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data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Division of the lifetime of the cosmos</div> <p>A <b>cosmological decade</b> (<b>CÐ</b>) is a division of the <a href="/wiki/Chronology_of_the_universe" title="Chronology of the universe">lifetime of the cosmos</a>. The divisions are <a href="/wiki/Logarithmic_scale" title="Logarithmic scale">logarithmic in size</a>, with base 10. Each successive cosmological decade represents a <a href="/w/index.php?title=Ten-fold&action=edit&redlink=1" class="new" title="Ten-fold (page does not exist)">ten-fold</a> increase in the total <a href="/wiki/Age_of_the_universe" title="Age of the universe">age of the universe</a>.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="As_expressed_in_log_(seconds_per_Ðecade)"><span id="As_expressed_in_log_.28seconds_per_.C3.90ecade.29"></span>As expressed in log (seconds per Ðecade)</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Cosmological_decade&action=edit&section=1" title="Edit section: As expressed in log (seconds per Ðecade)"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>When CÐ is measured in log( seconds/Ð ), <i>CÐ</i> 1 begins at 10 <a href="/wiki/Second" title="Second">seconds</a> and lasts 90 seconds (until 100 seconds after Time Zero). <i>CÐ</i> 100, the 100th cosmological decade, lasts from 10<sup>100</sup> to 10<sup>101</sup> seconds after Time Zero. CÐ <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle -\infty }"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mo>−</mo> <mi mathvariant="normal">∞</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle -\infty }</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ca2608c4b5fd3bffc73585f8c67e379b4e99b6f1" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:4.132ex; height:2.176ex;" alt="{\displaystyle -\infty }"></span> is Time Zero. </p><p>The <a href="/wiki/Epoch_(astronomy)" title="Epoch (astronomy)">epoch</a> <i>CÐ</i> −43.2683 was 10<sup>(−43.2683)</sup> seconds, which represents the <a href="/wiki/Planck_time" class="mw-redirect" title="Planck time">Planck time</a> since the <a href="/wiki/Big_Bang" title="Big Bang">Big Bang</a> (Time Zero). There were an infinite number of cosmological decades between the Big Bang and the Planck epoch (or any other point in time). The current epoch, <i>CÐ</i> 17.6389, is 10<sup>(17.6389)</sup> seconds, or 13.799(21) billion years, since the Big Bang.<sup id="cite_ref-Planck_2015_2-0" class="reference"><a href="#cite_note-Planck_2015-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> There have been 60.9 cosmological decades between the Planck epoch, CÐ −43.2683, and the current epoch, CÐ 17.6389. </p> <div class="mw-heading mw-heading2"><h2 id="As_expressed_in_log_(years_per_Ðecade)"><span id="As_expressed_in_log_.28years_per_.C3.90ecade.29"></span>As expressed in log (years per Ðecade)</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Cosmological_decade&action=edit&section=2" title="Edit section: As expressed in log (years per Ðecade)"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The cosmological decade can be expressed in log years per decade. In this definition, the 100th cosmological decade lasts from 10<sup>100</sup> years to 10<sup>101</sup> years after Time Zero. To convert to this format, simply divide by seconds per year; or in logarithmic terms, subtract 7.4991116 from the values listed above. Thus when CÐ is expressed in log( years/Ð ), the Planck time could also be expressed as 10<sup>(−43.2683 − 7.4991116)</sup> years = 10<sup>(−50.7674)</sup> years. </p><p>In this definition, the current epoch is CÐ (17.6355 − 7.4991116), or CÐ 10.1364. As before, there have been 60.9 cosmological decades between the Planck epoch and the current epoch. </p><p>In theories of physical cosmology, the history of the universe can be segmented into <a href="/wiki/The_Five_Ages_of_the_Universe" title="The Five Ages of the Universe">five eras</a>: </p> <table class="wikitable"> <tbody><tr> <th>Age</th> <th>Ðecades</th> <th>Process </th></tr> <tr> <td>Primordial</td> <td>−50 to +5</td> <td><a href="/wiki/Timeline_of_the_Big_Bang" class="mw-redirect" title="Timeline of the Big Bang">from the Planck time until universe becomes transparent to radiation</a> </td></tr> <tr> <td><a href="/wiki/Timeline_of_cosmological_eras#Structure_formation" class="mw-redirect" title="Timeline of cosmological eras">Stelliferous</a></td> <td>6 to 14</td> <td>stars shine brightly (our current epoch is +10.1364) </td></tr> <tr> <td>Degenerate</td> <td>15 to 37</td> <td>stars degenerate, get dimmer </td></tr> <tr> <td>Black Hole</td> <td>38 to 99</td> <td>stars evaporate, galactic black holes evaporate </td></tr> <tr> <td>Dark Era</td> <td>100 onward</td> <td><a href="/wiki/Timeline_of_cosmological_eras" class="mw-redirect" title="Timeline of cosmological eras">lone protons and other particles get even farther and farther apart from each other</a> </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Cosmological_decade&action=edit&section=3" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><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="CITEREFAdamsGreg_Laughlin2000" class="citation book cs1">Adams, Fred; Greg Laughlin (2000). <i>The Five Ages of the Universe</i>. Free Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-684-86576-8" title="Special:BookSources/978-0-684-86576-8"><bdi>978-0-684-86576-8</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+Five+Ages+of+the+Universe&rft.pub=Free+Press&rft.date=2000&rft.isbn=978-0-684-86576-8&rft.aulast=Adams&rft.aufirst=Fred&rft.au=Greg+Laughlin&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACosmological+decade" class="Z3988"></span></span> </li> <li id="cite_note-Planck_2015-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-Planck_2015_2-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFPlanck_Collaboration2016" class="citation journal cs1">Planck Collaboration (2016). "Planck 2015 results. XIII. Cosmological parameters (See Table 4 on page 31 of pfd)". <i>Astronomy & Astrophysics</i>. <b>594</b>: A13. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1502.01589">1502.01589</a></span>. <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/2016A&A...594A..13P">2016A&A...594A..13P</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%2F201525830">10.1051/0004-6361/201525830</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" 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title="Chronology">Chronology</a></li> <li><a href="/wiki/Duration_(philosophy)" title="Duration (philosophy)">Duration</a> <ul><li><a href="/wiki/Duration_(music)" title="Duration (music)">music</a></li></ul></li> <li><a href="/wiki/Mental_chronometry" title="Mental chronometry">Mental chronometry</a></li> <li><a href="/wiki/Decimal_time" title="Decimal time">Decimal time</a></li> <li><a href="/wiki/Metric_time" title="Metric time">Metric time</a></li> <li><a href="/wiki/System_time" title="System time">System time</a></li> <li><a href="/wiki/Time_metrology" class="mw-redirect" title="Time metrology">Time metrology</a></li> <li><a href="/wiki/Time_value_of_money" title="Time value of money">Time value of money</a></li> <li><a href="/wiki/Timekeeper" title="Timekeeper">Timekeeper</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" 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