Pascal_Lee" title="Pascal Lee">Pascal Lee</a> of the <a href="/wiki/SETI_Institute" title="SETI Institute">SETI Institute</a> proposes that this fraction is very low (0.0002). He based this estimate on how long it took Earth to develop intelligent life (1 million years since <a href="/wiki/Homo_erectus" title="Homo erectus">Homo erectus</a> evolved, compared to 4.6 billion years since Earth formed).<a href="#cite_note-47">[47]</a><a href="#cite_note-48">[48]</a> <div class="mw-heading mw-heading4"><h4 id="Fraction_of_the_above_revealing_their_existence_via_signal_release_into_space,_fc">Fraction of the above revealing their existence via signal release into space, fc</h4>[<a href="/w/index.php?title=Drake_equation&action=edit&section=12" title="Edit section: Fraction of the above revealing their existence via signal release into space, fc">edit</a>]</div> For deliberate communication, the one example we have (the Earth) does not do much explicit communication, though there are <a href="/wiki/Active_SETI" title="Active SETI">some efforts</a> covering only a tiny fraction of the stars that might look for human presence. (See <a href="/wiki/Arecibo_message" title="Arecibo message">Arecibo message</a>, for example). There is <a href="/wiki/Fermi_paradox#They_choose_not_to_interact_with_us" title="Fermi paradox">considerable speculation</a> why an extraterrestrial civilization might exist but choose not to communicate. However, deliberate communication is not required, and calculations indicate that current or near-future Earth-level technology might well be detectable to civilizations not too much more advanced than present day humans.<a href="#cite_note-49">[49]</a> By this standard, the Earth is a communicating civilization. Another question is what percentage of civilizations in the galaxy are close enough for us to detect, assuming that they send out signals. For example, existing Earth radio telescopes could only detect Earth radio transmissions from roughly a light year away.<a href="#cite_note-50">[50]</a> <div class="mw-heading mw-heading4"><h4 id="Lifetime_of_such_a_civilization_wherein_it_communicates_its_signals_into_space,_L">Lifetime of such a civilization wherein it communicates its signals into space, L</h4>[<a href="/w/index.php?title=Drake_equation&action=edit&section=13" title="Edit section: Lifetime of such a civilization wherein it communicates its signals into space, L">edit</a>]</div> <a href="/wiki/Michael_Shermer" title="Michael Shermer">Michael Shermer</a> estimated L as 420 years, based on the duration of sixty historical Earthly civilizations.<a href="#cite_note-Why_ET_Hasn’t_Called-51">[51]</a> Using 28 civilizations more recent than the Roman Empire, he calculates a figure of 304 years for "modern" civilizations. It could also be argued from Michael Shermer's results that the fall of most of these civilizations was followed by later civilizations that carried on the technologies, so it is doubtful that they are separate civilizations in the context of the Drake equation. In the expanded version, including reappearance number, this lack of specificity in defining single civilizations does not matter for the result, since such a civilization turnover could be described as an increase in the reappearance number rather than increase in L, stating that a civilization reappears in the form of the succeeding cultures. Furthermore, since none could communicate over interstellar space, the method of comparing with historical civilizations could be regarded as invalid. <a href="/wiki/David_Grinspoon" title="David Grinspoon">David Grinspoon</a> has argued that once a civilization has developed enough, it might overcome all threats to its survival. It will then last for an indefinite period of time, making the value for L potentially billions of years. If this is the case, then he proposes that the Milky Way Galaxy may have been steadily accumulating advanced civilizations since it formed.<a href="#cite_note-David_Grinspoon_2004-52">[52]</a> He proposes that the last factor L be replaced with fIC · T, where fIC is the fraction of communicating civilizations that become "immortal" (in the sense that they simply do not die out), and T representing the length of time during which this process has been going on. This has the advantage that T would be a relatively easy-to-discover number, as it would simply be some fraction of the age of the universe. It has also been hypothesized that once a civilization has learned of a more advanced one, its longevity could increase because it can learn from the experiences of the other.<a href="#cite_note-GoldsmithOwen-53">[53]</a> The astronomer <a href="/wiki/Carl_Sagan" title="Carl Sagan">Carl Sagan</a> speculated that all of the terms, except for the lifetime of a civilization, are relatively high and the determining factor in whether there are large or small numbers of civilizations in the universe is the civilization lifetime, or in other words, the ability of technological civilizations to avoid self-destruction. In Sagan's case, the Drake equation was a strong motivating factor for his interest in environmental issues and his efforts to warn against the dangers of <a href="/wiki/Nuclear_warfare" title="Nuclear warfare">nuclear warfare</a>. Paleobiologist <a href="/wiki/Olev_Vinn" title="Olev Vinn">Olev Vinn</a> suggests that the lifetime of most technological civilizations is brief due to inherited behavior patterns present in all intelligent organisms. These behaviors, incompatible with civilized conditions, inevitably lead to self-destruction soon after the emergence of advanced technologies.<a href="#cite_note-vinn2024-54">[54]</a> An intelligent civilization might not be organic, as some have suggested that <a href="/wiki/Artificial_general_intelligence" title="Artificial general intelligence">artificial general intelligence</a> may replace humanity.<a href="#cite_note-55">[55]</a> <div class="mw-heading mw-heading3"><h3 id="Range_of_results">Range of results</h3>[<a href="/w/index.php?title=Drake_equation&action=edit&section=14" title="Edit section: Range of results">edit</a>]</div> As many skeptics have pointed out, the Drake equation can give a very wide range of values, depending on the assumptions,<a href="#cite_note-56">[56]</a> as the values used in portions of the Drake equation are not well established.<a href="#cite_note-schilling2011-30">[30]</a><a href="#cite_note-renamed_from_2011_on_20160211035411-57">[57]</a><a href="#cite_note-58">[58]</a><a href="#cite_note-schilling2009-59">[59]</a> In particular, the result can be N ≪ 1, meaning we are likely alone in the galaxy, or N ≫ 1, implying there are many civilizations we might contact. One of the few points of wide agreement is that the presence of humanity implies a probability of intelligence arising of greater than zero.<a href="#cite_note-Dean-60">[60]</a> As an example of a low estimate, combining NASA's star formation rates, the <a href="/wiki/Rare_Earth_hypothesis" title="Rare Earth hypothesis">rare Earth hypothesis</a> value of fp · ne · fl = 10−5,<a href="#cite_note-61">[61]</a> Mayr's view on intelligence arising, Drake's view of communication, and Shermer's estimate of lifetime: <dl><dd>R∗ = 1.5–3 yr−1,<a href="#cite_note-Robitaille-22">[22]</a> fp · ne · fl = 10−5,<a href="#cite_note-RareEarth-36">[36]</a> fi = 10−9,<a href="#cite_note-Ernst_Mayr_on_SETI-41">[41]</a> fc = 0.2[Drake, above], and L = 304 years<a href="#cite_note-Why_ET_Hasn’t_Called-51">[51]</a></dd></dl> gives: <dl><dd>N = 1.5 × 10−5 × 10−9 × 0.2 × 304 = 9.1 × 10−13</dd></dl> i.e., suggesting that we are probably alone in this galaxy, and possibly in the <a href="/wiki/Observable_universe" title="Observable universe">observable universe</a>. On the other hand, with larger values for each of the parameters above, values of N can be derived that are greater than 1. The following higher values that have been proposed for each of the parameters: <dl><dd>R∗ = 1.5–3 yr−1,<a href="#cite_note-Robitaille-22">[22]</a> fp = 1,<a href="#cite_note-bbc.co.uk-25">[25]</a> ne = 0.2,<a href="#cite_note-W._von_Bloh,_C.Bounama,_M._Cuntz,_and_S._Franck._2007_1365-62">[62]</a><a href="#cite_note-F._Selsis,_J.F._Kasting,_B._Levrard,_J._Paillet,_I._Ribas,_and_X._Delfosse._2007_1373-63">[63]</a> fl = 0.13,<a href="#cite_note-Lineweaver,_C._H._&_Davis,_T._M._2002_293–304-64">[64]</a> fi = 1,<a href="#cite_note-acampbell.ukfsn.org-43">[43]</a> fc = 0.2[Drake, above], and L = 109 years<a href="#cite_note-David_Grinspoon_2004-52">[52]</a></dd></dl> Use of these parameters gives: <dl><dd>N = 3 × 1 × 0.2 × 0.13 × 1 × 0.2 × 109 = 15,600,000</dd></dl> <a href="/wiki/Monte_Carlo_method" title="Monte Carlo method">Monte Carlo</a> simulations of estimates of the Drake equation factors based on a stellar and planetary model of the Milky Way have resulted in the number of civilizations varying by a factor of 100.<a href="#cite_note-65">[65]</a> <div class="mw-heading mw-heading3"><h3 id="Possible_former_technological_civilizations">Possible former technological civilizations</h3>[<a href="/w/index.php?title=Drake_equation&action=edit&section=15" title="Edit section: Possible former technological civilizations">edit</a>]</div> In 2016, Adam Frank and Woodruff Sullivan modified the Drake equation to determine just how unlikely the event of a technological species arising on a given habitable planet must be, to give the result that Earth hosts the only technological species that has ever arisen, for two cases: (a) this Galaxy, and (b) the universe as a whole. By asking this different question, one removes the lifetime and simultaneous communication uncertainties. Since the numbers of habitable planets per star can today be reasonably estimated, the only remaining unknown in the Drake equation is the probability that a habitable planet ever develops a technological species over its lifetime. For Earth to have the only technological species that has ever occurred in the universe, they calculate the probability of any given habitable planet ever developing a technological species must be less than 2.5×10−24. Similarly, for Earth to have been the only case of hosting a technological species over the history of this Galaxy, the odds of a habitable zone planet ever hosting a technological species must be less than 1.7×10−11 (about 1 in 60 billion). The figure for the universe implies that it is extremely unlikely that Earth hosts the only technological species that has ever occurred. On the other hand, for this Galaxy one must think that fewer than 1 in 60 billion habitable planets develop a technological species for there not to have been at least a second case of such a species over the past history of this Galaxy.<a href="#cite_note-66">[66]</a><a href="#cite_note-67">[67]</a><a href="#cite_note-68">[68]</a><a href="#cite_note-69">[69]</a> <div class="mw-heading mw-heading2"><h2 id="Modifications">Modifications</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=16" title="Edit section: Modifications">edit</a>]</div> As many observers have pointed out, the Drake equation is a very simple model that omits potentially relevant parameters,<a href="#cite_note-70">[70]</a> and many changes and modifications to the equation have been proposed. One line of modification, for example, attempts to account for the uncertainty inherent in many of the terms.<a href="#cite_note-71">[71]</a> Combining the estimates of the original six factors by major researchers via a Monte Carlo procedure leads to a best value for the non-longevity factors of 0.85 1/years.<a href="#cite_note-72">[72]</a> This result differs insignificantly from the estimate of unity given both by Drake and the Cyclops report. Others note that the Drake equation ignores many concepts that might be relevant to the odds of contacting other civilizations. For example, <a href="/wiki/David_Brin" title="David Brin">David Brin</a> states: "The Drake equation merely speaks of the number of sites at which ETIs spontaneously arise. The equation says nothing directly about the contact cross-section between an ETIS and contemporary human society".<a href="#cite_note-GS-73">[73]</a> Because it is the contact cross-section that is of interest to the SETI community, many additional factors and modifications of the Drake equation have been proposed. <dl><dt>Colonization</dt> <dd>It has been proposed to generalize the Drake equation to include additional effects of alien civilizations colonizing other <a href="/wiki/Star_system" title="Star system">star systems</a>. Each original site expands with an expansion velocity v, and establishes additional sites that survive for a lifetime L. The result is a more complex set of 3 equations.<a href="#cite_note-GS-73">[73]</a></dd></dl> <dl><dt>Reappearance factor</dt> <dd>The Drake equation may furthermore be multiplied by how many times an intelligent civilization may occur on planets where it has happened once. Even if an intelligent civilization reaches the end of its lifetime after, for example, 10,000 years, life may still prevail on the planet for billions of years, permitting the next <a href="/wiki/Sociocultural_evolution" title="Sociocultural evolution">civilization to evolve</a>. Thus, several civilizations may come and go during the lifespan of one and the same planet. Thus, if nr is the average number of times a new civilization reappears on the same planet where a previous civilization once has appeared and ended, then the total number of civilizations on such a planet would be 1 + nr, which is the actual reappearance factor added to the equation.</dd></dl> <dl><dd>The factor depends on what generally is the cause of <a href="/wiki/Civilization_extinction" class="mw-redirect" title="Civilization extinction">civilization extinction</a>. If it is generally by temporary uninhabitability, for example a <a href="/wiki/Nuclear_winter" title="Nuclear winter">nuclear winter</a>, then nr may be relatively high. On the other hand, if it is generally by permanent uninhabitability, such as <a href="/wiki/Stellar_evolution" title="Stellar evolution">stellar evolution</a>, then nr may be almost zero. In the case of total life extinction, a similar factor may be applicable for fl, that is, how many times life may appear on a planet where it has appeared once.</dd></dl> <dl><dt>METI factor</dt> <dd><a href="/wiki/Aleksandr_Leonidovich_Zaitsev" class="mw-redirect" title="Aleksandr Leonidovich Zaitsev">Alexander Zaitsev</a> said that to be in a communicative phase and emit dedicated messages are not the same. For example, humans, although being in a communicative phase, are not a communicative civilization; we do not practise such activities as the purposeful and regular transmission of interstellar messages. For this reason, he suggested introducing the METI factor (messaging to extraterrestrial intelligence) to the classical Drake equation.<a href="#cite_note-74">[74]</a> He defined the factor as "the fraction of communicative civilizations with clear and non-paranoid planetary consciousness", or alternatively expressed, the fraction of communicative civilizations that actually engage in deliberate interstellar transmission.</dd></dl> <dl><dd>The METI factor is somewhat misleading since active, purposeful transmission of messages by a civilization is not required for them to receive a broadcast sent by another that is seeking first contact. It is merely required they have capable and compatible receiver systems operational; however, this is a variable humans cannot accurately estimate.</dd></dl> <dl><dt>Biogenic gases</dt> <dd>Astronomer <a href="/wiki/Sara_Seager" title="Sara Seager">Sara Seager</a> proposed a revised equation that focuses on the search for planets with biosignature gases.<a href="#cite_note-NYT-20161207-75">[75]</a> These gases are produced by living organisms that can accumulate in a planet atmosphere to levels that can be detected with remote space telescopes.<a href="#cite_note-equation-76">[76]</a></dd></dl> <dl><dd>The Seager equation looks like this:<a href="#cite_note-equation-76">[76]</a><a href="#cite_note-77">[a]</a> <dl><dd><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle N=N_{*}\cdot F_{\mathrm {Q} }\cdot F_{\mathrm {HZ} }\cdot F_{\mathrm {O} }\cdot F_{\mathrm {L} }\cdot F_{\mathrm {S} }}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>N</mi> <mo>=</mo> <msub> <mi>N</mi> <mrow class="MJX-TeXAtom-ORD"> <mo>∗</mo> </mrow> </msub> <mo>⋅</mo> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">Q</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">H</mi> <mi mathvariant="normal">Z</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">O</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">L</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>F</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">S</mi> </mrow> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle N=N_{*}\cdot F_{\mathrm {Q} }\cdot F_{\mathrm {HZ} }\cdot F_{\mathrm {O} }\cdot F_{\mathrm {L} }\cdot F_{\mathrm {S} }}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f01ca643a8fb7bbdf504deae3e8653fed6433b4f" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:31.847ex; height:2.843ex;" alt="{\displaystyle N=N_{*}\cdot F_{\mathrm {Q} }\cdot F_{\mathrm {HZ} }\cdot F_{\mathrm {O} }\cdot F_{\mathrm {L} }\cdot F_{\mathrm {S} }}"></dd></dl></dd> <dd>where: <dl><dd>N = the number of planets with detectable signs of life</dd> <dd>N∗ = the number of stars observed</dd> <dd>FQ = the fraction of stars that are quiet</dd> <dd>FHZ = the fraction of stars with rocky planets in the habitable zone</dd> <dd>FO = the fraction of those planets that can be observed</dd> <dd>FL = the fraction that have life</dd> <dd>FS = the fraction on which life produces a detectable signature gas</dd></dl></dd></dl> <dl><dd>Seager stresses, "We're not throwing out the Drake Equation, which is really a different topic," explaining, "Since Drake came up with the equation, we have discovered thousands of exoplanets. We as a community have had our views revolutionized as to what could possibly be out there. And now we have a real question on our hands, one that's not related to intelligent life: Can we detect any signs of life in any way in the very near future?"<a href="#cite_note-78">[77]</a></dd></dl> <dl><dt>Carl Sagan's version of the Drake equation</dt> <dd>American astronomer <a href="/wiki/Carl_Sagan" title="Carl Sagan">Carl Sagan</a> made some modifications<a href="#cite_note-79">[78]</a> in the Drake equation and presented it in the 1980 program <a href="/wiki/Cosmos:_A_Personal_Voyage" title="Cosmos: A Personal Voyage">Cosmos: A Personal Voyage</a>.<a href="#cite_note-80">[79]</a> The modified equation is shown below</dd></dl> <math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle N=N_{\mathrm {*} }\cdot f_{\mathrm {p} }\cdot n_{\mathrm {e} }\cdot f_{\mathrm {l} }\cdot f_{\mathrm {i} }\cdot f_{\mathrm {c} }\cdot f_{\mathrm {L} }}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>N</mi> <mo>=</mo> <msub> <mi>N</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mo>∗</mo> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">p</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>n</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">e</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">l</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">i</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">c</mi> </mrow> </mrow> </msub> <mo>⋅</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">L</mi> </mrow> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle N=N_{\mathrm {*} }\cdot f_{\mathrm {p} }\cdot n_{\mathrm {e} }\cdot f_{\mathrm {l} }\cdot f_{\mathrm {i} }\cdot f_{\mathrm {c} }\cdot f_{\mathrm {L} }}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/512d1e1370d31fd6c06357637cd50909dd3d8ad3" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:30.958ex; height:2.843ex;" alt="{\displaystyle N=N_{\mathrm {*} }\cdot f_{\mathrm {p} }\cdot n_{\mathrm {e} }\cdot f_{\mathrm {l} }\cdot f_{\mathrm {i} }\cdot f_{\mathrm {c} }\cdot f_{\mathrm {L} }}"><a href="#cite_note-81">[80]</a> where <ul><li>N = the number of <a href="/wiki/Civilization" title="Civilization">civilizations</a> in the Milky Way galaxy with which communication might be possible (i.e. which are on the current past <a href="/wiki/Light_cone" title="Light cone">light cone</a>);</li></ul> and <ul><li>N∗ = Number of <a href="/wiki/Stars" class="mw-redirect" title="Stars">stars</a> in the <a href="/wiki/Milky_Way_Galaxy" class="mw-redirect" title="Milky Way Galaxy">Milky Way Galaxy</a></li> <li>fp = the fraction of those stars that have <a href="/wiki/Planet" title="Planet">planets</a>.</li> <li>ne = the average number of planets that can potentially support <a href="/wiki/Life" title="Life">life</a> per star that has planets.</li> <li>fl = the fraction of planets that could support life that actually develop life at some point.</li> <li>fi = the fraction of planets with life that go on to develop <a href="/wiki/Intelligence" title="Intelligence">intelligent</a> life (civilizations).</li> <li>fc = the fraction of civilizations that develop a technology that releases <a href="/wiki/Technosignature" title="Technosignature">detectable signs of their existence into space</a>.</li> <li>fL = fraction of a planetary lifetime graced by a technological civilization</li></ul> <div class="mw-heading mw-heading2"><h2 id="Criticism">Criticism</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=17" title="Edit section: Criticism">edit</a>]</div> Criticism of the Drake equation is varied. Firstly, many of the terms in the equation are largely or entirely based on conjecture.<a href="#cite_note-82">[81]</a><a href="#cite_note-83">[82]</a> Star formation rates are well-known, and the incidence of planets has a sound theoretical and observational basis, but the other terms in the equation become very speculative. The uncertainties revolve around the present day understanding of the evolution of life, intelligence, and civilization, not physics. No statistical estimates are possible for some of the parameters, where only one example is known. The net result is that the equation cannot be used to draw firm conclusions of any kind, and the resulting margin of error is huge, far beyond what some consider acceptable or meaningful.<a href="#cite_note-84">[83]</a><a href="#cite_note-85">[84]</a> Others point out that the equation was formulated before our understanding of the universe had matured. Astrophysicist Ethan Siegel, said: <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1244412712"><blockquote class="templatequote">The Drake equation, when it was put forth, made an assumption about the Universe that we now know is untrue: It assumed that the Universe was eternal and static in time. As we learned only a few years after Frank Drake first proposed his equation, the Universe doesn’t exist in a steady state, where it’s unchanging in time, but rather has evolved from a hot, dense, energetic, and rapidly expanding state: a hot Big Bang that occurred over a finite duration in our cosmic past.<a href="#cite_note-86">[85]</a></blockquote> One reply to such criticisms<a href="#cite_note-87">[86]</a> is that even though the Drake equation currently involves speculation about unmeasured parameters, it was intended as a way to stimulate dialogue on these topics. Then the focus becomes how to proceed experimentally. Indeed, Drake originally formulated the equation merely as an agenda for discussion at the Green Bank conference.<a href="#cite_note-88">[87]</a> <div class="mw-heading mw-heading3"><h3 id="Fermi_paradox">Fermi paradox</h3>[<a href="/w/index.php?title=Drake_equation&action=edit&section=18" title="Edit section: Fermi paradox">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Fermi_paradox" title="Fermi paradox">Fermi paradox</a></div> A civilization lasting for tens of millions of years could be able to spread throughout the galaxy, even at the slow speeds foreseeable with present-day technology. However, no confirmed signs of civilizations or intelligent life elsewhere have been found, either in this Galaxy or in the <a href="/wiki/Observable_universe" title="Observable universe">observable universe</a> of 2 <a href="/wiki/Trillion_(short_scale)" class="mw-redirect" title="Trillion (short scale)">trillion</a> galaxies.<a href="#cite_note-Conselice-89">[88]</a><a href="#cite_note-NYT-20161017-90">[89]</a> According to this line of thinking, the tendency to fill (or at least explore) all available territory seems to be a universal trait of living things, so the Earth should have already been colonized, or at least visited, but no evidence of this exists. Hence Fermi's question "Where is everybody?".<a href="#cite_note-OSTI-19850301-91">[90]</a><a href="#cite_note-92">[91]</a> A large number of explanations have been proposed to explain this lack of contact; a book published in 2015 elaborated on 75 different explanations.<a href="#cite_note-93">[92]</a> In terms of the Drake Equation, the explanations can be divided into three classes: <ul><li>Few intelligent civilizations ever arise. This is an argument that at least one of the first few terms, R∗ · fp · ne · fl · fi, has a low value. The most common suspect is fi, but explanations such as the rare Earth hypothesis argue that ne is the small term.</li> <li>Intelligent civilizations exist, but we see no evidence, meaning fc is small. Typical arguments include that civilizations are too far apart, it is too expensive to spread throughout the galaxy, civilizations broadcast signals for only a brief period of time, communication is dangerous, and many others.</li> <li>The lifetime of intelligent, communicative civilizations is short, meaning the value of L is small. Drake suggested that a large number of extraterrestrial civilizations would form, and he further speculated that the lack of evidence of such civilizations may be because technological civilizations tend to disappear rather quickly. Typical explanations include it is the nature of intelligent life to destroy itself, it is the nature of intelligent life to destroy others, they tend to be destroyed by natural events, and others.</li></ul> These lines of reasoning lead to the <a href="/wiki/Great_Filter" title="Great Filter">Great Filter</a> hypothesis,<a href="#cite_note-94">[93]</a> which states that since there are no observed extraterrestrial civilizations despite the vast number of stars, at least one step in the process must be acting as a filter to reduce the final value. According to this view, either it is very difficult for intelligent life to arise, or the lifetime of technologically advanced civilizations, or the period of time they reveal their existence must be relatively short. An analysis by <a href="/wiki/Anders_Sandberg" title="Anders Sandberg">Anders Sandberg</a>, <a href="/wiki/Eric_Drexler" class="mw-redirect" title="Eric Drexler">Eric Drexler</a> and <a href="/wiki/Toby_Ord" title="Toby Ord">Toby Ord</a> suggests "a substantial ex ante (predicted) probability of there being no other intelligent life in our observable universe".<a href="#cite_note-95">[94]</a> <div class="mw-heading mw-heading2"><h2 id="In_fiction_and_popular_culture">In fiction and popular culture</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=19" title="Edit section: In fiction and popular culture">edit</a>]</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Europa_Clipper_commemorative_plate.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Europa_Clipper_commemorative_plate.jpg/220px-Europa_Clipper_commemorative_plate.jpg" decoding="async" width="220" height="286" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Europa_Clipper_commemorative_plate.jpg/330px-Europa_Clipper_commemorative_plate.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Europa_Clipper_commemorative_plate.jpg/440px-Europa_Clipper_commemorative_plate.jpg 2x" data-file-width="1537" data-file-height="2000" /></a><figcaption>Commemorative plate on <a href="/wiki/Europa_Clipper" title="Europa Clipper">Europa Clipper</a></figcaption></figure> The equation was cited by <a href="/wiki/Gene_Roddenberry" title="Gene Roddenberry">Gene Roddenberry</a> as supporting the multiplicity of inhabited planets shown on <a href="/wiki/Star_Trek" title="Star Trek">Star Trek</a>, the television series he created. However, Roddenberry did not have the equation with him, and he was forced to "invent" it for his original proposal.<a href="#cite_note-96">[95]</a> The invented equation created by Roddenberry is: <math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle Ff^{2}(MgE)-C^{1}Ri^{1}\cdot M=L/So}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>F</mi> <msup> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo stretchy="false">(</mo> <mi>M</mi> <mi>g</mi> <mi>E</mi> <mo stretchy="false">)</mo> <mo>−</mo> <msup> <mi>C</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msup> <mi>R</mi> <msup> <mi>i</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msup> <mo>⋅</mo> <mi>M</mi> <mo>=</mo> <mi>L</mi> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mi>S</mi> <mi>o</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle Ff^{2}(MgE)-C^{1}Ri^{1}\cdot M=L/So}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2fc6562bbd50933ae0b7c346a0e654d296161aca" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:33.164ex; height:3.176ex;" alt="{\displaystyle Ff^{2}(MgE)-C^{1}Ri^{1}\cdot M=L/So}"> Regarding Roddenberry's fictional version of the equation, Drake himself commented that a number raised to the first power is just the number itself.<a href="#cite_note-97">[96]</a> A commemorative plate on NASA's <a href="/wiki/Europa_Clipper" title="Europa Clipper">Europa Clipper</a> mission, planned for launch in October 2024, features a poem by the U.S. Poet Laureate <a href="/wiki/Ada_Lim%C3%B3n" title="Ada Limón">Ada Limón</a>, waveforms of the word 'water' in 103 languages, a schematic of the <a href="/wiki/Water_hole_(radio)" title="Water hole (radio)">water hole</a>, the Drake equation, and a portrait of planetary scientist <a href="/wiki/Ron_Greeley" class="mw-redirect" title="Ron Greeley">Ron Greeley</a> on it.<a href="#cite_note-98">[97]</a> The track Abiogenesis on the <a href="/wiki/Carbon_Based_Lifeforms" title="Carbon Based Lifeforms">Carbon Based Lifeforms</a> album <a href="/wiki/World_of_Sleepers" title="World of Sleepers">World of Sleepers</a> features the Drake equation in a spoken voice-over. <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=20" title="Edit section: See also">edit</a>]</div> <ul><li><a href="/wiki/Astrobiology" title="Astrobiology">Astrobiology</a> – Science concerned with life in the universe</li> <li><a href="/wiki/Goldilocks_principle" title="Goldilocks principle">Goldilocks principle</a> – Analogy for optimal conditions</li> <li><a href="/wiki/Kardashev_scale" title="Kardashev scale">Kardashev scale</a> – Measure of a civilization's evolution</li> <li><a href="/wiki/Planetary_habitability" title="Planetary habitability">Planetary habitability</a> – Known extent to which a planet is suitable for life</li> <li><a href="/wiki/Ufology" title="Ufology">Ufology</a> – Study of UFOs</li> <li><a href="/wiki/Lincoln_index" title="Lincoln index">Lincoln index</a> – Statistical measure</li> <li><a href="/wiki/The_Search_for_Life:_The_Drake_Equation" title="The Search for Life: The Drake Equation">The Search for Life: The Drake Equation</a>, BBC documentary</li></ul> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=21" title="Edit section: Notes">edit</a>]</div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-lower-alpha"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-77"><a href="#cite_ref-77">^</a> The rendering of the equation here is slightly modified for clarity of presentation from the rendering in the cited source.<a href="#cite_note-equation-76">[76]</a> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=22" title="Edit section: References">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist reflist-columns references-column-width" style="column-width: 38em;"> <ol class="references"> <li id="cite_note-Drake_1961-1">^ <a href="#cite_ref-Drake_1961_1-0">a</a> <a href="#cite_ref-Drake_1961_1-1">b</a> <a href="#cite_ref-Drake_1961_1-2">c</a> <a href="/wiki/Physics_Today" title="Physics Today">Physics Today</a> 14 (4), 40–46 (1961). <style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFDrake1961" class="citation web cs1">Drake, F. D. (April 1961). <a rel="nofollow" class="external text" href="https://pubs.aip.org/physicstoday/article/14/4/40/422237/Project-Ozma">"Project Ozma"</a>. pubs.aip.org. American Institute of Physics. Retrieved 27 April 2023. <q>The question of the existence of intelligent life elsewhere in space has long fascinated people, but, until recently, has been properly left to the science‐fiction writers.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=pubs.aip.org&rft.atitle=Project+Ozma&rft.date=1961-04&rft.aulast=Drake&rft.aufirst=F.+D.&rft_id=https%3A%2F%2Fpubs.aip.org%2Fphysicstoday%2Farticle%2F14%2F4%2F40%2F422237%2FProject-Ozma&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-Burchell-2">^ <a href="#cite_ref-Burchell_2-0">a</a> <a href="#cite_ref-Burchell_2-1">b</a> <a href="#cite_ref-Burchell_2-2">c</a> <a href="#cite_ref-Burchell_2-3">d</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBurchell2006" class="citation journal cs1">Burchell, M. J. (2006). "W(h)ither the Drake equation?". International Journal of Astrobiology. 5 (3): 243–250. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2006IJAsB...5..243B">2006IJAsB...5..243B</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2FS1473550406003107">10.1017/S1473550406003107</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:121060763">121060763</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=International+Journal+of+Astrobiology&rft.atitle=W%28h%29ither+the+Drake+equation%3F&rft.volume=5&rft.issue=3&rft.pages=243-250&rft.date=2006&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A121060763%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1017%2FS1473550406003107&rft_id=info%3Abibcode%2F2006IJAsB...5..243B&rft.aulast=Burchell&rft.aufirst=M.+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-3"><a href="#cite_ref-3">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGladeBalletBastien2012" class="citation journal cs1">Glade, N.; Ballet, P.; Bastien, O. (2012). "A stochastic process approach of the drake equation parameters". <a href="/wiki/International_Journal_of_Astrobiology" title="International Journal of Astrobiology">International Journal of Astrobiology</a>. 11 (2): 103–108. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1112.1506">1112.1506</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2012IJAsB..11..103G">2012IJAsB..11..103G</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2FS1473550411000413">10.1017/S1473550411000413</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:119250730">119250730</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=International+Journal+of+Astrobiology&rft.atitle=A+stochastic+process+approach+of+the+drake+equation+parameters&rft.volume=11&rft.issue=2&rft.pages=103-108&rft.date=2012&rft_id=info%3Aarxiv%2F1112.1506&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A119250730%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1017%2FS1473550411000413&rft_id=info%3Abibcode%2F2012IJAsB..11..103G&rft.aulast=Glade&rft.aufirst=N.&rft.au=Ballet%2C+P.&rft.au=Bastien%2C+O.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-December_2002-4">^ <a href="#cite_ref-December_2002_4-0">a</a> <a href="#cite_ref-December_2002_4-1">b</a> <a href="#cite_ref-December_2002_4-2">c</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.setileague.org/askdr/drake.htm">"Chapter 3 – Philosophy: "Solving the Drake Equation"</a>. Ask Dr. SETI. SETI League. December 2002. Retrieved 10 April 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Ask+Dr.+SETI&rft.atitle=Chapter+3+%E2%80%93+Philosophy%3A+%22Solving+the+Drake+Equation&rft.date=2002-12&rft_id=http%3A%2F%2Fwww.setileague.org%2Faskdr%2Fdrake.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-5"><a href="#cite_ref-5">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDrake2014" class="citation web cs1"><a href="/wiki/Nadia_Drake" title="Nadia Drake">Drake, N.</a> (30 June 2014). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20140705053200/http://news.nationalgeographic.com/news/2014/06/140630-drake-equation-50-years-later-aliens-science/">"How my Dad's Equation Sparked the Search for Extraterrestrial Intelligence"</a>. <a href="/wiki/National_Geographic_(magazine)" class="mw-redirect" title="National Geographic (magazine)">National Geographic</a>. Archived from <a rel="nofollow" class="external text" href="http://news.nationalgeographic.com/news/2014/06/140630-drake-equation-50-years-later-aliens-science/">the original</a> on 5 July 2014. Retrieved 2 October 2016.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=National+Geographic&rft.atitle=How+my+Dad%27s+Equation+Sparked+the+Search+for+Extraterrestrial+Intelligence&rft.date=2014-06-30&rft.aulast=Drake&rft.aufirst=N.&rft_id=http%3A%2F%2Fnews.nationalgeographic.com%2Fnews%2F2014%2F06%2F140630-drake-equation-50-years-later-aliens-science%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-NOVA-6">^ <a href="#cite_ref-NOVA_6-0">a</a> <a href="#cite_ref-NOVA_6-1">b</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAguirre2008" class="citation web cs1">Aguirre, L. (1 July 2008). <a rel="nofollow" class="external text" href="https://www.pbs.org/wgbh/nova/origins/drake.html">"The Drake Equation"</a>. <a href="/wiki/Nova_ScienceNow" title="Nova ScienceNow">Nova ScienceNow</a>. <a href="/wiki/PBS" title="PBS">PBS</a>. Retrieved 7 March 2010.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Nova+ScienceNow&rft.atitle=The+Drake+Equation&rft.date=2008-07-01&rft.aulast=Aguirre&rft.aufirst=L.&rft_id=https%3A%2F%2Fwww.pbs.org%2Fwgbh%2Fnova%2Forigins%2Fdrake.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-SETI-Drake-Equation-7"><a href="#cite_ref-SETI-Drake-Equation_7-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.seti.org/drakeequation">"What do we need to know about to discover life in space?"</a>. <a href="/wiki/SETI_Institute" title="SETI Institute">SETI Institute</a>. Retrieved 16 April 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=What+do+we+need+to+know+about+to+discover+life+in+space%3F&rft.pub=SETI+Institute&rft_id=http%3A%2F%2Fwww.seti.org%2Fdrakeequation&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-8"><a href="#cite_ref-8">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDrake1965" class="citation book cs1">Drake, Frank D. (1 January 1965). <a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1965cae..book..323D">The Radio Search for Intelligent Extraterrestrial Life</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1965cae..book..323D">1965cae..book..323D</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Radio+Search+for+Intelligent+Extraterrestrial+Life&rft.date=1965-01-01&rft_id=info%3Abibcode%2F1965cae..book..323D&rft.aulast=Drake&rft.aufirst=Frank+D.&rft_id=https%3A%2F%2Fui.adsabs.harvard.edu%2Fabs%2F1965cae..book..323D&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-9"><a href="#cite_ref-9">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFjtw132019" class="citation web cs1">jtw13 (31 July 2019). <a rel="nofollow" class="external text" href="https://sites.psu.edu/astrowright/2019/07/31/freeman-dysons-first-law-of-seti-investigations/">"Freeman Dyson's First Law of SETI Investigations"</a>. AstroWright. Retrieved 2 August 2024.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=AstroWright&rft.atitle=Freeman+Dyson%27s+First+Law+of+SETI+Investigations&rft.date=2019-07-31&rft.au=jtw13&rft_id=https%3A%2F%2Fsites.psu.edu%2Fastrowright%2F2019%2F07%2F31%2Ffreeman-dysons-first-law-of-seti-investigations%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: numeric names: authors list (<a href="/wiki/Category:CS1_maint:_numeric_names:_authors_list" title="Category:CS1 maint: numeric names: authors list">link</a>) </li> <li id="cite_note-Cocconi_1959-10"><a href="#cite_ref-Cocconi_1959_10-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCocconiMorisson1959" class="citation journal cs1">Cocconi, G.; Morisson, P. (1959). <a rel="nofollow" class="external text" href="http://www.iaragroup.org/_OLD/seti/pdf_IARA/cocconi.pdf">"Searching for Interstellar Communications"</a> (PDF). <a href="/wiki/Nature_(journal)" title="Nature (journal)">Nature</a>. 184 (4690): 844–846. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1959Natur.184..844C">1959Natur.184..844C</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2F184844a0">10.1038/184844a0</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:4220318">4220318</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110728025232/http://www.iaragroup.org/_OLD/seti/pdf_IARA/cocconi.pdf">Archived</a> (PDF) from the original on 28 July 2011. Retrieved 10 April 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=Searching+for+Interstellar+Communications&rft.volume=184&rft.issue=4690&rft.pages=844-846&rft.date=1959&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A4220318%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1038%2F184844a0&rft_id=info%3Abibcode%2F1959Natur.184..844C&rft.aulast=Cocconi&rft.aufirst=G.&rft.au=Morisson%2C+P.&rft_id=http%3A%2F%2Fwww.iaragroup.org%2F_OLD%2Fseti%2Fpdf_IARA%2Fcocconi.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-history-11">^ <a href="#cite_ref-history_11-0">a</a> <a href="#cite_ref-history_11-1">b</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSchillingMacRobert2013" class="citation web cs1">Schilling, G.; MacRobert, A. M. (2013). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20130214073858/http://www.skyandtelescope.com/resources/seti/3304541.html">"The Chance of Finding Aliens"</a>. <a href="/wiki/Sky_%26_Telescope" title="Sky & Telescope">Sky & Telescope</a>. Archived from <a rel="nofollow" class="external text" href="https://skyandtelescope.org/astronomy-news/the-chance-of-finding-aliens/">the original</a> on 14 February 2013. Retrieved 10 April 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Sky+%26+Telescope&rft.atitle=The+Chance+of+Finding+Aliens&rft.date=2013&rft.aulast=Schilling&rft.aufirst=G.&rft.au=MacRobert%2C+A.+M.&rft_id=https%3A%2F%2Fskyandtelescope.org%2Fastronomy-news%2Fthe-chance-of-finding-aliens%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-SydneyMorningHerald-12"><a href="#cite_ref-SydneyMorningHerald_12-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFnewspaper1959" class="citation news cs1">newspaper, staff (8 November 1959). <a rel="nofollow" class="external text" href="https://news.google.com/newspapers?nid=1301&dat=19591108&id=s39WAAAAIBAJ&pg=2212,2112869&hl=en">"Life On Other Planets?"</a>. <a href="/wiki/Sydney_Morning_Herald" class="mw-redirect" title="Sydney Morning Herald">Sydney Morning Herald</a>. Retrieved 2 October 2015.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Sydney+Morning+Herald&rft.atitle=Life+On+Other+Planets%3F&rft.date=1959-11-08&rft.aulast=newspaper&rft.aufirst=staff&rft_id=https%3A%2F%2Fnews.google.com%2Fnewspapers%3Fnid%3D1301%26dat%3D19591108%26id%3Ds39WAAAAIBAJ%26pg%3D2212%2C2112869%26hl%3Den&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-Astrobiology_Magazine-13"><a href="#cite_ref-Astrobiology_Magazine_13-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20210225062139/http://www.astrobio.net/alien-life/the-drake-equation-revisited-part-i/">"The Drake Equation Revisited: Part I"</a>. <a href="/wiki/Astrobiology_Magazine" title="Astrobiology Magazine">Astrobiology Magazine</a>. 29 September 2003. Archived from the original on 25 February 2021. Retrieved 20 May 2017.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Astrobiology+Magazine&rft.atitle=The+Drake+Equation+Revisited%3A+Part+I&rft.date=2003-09-29&rft_id=http%3A%2F%2Fwww.astrobio.net%2Falien-life%2Fthe-drake-equation-revisited-part-i%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: unfit URL (<a href="/wiki/Category:CS1_maint:_unfit_URL" title="Category:CS1 maint: unfit URL">link</a>) </li> <li id="cite_note-Wende-14"><a href="#cite_ref-Wende_14-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFZaun2011" class="citation news cs1 cs1-prop-foreign-lang-source">Zaun, H. (1 November 2011). <a rel="nofollow" class="external text" href="http://www.heise.de/tp/artikel/35/35756/1.html">"Es war wie eine 180-Grad-Wende von diesem peinlichen Geheimnis!"</a> [It was like a 180 degree turn from this embarrassing secret]. <a href="/wiki/Telepolis" title="Telepolis">Telepolis</a> (in German). Retrieved 13 August 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Telepolis&rft.atitle=Es+war+wie+eine+180-Grad-Wende+von+diesem+peinlichen+Geheimnis%21&rft.date=2011-11-01&rft.aulast=Zaun&rft.aufirst=H.&rft_id=http%3A%2F%2Fwww.heise.de%2Ftp%2Fartikel%2F35%2F35756%2F1.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-15"><a href="#cite_ref-15">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.setileague.org/photos/miscpix/drakeqn.jpg">"Drake Equation Plaque"</a>. Retrieved 13 August 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Drake+Equation+Plaque&rft_id=http%3A%2F%2Fwww.setileague.org%2Fphotos%2Fmiscpix%2Fdrakeqn.jpg&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-16"><a href="#cite_ref-16">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDarling" class="citation encyclopaedia cs1">Darling, D. J. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20240221024436/https://www.daviddarling.info/encyclopedia/G/GreenBank.html#Green_Bank_SETI_conference">"Green Bank conference (1961)"</a>. <a href="/wiki/The_Encyclopedia_of_Science" class="mw-redirect" title="The Encyclopedia of Science">The Encyclopedia of Science</a>. Archived from <a rel="nofollow" class="external text" href="https://www.daviddarling.info/encyclopedia/G/GreenBank.html#Green_Bank_SETI_conference">the original</a> on 21 February 2024. Retrieved 13 August 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Green+Bank+conference+%281961%29&rft.btitle=The+Encyclopedia+of+Science&rft.aulast=Darling&rft.aufirst=D.+J.&rft_id=https%3A%2F%2Fwww.daviddarling.info%2Fencyclopedia%2FG%2FGreenBank.html%23Green_Bank_SETI_conference&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-17"><a href="#cite_ref-17">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJones2001" class="citation web cs1">Jones, D. S. (26 September 2001). <a rel="nofollow" class="external text" href="http://frombob.to/drake.html">"Beyond the Drake Equation"</a>. Retrieved 17 April 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Beyond+the+Drake+Equation&rft.date=2001-09-26&rft.aulast=Jones&rft.aufirst=D.+S.&rft_id=http%3A%2F%2Ffrombob.to%2Fdrake.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-18"><a href="#cite_ref-18">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.youtube.com/watch?list=PL56DCB81E2F59166A&v=U3UyAoYkhTo&feature=player_embedded">"The Search For Life : The Drake Equation 2010 – Part 1"</a>. <a href="/wiki/BBC_Four" title="BBC Four">BBC Four</a>. 2010. Retrieved 17 April 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+Search+For+Life+%3A+The+Drake+Equation+2010+%E2%80%93+Part+1&rft.pub=BBC+Four&rft.date=2010&rft_id=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Flist%3DPL56DCB81E2F59166A%26v%3DU3UyAoYkhTo%26feature%3Dplayer_embedded&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-19"><a href="#cite_ref-19">^</a> <a rel="nofollow" class="external text" href="http://www.astronomynow.com/news/n1004/SETI/">SETI: A celebration of the first 50 years</a>. Keith Cooper. Astronomy Now. 2000 </li> <li id="cite_note-20"><a href="#cite_ref-20">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDrakeSobel1992" class="citation book cs1">Drake, F.; Sobel, D. (1992). Is Anyone Out There? The Scientific Search for Extraterrestrial Intelligence. <a href="/w/index.php?title=Delta_(publisher)&action=edit&redlink=1" class="new" title="Delta (publisher) (page does not exist)">Delta</a>. pp. 55–62. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-385-31122-2" title="Special:BookSources/0-385-31122-2"><bdi>0-385-31122-2</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Is+Anyone+Out+There%3F+The+Scientific+Search+for+Extraterrestrial+Intelligence&rft.pages=55-62&rft.pub=Delta&rft.date=1992&rft.isbn=0-385-31122-2&rft.aulast=Drake&rft.aufirst=F.&rft.au=Sobel%2C+D.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-21"><a href="#cite_ref-21">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGladeBalletBastien2012" class="citation journal cs1">Glade, N.; Ballet, P.; Bastien, O. (2012). "A stochastic process approach of the drake equation parameters". <a href="/wiki/International_Journal_of_Astrobiology" title="International Journal of Astrobiology">International Journal of Astrobiology</a>. 11 (2): 103–108. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1112.1506">1112.1506</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2012IJAsB..11..103G">2012IJAsB..11..103G</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2FS1473550411000413">10.1017/S1473550411000413</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:119250730">119250730</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=International+Journal+of+Astrobiology&rft.atitle=A+stochastic+process+approach+of+the+drake+equation+parameters&rft.volume=11&rft.issue=2&rft.pages=103-108&rft.date=2012&rft_id=info%3Aarxiv%2F1112.1506&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A119250730%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1017%2FS1473550411000413&rft_id=info%3Abibcode%2F2012IJAsB..11..103G&rft.aulast=Glade&rft.aufirst=N.&rft.au=Ballet%2C+P.&rft.au=Bastien%2C+O.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> Note: This reference has a table of 1961 values, claimed to be taken from Drake & Sobel, but these differ from the book. </li> <li id="cite_note-Robitaille-22">^ <a href="#cite_ref-Robitaille_22-0">a</a> <a href="#cite_ref-Robitaille_22-1">b</a> <a href="#cite_ref-Robitaille_22-2">c</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRobitaille,_Thomas_P.Barbara_A._Whitney2010" class="citation journal cs1">Robitaille, Thomas P.; Barbara A. Whitney (2010). "The present-day star formation rate of the Milky Way determined from Spitzer-detected young stellar objects". The Astrophysical Journal Letters. 710 (1): L11. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1001.3672">1001.3672</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2010ApJ...710L..11R">2010ApJ...710L..11R</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1088%2F2041-8205%2F710%2F1%2FL11">10.1088/2041-8205/710/1/L11</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:118703635">118703635</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal+Letters&rft.atitle=The+present-day+star+formation+rate+of+the+Milky+Way+determined+from+Spitzer-detected+young+stellar+objects&rft.volume=710&rft.issue=1&rft.pages=L11&rft.date=2010&rft_id=info%3Aarxiv%2F1001.3672&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A118703635%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1088%2F2041-8205%2F710%2F1%2FL11&rft_id=info%3Abibcode%2F2010ApJ...710L..11R&rft.au=Robitaille%2C+Thomas+P.&rft.au=Barbara+A.+Whitney&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-The_Drake_Equation-23"><a href="#cite_ref-The_Drake_Equation_23-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWanjek2015" class="citation book cs1">Wanjek, C. (2015). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=jcnSCQAAQBAJ&q=Robitaille+and+Whitney+came+up+with+a+figure+for+R*+between+0.68+and+1.45&pg=PA45">The Drake Equation</a>. <a href="/wiki/Cambridge_University_Press" title="Cambridge University Press">Cambridge University Press</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9781107073654" title="Special:BookSources/9781107073654"><bdi>9781107073654</bdi></a>. Retrieved 9 September 2016.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Drake+Equation&rft.pub=Cambridge+University+Press&rft.date=2015&rft.isbn=9781107073654&rft.aulast=Wanjek&rft.aufirst=C.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DjcnSCQAAQBAJ%26q%3DRobitaille%2Band%2BWhitney%2Bcame%2Bup%2Bwith%2Ba%2Bfigure%2Bfor%2BR%2A%2Bbetween%2B0.68%2Band%2B1.45%26pg%3DPA45&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-24"><a href="#cite_ref-24">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKennicuttEvans2012" class="citation journal cs1">Kennicutt, Robert C.; Evans, Neal J. (22 September 2012). "Star Formation in the Milky Way and Nearby Galaxies". Annual Review of Astronomy and Astrophysics. 50 (1): 531–608. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1204.3552">1204.3552</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2012ARA&A..50..531K">2012ARA&A..50..531K</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1146%2Fannurev-astro-081811-125610">10.1146/annurev-astro-081811-125610</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:118667387">118667387</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Annual+Review+of+Astronomy+and+Astrophysics&rft.atitle=Star+Formation+in+the+Milky+Way+and+Nearby+Galaxies&rft.volume=50&rft.issue=1&rft.pages=531-608&rft.date=2012-09-22&rft_id=info%3Aarxiv%2F1204.3552&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A118667387%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1146%2Fannurev-astro-081811-125610&rft_id=info%3Abibcode%2F2012ARA%26A..50..531K&rft.aulast=Kennicutt&rft.aufirst=Robert+C.&rft.au=Evans%2C+Neal+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-bbc.co.uk-25">^ <a href="#cite_ref-bbc.co.uk_25-0">a</a> <a href="#cite_ref-bbc.co.uk_25-1">b</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFPalmer2012" class="citation news cs1">Palmer, J. (11 January 2012). <a rel="nofollow" class="external text" href="https://www.bbc.co.uk/news/science-environment-16515944">"Exoplanets are around every star, study suggests"</a>. <a href="/wiki/BBC" title="BBC">BBC</a>. Retrieved 12 January 2012.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Exoplanets+are+around+every+star%2C+study+suggests&rft.date=2012-01-11&rft.aulast=Palmer&rft.aufirst=J.&rft_id=https%3A%2F%2Fwww.bbc.co.uk%2Fnews%2Fscience-environment-16515944&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-Nature-20120111-26"><a href="#cite_ref-Nature-20120111_26-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCassan2012" class="citation journal cs1">Cassan, A.; et al. (11 January 2012). "One or more bound planets per Milky Way star from microlensing observations". <a href="/wiki/Nature_(journal)" title="Nature (journal)">Nature</a>. 481 (7380): 167–169. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1202.0903">1202.0903</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2012Natur.481..167C">2012Natur.481..167C</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2Fnature10684">10.1038/nature10684</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/22237108">22237108</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:2614136">2614136</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=One+or+more+bound+planets+per+Milky+Way+star+from+microlensing+observations&rft.volume=481&rft.issue=7380&rft.pages=167-169&rft.date=2012-01-11&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A2614136%23id-name%3DS2CID&rft_id=info%3Abibcode%2F2012Natur.481..167C&rft_id=info%3Aarxiv%2F1202.0903&rft_id=info%3Apmid%2F22237108&rft_id=info%3Adoi%2F10.1038%2Fnature10684&rft.aulast=Cassan&rft.aufirst=A.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-NYT-20131104-27"><a href="#cite_ref-NYT-20131104_27-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFOverbye2013" class="citation news cs1">Overbye, Dennis (4 November 2013). <a rel="nofollow" class="external text" href="https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2013/11/05/science/cosmic-census-finds-billions-of-planets-that-could-be-like-earth.html">"Far-Off Planets Like the Earth Dot the Galaxy"</a>. <a href="/wiki/The_New_York_Times" title="The New York Times">The New York Times</a>. Archived from <a rel="nofollow" class="external text" href="https://www.nytimes.com/2013/11/05/science/cosmic-census-finds-billions-of-planets-that-could-be-like-earth.html">the original</a> on 1 January 2022. Retrieved 5 November 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+New+York+Times&rft.atitle=Far-Off+Planets+Like+the+Earth+Dot+the+Galaxy&rft.date=2013-11-04&rft.aulast=Overbye&rft.aufirst=Dennis&rft_id=https%3A%2F%2Fwww.nytimes.com%2F2013%2F11%2F05%2Fscience%2Fcosmic-census-finds-billions-of-planets-that-could-be-like-earth.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-PNAS-20131031-28"><a href="#cite_ref-PNAS-20131031_28-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFPetiguraHowardMarcy2013" class="citation journal cs1">Petigura, Eric A.; Howard, Andrew W.; Marcy, Geoffrey W. (31 October 2013). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845182">"Prevalence of Earth-size planets orbiting Sun-like stars"</a>. <a href="/wiki/Proceedings_of_the_National_Academy_of_Sciences_of_the_United_States_of_America" title="Proceedings of the National Academy of Sciences of the United States of America">Proceedings of the National Academy of Sciences of the United States of America</a>. 110 (48): 19273–19278. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1311.6806">1311.6806</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2013PNAS..11019273P">2013PNAS..11019273P</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1073%2Fpnas.1319909110">10.1073/pnas.1319909110</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845182">3845182</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/24191033">24191033</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Proceedings+of+the+National+Academy+of+Sciences+of+the+United+States+of+America&rft.atitle=Prevalence+of+Earth-size+planets+orbiting+Sun-like+stars&rft.volume=110&rft.issue=48&rft.pages=19273-19278&rft.date=2013-10-31&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3845182%23id-name%3DPMC&rft_id=info%3Abibcode%2F2013PNAS..11019273P&rft_id=info%3Aarxiv%2F1311.6806&rft_id=info%3Apmid%2F24191033&rft_id=info%3Adoi%2F10.1073%2Fpnas.1319909110&rft.aulast=Petigura&rft.aufirst=Eric+A.&rft.au=Howard%2C+Andrew+W.&rft.au=Marcy%2C+Geoffrey+W.&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3845182&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-LATimes-20131104-29"><a href="#cite_ref-LATimes-20131104_29-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKhan2013" class="citation news cs1">Khan, Amina (4 November 2013). <a rel="nofollow" class="external text" href="http://www.latimes.com/science/la-sci-earth-like-planets-20131105,0,2673237.story">"Milky Way may host billions of Earth-size planets"</a>. <a href="/wiki/Los_Angeles_Times" title="Los Angeles Times">Los Angeles Times</a>. Retrieved 5 November 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Los+Angeles+Times&rft.atitle=Milky+Way+may+host+billions+of+Earth-size+planets&rft.date=2013-11-04&rft.aulast=Khan&rft.aufirst=Amina&rft_id=http%3A%2F%2Fwww.latimes.com%2Fscience%2Fla-sci-earth-like-planets-20131105%2C0%2C2673237.story&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-schilling2011-30">^ <a href="#cite_ref-schilling2011_30-0">a</a> <a href="#cite_ref-schilling2011_30-1">b</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSchilling2011" class="citation web cs1">Schilling, Govert (November 2011). <a rel="nofollow" class="external text" href="http://www.astro-tom.com/technical_data/alien_life.htm">"The Chance of Finding Aliens: Reevaluating the Drake Equation"</a>. astro-tom.com.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=astro-tom.com&rft.atitle=The+Chance+of+Finding+Aliens%3A+Reevaluating+the+Drake+Equation&rft.date=2011-11&rft.aulast=Schilling&rft.aufirst=Govert&rft_id=http%3A%2F%2Fwww.astro-tom.com%2Ftechnical_data%2Falien_life.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-Trimble-31"><a href="#cite_ref-Trimble_31-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTrimble1997" class="citation journal cs1">Trimble, V. (1997). "Origin of the biologically important elements". <a href="/wiki/Origins_of_Life_and_Evolution_of_the_Biosphere" class="mw-redirect" title="Origins of Life and Evolution of the Biosphere">Origins of Life and Evolution of the Biosphere</a>. 27 (1–3): 3–21. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1997OLEB...27....3T">1997OLEB...27....3T</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1023%2FA%3A1006561811750">10.1023/A:1006561811750</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/9150565">9150565</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:7612499">7612499</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Origins+of+Life+and+Evolution+of+the+Biosphere&rft.atitle=Origin+of+the+biologically+important+elements&rft.volume=27&rft.issue=1%E2%80%933&rft.pages=3-21&rft.date=1997&rft_id=info%3Adoi%2F10.1023%2FA%3A1006561811750&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A7612499%23id-name%3DS2CID&rft_id=info%3Apmid%2F9150565&rft_id=info%3Abibcode%2F1997OLEB...27....3T&rft.aulast=Trimble&rft.aufirst=V.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-32"><a href="#cite_ref-32">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLineweaverFennerGibson2004" class="citation journal cs1">Lineweaver, C. H.; Fenner, Y.; Gibson, B. K. (2004). "The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way". <a href="/wiki/Science_(journal)" title="Science (journal)">Science</a>. 303 (5654): 59–62. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0401024">astro-ph/0401024</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2004Sci...303...59L">2004Sci...303...59L</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.1092322">10.1126/science.1092322</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/14704421">14704421</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:18140737">18140737</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science&rft.atitle=The+Galactic+Habitable+Zone+and+the+Age+Distribution+of+Complex+Life+in+the+Milky+Way&rft.volume=303&rft.issue=5654&rft.pages=59-62&rft.date=2004&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A18140737%23id-name%3DS2CID&rft_id=info%3Abibcode%2F2004Sci...303...59L&rft_id=info%3Aarxiv%2Fastro-ph%2F0401024&rft_id=info%3Apmid%2F14704421&rft_id=info%3Adoi%2F10.1126%2Fscience.1092322&rft.aulast=Lineweaver&rft.aufirst=C.+H.&rft.au=Fenner%2C+Y.&rft.au=Gibson%2C+B.+K.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-33"><a href="#cite_ref-33">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDressingCharbonneau2013" class="citation journal cs1">Dressing, C. D.; Charbonneau, D. (2013). "The Occurrence Rate of Small Planets around Small Stars". <a href="/wiki/The_Astrophysical_Journal" title="The Astrophysical Journal">The Astrophysical Journal</a>. 767 (1): 95. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1302.1647">1302.1647</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2013ApJ...767...95D">2013ApJ...767...95D</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1088%2F0004-637X%2F767%2F1%2F95">10.1088/0004-637X/767/1/95</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:29441006">29441006</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=The+Occurrence+Rate+of+Small+Planets+around+Small+Stars&rft.volume=767&rft.issue=1&rft.pages=95&rft.date=2013&rft_id=info%3Aarxiv%2F1302.1647&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A29441006%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1088%2F0004-637X%2F767%2F1%2F95&rft_id=info%3Abibcode%2F2013ApJ...767...95D&rft.aulast=Dressing&rft.aufirst=C.+D.&rft.au=Charbonneau%2C+D.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-34"><a href="#cite_ref-34">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://scitechdaily.com/red-dwarf-stars-could-leave-habitable-earth-like-planets-vulnerable-to-radiation/">"Red Dwarf Stars Could Leave Habitable Earth-Like Planets Vulnerable to Radiation"</a>. SciTech Daily. 2 July 2013. Retrieved 22 September 2015.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=SciTech+Daily&rft.atitle=Red+Dwarf+Stars+Could+Leave+Habitable+Earth-Like+Planets+Vulnerable+to+Radiation&rft.date=2013-07-02&rft_id=http%3A%2F%2Fscitechdaily.com%2Fred-dwarf-stars-could-leave-habitable-earth-like-planets-vulnerable-to-radiation%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-35"><a href="#cite_ref-35">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHellerBarnes2014" class="citation journal cs1">Heller, René; Barnes, Rory (29 April 2014). "Constraints on the Habitability of Extrasolar Moons". Proceedings of the International Astronomical Union. 8 (S293): 159–164. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1210.5172">1210.5172</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2014IAUS..293..159H">2014IAUS..293..159H</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2FS1743921313012738">10.1017/S1743921313012738</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:92988047">92988047</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Proceedings+of+the+International+Astronomical+Union&rft.atitle=Constraints+on+the+Habitability+of+Extrasolar+Moons&rft.volume=8&rft.issue=S293&rft.pages=159-164&rft.date=2014-04-29&rft_id=info%3Aarxiv%2F1210.5172&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A92988047%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1017%2FS1743921313012738&rft_id=info%3Abibcode%2F2014IAUS..293..159H&rft.aulast=Heller&rft.aufirst=Ren%C3%A9&rft.au=Barnes%2C+Rory&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-RareEarth-36">^ <a href="#cite_ref-RareEarth_36-0">a</a> <a href="#cite_ref-RareEarth_36-1">b</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWardBrownlee2000" class="citation book cs1">Ward, Peter D.; Brownlee, Donald (2000). Rare Earth: Why Complex Life is Uncommon in the Universe. Copernicus Books (Springer Verlag). <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-387-98701-0" title="Special:BookSources/0-387-98701-0"><bdi>0-387-98701-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Rare+Earth%3A+Why+Complex+Life+is+Uncommon+in+the+Universe&rft.pub=Copernicus+Books+%28Springer+Verlag%29&rft.date=2000&rft.isbn=0-387-98701-0&rft.aulast=Ward&rft.aufirst=Peter+D.&rft.au=Brownlee%2C+Donald&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-37"><a href="#cite_ref-37">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDavies2007" class="citation journal cs1">Davies, P. (2007). "Are Aliens Among Us?". <a href="/wiki/Scientific_American" title="Scientific American">Scientific American</a>. 297 (6): 62–69. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2007SciAm.297f..62D">2007SciAm.297f..62D</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2Fscientificamerican1207-62">10.1038/scientificamerican1207-62</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Scientific+American&rft.atitle=Are+Aliens+Among+Us%3F&rft.volume=297&rft.issue=6&rft.pages=62-69&rft.date=2007&rft_id=info%3Adoi%2F10.1038%2Fscientificamerican1207-62&rft_id=info%3Abibcode%2F2007SciAm.297f..62D&rft.aulast=Davies&rft.aufirst=P.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-38"><a href="#cite_ref-38">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCrickOrgel1973" class="citation journal cs1">Crick, F. H. C.; Orgel, L. E. (1973). <a rel="nofollow" class="external text" href="http://profiles.nlm.nih.gov/ps/access/SCBCCP.pdf">"Directed Panspermia"</a> (PDF). <a href="/wiki/Icarus_(journal)" title="Icarus (journal)">Icarus</a>. 19 (3): 341–346. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1973Icar...19..341C">1973Icar...19..341C</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2F0019-1035%2873%2990110-3">10.1016/0019-1035(73)90110-3</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20111029060655/http://profiles.nlm.nih.gov/ps/access/SCBCCP.pdf">Archived</a> (PDF) from the original on 29 October 2011.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Icarus&rft.atitle=Directed+Panspermia&rft.volume=19&rft.issue=3&rft.pages=341-346&rft.date=1973&rft_id=info%3Adoi%2F10.1016%2F0019-1035%2873%2990110-3&rft_id=info%3Abibcode%2F1973Icar...19..341C&rft.aulast=Crick&rft.aufirst=F.+H.+C.&rft.au=Orgel%2C+L.+E.&rft_id=http%3A%2F%2Fprofiles.nlm.nih.gov%2Fps%2Faccess%2FSCBCCP.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-39"><a href="#cite_ref-39">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWestbyConselice2020" class="citation journal cs1">Westby, Tom; Conselice, Christopher J. (15 June 2020). <a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F1538-4357%2Fab8225">"The Astrobiological Copernican Weak and Strong Limits for Intelligent Life"</a>. The Astrophysical Journal. 896 (1): 58. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/2004.03968">2004.03968</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2020ApJ...896...58W">2020ApJ...896...58W</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F1538-4357%2Fab8225">10.3847/1538-4357/ab8225</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:215415788">215415788</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=The+Astrobiological+Copernican+Weak+and+Strong+Limits+for+Intelligent+Life&rft.volume=896&rft.issue=1&rft.pages=58&rft.date=2020-06-15&rft_id=info%3Aarxiv%2F2004.03968&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A215415788%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.3847%2F1538-4357%2Fab8225&rft_id=info%3Abibcode%2F2020ApJ...896...58W&rft.aulast=Westby&rft.aufirst=Tom&rft.au=Conselice%2C+Christopher+J.&rft_id=https%3A%2F%2Fdoi.org%2F10.3847%252F1538-4357%252Fab8225&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-40"><a href="#cite_ref-40">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDavis2020" class="citation news cs1">Davis, Nicola (15 June 2020). <a rel="nofollow" class="external text" href="https://www.theguardian.com/science/2020/jun/15/scientists-say-most-likely-number-of-contactable-alien-civilisations-is-36">"Scientists say most likely number of contactable alien civilisations is 36"</a>. The Guardian. Retrieved 19 June 2020.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Guardian&rft.atitle=Scientists+say+most+likely+number+of+contactable+alien+civilisations+is+36&rft.date=2020-06-15&rft.aulast=Davis&rft.aufirst=Nicola&rft_id=https%3A%2F%2Fwww.theguardian.com%2Fscience%2F2020%2Fjun%2F15%2Fscientists-say-most-likely-number-of-contactable-alien-civilisations-is-36&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-Ernst_Mayr_on_SETI-41">^ <a href="#cite_ref-Ernst_Mayr_on_SETI_41-0">a</a> <a href="#cite_ref-Ernst_Mayr_on_SETI_41-1">b</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20101206171624/http://www.planetary.org/explore/topics/search_for_life/seti/mayr.html">"Ernst Mayr on SETI"</a>. <a href="/wiki/The_Planetary_Society" title="The Planetary Society">The Planetary Society</a>. Archived from <a rel="nofollow" class="external text" href="http://www.planetary.org/explore/topics/search_for_life/seti/mayr.html">the original</a> on 6 December 2010.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Ernst+Mayr+on+SETI&rft.pub=The+Planetary+Society&rft_id=http%3A%2F%2Fwww.planetary.org%2Fexplore%2Ftopics%2Fsearch_for_life%2Fseti%2Fmayr.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-42"><a href="#cite_ref-42">^</a> Rare Earth, p. xviii.: "We believe that life in the form of microbes or their equivalents is very common in the universe, perhaps more common than even Drake or Sagan envisioned. However, complex life—animals and higher plants—is likely to be far more rare than commonly assumed." </li> <li id="cite_note-acampbell.ukfsn.org-43">^ <a href="#cite_ref-acampbell.ukfsn.org_43-0">a</a> <a href="#cite_ref-acampbell.ukfsn.org_43-1">b</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCampbell2005" class="citation web cs1">Campbell, A. (13 March 2005). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110716063324/http://www.acampbell.ukfsn.org/bookreviews/r/morris.html">"Review of Life's Solution by Simon Conway Morris"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.acampbell.ukfsn.org/bookreviews/r/morris.html">the original</a> on 16 July 2011.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Review+of+Life%27s+Solution+by+Simon+Conway+Morris&rft.date=2005-03-13&rft.aulast=Campbell&rft.aufirst=A.&rft_id=http%3A%2F%2Fwww.acampbell.ukfsn.org%2Fbookreviews%2Fr%2Fmorris.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-44"><a href="#cite_ref-44">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBonner1988" class="citation book cs1">Bonner, J. T. (1988). <a rel="nofollow" class="external text" href="https://archive.org/details/evolutionofcompl0000bonn">The evolution of complexity by means of natural selection</a>. <a href="/wiki/Princeton_University_Press" title="Princeton University Press">Princeton University Press</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-691-08494-7" title="Special:BookSources/0-691-08494-7"><bdi>0-691-08494-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+evolution+of+complexity+by+means+of+natural+selection&rft.pub=Princeton+University+Press&rft.date=1988&rft.isbn=0-691-08494-7&rft.aulast=Bonner&rft.aufirst=J.+T.&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fevolutionofcompl0000bonn&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-Kipping2020-45"><a href="#cite_ref-Kipping2020_45-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKipping2020" class="citation journal cs1">Kipping, David (18 May 2020). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7275750">"An objective Bayesian analysis of life's early start and our late arrival"</a>. <a href="/wiki/Proceedings_of_the_National_Academy_of_Sciences" class="mw-redirect" title="Proceedings of the National Academy of Sciences">Proceedings of the National Academy of Sciences</a>. 117 (22): 11995–12003. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/2005.09008">2005.09008</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2020PNAS..11711995K">2020PNAS..11711995K</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1073%2Fpnas.1921655117">10.1073/pnas.1921655117</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7275750">7275750</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/32424083">32424083</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Proceedings+of+the+National+Academy+of+Sciences&rft.atitle=An+objective+Bayesian+analysis+of+life%27s+early+start+and+our+late+arrival&rft.volume=117&rft.issue=22&rft.pages=11995-12003&rft.date=2020-05-18&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC7275750%23id-name%3DPMC&rft_id=info%3Abibcode%2F2020PNAS..11711995K&rft_id=info%3Aarxiv%2F2005.09008&rft_id=info%3Apmid%2F32424083&rft_id=info%3Adoi%2F10.1073%2Fpnas.1921655117&rft.aulast=Kipping&rft.aufirst=David&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC7275750&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-ColumbiaPR-46"><a href="#cite_ref-ColumbiaPR_46-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFColumbia_University" class="citation web cs1">Columbia University. <a rel="nofollow" class="external text" href="https://phys.org/news/2020-05-odds-life-intelligence-emerging-planet.html">"New study estimates the odds of life and intelligence emerging beyond our planet"</a>. Phys.org. Retrieved 23 May 2020.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Phys.org&rft.atitle=New+study+estimates+the+odds+of+life+and+intelligence+emerging+beyond+our+planet&rft.au=Columbia+University&rft_id=https%3A%2F%2Fphys.org%2Fnews%2F2020-05-odds-life-intelligence-emerging-planet.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-47"><a href="#cite_ref-47">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLee2020" class="citation web cs1">Lee, Pascal (24 October 2020). <a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=cuJDkIUuDBg">"N~1: Alone in the Milky Way, Mt Tam"</a>. <a href="/wiki/YouTube" title="YouTube">YouTube</a>. <a rel="nofollow" class="external text" href="https://ghostarchive.org/varchive/youtube/20211211/cuJDkIUuDBg">Archived</a> from the original on 11 December 2021.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=YouTube&rft.atitle=N~1%3A+Alone+in+the+Milky+Way%2C+Mt+Tam&rft.date=2020-10-24&rft.aulast=Lee&rft.aufirst=Pascal&rft_id=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DcuJDkIUuDBg&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-48"><a href="#cite_ref-48">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLee2021" class="citation web cs1">Lee, Pascal (6 March 2021). <a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=wj5nmgoQr50">"N~1: Alone in the Milky Way – Kalamazoo Astronomical Society"</a>. <a href="/wiki/YouTube" title="YouTube">YouTube</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20210315085249/https://www.youtube.com/watch?v=wj5nmgoQr50">Archived</a> from the original on 15 March 2021.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=YouTube&rft.atitle=N~1%3A+Alone+in+the+Milky+Way+%E2%80%93+Kalamazoo+Astronomical+Society&rft.date=2021-03-06&rft.aulast=Lee&rft.aufirst=Pascal&rft_id=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Dwj5nmgoQr50&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-49"><a href="#cite_ref-49">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFForganElvis2011" class="citation journal cs1">Forgan, D.; Elvis, M. (2011). "Extrasolar Asteroid Mining as Forensic Evidence for Extraterrestrial Intelligence". <a href="/wiki/International_Journal_of_Astrobiology" title="International Journal of Astrobiology">International Journal of Astrobiology</a>. 10 (4): 307–313. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1103.5369">1103.5369</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2011IJAsB..10..307F">2011IJAsB..10..307F</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2FS1473550411000127">10.1017/S1473550411000127</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:119111392">119111392</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=International+Journal+of+Astrobiology&rft.atitle=Extrasolar+Asteroid+Mining+as+Forensic+Evidence+for+Extraterrestrial+Intelligence&rft.volume=10&rft.issue=4&rft.pages=307-313&rft.date=2011&rft_id=info%3Aarxiv%2F1103.5369&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A119111392%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1017%2FS1473550411000127&rft_id=info%3Abibcode%2F2011IJAsB..10..307F&rft.aulast=Forgan&rft.aufirst=D.&rft.au=Elvis%2C+M.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-50"><a href="#cite_ref-50">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTarter2001" class="citation journal cs1"><a href="/wiki/Jill_Tarter" title="Jill Tarter">Tarter, Jill C.</a> (September 2001). "The Search for Extraterrestrial Intelligence (SETI)". Annual Review of Astronomy and Astrophysics. 39: 511–548. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2001ARA&A..39..511T">2001ARA&A..39..511T</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1146%2Fannurev.astro.39.1.511">10.1146/annurev.astro.39.1.511</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:261531924">261531924</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Annual+Review+of+Astronomy+and+Astrophysics&rft.atitle=The+Search+for+Extraterrestrial+Intelligence+%28SETI%29&rft.volume=39&rft.pages=511-548&rft.date=2001-09&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A261531924%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1146%2Fannurev.astro.39.1.511&rft_id=info%3Abibcode%2F2001ARA%26A..39..511T&rft.aulast=Tarter&rft.aufirst=Jill+C.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-Why_ET_Hasn’t_Called-51">^ <a href="#cite_ref-Why_ET_Hasn’t_Called_51-0">a</a> <a href="#cite_ref-Why_ET_Hasn’t_Called_51-1">b</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFShermer2002" class="citation journal cs1">Shermer, M. (August 2002). <a rel="nofollow" class="external text" href="http://www.michaelshermer.com/2002/08/why-et-hasnt-called/">"Why ET Hasn't Called"</a>. <a href="/wiki/Scientific_American" title="Scientific American">Scientific American</a>. 287 (2): 21. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2002SciAm.287b..33S">2002SciAm.287b..33S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2Fscientificamerican0802-33">10.1038/scientificamerican0802-33</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Scientific+American&rft.atitle=Why+ET+Hasn%27t+Called&rft.volume=287&rft.issue=2&rft.pages=21&rft.date=2002-08&rft_id=info%3Adoi%2F10.1038%2Fscientificamerican0802-33&rft_id=info%3Abibcode%2F2002SciAm.287b..33S&rft.aulast=Shermer&rft.aufirst=M.&rft_id=http%3A%2F%2Fwww.michaelshermer.com%2F2002%2F08%2Fwhy-et-hasnt-called%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-David_Grinspoon_2004-52">^ <a href="#cite_ref-David_Grinspoon_2004_52-0">a</a> <a href="#cite_ref-David_Grinspoon_2004_52-1">b</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGrinspoon2004" class="citation book cs1">Grinspoon, D. (2004). Lonely Planets.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Lonely+Planets&rft.date=2004&rft.aulast=Grinspoon&rft.aufirst=D.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-GoldsmithOwen-53"><a href="#cite_ref-GoldsmithOwen_53-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGoldsmithOwen1992" class="citation book cs1">Goldsmith, D.; Owen, T. (1992). The Search for Life in the Universe (2nd ed.). <a href="/wiki/Addison-Wesley" title="Addison-Wesley">Addison-Wesley</a>. p. 415. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1-891389-16-5" title="Special:BookSources/1-891389-16-5"><bdi>1-891389-16-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Search+for+Life+in+the+Universe&rft.pages=415&rft.edition=2nd&rft.pub=Addison-Wesley&rft.date=1992&rft.isbn=1-891389-16-5&rft.aulast=Goldsmith&rft.aufirst=D.&rft.au=Owen%2C+T.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-vinn2024-54"><a href="#cite_ref-vinn2024_54-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFVinn2024" class="citation journal cs1">Vinn, O. (2024). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11307330">"Potential incompatibility of inherited behavior patterns with civilization: Implications for Fermi paradox"</a>. Science Progress. 107 (3): 1–6. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1177%2F00368504241272491">10.1177/00368504241272491</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11307330">11307330</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/39105260">39105260</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science+Progress&rft.atitle=Potential+incompatibility+of+inherited+behavior+patterns+with+civilization%3A+Implications+for+Fermi+paradox&rft.volume=107&rft.issue=3&rft.pages=1-6&rft.date=2024&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC11307330%23id-name%3DPMC&rft_id=info%3Apmid%2F39105260&rft_id=info%3Adoi%2F10.1177%2F00368504241272491&rft.aulast=Vinn&rft.aufirst=O.&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC11307330&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-55"><a href="#cite_ref-55">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSulleyman2017" class="citation news cs1">Sulleyman, Aatif (2 November 2017). <a rel="nofollow" class="external text" href="https://www.independent.co.uk/life-style/gadgets-and-tech/news/stephen-hawking-artificial-intelligence-fears-ai-will-replace-humans-virus-life-a8034341.html">"Stephen Hawking warns artificial intelligence 'may replace humans altogether'"</a>. independent.co.uk.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=independent.co.uk&rft.atitle=Stephen+Hawking+warns+artificial+intelligence+%27may+replace+humans+altogether%27&rft.date=2017-11-02&rft.aulast=Sulleyman&rft.aufirst=Aatif&rft_id=https%3A%2F%2Fwww.independent.co.uk%2Flife-style%2Fgadgets-and-tech%2Fnews%2Fstephen-hawking-artificial-intelligence-fears-ai-will-replace-humans-virus-life-a8034341.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-56"><a href="#cite_ref-56">^</a> "The value of N remains highly uncertain. Even if we had a perfect knowledge of the first two terms in the equation, there are still five remaining terms, each of which could be uncertain by factors of 1,000." from <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWilson,_TL2001" class="citation journal cs1">Wilson, TL (2001). "The search for extraterrestrial intelligence". Nature. 409 (6823). Nature Publishing Group: 1110–1114. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2001Natur.409.1110W">2001Natur.409.1110W</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2F35059235">10.1038/35059235</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/11234025">11234025</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:205014501">205014501</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=The+search+for+extraterrestrial+intelligence&rft.volume=409&rft.issue=6823&rft.pages=1110-1114&rft.date=2001&rft_id=info%3Adoi%2F10.1038%2F35059235&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A205014501%23id-name%3DS2CID&rft_id=info%3Apmid%2F11234025&rft_id=info%3Abibcode%2F2001Natur.409.1110W&rft.au=Wilson%2C+TL&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988">, or more informally, "The Drake Equation can have any value from "billions and billions" to zero", Michael Crichton, as quoted in <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDouglas_A._Vakoch2015" class="citation book cs1">Douglas A. Vakoch; et al. (2015). The Drake Equation: Estimating the prevalence of extraterrestrial life through the ages. Cambridge University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-10-707365-4" title="Special:BookSources/978-1-10-707365-4"><bdi>978-1-10-707365-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Drake+Equation%3A+Estimating+the+prevalence+of+extraterrestrial+life+through+the+ages&rft.pub=Cambridge+University+Press&rft.date=2015&rft.isbn=978-1-10-707365-4&rft.au=Douglas+A.+Vakoch&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988">, p. 13 </li> <li id="cite_note-renamed_from_2011_on_20160211035411-57"><a href="#cite_ref-renamed_from_2011_on_20160211035411_57-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.e-education.psu.edu/astro801/content/l12_p5.html">"The Drake Equation"</a>. psu.edu.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=psu.edu&rft.atitle=The+Drake+Equation&rft_id=https%3A%2F%2Fwww.e-education.psu.edu%2Fastro801%2Fcontent%2Fl12_p5.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-58"><a href="#cite_ref-58">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDevin_Powell,_Astrobiology_Magazine2013" class="citation web cs1">Devin Powell, Astrobiology Magazine (4 September 2013). <a rel="nofollow" class="external text" href="http://www.space.com/22648-drake-equation-alien-life-seager.html">"The Drake Equation Revisited: Interview with Planet Hunter Sara Seager"</a>. Space.com.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Space.com&rft.atitle=The+Drake+Equation+Revisited%3A+Interview+with+Planet+Hunter+Sara+Seager&rft.date=2013-09-04&rft.au=Devin+Powell%2C+Astrobiology+Magazine&rft_id=http%3A%2F%2Fwww.space.com%2F22648-drake-equation-alien-life-seager.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-schilling2009-59"><a href="#cite_ref-schilling2009_59-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGovert_SchillingAlan_M._MacRobert2009" class="citation news cs1">Govert Schilling; Alan M. MacRobert (3 June 2009). <a rel="nofollow" class="external text" href="https://skyandtelescope.org/astronomy-news/the-chance-of-finding-aliens/">"The Chance of Finding Aliens"</a>. Sky & Telescope.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Sky+%26+Telescope&rft.atitle=The+Chance+of+Finding+Aliens&rft.date=2009-06-03&rft.au=Govert+Schilling&rft.au=Alan+M.+MacRobert&rft_id=https%3A%2F%2Fskyandtelescope.org%2Fastronomy-news%2Fthe-chance-of-finding-aliens%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-Dean-60"><a href="#cite_ref-Dean_60-0">^</a> [<a href="/wiki/Wikipedia:NOTRS" class="mw-redirect" title="Wikipedia:NOTRS">better source needed</a>] <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDean2009" class="citation web cs1">Dean, T. (10 August 2009). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20130603043832/http://www.cosmosmagazine.com/features/are-we-alone-a-review-drake-equation/">"A review of the Drake Equation"</a>. <a href="/wiki/Cosmos_Magazine" class="mw-redirect" title="Cosmos Magazine">Cosmos Magazine</a>. Archived from <a rel="nofollow" class="external text" href="http://www.cosmosmagazine.com/features/are-we-alone-a-review-drake-equation/">the original</a> on 3 June 2013. Retrieved 16 April 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Cosmos+Magazine&rft.atitle=A+review+of+the+Drake+Equation&rft.date=2009-08-10&rft.aulast=Dean&rft.aufirst=T.&rft_id=http%3A%2F%2Fwww.cosmosmagazine.com%2Ffeatures%2Fare-we-alone-a-review-drake-equation%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-61"><a href="#cite_ref-61">^</a> Rare Earth, page 270: "When we take into account factors such as the abundance of planets and the location and lifetime of the habitable zone, the Drake Equation suggests that only between 1% and 0.001% of all stars might have planets with habitats similar to Earth. [...] If microbial life forms readily, then millions to hundreds of millions of planets in the galaxy have the potential for developing advanced life. (We expect that a much higher number will have microbial life.)" </li> <li id="cite_note-W._von_Bloh,_C.Bounama,_M._Cuntz,_and_S._Franck._2007_1365-62"><a href="#cite_ref-W._von_Bloh,_C.Bounama,_M._Cuntz,_and_S._Franck._2007_1365_62-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFvon_BlohBounamaCuntzFranck2007" class="citation journal cs1">von Bloh, W.; Bounama, C.; Cuntz, M.; Franck, S. (2007). "The habitability of super-Earths in Gliese 581". <a href="/wiki/Astronomy_%26_Astrophysics" title="Astronomy & Astrophysics">Astronomy & Astrophysics</a>. 476 (3): 1365–1371. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/0705.3758">0705.3758</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2007A&A...476.1365V">2007A&A...476.1365V</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1051%2F0004-6361%3A20077939">10.1051/0004-6361:20077939</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:14475537">14475537</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astronomy+%26+Astrophysics&rft.atitle=The+habitability+of+super-Earths+in+Gliese+581&rft.volume=476&rft.issue=3&rft.pages=1365-1371&rft.date=2007&rft_id=info%3Aarxiv%2F0705.3758&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A14475537%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1051%2F0004-6361%3A20077939&rft_id=info%3Abibcode%2F2007A%26A...476.1365V&rft.aulast=von+Bloh&rft.aufirst=W.&rft.au=Bounama%2C+C.&rft.au=Cuntz%2C+M.&rft.au=Franck%2C+S.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-F._Selsis,_J.F._Kasting,_B._Levrard,_J._Paillet,_I._Ribas,_and_X._Delfosse._2007_1373-63"><a href="#cite_ref-F._Selsis,_J.F._Kasting,_B._Levrard,_J._Paillet,_I._Ribas,_and_X._Delfosse._2007_1373_63-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="Selsis" class="citation journal cs1">Selsis, Franck; Kasting, James F.; Levrard, Benjamin; Paillet, Jimmy; Ribas, Ignasi; Delfosse, Xavier (2007). <a rel="nofollow" class="external text" href="https://hal.archives-ouvertes.fr/hal-00182743">"Habitable planets around the star Gl 581?"</a>. <a href="/wiki/Astronomy_and_Astrophysics" class="mw-redirect" title="Astronomy and Astrophysics">Astronomy and Astrophysics</a>. 476 (3): 1373–1387. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/0710.5294">0710.5294</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2007A&A...476.1373S">2007A&A...476.1373S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1051%2F0004-6361%3A20078091">10.1051/0004-6361:20078091</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:11492499">11492499</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astronomy+and+Astrophysics&rft.atitle=Habitable+planets+around+the+star+Gl+581%3F&rft.volume=476&rft.issue=3&rft.pages=1373-1387&rft.date=2007&rft_id=info%3Aarxiv%2F0710.5294&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A11492499%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1051%2F0004-6361%3A20078091&rft_id=info%3Abibcode%2F2007A%26A...476.1373S&rft.aulast=Selsis&rft.aufirst=Franck&rft.au=Kasting%2C+James+F.&rft.au=Levrard%2C+Benjamin&rft.au=Paillet%2C+Jimmy&rft.au=Ribas%2C+Ignasi&rft.au=Delfosse%2C+Xavier&rft_id=https%3A%2F%2Fhal.archives-ouvertes.fr%2Fhal-00182743&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-Lineweaver,_C._H._&_Davis,_T._M._2002_293–304-64"><a href="#cite_ref-Lineweaver,_C._H._&_Davis,_T._M._2002_293–304_64-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFLineweaverDavis2002" class="citation journal cs1">Lineweaver, C. H.; Davis, T. M. (2002). "Does the rapid appearance of life on Earth suggest that life is common in the universe?". <a href="/wiki/Astrobiology_(journal)" title="Astrobiology (journal)">Astrobiology</a>. 2 (3): 293–304. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0205014">astro-ph/0205014</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2002AsBio...2..293L">2002AsBio...2..293L</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1089%2F153110702762027871">10.1089/153110702762027871</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/12530239">12530239</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:431699">431699</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astrobiology&rft.atitle=Does+the+rapid+appearance+of+life+on+Earth+suggest+that+life+is+common+in+the+universe%3F&rft.volume=2&rft.issue=3&rft.pages=293-304&rft.date=2002&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A431699%23id-name%3DS2CID&rft_id=info%3Abibcode%2F2002AsBio...2..293L&rft_id=info%3Aarxiv%2Fastro-ph%2F0205014&rft_id=info%3Apmid%2F12530239&rft_id=info%3Adoi%2F10.1089%2F153110702762027871&rft.aulast=Lineweaver&rft.aufirst=C.+H.&rft.au=Davis%2C+T.+M.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-65"><a href="#cite_ref-65">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFForgan2009" class="citation journal cs1">Forgan, D. (2009). "A numerical testbed for hypotheses of extraterrestrial life and intelligence". <a href="/wiki/International_Journal_of_Astrobiology" title="International Journal of Astrobiology">International Journal of Astrobiology</a>. 8 (2): 121–131. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/0810.2222">0810.2222</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2009IJAsB...8..121F">2009IJAsB...8..121F</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2FS1473550408004321">10.1017/S1473550408004321</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:17469638">17469638</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=International+Journal+of+Astrobiology&rft.atitle=A+numerical+testbed+for+hypotheses+of+extraterrestrial+life+and+intelligence&rft.volume=8&rft.issue=2&rft.pages=121-131&rft.date=2009&rft_id=info%3Aarxiv%2F0810.2222&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A17469638%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1017%2FS1473550408004321&rft_id=info%3Abibcode%2F2009IJAsB...8..121F&rft.aulast=Forgan&rft.aufirst=D.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-66"><a href="#cite_ref-66">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation news cs1"><a rel="nofollow" class="external text" href="http://phys.org/news/2016-04-limits-uniqueness.html">"Are we alone? Setting some limits to our uniqueness"</a>. phys.org. 28 April 2016.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Are+we+alone%3F+Setting+some+limits+to+our+uniqueness&rft.date=2016-04-28&rft_id=http%3A%2F%2Fphys.org%2Fnews%2F2016-04-limits-uniqueness.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-67"><a href="#cite_ref-67">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation episode cs1">"Are We Alone? Galactic Civilization Challenge". PBS Space Time. 5 October 2016. PBS Digital Studios.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=PBS+Space+Time&rft.date=2016-10-05&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-68"><a href="#cite_ref-68">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFrank2016" class="citation news cs1">Frank, Adam (10 June 2016). <a rel="nofollow" class="external text" href="https://www.nytimes.com/2016/06/12/opinion/sunday/yes-there-have-been-aliens.html">"Yes, There Have Been Aliens"</a>. The New York Times.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+New+York+Times&rft.atitle=Yes%2C+There+Have+Been+Aliens&rft.date=2016-06-10&rft.aulast=Frank&rft.aufirst=Adam&rft_id=https%3A%2F%2Fwww.nytimes.com%2F2016%2F06%2F12%2Fopinion%2Fsunday%2Fyes-there-have-been-aliens.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-69"><a href="#cite_ref-69">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFrankSullivan_III2016" class="citation journal cs1">Frank, Adam; Sullivan III, W. T. (22 April 2016). "A New Empirical Constraint on the Prevalence of Technological Species in the Universe". Astrobiology. 16 (5) (published 13 May 2016): 359–362. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1510.08837">1510.08837</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2016AsBio..16..359F">2016AsBio..16..359F</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1089%2Fast.2015.1418">10.1089/ast.2015.1418</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/27105054">27105054</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astrobiology&rft.atitle=A+New+Empirical+Constraint+on+the+Prevalence+of+Technological+Species+in+the+Universe&rft.volume=16&rft.issue=5&rft.pages=359-362&rft.date=2016-04-22&rft_id=info%3Aarxiv%2F1510.08837&rft_id=info%3Apmid%2F27105054&rft_id=info%3Adoi%2F10.1089%2Fast.2015.1418&rft_id=info%3Abibcode%2F2016AsBio..16..359F&rft.aulast=Frank&rft.aufirst=Adam&rft.au=Sullivan+III%2C+W.+T.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-70"><a href="#cite_ref-70">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHetesiRegaly2006" class="citation journal cs1">Hetesi, Z.; Regaly, Z. (2006). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20090205123935/http://astro.elte.hu/~hetesizs/Hetesi%20Zsolt%20cikkei/new%20interpretation%20fo%20drake%20eq.pdf">"A new interpretation of Drake-equation"</a> (PDF). <a href="/wiki/Journal_of_the_British_Interplanetary_Society" title="Journal of the British Interplanetary Society">Journal of the British Interplanetary Society</a>. 59: 11–14. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2006JBIS...59...11H">2006JBIS...59...11H</a>. Archived from <a rel="nofollow" class="external text" href="http://astro.elte.hu/~hetesizs/Hetesi%20Zsolt%20cikkei/new%20interpretation%20fo%20drake%20eq.pdf">the original</a> (PDF) on 5 February 2009.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+the+British+Interplanetary+Society&rft.atitle=A+new+interpretation+of+Drake-equation&rft.volume=59&rft.pages=11-14&rft.date=2006&rft_id=info%3Abibcode%2F2006JBIS...59...11H&rft.aulast=Hetesi&rft.aufirst=Z.&rft.au=Regaly%2C+Z.&rft_id=http%3A%2F%2Fastro.elte.hu%2F~hetesizs%2FHetesi%2520Zsolt%2520cikkei%2Fnew%2520interpretation%2520fo%2520drake%2520eq.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-71"><a href="#cite_ref-71">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMaccone2010" class="citation journal cs1">Maccone, C. (2010). "The Statistical Drake Equation". <a href="/wiki/Acta_Astronautica" title="Acta Astronautica">Acta Astronautica</a>. 67 (11–12): 1366–1383. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2010AcAau..67.1366M">2010AcAau..67.1366M</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.actaastro.2010.05.003">10.1016/j.actaastro.2010.05.003</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:121239391">121239391</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Acta+Astronautica&rft.atitle=The+Statistical+Drake+Equation&rft.volume=67&rft.issue=11%E2%80%9312&rft.pages=1366-1383&rft.date=2010&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A121239391%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1016%2Fj.actaastro.2010.05.003&rft_id=info%3Abibcode%2F2010AcAau..67.1366M&rft.aulast=Maccone&rft.aufirst=C.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-72"><a href="#cite_ref-72">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGolden2021" class="citation journal cs1">Golden, Leslie M. (1 August 2021). <a rel="nofollow" class="external text" href="https://www.sciencedirect.com/science/article/pii/S0094576521001338">"A joint mind consideration of the Drake equation in the search for extraterrestrial intelligence"</a>. Acta Astronautica. 185: 333–336. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2021AcAau.185..333G">2021AcAau.185..333G</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.actaastro.2021.03.020">10.1016/j.actaastro.2021.03.020</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0094-5765">0094-5765</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:233663920">233663920</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Acta+Astronautica&rft.atitle=A+joint+mind+consideration+of+the+Drake+equation+in+the+search+for+extraterrestrial+intelligence&rft.volume=185&rft.pages=333-336&rft.date=2021-08-01&rft_id=info%3Adoi%2F10.1016%2Fj.actaastro.2021.03.020&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A233663920%23id-name%3DS2CID&rft.issn=0094-5765&rft_id=info%3Abibcode%2F2021AcAau.185..333G&rft.aulast=Golden&rft.aufirst=Leslie+M.&rft_id=https%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0094576521001338&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-GS-73">^ <a href="#cite_ref-GS_73-0">a</a> <a href="#cite_ref-GS_73-1">b</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBrin1983" class="citation journal cs1">Brin, G. D. (1983). "The Great Silence – The Controversy Concerning Extraterrestrial Intelligent Life". <a href="/wiki/Quarterly_Journal_of_the_Royal_Astronomical_Society" class="mw-redirect" title="Quarterly Journal of the Royal Astronomical Society">Quarterly Journal of the Royal Astronomical Society</a>. 24 (3): 283–309. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1983QJRAS..24..283B">1983QJRAS..24..283B</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Quarterly+Journal+of+the+Royal+Astronomical+Society&rft.atitle=The+Great+Silence+%E2%80%93+The+Controversy+Concerning+Extraterrestrial+Intelligent+Life&rft.volume=24&rft.issue=3&rft.pages=283-309&rft.date=1983&rft_id=info%3Abibcode%2F1983QJRAS..24..283B&rft.aulast=Brin&rft.aufirst=G.+D.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-74"><a href="#cite_ref-74">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFZaitsev2005" class="citation web cs1">Zaitsev, A. (May 2005). <a rel="nofollow" class="external text" href="http://www.cplire.ru/html/ra&sr/irm/Drake_equation.html">"The Drake Equation: Adding a METI Factor"</a>. <a href="/w/index.php?title=SETI_League&action=edit&redlink=1" class="new" title="SETI League (page does not exist)">SETI League</a>. Retrieved 20 April 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+Drake+Equation%3A+Adding+a+METI+Factor&rft.pub=SETI+League&rft.date=2005-05&rft.aulast=Zaitsev&rft.aufirst=A.&rft_id=http%3A%2F%2Fwww.cplire.ru%2Fhtml%2Fra%26sr%2Firm%2FDrake_equation.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-NYT-20161207-75"><a href="#cite_ref-NYT-20161207_75-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJones2016" class="citation news cs1">Jones, Chris (7 December 2016). <a rel="nofollow" class="external text" href="https://www.nytimes.com/2016/12/07/magazine/the-world-sees-me-as-the-one-who-will-find-another-earth.html">"'The World Sees Me as the One Who Will Find Another Earth' – The star-crossed life of Sara Seager, an astrophysicist obsessed with discovering distant planets"</a>. <a href="/wiki/The_New_York_Times" title="The New York Times">The New York Times</a>. Retrieved 8 December 2016.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+New+York+Times&rft.atitle=%27The+World+Sees+Me+as+the+One+Who+Will+Find+Another+Earth%27+%E2%80%93+The+star-crossed+life+of+Sara+Seager%2C+an+astrophysicist+obsessed+with+discovering+distant+planets.&rft.date=2016-12-07&rft.aulast=Jones&rft.aufirst=Chris&rft_id=https%3A%2F%2Fwww.nytimes.com%2F2016%2F12%2F07%2Fmagazine%2Fthe-world-sees-me-as-the-one-who-will-find-another-earth.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-equation-76">^ <a href="#cite_ref-equation_76-0">a</a> <a href="#cite_ref-equation_76-1">b</a> <a href="#cite_ref-equation_76-2">c</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDevin_Powell2013" class="citation web cs1">Devin Powell (4 September 2013). <a rel="nofollow" class="external text" href="https://www.space.com/22648-drake-equation-alien-life-seager.html">"The Drake Equation Revisited: Interview with Planet Hunter Sara Seager"</a>. Space.com. Retrieved 6 October 2023.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Space.com&rft.atitle=The+Drake+Equation+Revisited%3A+Interview+with+Planet+Hunter+Sara+Seager&rft.date=2013-09-04&rft.au=Devin+Powell&rft_id=https%3A%2F%2Fwww.space.com%2F22648-drake-equation-alien-life-seager.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-78"><a href="#cite_ref-78">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://io9.com/what-a-brand-new-equation-reveals-about-our-odds-of-fin-531575395">"A New Equation Reveals Our Exact Odds of Finding Alien Life"</a>. <a href="/wiki/Io9" title="Io9">io9</a>. 21 June 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=A+New+Equation+Reveals+Our+Exact+Odds+of+Finding+Alien+Life&rft.pub=io9&rft.date=2013-06-21&rft_id=http%3A%2F%2Fio9.com%2Fwhat-a-brand-new-equation-reveals-about-our-odds-of-fin-531575395&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-79"><a href="#cite_ref-79">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://phys.libretexts.org/Bookshelves/Astronomy__Cosmology/Supplemental_Modules_(Astronomy_and_Cosmology)/Astronomy/Life_beyond_the_Earth/The_Drake_Equation#:~:text=Another%20version%20of%20the%20Drake,graced%20by%20a%20technological%20civilization.">"The Drake Equation"</a>. phys.libretexts.org. 13 August 2014. Retrieved 4 February 2024.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=phys.libretexts.org&rft.atitle=The+Drake+Equation&rft.date=2014-08-13&rft_id=https%3A%2F%2Fphys.libretexts.org%2FBookshelves%2FAstronomy__Cosmology%2FSupplemental_Modules_%28Astronomy_and_Cosmology%29%2FAstronomy%2FLife_beyond_the_Earth%2FThe_Drake_Equation%23%3A~%3Atext%3DAnother%2520version%2520of%2520the%2520Drake%2Cgraced%2520by%2520a%2520technological%2520civilization.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-80"><a href="#cite_ref-80">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=MlikCebQSlY">"Carl Sagan - Cosmos - Drake Equation"</a>. <a href="/wiki/YouTube" title="YouTube">YouTube</a>. 24 March 2009.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=YouTube&rft.atitle=Carl+Sagan+-+Cosmos+-+Drake+Equation&rft.date=2009-03-24&rft_id=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DMlikCebQSlY&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-81"><a href="#cite_ref-81">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=MlikCebQSlY">"Carl Sagan - Cosmos - Drake Equation"</a>. <a href="/wiki/YouTube" title="YouTube">YouTube</a>. 24 March 2009. Retrieved 4 February 2024.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=YouTube&rft.atitle=Carl+Sagan+-+Cosmos+-+Drake+Equation&rft.date=2009-03-24&rft_id=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DMlikCebQSlY&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-82"><a href="#cite_ref-82">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHartsfield2015" class="citation web cs1">Hartsfield, Tom (11 March 2015). <a rel="nofollow" class="external text" href="https://www.realclearscience.com/blog/2015/03/why_the_drake_equation_is_useless.html">"Why the Drake Equation Is Useless | RealClearScience"</a>. www.realclearscience.com. Retrieved 29 April 2024.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.realclearscience.com&rft.atitle=Why+the+Drake+Equation+Is+Useless+%7C+RealClearScience&rft.date=2015-03-11&rft.aulast=Hartsfield&rft.aufirst=Tom&rft_id=https%3A%2F%2Fwww.realclearscience.com%2Fblog%2F2015%2F03%2Fwhy_the_drake_equation_is_useless.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-83"><a href="#cite_ref-83">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.seti.org/drake-equation-could-it-be-wrong">"The Drake Equation: Could It Be Wrong?"</a>. SETI Institute. Retrieved 29 April 2024.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=SETI+Institute&rft.atitle=The+Drake+Equation%3A+Could+It+Be+Wrong%3F&rft_id=https%3A%2F%2Fwww.seti.org%2Fdrake-equation-could-it-be-wrong&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-84"><a href="#cite_ref-84">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDvorsky2007" class="citation web cs1">Dvorsky, G. (31 May 2007). <a rel="nofollow" class="external text" href="http://www.sentientdevelopments.com/2007/05/drake-equation-is-obsolete.html">"The Drake Equation is obsolete"</a>. Sentient Developments. Retrieved 21 August 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Sentient+Developments&rft.atitle=The+Drake+Equation+is+obsolete&rft.date=2007-05-31&rft.aulast=Dvorsky&rft.aufirst=G.&rft_id=http%3A%2F%2Fwww.sentientdevelopments.com%2F2007%2F05%2Fdrake-equation-is-obsolete.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-85"><a href="#cite_ref-85">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSutter2018" class="citation web cs1">Sutter, Paul (27 December 2018). <a rel="nofollow" class="external text" href="https://www.space.com/42739-stop-using-the-drake-equation.html">"Alien Hunters, Stop Using the Drake Equation"</a>. Space.com. Retrieved 18 February 2019.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Space.com&rft.atitle=Alien+Hunters%2C+Stop+Using+the+Drake+Equation&rft.date=2018-12-27&rft.aulast=Sutter&rft.aufirst=Paul&rft_id=https%3A%2F%2Fwww.space.com%2F42739-stop-using-the-drake-equation.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-86"><a href="#cite_ref-86">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://bigthink.com/starts-with-a-bang/unsurprising-non-detection-intelligent-aliens/">"The unsurprising non-detection of intelligent aliens"</a>. Big Think. 23 April 2024. Retrieved 29 April 2024.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Big+Think&rft.atitle=The+unsurprising+non-detection+of+intelligent+aliens&rft.date=2024-04-23&rft_id=https%3A%2F%2Fbigthink.com%2Fstarts-with-a-bang%2Funsurprising-non-detection-intelligent-aliens%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-87"><a href="#cite_ref-87">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTarter2006" class="citation journal cs1">Tarter, Jill C. (May–June 2006). <a rel="nofollow" class="external text" href="http://www.csicop.org/si/show/cosmic_haystack_is_large/">"The Cosmic Haystack Is Large"</a>. <a href="/wiki/Skeptical_Inquirer" title="Skeptical Inquirer">Skeptical Inquirer</a>. 30 (3). Retrieved 21 August 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Skeptical+Inquirer&rft.atitle=The+Cosmic+Haystack+Is+Large&rft.volume=30&rft.issue=3&rft.date=2006-05%2F2006-06&rft.aulast=Tarter&rft.aufirst=Jill+C.&rft_id=http%3A%2F%2Fwww.csicop.org%2Fsi%2Fshow%2Fcosmic_haystack_is_large%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-88"><a href="#cite_ref-88">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAlexander" class="citation web cs1">Alexander, A. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20050306072552/http://www.planetary.org/html/UPDATES/seti/history/History07.htm">"The Search for Extraterrestrial Intelligence: A Short History – Part 7: The Birth of the Drake Equation"</a>. <a href="/wiki/The_Planetary_Society" title="The Planetary Society">The Planetary Society</a>. Archived from <a rel="nofollow" class="external text" href="http://www.planetary.org/html/UPDATES/seti/history/History07.htm">the original</a> on 6 March 2005.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+Search+for+Extraterrestrial+Intelligence%3A+A+Short+History+%E2%80%93+Part+7%3A+The+Birth+of+the+Drake+Equation&rft.pub=The+Planetary+Society&rft.aulast=Alexander&rft.aufirst=A.&rft_id=http%3A%2F%2Fwww.planetary.org%2Fhtml%2FUPDATES%2Fseti%2Fhistory%2FHistory07.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-Conselice-89"><a href="#cite_ref-Conselice_89-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFChristopher_J._Conselice2016" class="citation journal cs1">Christopher J. Conselice; et al. (2016). <a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F0004-637X%2F830%2F2%2F83">"The Evolution of Galaxy Number Density at z < 8 and its Implications"</a>. The Astrophysical Journal. 830 (2): 83. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1607.03909">1607.03909</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2016ApJ...830...83C">2016ApJ...830...83C</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F0004-637X%2F830%2F2%2F83">10.3847/0004-637X/830/2/83</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:17424588">17424588</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=The+Evolution+of+Galaxy+Number+Density+at+%3Cspan+class%3D%22texhtml+%22+%3Ez+%3C+8%3C%2Fspan%3E+and+its+Implications&rft.volume=830&rft.issue=2&rft.pages=83&rft.date=2016&rft_id=info%3Aarxiv%2F1607.03909&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A17424588%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.3847%2F0004-637X%2F830%2F2%2F83&rft_id=info%3Abibcode%2F2016ApJ...830...83C&rft.au=Christopher+J.+Conselice&rft_id=https%3A%2F%2Fdoi.org%2F10.3847%252F0004-637X%252F830%252F2%252F83&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-NYT-20161017-90"><a href="#cite_ref-NYT-20161017_90-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFountain2016" class="citation news cs1">Fountain, Henry (17 October 2016). <a rel="nofollow" class="external text" href="https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2016/10/18/science/two-trillion-galaxies-at-the-very-least.html">"Two Trillion Galaxies, at the Very Least"</a>. <a href="/wiki/The_New_York_Times" title="The New York Times">The New York Times</a>. Archived from <a rel="nofollow" class="external text" href="https://www.nytimes.com/2016/10/18/science/two-trillion-galaxies-at-the-very-least.html">the original</a> on 1 January 2022. Retrieved 17 October 2016.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+New+York+Times&rft.atitle=Two+Trillion+Galaxies%2C+at+the+Very+Least&rft.date=2016-10-17&rft.aulast=Fountain&rft.aufirst=Henry&rft_id=https%3A%2F%2Fwww.nytimes.com%2F2016%2F10%2F18%2Fscience%2Ftwo-trillion-galaxies-at-the-very-least.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-OSTI-19850301-91"><a href="#cite_ref-OSTI-19850301_91-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFJones1985" class="citation report cs1">Jones, E. M. (1 March 1985). <a rel="nofollow" class="external text" href="https://www.osti.gov/accomplishments/documents/fullText/ACC0055.pdf">"Where is everybody?" An account of Fermi's question</a> (PDF) (Report). <a href="/wiki/Los_Alamos_National_Laboratory" title="Los Alamos National Laboratory">Los Alamos National Laboratory</a>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1985STIN...8530988J">1985STIN...8530988J</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.2172%2F5746675">10.2172/5746675</a>. <a href="/wiki/OSTI_(identifier)" class="mw-redirect" title="OSTI (identifier)">OSTI</a> <a rel="nofollow" class="external text" href="https://www.osti.gov/biblio/5746675">5746675</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071012123516/http://www.osti.gov/accomplishments/documents/fullText/ACC0055.pdf">Archived</a> (PDF) from the original on 12 October 2007. Retrieved 21 August 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=report&rft.btitle=%22Where+is+everybody%3F%22+An+account+of+Fermi%27s+question&rft.pub=Los+Alamos+National+Laboratory&rft.date=1985-03-01&rft_id=info%3Adoi%2F10.2172%2F5746675&rft_id=https%3A%2F%2Fwww.osti.gov%2Fbiblio%2F5746675%23id-name%3DOSTI&rft_id=info%3Abibcode%2F1985STIN...8530988J&rft.aulast=Jones&rft.aufirst=E.+M.&rft_id=http%3A%2F%2Fwww.osti.gov%2Faccomplishments%2Fdocuments%2FfullText%2FACC0055.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-92"><a href="#cite_ref-92">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKrauthammer2011" class="citation news cs1">Krauthammer, C. (29 December 2011). <a rel="nofollow" class="external text" href="https://www.washingtonpost.com/opinions/are-we-alone-in-the-universe/2011/12/29/gIQA2wSOPP_story.html">"Are we alone in the Universe?"</a>. <a href="/wiki/The_Washington_Post" title="The Washington Post">The Washington Post</a>. Retrieved 21 August 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Washington+Post&rft.atitle=Are+we+alone+in+the+Universe%3F&rft.date=2011-12-29&rft.aulast=Krauthammer&rft.aufirst=C.&rft_id=https%3A%2F%2Fwww.washingtonpost.com%2Fopinions%2Fare-we-alone-in-the-universe%2F2011%2F12%2F29%2FgIQA2wSOPP_story.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-93"><a href="#cite_ref-93">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWebb2015" class="citation book cs1">Webb, S. (2015). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=QWKyrQEACAAJ&q=Universe-Teeming-Aliens-WHERE-EVERYBODY">If the Universe Is Teeming with Aliens ... WHERE IS EVERYBODY?: Seventy-Five Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life</a>. Springer International Publishing. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-3319132358" title="Special:BookSources/978-3319132358"><bdi>978-3319132358</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=If+the+Universe+Is+Teeming+with+Aliens+...+WHERE+IS+EVERYBODY%3F%3A+Seventy-Five+Solutions+to+the+Fermi+Paradox+and+the+Problem+of+Extraterrestrial+Life&rft.pub=Springer+International+Publishing&rft.date=2015&rft.isbn=978-3319132358&rft.aulast=Webb&rft.aufirst=S.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DQWKyrQEACAAJ%26q%3DUniverse-Teeming-Aliens-WHERE-EVERYBODY&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-94"><a href="#cite_ref-94">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHanson1998" class="citation web cs1">Hanson, R. (15 September 1998). <a rel="nofollow" class="external text" href="http://hanson.gmu.edu/greatfilter.html">"The Great Filter – Are We Almost Past It?"</a>. Retrieved 21 August 2013.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+Great+Filter+%E2%80%93+Are+We+Almost+Past+It%3F&rft.date=1998-09-15&rft.aulast=Hanson&rft.aufirst=R.&rft_id=http%3A%2F%2Fhanson.gmu.edu%2Fgreatfilter.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-95"><a href="#cite_ref-95">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSandbergDrexlerOrd2018" class="citation arxiv cs1">Sandberg, Anders; Drexler, Eric; Ord, Toby (6 June 2018). "Dissolving the Fermi Paradox". <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/1806.02404">1806.02404</a> [<a rel="nofollow" class="external text" href="https://arxiv.org/archive/physics.pop-ph">physics.pop-ph</a>].</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=preprint&rft.jtitle=arXiv&rft.atitle=Dissolving+the+Fermi+Paradox&rft.date=2018-06-06&rft_id=info%3Aarxiv%2F1806.02404&rft.aulast=Sandberg&rft.aufirst=Anders&rft.au=Drexler%2C+Eric&rft.au=Ord%2C+Toby&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> </li> <li id="cite_note-96"><a href="#cite_ref-96">^</a> The Making of Star Trek by Stephen E. Whitfield and Gene Roddenberry, New York: Ballantine Books, 1968 </li> <li id="cite_note-97"><a href="#cite_ref-97">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFOkuda,_Mike_and_Denise_Okuda,_with_Debbie_Mirek1999" class="citation book cs1"><a href="/wiki/Michael_Okuda" title="Michael Okuda">Okuda, Mike</a> and Denise Okuda, with Debbie Mirek (1999). <a href="/wiki/The_Star_Trek_Encyclopedia" title="The Star Trek Encyclopedia">The Star Trek Encyclopedia</a>. Pocket Books. p. 122. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-671-53609-5" title="Special:BookSources/0-671-53609-5"><bdi>0-671-53609-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Star+Trek+Encyclopedia&rft.pages=122&rft.pub=Pocket+Books&rft.date=1999&rft.isbn=0-671-53609-5&rft.au=Okuda%2C+Mike+and+Denise+Okuda%2C+with+Debbie+Mirek&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"><code class="cs1-code">{{<a href="/wiki/Template:Cite_book" title="Template:Cite book">cite book</a>}}</code>: CS1 maint: multiple names: authors list (<a href="/wiki/Category:CS1_maint:_multiple_names:_authors_list" title="Category:CS1 maint: multiple names: authors list">link</a>) </li> <li id="cite_note-98"><a href="#cite_ref-98">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.jpl.nasa.gov/news/nasa-unveils-design-for-message-heading-to-jupiters-moon-europa">"NASA Unveils Design for Message Heading to Jupiter's Moon Europa"</a>. NASA Jet Propulsion Laboratory (JPL). Retrieved 11 March 2024.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=NASA+Jet+Propulsion+Laboratory+%28JPL%29&rft.atitle=NASA+Unveils+Design+for+Message+Heading+to+Jupiter%27s+Moon+Europa&rft_id=https%3A%2F%2Fwww.jpl.nasa.gov%2Fnews%2Fnasa-unveils-design-for-message-heading-to-jupiters-moon-europa&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"> <img alt="Public Domain" src="//upload.wikimedia.org/wikipedia/en/thumb/6/62/PD-icon.svg/12px-PD-icon.svg.png" decoding="async" width="12" height="12" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/6/62/PD-icon.svg/18px-PD-icon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/6/62/PD-icon.svg/24px-PD-icon.svg.png 2x" data-file-width="196" data-file-height="196" /> This article incorporates text from this source, which is in the <a href="/wiki/Public_domain" title="Public domain">public domain</a>. </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=23" title="Edit section: Further reading">edit</a>]</div> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMorton2002" class="citation book cs1">Morton, Oliver (2002). "A Mirror in the Sky". In Graham Formelo (ed.). It Must Be Beautiful. Granta Books. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1-86207-555-7" title="Special:BookSources/1-86207-555-7"><bdi>1-86207-555-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=A+Mirror+in+the+Sky&rft.btitle=It+Must+Be+Beautiful&rft.pub=Granta+Books&rft.date=2002&rft.isbn=1-86207-555-7&rft.aulast=Morton&rft.aufirst=Oliver&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRoodJames_S._Trefil1981" class="citation book cs1">Rood, Robert T.; James S. Trefil (1981). Are We Alone? The Possibility of Extraterrestrial Civilizations. New York: Scribner. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0684178427" title="Special:BookSources/0684178427"><bdi>0684178427</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Are+We+Alone%3F+The+Possibility+of+Extraterrestrial+Civilizations&rft.place=New+York&rft.pub=Scribner&rft.date=1981&rft.isbn=0684178427&rft.aulast=Rood&rft.aufirst=Robert+T.&rft.au=James+S.+Trefil&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFVakochDowd2015" class="citation book cs1"><a href="/wiki/Douglas_Vakoch" title="Douglas Vakoch">Vakoch, Douglas A.</a>; Dowd, Matthew F., eds. (2015). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=jcnSCQAAQBAJ">The Drake Equation: Estimating the Prevalence of Extraterrestrial Life Through the Ages</a>. Cambridge, UK: Cambridge University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-10-707365-4" title="Special:BookSources/978-1-10-707365-4"><bdi>978-1-10-707365-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Drake+Equation%3A+Estimating+the+Prevalence+of+Extraterrestrial+Life+Through+the+Ages&rft.place=Cambridge%2C+UK&rft.pub=Cambridge+University+Press&rft.date=2015&rft.isbn=978-1-10-707365-4&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DjcnSCQAAQBAJ&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"></li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2>[<a href="/w/index.php?title=Drake_equation&action=edit&section=24" title="Edit section: External links">edit</a>]</div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}</style><div class="side-box side-box-right plainlinks sistersitebox"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style> <div class="side-box-flex"> <div class="side-box-image"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/40px-Wiktionary-logo-en-v2.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/60px-Wiktionary-logo-en-v2.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/80px-Wiktionary-logo-en-v2.svg.png 2x" data-file-width="512" data-file-height="512" /></div> <div class="side-box-text plainlist">Look up <a href="https://en.wiktionary.org/wiki/Drake_equation" class="extiw" title="wiktionary:Drake equation">Drake equation</a> in Wiktionary, the free dictionary.</div></div> </div> <ul><li><a rel="nofollow" class="external text" href="http://spacegeek.org/calc/">Interactive Drake Equation Calculator</a></li> <li><a rel="nofollow" class="external text" href="https://astrosociety.org/file_download/inline/58ee6041-5f61-4f88-8b15-d2d3d22ab83d">Frank Drake's 2010 article on "The Origin of the Drake Equation"</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20100411202244/http://www.cosmosmagazine.com/features/online/3384/qa-with-frank-drake">"Only a matter of time, says Frank Drake"</a>. A Q&A with Frank Drake in February 2010</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDrake2004" class="citation magazine cs1"><a href="/wiki/Frank_Drake" title="Frank Drake">Drake, Frank</a> (December 2004). <a rel="nofollow" class="external text" href="https://www.wired.com/wired/archive/12.12/life.html">"The E.T. Equation, Recalculated"</a>. <a href="/wiki/Wired_(magazine)" title="Wired (magazine)">Wired</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Wired&rft.atitle=The+E.T.+Equation%2C+Recalculated&rft.date=2004-12&rft.aulast=Drake&rft.aufirst=Frank&rft_id=https%3A%2F%2Fwww.wired.com%2Fwired%2Farchive%2F12.12%2Flife.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADrake+equation" class="Z3988"></li> <li><a rel="nofollow" class="external text" href="https://www.pbs.org/wgbh/nova/origins/drake.html">Macromedia Flash page allowing the user to modify Drake's values</a> from <a href="/wiki/Public_Broadcasting_Service" class="mw-redirect" title="Public Broadcasting Service">PBS</a>'s <a href="/wiki/Nova_(American_TV_series)" class="mw-redirect" title="Nova (American TV series)">Nova</a></li> <li><a rel="nofollow" class="external text" href="http://www.astronomycast.com/solar-system/episode-23-the-drake-equation/">"The Drake Equation"</a>, <a href="/wiki/Astronomy_Cast" title="Astronomy Cast">Astronomy Cast</a> episode #23; includes full transcript</li> <li><a rel="nofollow" class="external text" href="http://www.area52online.com/sections/simulations/drake/guessinggame.htm">Animated simulation of the Drake equation</a>. (<a rel="nofollow" class="external text" href="https://web.archive.org/web/20151208133744/http://www.area52online.com/sections/simulations/drake/guessinggame.htm">Archived</a> 8 December 2015 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>)</li> <li><a rel="nofollow" class="external text" href="https://www.bbc.co.uk/programmes/p009rtr0">"The Alien Equation"</a>, BBC Radio program Discovery (22 September 2010)</li> <li><a rel="nofollow" class="external text" href="https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1473550413000207">"Reflections on the Equation"</a> (PDF), by Frank Drake, 2013</li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output 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systems</a></li> <li><a href="/wiki/Habitability_of_red_dwarf_systems" title="Habitability of red dwarf systems">Habitability of red dwarf systems</a></li> <li><a href="/wiki/Habitability_of_K-type_main-sequence_star_systems" title="Habitability of K-type main-sequence star systems">Habitability of K-type main-sequence star systems</a></li> <li><a href="/wiki/Habitability_of_yellow_dwarf_systems" title="Habitability of yellow dwarf systems">Habitability of yellow dwarf systems</a></li> <li><a href="/wiki/Habitability_of_F-type_main-sequence_star_systems" title="Habitability of F-type main-sequence star systems">Habitability of F-type main-sequence star systems</a></li> <li><a href="/wiki/Habitable_zone_for_complex_life" title="Habitable zone for complex life">Habitable zone for complex life</a></li> <li><a href="/wiki/List_of_potentially_habitable_exoplanets" title="List of potentially habitable exoplanets">List of potentially habitable exoplanets</a></li> <li><a href="/wiki/Tholin" 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(satellite)">Bion</a></li> <li><a href="/wiki/BIOPAN" title="BIOPAN">BIOPAN</a></li> <li><a href="/wiki/Biosatellite_program" title="Biosatellite program">Biosatellite program</a></li> <li><a href="/wiki/Exposing_Microorganisms_in_the_Stratosphere" title="Exposing Microorganisms in the Stratosphere">E-MIST</a></li> <li><a href="/wiki/Exobiology_Radiation_Assembly" title="Exobiology Radiation Assembly">ERA</a></li> <li><a href="/wiki/EuCROPIS" title="EuCROPIS">Eu:CROPIS</a></li> <li><a href="/wiki/Long_Duration_Exposure_Facility#EXOSTACK" title="Long Duration Exposure Facility">EXOSTACK</a></li> <li><a href="/wiki/EXPOSE" title="EXPOSE">EXPOSE</a></li> <li><a href="/wiki/Chang%27e_4#Lunar_lander" title="Chang'e 4">Lunar Micro Ecosystem</a></li> <li><a href="/wiki/O/OREOS" title="O/OREOS">O/OREOS</a></li> <li><a href="/wiki/OREOcube" title="OREOcube">OREOcube</a></li> <li><a href="/wiki/Tanpopo_(mission)" class="mw-redirect" title="Tanpopo (mission)">Tanpopo</a></li> <li><a href="/wiki/Vegetable_Production_System" title="Vegetable Production System">VEGGIE</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Mars</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Beagle_2" title="Beagle 2">Beagle 2</a></li> <li><a href="/wiki/Fobos-Grunt" title="Fobos-Grunt">Fobos-Grunt</a></li> <li><a href="/wiki/Mars_Science_Laboratory" title="Mars Science Laboratory">Mars Science Laboratory</a> <ul><li><a href="/wiki/Curiosity_(rover)" title="Curiosity (rover)">Curiosity rover</a></li></ul></li> <li><a href="/wiki/Mars_2020" title="Mars 2020">Mars 2020</a> <ul><li><a href="/wiki/Perseverance_(rover)" title="Perseverance (rover)">Perseverance rover</a></li></ul></li> <li><a href="/wiki/Phoenix_(spacecraft)" title="Phoenix (spacecraft)">Phoenix</a></li> <li><a href="/wiki/Tianwen-1" title="Tianwen-1">Tianwen-1</a> <ul><li><a href="/wiki/Zhurong_(rover)" title="Zhurong (rover)">Zhurong rover</a></li></ul></li> <li><a href="/wiki/Trace_Gas_Orbiter" title="Trace Gas Orbiter">Trace Gas Orbiter</a></li> <li><a href="/wiki/Viking_lander_biological_experiments" title="Viking lander biological experiments">Viking</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Comets and asteroids</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Hayabusa2" title="Hayabusa2">Hayabusa2</a></li> <li><a href="/wiki/OSIRIS-REx" title="OSIRIS-REx">OSIRIS-REx</a></li> <li><a href="/wiki/Rosetta_(spacecraft)" title="Rosetta (spacecraft)">Rosetta</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Heliocentric</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/BioSentinel" title="BioSentinel">BioSentinel</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Planned</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Dragonfly_(Titan_space_probe)" title="Dragonfly (Titan space probe)">Dragonfly</a></li> <li><a href="/wiki/Europa_Clipper" title="Europa Clipper">Europa Clipper</a></li> <li><a href="/wiki/ExoMars" title="ExoMars">ExoMars</a> <ul><li><a href="/wiki/Rosalind_Franklin_(rover)" title="Rosalind Franklin (rover)">Rosalind Franklin rover</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Proposed</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Breakthrough_Enceladus_mission" title="Breakthrough Enceladus mission">Breakthrough Enceladus</a></li> <li><a href="/wiki/BRUIE" title="BRUIE">BRUIE</a></li> <li><a href="/wiki/CAESAR_(spacecraft)" title="CAESAR (spacecraft)">CAESAR</a></li> <li><a href="/wiki/Enceladus_Explorer" title="Enceladus Explorer">Enceladus Explorer</a></li> <li><a href="/wiki/Enceladus_Life_Finder" title="Enceladus Life Finder">Enceladus Life Finder‎</a></li> <li><a href="/wiki/Enceladus_Life_Signatures_and_Habitability" title="Enceladus Life Signatures and Habitability">Enceladus Life Signatures and Habitability</a></li> <li><a href="/wiki/Enceladus_Orbilander" title="Enceladus Orbilander">Enceladus Orbilander</a></li> <li><a href="/wiki/Europa_Lander_(NASA)" class="mw-redirect" title="Europa Lander (NASA)">Europa Lander</a></li> <li><a href="/wiki/ExoLance" title="ExoLance">ExoLance</a></li> <li><a href="/wiki/Explorer_of_Enceladus_and_Titan" title="Explorer of Enceladus and Titan">Explorer of Enceladus and Titan</a></li> <li><a href="/wiki/Icebreaker_Life" title="Icebreaker Life">Icebreaker Life</a></li> <li><a href="/wiki/Journey_to_Enceladus_and_Titan" title="Journey to Enceladus and Titan">Journey to Enceladus and Titan</a></li> <li><a href="/wiki/Laplace-P" title="Laplace-P">Laplace-P</a></li> <li><a href="/wiki/Life_Investigation_For_Enceladus" title="Life Investigation For Enceladus">Life Investigation For Enceladus</a></li> <li><a href="/wiki/Mars_sample_return_mission" class="mw-redirect" title="Mars sample return mission">Mars sample return mission</a></li> <li><a href="/wiki/Oceanus_(Titan_orbiter)" title="Oceanus (Titan orbiter)">Oceanus</a></li> <li><a href="/wiki/THEO" title="THEO">THEO</a></li> <li><a href="/wiki/Trident_(spacecraft)" title="Trident (spacecraft)">Trident</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Cancelled and undeveloped</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astrobiology_Field_Laboratory" title="Astrobiology Field Laboratory">Astrobiology Field Laboratory</a></li> <li><a href="/wiki/Beagle_3" title="Beagle 3">Beagle 3</a></li> <li><a href="/wiki/Biological_Oxidant_and_Life_Detection" title="Biological Oxidant and Life Detection">Biological Oxidant and Life Detection</a></li> <li><a href="/wiki/Kazachok" title="Kazachok">Kazachok</a></li> <li><a href="/wiki/Living_Interplanetary_Flight_Experiment" title="Living Interplanetary Flight Experiment">Living Interplanetary Flight Experiment</a></li> <li><a href="/wiki/Mars_Astrobiology_Explorer-Cacher" title="Mars Astrobiology Explorer-Cacher">Mars Astrobiology Explorer-Cacher</a></li> <li><a href="/wiki/MELOS" title="MELOS">MELOS</a></li> <li><a href="/wiki/Northern_Light_(spacecraft)" title="Northern Light (spacecraft)">Northern Light</a></li> <li><a href="/wiki/SpaceX_Red_Dragon" title="SpaceX Red Dragon">Red Dragon</a></li> <li><a href="/wiki/Terrestrial_Planet_Finder" title="Terrestrial Planet Finder">Terrestrial Planet Finder</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Institutions and programs</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astrobiology_Society_of_Britain" title="Astrobiology Society of Britain">Astrobiology Society of Britain</a></li> <li><a href="/wiki/Astrobiology_Science_and_Technology_for_Exploring_Planets" title="Astrobiology Science and Technology for Exploring Planets">Astrobiology Science and Technology for Exploring Planets</a></li> <li><a href="/wiki/Breakthrough_Initiatives" title="Breakthrough Initiatives">Breakthrough Initiatives</a> <ul><li><a href="/wiki/Breakthrough_Listen" title="Breakthrough Listen">Breakthrough Listen</a></li> <li><a href="/wiki/Breakthrough_Message" class="mw-redirect" title="Breakthrough Message">Breakthrough Message</a></li> <li><a href="/wiki/Breakthrough_Starshot" title="Breakthrough Starshot">Breakthrough Starshot</a></li></ul></li> <li><a href="/wiki/Carl_Sagan_Institute" title="Carl Sagan Institute">Carl Sagan Institute</a></li> <li><a href="/wiki/Center_for_Life_Detection_Science" class="mw-redirect" title="Center for Life Detection Science">Center for Life Detection Science</a></li> <li><a href="/wiki/European_Astrobiology_Network_Association" title="European Astrobiology Network Association">European Astrobiology Network Association</a></li> <li><a href="/wiki/MERMOZ" title="MERMOZ">MERMOZ</a></li> <li><a href="/wiki/NASA_Astrobiology_Institute" title="NASA Astrobiology Institute">NASA Astrobiology Institute</a></li> <li><a href="/wiki/Nexus_for_Exoplanet_System_Science" title="Nexus for Exoplanet System Science">Nexus for Exoplanet System Science</a></li> <li><a href="/wiki/Ocean_Worlds_Exploration_Program" title="Ocean Worlds Exploration Program">Ocean Worlds Exploration Program</a></li> <li><a href="/wiki/Spanish_Astrobiology_Center" title="Spanish Astrobiology Center">Spanish Astrobiology Center‎</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2" style="text-align: center;"><div> <ul><li><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /> <a href="/wiki/Category:Astrobiology" title="Category:Astrobiology">Category</a></li> <li><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/12px-Commons-logo.svg.png" decoding="async" width="12" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/18px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/24px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /> <a href="https://commons.wikimedia.org/wiki/Category:Astrobiology" class="extiw" title="commons:Category:Astrobiology">Commons</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Extraterrestrial_life" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2" style="text-align: center;"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Extraterrestrial_life" title="Template:Extraterrestrial life"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Extraterrestrial_life" title="Template talk:Extraterrestrial life"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Extraterrestrial_life" title="Special:EditPage/Template:Extraterrestrial life"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Extraterrestrial_life" style="font-size:114%;margin:0 4em"><a href="/wiki/Extraterrestrial_life" title="Extraterrestrial life">Extraterrestrial life</a></div></th></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Events and objects</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Shergotty_meteorite" title="Shergotty meteorite">Shergotty meteorite</a> (1865)</li> <li><a href="/wiki/Nakhla_meteorite" title="Nakhla meteorite">Nakhla meteorite</a> (1911)</li> <li><a href="/wiki/Murchison_meteorite" title="Murchison meteorite">Murchison meteorite</a> (1969)</li> <li><a href="/wiki/Viking_lander_biological_experiments" title="Viking lander biological experiments">Viking lander biological experiments</a> (1976)</li> <li><a href="/wiki/Allan_Hills_77005" title="Allan Hills 77005">Allan Hills 77005</a> (1977)</li> <li><a href="/wiki/Allan_Hills_84001" title="Allan Hills 84001">Allan Hills 84001</a> (1984)</li> <li><a href="/wiki/Yamato_000593" title="Yamato 000593">Yamato 000593</a> (2000)</li> <li><a href="/wiki/CI1_fossils" title="CI1 fossils">CI1 fossils</a> (2011)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Signals of interest</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Misidentified</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/PSR_B1919%2B21" title="PSR B1919+21">CP 1919</a> (misidentified pulsar)</li> <li><a href="/wiki/CTA-102" title="CTA-102">CTA-102</a> (misidentified quasar)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Stars</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Tabby%27s_Star" title="Tabby's Star">KIC 8462852</a> (unusual light fluctuations)</li> <li><a href="/wiki/EPIC_204278916" title="EPIC 204278916">EPIC 204278916</a> (unusual light fluctuations)</li> <li><a href="/wiki/VVV-WIT-07" title="VVV-WIT-07">VVV-WIT-07</a> (unusual light fluctuations)</li> <li><a href="/wiki/HD_164595" title="HD 164595">HD 164595 signal</a> (unknown origin)</li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;">Other</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/SHGb02%2B14a" title="SHGb02+14a">SHGb02+14a</a> (radio source)</li> <li><a href="/wiki/Wow!_signal" title="Wow! signal">Wow! signal</a> (inconclusive)</li> <li><a href="/wiki/Fast_radio_burst" title="Fast radio burst">Fast radio burst</a> (unknown origin)</li> <li><a href="/wiki/BLC1" title="BLC1">BLC1</a> (radio signal)</li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Life in the Universe</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Earliest_known_life_forms" title="Earliest known life forms">Earliest known life forms</a></li> <li><a href="/wiki/Planetary_habitability_in_the_Solar_System" title="Planetary habitability in the Solar System">Planetary habitability in the Solar System</a></li> <li><a href="/wiki/Life_on_Venus" title="Life on Venus">Life on Venus</a></li> <li><a href="/wiki/Life_on_Mars" title="Life on Mars">Life on Mars</a></li> <li><a href="/wiki/Life_on_Titan" title="Life on Titan">Life on Titan</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/Planetary_habitability" title="Planetary habitability">Planetary habitability</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Catalog_of_Nearby_Habitable_Systems" title="Catalog of Nearby Habitable Systems">Catalog of Nearby Habitable Systems</a></li> <li><a href="/wiki/Circumstellar_habitable_zone" class="mw-redirect" title="Circumstellar habitable zone">Circumstellar habitable zone</a></li> <li><a href="/wiki/Earth_analog" title="Earth analog">Earth analog</a></li> <li><a href="/wiki/Extraterrestrial_liquid_water" title="Extraterrestrial liquid water">Extraterrestrial liquid water</a></li> <li><a href="/wiki/Galactic_habitable_zone" title="Galactic habitable zone">Galactic habitable zone</a></li> <li><a href="/wiki/Habitability_of_binary_star_systems" title="Habitability of binary star systems">Habitability of binary star systems</a></li> <li><a href="/wiki/Habitability_of_natural_satellites" title="Habitability of natural satellites">Habitability of natural satellites</a></li> <li><a href="/wiki/Habitability_of_neutron_star_systems" title="Habitability of neutron star systems">Habitability of neutron star systems</a></li> <li><a href="/wiki/Habitability_of_red_dwarf_systems" title="Habitability of red dwarf systems">Habitability of red dwarf systems</a></li> <li><a href="/wiki/Habitability_of_K-type_main-sequence_star_systems" title="Habitability of K-type main-sequence star systems">Habitability of K-type main-sequence star systems</a></li> <li><a href="/wiki/Habitability_of_yellow_dwarf_systems" title="Habitability of yellow dwarf systems">Habitability of yellow dwarf systems</a></li> <li><a href="/wiki/Habitability_of_F-type_main-sequence_star_systems" title="Habitability of F-type main-sequence star systems">Habitability of F-type main-sequence star systems</a></li> <li><a href="/wiki/List_of_potentially_habitable_exoplanets" title="List of potentially habitable exoplanets">List of potentially habitable exoplanets</a></li> <li><a href="/wiki/Planetary_habitability" title="Planetary habitability">Planetary habitability</a></li> <li><a href="/wiki/Superhabitable_planet" class="mw-redirect" title="Superhabitable planet">Superhabitable planet</a></li> <li><a href="/wiki/Tholin" title="Tholin">Tholin</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/Astrobiology#Missions" title="Astrobiology">Space missions</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Beagle_2" title="Beagle 2">Beagle 2</a></li> <li><a href="/wiki/Biological_Oxidant_and_Life_Detection" title="Biological Oxidant and Life Detection">Biological Oxidant and Life Detection</a></li> <li><a href="/wiki/BioSentinel" title="BioSentinel">BioSentinel</a></li> <li><a href="/wiki/Curiosity_(rover)" title="Curiosity (rover)">Curiosity rover</a></li> <li><a href="/wiki/Darwin_(spacecraft)" title="Darwin (spacecraft)">Darwin</a></li> <li><a href="/wiki/Dragonfly_(Titan_space_probe)" title="Dragonfly (Titan space probe)">Dragonfly</a></li> <li><a href="/wiki/Enceladus_Explorer" title="Enceladus Explorer">Enceladus Explorer</a></li> <li><a href="/wiki/Enceladus_Life_Finder" title="Enceladus Life Finder">Enceladus Life Finder</a></li> <li><a href="/wiki/Europa_Clipper" title="Europa Clipper">Europa Clipper</a></li> <li><a href="/wiki/ExoMars" title="ExoMars">ExoMars</a> <ul><li><a href="/wiki/Rosalind_Franklin_(rover)" title="Rosalind Franklin (rover)">Rosalind Franklin rover</a></li></ul></li> <li><a href="/wiki/ExoLance" title="ExoLance">ExoLance</a></li> <li><a href="/wiki/EXPOSE" title="EXPOSE">EXPOSE</a></li> <li><a href="/wiki/Foton-M" class="mw-redirect" title="Foton-M">Foton-M3</a></li> <li><a href="/wiki/Icebreaker_Life" title="Icebreaker Life">Icebreaker Life</a></li> <li><a href="/wiki/Journey_to_Enceladus_and_Titan" title="Journey to Enceladus and Titan">Journey to Enceladus and Titan</a></li> <li><a href="/wiki/Laplace-P" title="Laplace-P">Laplace-P</a></li> <li><a href="/wiki/Life_Investigation_For_Enceladus" title="Life Investigation For Enceladus">Life Investigation For Enceladus</a></li> <li><a href="/wiki/Living_Interplanetary_Flight_Experiment" title="Living Interplanetary Flight Experiment">Living Interplanetary Flight Experiment</a></li> <li><a href="/wiki/Mars_Geyser_Hopper" title="Mars Geyser Hopper">Mars Geyser Hopper</a></li> <li><a href="/wiki/Mars_sample-return_mission" title="Mars sample-return mission">Mars sample-return mission</a></li> <li><a href="/wiki/Mars_2020" title="Mars 2020">Mars 2020</a></li> <li><a href="/wiki/Northern_Light_(spacecraft)" title="Northern Light (spacecraft)">Northern Light</a></li> <li><a href="/wiki/Opportunity_(rover)" title="Opportunity (rover)">Opportunity rover</a></li> <li><a href="/wiki/Perseverance_(rover)" title="Perseverance (rover)">Perseverance rover</a></li> <li><a href="/wiki/SpaceX_Red_Dragon" title="SpaceX Red Dragon">SpaceX Red Dragon</a></li> <li><a href="/wiki/Spirit_(rover)" title="Spirit (rover)">Spirit rover</a></li> <li><a href="/wiki/Tanpopo_mission" title="Tanpopo mission">Tanpopo</a></li> <li><a href="/wiki/Titan_Mare_Explorer" title="Titan Mare Explorer">Titan Mare Explorer</a></li> <li><a href="/wiki/Venus_In_Situ_Explorer" title="Venus In Situ Explorer">Venus In Situ Explorer</a></li> <li><a href="/wiki/Viking_1" title="Viking 1">Viking 1</a></li> <li><a href="/wiki/Viking_2" title="Viking 2">Viking 2</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/Interstellar_communication" title="Interstellar communication">Interstellar communication</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Active_SETI" title="Active SETI">Active SETI</a></li> <li><a href="/wiki/Allen_Telescope_Array" title="Allen Telescope Array">Allen Telescope Array</a></li> <li><a href="/wiki/Arecibo_message" title="Arecibo message">Arecibo message</a></li> <li><a href="/wiki/Arecibo_Observatory" title="Arecibo Observatory">Arecibo Observatory</a></li> <li><a href="/wiki/Berkeley_SETI_Research_Center" title="Berkeley SETI Research Center">Berkeley SETI Research Center</a></li> <li><a href="/wiki/Bracewell_probe" title="Bracewell probe">Bracewell probe</a></li> <li><a href="/wiki/Breakthrough_Initiatives" title="Breakthrough Initiatives">Breakthrough Initiatives</a> <ul><li><a href="/wiki/Breakthrough_Listen" title="Breakthrough Listen">Breakthrough Listen</a></li> <li><a href="/wiki/Breakthrough_Message" class="mw-redirect" title="Breakthrough Message">Breakthrough Message</a></li></ul></li> <li><a href="/wiki/Communication_with_extraterrestrial_intelligence" title="Communication with extraterrestrial intelligence">Communication with extraterrestrial intelligence</a></li> <li><a href="/wiki/Gauss%27s_Pythagorean_right_triangle_proposal" title="Gauss's Pythagorean right triangle proposal">Gauss's Pythagorean right triangle proposal</a></li> <li><a href="/wiki/Astrolinguistics" title="Astrolinguistics">Astrolinguistics</a></li> <li><a href="/wiki/Lincos_language" title="Lincos language">Lincos language</a></li> <li><a href="/wiki/NIROSETI" title="NIROSETI">NIROSETI</a></li> <li><a href="/wiki/Pioneer_plaque" title="Pioneer plaque">Pioneer plaque</a></li> <li><a href="/wiki/Project_Cyclops" title="Project Cyclops">Project Cyclops</a></li> <li><a href="/wiki/Project_Ozma" title="Project Ozma">Project Ozma</a></li> <li><a href="/wiki/Project_Phoenix_(SETI)" title="Project Phoenix (SETI)">Project Phoenix</a></li> <li><a href="/wiki/SERENDIP" title="SERENDIP">SERENDIP</a></li> <li><a href="/wiki/Search_for_extraterrestrial_intelligence" title="Search for extraterrestrial intelligence">Search for extraterrestrial intelligence</a></li> <li><a href="/wiki/SETI@home" title="SETI@home">SETI@home</a></li> <li><a href="/wiki/SetiQuest" title="SetiQuest">setiQuest</a></li> <li><a href="/wiki/Voyager_Golden_Record" title="Voyager Golden Record">Voyager Golden Record</a></li> <li><a href="/wiki/Water_hole_(radio)" title="Water hole (radio)">Water hole</a></li> <li><a href="/wiki/Alien_language" title="Alien language">Xenolinguistics</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/List_of_alleged_extraterrestrial_beings" title="List of alleged extraterrestrial beings">Types of alleged extraterrestrial beings</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Energy_being" title="Energy being">Energy beings</a></li> <li><a href="/wiki/Grey_alien" title="Grey alien">Grey aliens</a></li> <li><a href="/wiki/Insectoids_in_science_fiction" class="mw-redirect" title="Insectoids in science fiction">Insectoids</a></li> <li><a href="/wiki/Little_green_men" title="Little green men">Little green men</a></li> <li><a href="/wiki/Nordic_aliens" title="Nordic aliens">Nordic aliens</a></li> <li><a href="/wiki/Reptilian_humanoid" title="Reptilian humanoid">Reptilian humanoids</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Hypotheses</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cosmic_pluralism" title="Cosmic pluralism">Cosmic pluralism</a></li> <li><a href="/wiki/Directed_panspermia" title="Directed panspermia">Directed panspermia</a></li> <li><a class="mw-selflink selflink">Drake equation</a></li> <li><a href="/wiki/Extraterrestrial_hypothesis" class="mw-redirect" title="Extraterrestrial hypothesis">Extraterrestrial hypothesis</a></li> <li><a href="/wiki/Fermi_paradox" title="Fermi paradox">Fermi paradox</a></li> <li><a href="/wiki/Hypothetical_types_of_biochemistry" title="Hypothetical types of biochemistry">Hypothetical types of biochemistry</a></li> <li><a href="/wiki/Interplanetary_contamination" title="Interplanetary contamination">Interplanetary contamination</a></li> <li><a href="/wiki/Kardashev_scale" title="Kardashev scale">Kardashev scale</a></li> <li><a href="/wiki/Mediocrity_principle" title="Mediocrity principle">Mediocrity principle</a></li> <li><a href="/wiki/Panspermia" title="Panspermia">Panspermia</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/Fermi_paradox" title="Fermi paradox">Fermi paradox</a> solutions</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Aestivation_hypothesis" title="Aestivation hypothesis">Aestivation hypothesis</a></li> <li><a href="/wiki/Berserker_hypothesis" title="Berserker hypothesis">Berserker hypothesis</a></li> <li><a href="/wiki/Dark_forest_hypothesis" title="Dark forest hypothesis">Dark forest hypothesis</a></li> <li><a href="/wiki/Firstborn_hypothesis" title="Firstborn hypothesis">Firstborn hypothesis</a></li> <li><a href="/wiki/Great_Filter" title="Great Filter">Great Filter</a></li> <li><a href="/wiki/Hart%E2%80%93Tipler_conjecture" title="Hart–Tipler conjecture">Hart–Tipler conjecture</a></li> <li><a href="/wiki/Neocatastrophism" title="Neocatastrophism">Neocatastrophism</a></li> <li><a href="/wiki/Planetarium_hypothesis" title="Planetarium hypothesis">Planetarium hypothesis</a></li> <li><a href="/wiki/Rare_Earth_hypothesis" title="Rare Earth hypothesis">Rare Earth hypothesis</a></li> <li><a href="/wiki/Zoo_hypothesis" title="Zoo hypothesis">Zoo hypothesis</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/Outline_of_extraterrestrial_life" title="Outline of extraterrestrial life">Related topics</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ancient_astronauts" title="Ancient astronauts">Ancient astronauts</a></li> <li><a href="/wiki/Astrobiology" title="Astrobiology">Astrobiology</a></li> <li><a href="/wiki/Astroecology" title="Astroecology">Astroecology</a></li> <li><a href="/wiki/Biosignature" title="Biosignature">Biosignature</a></li> <li><a href="/wiki/Brookings_Report" title="Brookings Report">Brookings Report</a></li> <li><a href="/wiki/Exotheology" title="Exotheology">Exotheology</a></li> <li><a href="/wiki/Extraterrestrials_in_fiction" title="Extraterrestrials in fiction">Extraterrestrials in fiction</a></li> <li><a href="/wiki/Extremophile" title="Extremophile">Extremophile</a></li> <li><a href="/wiki/Hemolithin" title="Hemolithin">Hemolithin</a></li> <li><a href="/wiki/History_of_the_extraterrestrial_life_debate" title="History of the extraterrestrial life debate">History of the extraterrestrial life debate</a></li> <li><a href="/wiki/MERMOZ" title="MERMOZ">MERMOZ</a></li> <li><a href="/wiki/Nexus_for_Exoplanet_System_Science" title="Nexus for Exoplanet System Science">Nexus for Exoplanet System Science</a></li> <li><a href="/wiki/Noosphere" title="Noosphere">Noogenesis</a></li> <li><a href="/wiki/Planetary_protection" title="Planetary protection">Planetary protection</a></li> <li><a href="/wiki/Potential_cultural_impact_of_extraterrestrial_contact" title="Potential cultural impact of extraterrestrial contact">Potential cultural impact of extraterrestrial contact</a></li> <li><a href="/wiki/Post-detection_policy" title="Post-detection policy">Post-detection policy</a></li> <li><a href="/wiki/San_Marino_Scale" title="San Marino Scale">San Marino Scale</a></li> <li><a href="/wiki/Technosignature" title="Technosignature">Technosignature</a></li> <li><a href="/wiki/UFO_religion" title="UFO religion">UFO religion</a></li> <li><a href="/wiki/Xenoarchaeology" title="Xenoarchaeology">Xenoarchaeology</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Interstellar_communications" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2" style="text-align: center;"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Interstellar_messages" title="Template:Interstellar messages"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Interstellar_messages" title="Template talk:Interstellar messages"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Interstellar_messages" title="Special:EditPage/Template:Interstellar messages"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Interstellar_communications" style="font-size:114%;margin:0 4em"><a href="/wiki/Interstellar_communication" title="Interstellar communication">Interstellar communications</a></div></th></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Programs</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Active_SETI" title="Active SETI">Active SETI</a></li> <li><a href="/wiki/Breakthrough_Initiatives" title="Breakthrough Initiatives">Breakthrough Initiatives</a> <ul><li><a href="/wiki/Breakthrough_Listen" title="Breakthrough Listen">Breakthrough Listen</a></li> <li><a href="/wiki/Breakthrough_Message" class="mw-redirect" title="Breakthrough Message">Breakthrough Message</a></li></ul></li> <li><a href="/wiki/Communication_with_extraterrestrial_intelligence" title="Communication with extraterrestrial intelligence">Communication with extraterrestrial intelligence</a></li> <li><a href="/wiki/Search_for_extraterrestrial_intelligence" title="Search for extraterrestrial intelligence">Search for extraterrestrial intelligence</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Messages</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/List_of_interstellar_radio_messages" title="List of interstellar radio messages">List of interstellar radio messages</a></li> <li><a href="/wiki/A_Message_from_Earth" class="mw-redirect" title="A Message from Earth">A Message from Earth</a></li> <li><a href="/wiki/Across_the_Universe_(message)" title="Across the Universe (message)">Across the Universe</a></li> <li><a href="/wiki/Arecibo_message" title="Arecibo message">Arecibo message</a></li> <li><a href="/wiki/Bracewell_probe" title="Bracewell probe">Bracewell probe</a></li> <li><a href="/wiki/Cosmic_Call" title="Cosmic Call">Cosmic Call</a></li> <li><a href="/wiki/CosmicOS" title="CosmicOS">CosmicOS</a></li> <li><a href="/wiki/Hello_from_Earth" class="mw-redirect" title="Hello from Earth">Hello from Earth</a></li> <li><a href="/wiki/Pioneer_plaque" title="Pioneer plaque">Pioneer plaque</a></li> <li><a href="/wiki/Teen_Age_Message" title="Teen Age Message">Teen Age Message</a></li> <li><a href="/wiki/Voyager_Golden_Record" title="Voyager Golden Record">Voyager Golden Record</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">People</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Frank_Drake" title="Frank Drake">Frank Drake</a></li> <li><a href="/wiki/Ann_Druyan" title="Ann Druyan">Ann Druyan</a></li> <li><a href="/wiki/Hans_Freudenthal" title="Hans Freudenthal">Hans Freudenthal</a></li> <li><a href="/wiki/Sebastian_von_Hoerner" title="Sebastian von Hoerner">Sebastian von Hoerner</a></li> <li><a href="/wiki/Nikolai_Kardashev" title="Nikolai Kardashev">Nikolai Kardashev</a></li> <li><a href="/wiki/Jon_Lomberg" title="Jon Lomberg">Jon Lomberg</a></li> <li><a href="/wiki/Carl_Sagan" title="Carl Sagan">Carl Sagan</a></li> <li><a href="/wiki/Linda_Salzman_Sagan" title="Linda Salzman Sagan">Linda Salzman Sagan</a></li> <li><a href="/wiki/Iosif_Shklovsky" title="Iosif Shklovsky">Iosif Shklovsky</a></li> <li><a href="/wiki/Aleksandr_Leonidovich_Zaitsev" class="mw-redirect" title="Aleksandr Leonidovich Zaitsev">Aleksandr Zaitsev</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Other</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Alien_language" title="Alien language">Alien language</a></li> <li><a href="/wiki/Archaeology,_Anthropology,_and_Interstellar_Communication" title="Archaeology, Anthropology, and Interstellar Communication">Archaeology, Anthropology, and Interstellar Communication</a></li> <li><a href="/wiki/Astrobiology" title="Astrobiology">Astrobiology</a></li> <li><a href="/wiki/Astrolinguistics" title="Astrolinguistics">Astrolinguistics</a></li> <li><a class="mw-selflink selflink">Drake equation</a></li> <li><a href="/wiki/Extraterrestrial_life" title="Extraterrestrial life">Extraterrestrial life</a></li> <li><a href="/wiki/Lincos_language" title="Lincos language">Lincos</a></li> <li><a href="/wiki/Fermi_paradox" title="Fermi paradox">Fermi paradox</a></li> <li><a href="/wiki/Prix_Guzman" title="Prix Guzman">Prix Guzman</a></li> <li><a href="/wiki/San_Marino_Scale" title="San Marino Scale">San Marino Scale</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow hlist" colspan="2" style="text-align: center;"><div> <ul><li><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /> <a href="/wiki/Category:Interstellar_messages" title="Category:Interstellar messages">Category</a></li> <li><a href="/wiki/File:Symbol_portal_class.svg" class="mw-file-description" title="Portal"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/16px-Symbol_portal_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/23px-Symbol_portal_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/31px-Symbol_portal_class.svg.png 2x" data-file-width="180" data-file-height="185" /></a> <a href="/wiki/Portal:Space" class="mw-redirect" title="Portal:Space">Space Portal</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Molecules_detected_in_outer_space" style="padding:3px"><table class="nowraplinks hlist mw-collapsible mw-collapsed navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Molecules_detected_in_outer_space" title="Template:Molecules detected in outer space"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Molecules_detected_in_outer_space" title="Template talk:Molecules detected in outer space"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Molecules_detected_in_outer_space" title="Special:EditPage/Template:Molecules detected in outer space"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Molecules_detected_in_outer_space" style="font-size:114%;margin:0 4em"><a href="/wiki/List_of_interstellar_and_circumstellar_molecules" title="List of interstellar and circumstellar molecules">Molecules detected in outer space</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Molecule" title="Molecule">Molecules</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Diatomic_molecule" title="Diatomic molecule">Diatomic</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Aluminium_monochloride" title="Aluminium monochloride">Aluminium monochloride</a></li> <li><a href="/wiki/Aluminium_monofluoride" title="Aluminium monofluoride">Aluminium monofluoride</a></li> <li><a href="/wiki/Aluminium(II)_oxide" title="Aluminium(II) oxide">Aluminium(II) oxide</a></li> <li><a href="/wiki/Argonium" title="Argonium">Argonium</a></li> <li><a href="/wiki/Carbon_cation" class="mw-redirect" title="Carbon cation">Carbon cation</a></li> <li><a href="/wiki/Carbon_monophosphide" title="Carbon monophosphide">Carbon monophosphide</a></li> <li><a href="/wiki/Carbon_monosulfide" title="Carbon monosulfide">Carbon monosulfide</a></li> <li><a href="/wiki/Carbon_monoxide" title="Carbon monoxide">Carbon monoxide</a></li> <li><a href="/wiki/Cyano_radical" title="Cyano radical">Cyano radical</a></li> <li><a href="/wiki/Diatomic_carbon" title="Diatomic carbon">Diatomic carbon</a></li> <li><a href="/w/index.php?title=Fluoromethylidynium&action=edit&redlink=1" class="new" title="Fluoromethylidynium (page does not exist)">Fluoromethylidynium</a></li> <li><a href="/wiki/Helium_hydride_ion" title="Helium hydride ion">Helium hydride ion</a></li> <li><a href="/wiki/Hydrogen_chloride" title="Hydrogen chloride">Hydrogen chloride</a></li> <li><a href="/wiki/Hydrogen_fluoride" title="Hydrogen fluoride">Hydrogen fluoride</a></li> <li><a href="/wiki/Hydrogen" title="Hydrogen">Hydrogen</a> (molecular)</li> <li><a href="/wiki/Hydroxyl_radical" title="Hydroxyl radical">Hydroxyl radical</a></li> <li><a href="/wiki/Iron(II)_oxide" title="Iron(II) oxide">Iron(II) oxide</a></li> <li><a href="/wiki/Magnesium_monohydride" title="Magnesium monohydride">Magnesium monohydride</a></li> <li><a href="/wiki/Methylidyne_radical" title="Methylidyne radical">Methylidyne radical</a></li> <li><a href="/wiki/Nitric_oxide" title="Nitric oxide">Nitric oxide</a></li> <li><a href="/wiki/Nitrogen" title="Nitrogen">Nitrogen</a> (molecular)</li> <li><a href="/wiki/Imidogen" title="Imidogen">Imidogen</a></li> <li><a href="/wiki/Sulfur_mononitride" title="Sulfur mononitride">Sulfur mononitride</a></li> <li><a href="/wiki/Oxygen" title="Oxygen">Oxygen</a> (molecular)</li> <li><a href="/wiki/Phosphorus_monoxide" title="Phosphorus monoxide">Phosphorus monoxide</a></li> <li><a href="/wiki/Phosphorus_mononitride" title="Phosphorus mononitride">Phosphorus mononitride</a></li> <li><a href="/wiki/Potassium_chloride" title="Potassium chloride">Potassium chloride</a></li> <li><a href="/wiki/Silicon_carbide" title="Silicon carbide">Silicon carbide</a></li> <li><a href="/wiki/Silicon_monoxide" title="Silicon monoxide">Silicon monoxide</a></li> <li><a href="/wiki/Silicon_monosulfide" title="Silicon monosulfide">Silicon monosulfide</a></li> <li><a href="/wiki/Sodium_chloride" title="Sodium chloride">Sodium chloride</a></li> <li><a href="/wiki/Sodium_iodide" title="Sodium iodide">Sodium iodide</a></li> <li><a href="/wiki/Sulfanyl" title="Sulfanyl">Sulfanyl</a></li> <li><a href="/wiki/Sulfur_monoxide" title="Sulfur monoxide">Sulfur monoxide</a></li> <li><a href="/wiki/Titanium(II)_oxide" title="Titanium(II) oxide">Titanium(II) oxide</a></li></ul> </div></td><td class="noviewer navbox-image" rowspan="9" style="width:1px;padding:0 0 0 2px"><div><a href="/wiki/Nitrous_oxide" title="Nitrous oxide"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/93/Nitrous-oxide-3D-balls.png/60px-Nitrous-oxide-3D-balls.png" decoding="async" width="60" height="24" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/93/Nitrous-oxide-3D-balls.png/90px-Nitrous-oxide-3D-balls.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/93/Nitrous-oxide-3D-balls.png/120px-Nitrous-oxide-3D-balls.png 2x" data-file-width="1100" data-file-height="441" /></a> <a href="/wiki/Ethanol" title="Ethanol"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Ethanol-3D-balls.png/60px-Ethanol-3D-balls.png" decoding="async" width="60" height="41" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Ethanol-3D-balls.png/90px-Ethanol-3D-balls.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b0/Ethanol-3D-balls.png/120px-Ethanol-3D-balls.png 2x" data-file-width="1100" data-file-height="754" /></a> <a href="/wiki/Buckminsterfullerene" title="Buckminsterfullerene"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0f/Buckminsterfullerene-perspective-3D-balls.png/60px-Buckminsterfullerene-perspective-3D-balls.png" decoding="async" width="60" height="63" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0f/Buckminsterfullerene-perspective-3D-balls.png/90px-Buckminsterfullerene-perspective-3D-balls.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0f/Buckminsterfullerene-perspective-3D-balls.png/120px-Buckminsterfullerene-perspective-3D-balls.png 2x" data-file-width="1056" data-file-height="1100" /></a></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Triatomic_molecule" title="Triatomic molecule">Triatomic</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Aluminium(I)_hydroxide" class="mw-redirect" title="Aluminium(I) hydroxide">Aluminium(I) hydroxide</a></li> <li><a href="/w/index.php?title=Aluminium_isocyanide&action=edit&redlink=1" class="new" title="Aluminium isocyanide (page does not exist)">Aluminium isocyanide</a></li> <li><a href="/wiki/Amino_radical" title="Amino radical">Amino radical</a></li> <li><a href="/wiki/Carbon_dioxide" title="Carbon dioxide">Carbon dioxide</a></li> <li><a href="/wiki/Carbonyl_sulfide" title="Carbonyl sulfide">Carbonyl sulfide</a></li> <li><a href="/w/index.php?title=CCP_radical&action=edit&redlink=1" class="new" title="CCP radical (page does not exist)">CCP radical</a></li> <li><a href="/wiki/Halonium_ion" title="Halonium ion">Chloronium</a></li> <li><a href="/wiki/Diazenylium" title="Diazenylium">Diazenylium</a></li> <li><a href="/wiki/Dicarbon_monoxide" title="Dicarbon monoxide">Dicarbon monoxide</a></li> <li><a href="/w/index.php?title=Disilicon_carbide&action=edit&redlink=1" class="new" title="Disilicon carbide (page does not exist)">Disilicon carbide</a></li> <li><a href="/wiki/Ethynyl_radical" title="Ethynyl radical">Ethynyl radical</a></li> <li><a href="/w/index.php?title=Formyl_radical&action=edit&redlink=1" class="new" title="Formyl radical (page does not exist)">Formyl radical</a></li> <li><a href="/wiki/Hydrogen_cyanide" title="Hydrogen cyanide">Hydrogen cyanide</a> (HCN)</li> <li><a href="/wiki/Hydrogen_isocyanide" title="Hydrogen isocyanide">Hydrogen isocyanide</a> (HNC)</li> <li><a href="/wiki/Hydrogen_sulfide" title="Hydrogen sulfide">Hydrogen sulfide</a></li> <li><a href="/wiki/Hydroperoxyl" title="Hydroperoxyl">Hydroperoxyl</a></li> <li><a href="/w/index.php?title=Iron_cyanide&action=edit&redlink=1" class="new" title="Iron cyanide (page does not exist)">Iron cyanide</a></li> <li><a href="/w/index.php?title=Isoformyl&action=edit&redlink=1" class="new" title="Isoformyl (page does not exist)">Isoformyl</a></li> <li><a href="/wiki/Magnesium_cyanide" title="Magnesium cyanide">Magnesium cyanide</a></li> <li><a href="/w/index.php?title=Magnesium_isocyanide&action=edit&redlink=1" class="new" title="Magnesium isocyanide (page does not exist)">Magnesium isocyanide</a></li> <li><a href="/wiki/Methylene_(compound)" title="Methylene (compound)">Methylene</a></li> <li><a href="/wiki/Diazenylium" title="Diazenylium">N2H+</a></li> <li><a href="/wiki/Nitrous_oxide" title="Nitrous oxide">Nitrous oxide</a></li> <li><a href="/wiki/Nitroxyl" title="Nitroxyl">Nitroxyl</a></li> <li><a href="/wiki/Ozone" title="Ozone">Ozone</a></li> <li><a href="/wiki/Methylidynephosphane" title="Methylidynephosphane">Methylidynephosphane</a></li> <li><a href="/wiki/Potassium_cyanide" title="Potassium cyanide">Potassium cyanide</a></li> <li><a href="/wiki/Trihydrogen_cation" title="Trihydrogen cation">Trihydrogen cation</a></li> <li><a href="/wiki/Sodium_cyanide" title="Sodium cyanide">Sodium cyanide</a></li> <li><a href="/wiki/Sodium_hydroxide" title="Sodium hydroxide">Sodium hydroxide</a></li> <li><a href="/w/index.php?title=Silicon_carbonitride&action=edit&redlink=1" class="new" title="Silicon carbonitride (page does not exist)">Silicon carbonitride</a></li> <li><a href="/w/index.php?title=C-Silicon_dicarbide&action=edit&redlink=1" class="new" title="C-Silicon dicarbide (page does not exist)">c-Silicon dicarbide</a></li> <li><a href="/w/index.php?title=SiNC&action=edit&redlink=1" class="new" title="SiNC (page does not exist)">SiNC</a></li> <li><a href="/wiki/Sulfur_dioxide" title="Sulfur dioxide">Sulfur dioxide</a></li> <li><a href="/w/index.php?title=Thioformyl&action=edit&redlink=1" class="new" title="Thioformyl (page does not exist)">Thioformyl</a></li> <li><a href="/wiki/Thioxoethenylidene" title="Thioxoethenylidene">Thioxoethenylidene</a></li> <li><a href="/wiki/Titanium_dioxide" title="Titanium dioxide">Titanium dioxide</a></li> <li><a href="/wiki/Tricarbon" title="Tricarbon">Tricarbon</a></li> <li><a href="/wiki/Water" title="Water">Water</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_interstellar_and_circumstellar_molecules#Molecules" title="List of interstellar and circumstellar molecules">Four atoms</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Acetylene" title="Acetylene">Acetylene</a></li> <li><a href="/wiki/Ammonia" title="Ammonia">Ammonia</a></li> <li><a href="/wiki/Isocyanic_acid" title="Isocyanic acid">Isocyanic acid</a></li> <li><a href="/wiki/Polyyne" title="Polyyne">Cyanoethynyl</a></li> <li><a href="/wiki/Interstellar_formaldehyde" title="Interstellar formaldehyde">Formaldehyde</a></li> <li><a href="/wiki/Fulminic_acid" title="Fulminic acid">Fulminic acid</a></li> <li><a href="/w/index.php?title=HCCN&action=edit&redlink=1" class="new" title="HCCN (page does not exist)">HCCN</a></li> <li><a href="/wiki/Hydrogen_peroxide" title="Hydrogen peroxide">Hydrogen peroxide</a></li> <li><a href="/w/index.php?title=Hydromagnesium_isocyanide&action=edit&redlink=1" class="new" title="Hydromagnesium isocyanide (page does not exist)">Hydromagnesium isocyanide</a></li> <li><a href="/wiki/Isocyanic_acid" title="Isocyanic acid">Isocyanic acid</a></li> <li><a href="/wiki/Thiocyanic_acid" title="Thiocyanic acid">Isothiocyanic acid</a></li> <li><a href="/w/index.php?title=Ketenyl&action=edit&redlink=1" class="new" title="Ketenyl (page does not exist)">Ketenyl</a></li> <li><a href="/w/index.php?title=Methylene_amidogen&action=edit&redlink=1" class="new" title="Methylene amidogen (page does not exist)">Methylene amidogen</a></li> <li><a href="/wiki/Methyl_cation" class="mw-redirect" title="Methyl cation">Methyl cation</a></li> <li><a href="/wiki/Methyl_radical" title="Methyl radical">Methyl radical</a></li> <li><a href="/wiki/Propynylidyne" title="Propynylidyne">Propynylidyne</a></li> <li><a href="/w/index.php?title=Protonated_carbon_dioxide&action=edit&redlink=1" class="new" title="Protonated carbon dioxide (page does not exist)">Protonated carbon dioxide</a></li> <li><a href="/wiki/Protonated_hydrogen_cyanide" title="Protonated hydrogen cyanide">Protonated hydrogen cyanide</a></li> <li><a href="/w/index.php?title=Silicon_tricarbide&action=edit&redlink=1" class="new" title="Silicon tricarbide (page does not exist)">Silicon tricarbide</a></li> <li><a href="/wiki/Thioformaldehyde" title="Thioformaldehyde">Thioformaldehyde</a></li> <li><a href="/wiki/Tricarbon_monoxide" title="Tricarbon monoxide">Tricarbon monoxide</a></li> <li><a href="/wiki/Tricarbon_monosulfide" title="Tricarbon monosulfide">Tricarbon monosulfide</a></li> <li><a href="/wiki/Thiocyanic_acid" title="Thiocyanic acid">Thiocyanic acid</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_interstellar_and_circumstellar_molecules#Molecules" title="List of interstellar and circumstellar molecules">Five atoms</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ammonium" title="Ammonium">Ammonium</a> ion</li> <li><a href="/wiki/Polyyne" title="Polyyne">Butadiynyl</a></li> <li><a href="/wiki/Carbodiimide" title="Carbodiimide">Carbodiimide</a></li> <li><a href="/wiki/Cyanamide" title="Cyanamide">Cyanamide</a></li> <li><a href="/wiki/Cyanoacetylene" title="Cyanoacetylene">Cyanoacetylene</a></li> <li><a href="/w/index.php?title=Cyanoformaldehyde&action=edit&redlink=1" class="new" title="Cyanoformaldehyde (page does not exist)">Cyanoformaldehyde</a></li> <li><a href="/wiki/Cyanomethyl" title="Cyanomethyl">Cyanomethyl</a></li> <li><a href="/wiki/Cyclopropenylidene" title="Cyclopropenylidene">Cyclopropenylidene</a></li> <li><a href="/wiki/Formic_acid" title="Formic acid">Formic acid</a></li> <li><a href="/w/index.php?title=Isocyanoacetylene&action=edit&redlink=1" class="new" title="Isocyanoacetylene (page does not exist)">Isocyanoacetylene</a></li> <li><a href="/wiki/Ketene" title="Ketene">Ketene</a></li> <li><a href="/wiki/Methane" title="Methane">Methane</a></li> <li><a href="/wiki/Methoxy" class="mw-redirect" title="Methoxy">Methoxy radical</a></li> <li><a href="/w/index.php?title=Methylenimine&action=edit&redlink=1" class="new" title="Methylenimine (page does not exist)">Methylenimine</a></li> <li><a href="/w/index.php?title=Propadienylidene&action=edit&redlink=1" class="new" title="Propadienylidene (page does not exist)">Propadienylidene</a></li> <li><a href="/w/index.php?title=Protonated_formaldehyde&action=edit&redlink=1" class="new" title="Protonated formaldehyde (page does not exist)">Protonated formaldehyde</a></li> <li><a href="/wiki/Silane" title="Silane">Silane</a></li> <li><a href="/w/index.php?title=Silicon-carbide_cluster&action=edit&redlink=1" class="new" title="Silicon-carbide cluster (page does not exist)">Silicon-carbide cluster</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_interstellar_and_circumstellar_molecules#Molecules" title="List of interstellar and circumstellar molecules">Six atoms</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Acetonitrile" title="Acetonitrile">Acetonitrile</a></li> <li><a href="/w/index.php?title=Cyanobutadiynyl_radical&action=edit&redlink=1" class="new" title="Cyanobutadiynyl radical (page does not exist)">Cyanobutadiynyl radical</a></li> <li><a href="/w/index.php?title=E-Cyanomethanimine&action=edit&redlink=1" class="new" title="E-Cyanomethanimine (page does not exist)">E-Cyanomethanimine</a></li> <li><a href="/wiki/Cyclopropenone" title="Cyclopropenone">Cyclopropenone</a></li> <li><a href="/wiki/Diacetylene" title="Diacetylene">Diacetylene</a></li> <li><a href="/wiki/Ethylene" title="Ethylene">Ethylene</a></li> <li><a href="/wiki/Formamide" title="Formamide">Formamide</a></li> <li><a href="/w/index.php?title=HC4N&action=edit&redlink=1" class="new" title="HC4N (page does not exist)">HC4N</a></li> <li><a href="/wiki/Ketenimine" class="mw-redirect" title="Ketenimine">Ketenimine</a></li> <li><a href="/wiki/Methanethiol" title="Methanethiol">Methanethiol</a></li> <li><a href="/wiki/Methanol" title="Methanol">Methanol</a></li> <li><a href="/wiki/Methyl_isocyanide" title="Methyl isocyanide">Methyl isocyanide</a></li> <li><a href="/wiki/Polyyne" title="Polyyne">Pentynylidyne</a></li> <li><a href="/wiki/Propynal" class="mw-redirect" title="Propynal">Propynal</a></li> <li><a href="/w/index.php?title=Protonated_cyanoacetylene&action=edit&redlink=1" class="new" title="Protonated cyanoacetylene (page does not exist)">Protonated cyanoacetylene</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_interstellar_and_circumstellar_molecules#Molecules" title="List of interstellar and circumstellar molecules">Seven atoms</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Acetaldehyde" title="Acetaldehyde">Acetaldehyde</a></li> <li><a href="/wiki/Acrylonitrile" title="Acrylonitrile">Acrylonitrile</a> <ul><li><a href="/wiki/Vinyl_cyanide" class="mw-redirect" title="Vinyl cyanide">Vinyl cyanide</a></li></ul></li> <li><a href="/wiki/Cyanopolyyne" title="Cyanopolyyne">Cyanodiacetylene</a></li> <li><a href="/wiki/Ethylene_oxide" title="Ethylene oxide">Ethylene oxide</a></li> <li><a href="/wiki/Glycolonitrile" title="Glycolonitrile">Glycolonitrile</a></li> <li><a href="/wiki/Hexatriynyl_radical" title="Hexatriynyl radical">Hexatriynyl radical</a></li> <li><a href="/wiki/Propyne" title="Propyne">Propyne</a></li> <li><a href="/wiki/Methylamine" title="Methylamine">Methylamine</a></li> <li><a href="/wiki/Methyl_isocyanate" title="Methyl isocyanate">Methyl isocyanate</a></li> <li><a href="/wiki/Vinyl_alcohol" title="Vinyl alcohol">Vinyl alcohol</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_interstellar_and_circumstellar_molecules#Molecules" title="List of interstellar and circumstellar molecules">Eight atoms</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Acetic_acid" title="Acetic acid">Acetic acid</a></li> <li><a href="/wiki/Aminoacetonitrile" title="Aminoacetonitrile">Aminoacetonitrile</a></li> <li><a href="/w/index.php?title=Cyanoallene&action=edit&redlink=1" class="new" title="Cyanoallene (page does not exist)">Cyanoallene</a></li> <li><a href="/wiki/Ethanimine" title="Ethanimine">Ethanimine</a></li> <li><a href="/wiki/Glycolaldehyde" title="Glycolaldehyde">Glycolaldehyde</a></li> <li><a href="/wiki/Polyyne" title="Polyyne">Hexapentaenylidene</a></li> <li><a href="/wiki/Polyyne" title="Polyyne">Methylcyanoacetylene</a></li> <li><a href="/wiki/Methyl_formate" title="Methyl formate">Methyl formate</a></li> <li><a href="/wiki/Acrolein" title="Acrolein">Acrolein</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_interstellar_and_circumstellar_molecules#Molecules" title="List of interstellar and circumstellar molecules">Nine atoms</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Acetamide" title="Acetamide">Acetamide</a></li> <li><a href="/wiki/Cyanopolyyne" title="Cyanopolyyne">Cyanohexatriyne</a></li> <li><a href="/wiki/Dimethyl_ether" title="Dimethyl ether">Dimethyl ether</a></li> <li><a href="/wiki/Ethanol" title="Ethanol">Ethanol</a></li> <li><a href="/wiki/Polyyne" title="Polyyne">Methyldiacetylene</a></li> <li><a href="/wiki/Octatetraynyl_radical" title="Octatetraynyl radical">Octatetraynyl radical</a></li> <li><a href="/wiki/Propene" class="mw-redirect" title="Propene">Propene</a></li> <li><a href="/wiki/Ethanethiol" title="Ethanethiol">Ethanethiol</a></li> <li><a href="/wiki/Propionitrile" title="Propionitrile">Propionitrile</a></li> <li><a href="/wiki/N-Methylformamide" title="N-Methylformamide">N-Methylformamide</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_interstellar_and_circumstellar_molecules#Molecules" title="List of interstellar and circumstellar molecules">Ten atoms or more</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Acetone" title="Acetone">Acetone</a></li> <li><a href="/wiki/Benzene" title="Benzene">Benzene</a></li> <li><a href="/wiki/Benzonitrile" title="Benzonitrile">Benzonitrile</a></li> <li><a href="/wiki/Buckminsterfullerene" title="Buckminsterfullerene">Buckminsterfullerene</a> (C60, C60+, fullerene, buckyball)</li> <li><a href="/wiki/C70_fullerene" title="C70 fullerene">C70 fullerene</a></li> <li><a href="/wiki/Cyanopolyyne" title="Cyanopolyyne">Cyanodecapentayne</a></li> <li><a href="/wiki/Ethylene_glycol" title="Ethylene glycol">Ethylene glycol</a></li> <li><a href="/wiki/Ethyl_formate" title="Ethyl formate">Ethyl formate</a></li> <li><a href="/wiki/Methyl_acetate" title="Methyl acetate">Methyl acetate</a></li> <li><a href="/wiki/Cyanopolyyne" title="Cyanopolyyne">Methyl-cyano-diacetylene</a></li> <li><a href="/wiki/Polyyne" title="Polyyne">Methyltriacetylene</a></li> <li><a href="/wiki/Propionaldehyde" title="Propionaldehyde">Propionaldehyde</a></li> <li><a href="/wiki/Butyronitrile" title="Butyronitrile">Butyronitrile</a></li> <li><a href="/wiki/Pyrimidine" title="Pyrimidine">Pyrimidine</a></li> <li><a href="/w/index.php?title=Heptatrienyl_radical&action=edit&redlink=1" class="new" title="Heptatrienyl radical (page does not exist)">Heptatrienyl radical</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Deuterium" title="Deuterium">Deuterated</a> molecules</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ammonia" title="Ammonia">Ammonia</a></li> <li><a href="/wiki/Ammonium" title="Ammonium">Ammonium</a> ion</li> <li><a href="/wiki/Formaldehyde" title="Formaldehyde">Formaldehyde</a></li> <li><a href="/wiki/Interstellar_formaldehyde#Interstellar_reactions" title="Interstellar formaldehyde">Formyl radical</a></li> <li><a href="/wiki/Heavy_water" title="Heavy water">Heavy water</a></li> <li><a href="/wiki/Hydrogen_cyanide" title="Hydrogen cyanide">Hydrogen cyanide</a></li> <li><a href="/wiki/Hydrogen_deuteride" title="Hydrogen deuteride">Hydrogen deuteride</a></li> <li><a href="/wiki/Hydrogen_isocyanide" title="Hydrogen isocyanide">Hydrogen isocyanide</a></li> <li><a href="/wiki/Propyne" title="Propyne">Propyne</a></li> <li><a href="/wiki/Diazenylium" title="Diazenylium">N2D+</a></li> <li><a href="/wiki/Trihydrogen_cation" title="Trihydrogen cation">Trihydrogen cation</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_interstellar_and_circumstellar_molecules#Molecules" title="List of interstellar and circumstellar molecules">Unconfirmed</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Anthracene" title="Anthracene">Anthracene</a></li> <li><a href="/wiki/Dihydroxyacetone" title="Dihydroxyacetone">Dihydroxyacetone</a></li> <li><a href="/wiki/Methoxyethane" title="Methoxyethane">Methoxyethane</a></li> <li><a href="/wiki/Glycine" title="Glycine">Glycine</a></li> <li><a href="/wiki/Graphene" title="Graphene">Graphene</a></li> <li><a href="/wiki/Hemolithin" title="Hemolithin">Hemolithin</a></li> <li><a href="/w/index.php?title=H2NCO%2B&action=edit&redlink=1" class="new" title="H2NCO+ (page does not exist)">H2NCO+</a></li> <li><a href="/wiki/Carbon" title="Carbon">Linear C5</a></li> <li><a href="/wiki/Naphthalene" title="Naphthalene">Naphthalene cation</a></li> <li><a href="/wiki/Phosphine" title="Phosphine">Phosphine</a></li> <li><a href="/wiki/Pyrene" title="Pyrene">Pyrene</a></li> <li><a href="/wiki/Silylidyne" title="Silylidyne">Silylidyne</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_interstellar_and_circumstellar_molecules#See_also" title="List of interstellar and circumstellar molecules">Related</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Abiogenesis" title="Abiogenesis">Abiogenesis</a></li> <li><a href="/wiki/Astrobiology" title="Astrobiology">Astrobiology</a></li> <li><a href="/wiki/Astrochemistry" title="Astrochemistry">Astrochemistry</a></li> <li><a href="/wiki/Atomic_and_molecular_astrophysics" title="Atomic and molecular astrophysics">Atomic and molecular astrophysics</a></li> <li><a href="/wiki/Chemical_formula" title="Chemical formula">Chemical formula</a></li> <li><a href="/wiki/Circumstellar_dust" title="Circumstellar dust">Circumstellar dust</a></li> <li><a href="/wiki/Circumstellar_envelope" title="Circumstellar envelope">Circumstellar envelope</a></li> <li><a href="/wiki/Cosmic_dust" title="Cosmic dust">Cosmic dust</a></li> <li><a href="/wiki/Cosmic_ray" title="Cosmic ray">Cosmic ray</a></li> <li><a href="/wiki/Cosmochemistry" title="Cosmochemistry">Cosmochemistry</a></li> <li><a href="/wiki/Diffuse_interstellar_band" class="mw-redirect" title="Diffuse interstellar band">Diffuse interstellar band</a></li> <li><a href="/wiki/Earliest_known_life_forms" title="Earliest known life forms">Earliest known life forms</a></li> <li><a href="/wiki/Extraterrestrial_life" title="Extraterrestrial life">Extraterrestrial life</a></li> <li><a href="/wiki/Extraterrestrial_liquid_water" title="Extraterrestrial liquid water">Extraterrestrial liquid water</a></li> <li><a href="/wiki/Forbidden_mechanism" title="Forbidden mechanism">Forbidden mechanism</a></li> <li><a href="/wiki/Homochirality" title="Homochirality">Homochirality</a></li> <li><a href="/wiki/Intergalactic_dust" title="Intergalactic dust">Intergalactic dust</a></li> <li><a href="/wiki/Interplanetary_medium" title="Interplanetary medium">Interplanetary medium</a></li> <li><a href="/wiki/Interstellar_medium" title="Interstellar medium">Interstellar medium</a></li> <li><a href="/wiki/Photodissociation_region" title="Photodissociation region">Photodissociation region</a></li> <li><a href="/wiki/Iron%E2%80%93sulfur_world_theory" class="mw-redirect" title="Iron–sulfur world theory">Iron–sulfur world theory</a></li> <li><a href="/wiki/Kerogen" title="Kerogen">Kerogen</a></li> <li><a href="/wiki/Molecules_in_stars" title="Molecules in stars">Molecules in stars</a></li> <li><a href="/wiki/Nexus_for_Exoplanet_System_Science" title="Nexus for Exoplanet System Science">Nexus for Exoplanet System Science</a></li> <li><a href="/wiki/Organic_compound" title="Organic compound">Organic compound</a></li> <li><a href="/wiki/Outer_space" title="Outer space">Outer space</a></li> <li><a href="/wiki/PAH_world_hypothesis" title="PAH world hypothesis">PAH world hypothesis</a></li> <li><a href="/wiki/Pseudo-panspermia" 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