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#featured-post-5 article { margin-bottom: 0; } #featured-post-5 h4 { font-size: 2.6rem; font-weight: 600; padding-top: 0; } /* -- */ #media_video-3 { background-color: #f5f5f5; padding: 0px 0px 0px 0px; } @media only screen and (max-width: 800px) { .one-half { margin: 0; width: 100%; } } .home h1.entry-title { display: none; margin-bottom: 0; } .home h2.entry-title { display: none; margin-bottom: 0; } .entry-header::after { display: block; margin: 0 auto 0px; padding-bottom: 0px; width: 10%; border-bottom: none; } #text-6 .textwidget { padding-bottom: 5rem; } .home-section-2 { background-color: #f5f5f5; } #text-13 .widget-wrap a { font-weight: 600; color: #00A0B2; } #text-13 .widget-wrap { font-size: 2.6rem; text-align: left; line-height: 150%; color: #999; } /* ---- HOME Highlights ---- */ #highlights { display: flex; flex-wrap: wrap; align-content: flex-start; justify-content: center; margin-top: -80px; padding-bottom: 0%; } #highlights a { flex-grow: 1; flex-basis: 255px; max-width: 300px; margin: 10px; } #highlights img { width: 100%; } #highlights h3 { font-size: 2.6rem; font-weight: 600; } .home-even .wrap, .home-odd .wrap { max-width: 980px; padding-left: 20px; padding-right: 20px; } p.more-from-category { display: none; } .one-half { padding: 3%; background: black; /* For browsers that do not support gradients */ background: linear-gradient(to bottom, rgba(0,0,0,.1), rgba(0,0,0,.8), rgba(0,0,0,.3)); /* Standard syntax (must be last) */ } .two-sixths { padding: 3%; background: black; /* For browsers that do not support gradients */ background: linear-gradient(to bottom, rgba(0,0,0,.1), rgba(0,0,0,.8), rgba(0,0,0,.3)); /* Standard syntax (must be last) */ } .one-sixth { padding: 3%; background: black; /* For browsers that do not support gradients */ background: linear-gradient(to bottom, rgba(0,0,0,.1), rgba(0,0,0,.8), rgba(0,0,0,.3)); /* Standard syntax (must be last) */ } .home-even.home-section-4.widget-area { background-color: #f8f8f8; margin-top: 0; padding-top: 40px; } .home h2 { font-size: 3.5rem; } .home-section-1 p { font-size: 2.0rem; } .home-section-2 h3.widgettitle.widget-title { display: none; } .home-section-2 h1 { font-size: 4.0rem; } .home-section-2.widget-area { margin-bottom: -60pt; } /* ---- HOME News ---- */ .home-section-4.widget-area { background-color: #f5f5f5; margin-top: 2%; margin-bottom: -100pt; } .home-section-4 h3.widgettitle.widget-title { font-size: 4.0rem; margin-bottom: 30pt; } .home-section-4 h4 { margin-top: -30pt; margin-bottom: -30pt; font-size: 2.0rem; } /* ---- HOME Sponsors ---- */ #custom_html-6 > div { display: flex; } ul.sponsor { display: flex; flex-wrap: wrap; list-style-type: none; align-items: center; justify-content: space-around; } li.sponsor-item { flex: 0 0 35%; margin: 20px; list-style-type: none; } li.sponsor-page-item { flex: 0 0 45%; margin: 12px; list-style-type: none; } .entry-content ul > li.sponsor-item { list-style-type: none; } .entry-content ul > li.sponsor-page-item { list-style-type: none; } @media only screen and (max-width: 800px) { ul.sponsor { flex-direction: column; flex-wrap: wrap; flex: 0 1 180px; align-items: center; max-width: 350px } .post-102 .entry-content p { text-align: center; } li.sponsor-item { margin: 30px; } } #custom_html-6 h3 { color: #999; padding-bottom: 20px; } #text-9 h3 { font-size: 3.3rem; color: #999; } /* CATEGORY -- ARCHIVE */ .category h2 { font-size: 18px; } .category article { margin-bottom: auto } .category div.site-inner { margin-bottom: 10%; } .category #genesis-sidebar-primary.sidebar.sidebar-primary.widget-area { margin-top: 160px; } .category-meet-a-desi-member h2 { font-size: 26px; font-weight: 700; padding-top: 20px; border-top: 2px solid #dedede; } .entry-header, .entry-title a { color: #00a0af; text-align: left; padding-bottom: 1%; font-weight: 600; font-size: 2.6rem;} .archive #genesis-sidebar-primary { background-color: #f8f8f8; padding: 0px; margin-top: 15%; } .archive #genesis-sidebar-primary h3.widget-title { font-size: 2rem; font-weight: 500; padding-bottom: 10px; } .archive #genesis-sidebar-primary h4.entry-title { font-size: 3rem; color: #00a0af; margin-bottom: 0; } .archive .sidebar .entry-title a { font-size: 2rem; color: #00a0af; margin-bottom: 0; } /* ARCHIVE PAGES */ .archive-description, .author-box { border-bottom: none; border-top: none; } .archive-title { font-size: 4.667rem; color: #333; font-weight: 500; line-height: 1; margin-bottom: 0; text-align: left; } .archive-description, .author-box { margin-bottom: 30px; } /* SIDEBAR */ .sidebar li { font-family: open-sans, sans-serif; font-size: 100%; line-height: 1.25; margin-bottom: 5%} .sidebar a:visited { color: #999; } ul#menu-blog, ul#menu-blog-spanish, ul#menu-collaboration, ul#menu-education-outreach, ul#menu-for-scientists, ul#menu-gallery, ul#menu-instrument, ul#menu-instrument-catalan, ul#menu-instrument-italian, ul#menu-instrument-spanish, ul#menu-meet-a-member, ul#menu-meet-a-member-spanish, ul#menu-press, ul#menu-science, ul#menu-science-catalan, ul#menu-science-chinese, ul#menu-science-english, ul#menu-science-french, ul#menu-science-georgian, ul#menu-science-german, ul#menu-science-italian, ul#menu-science-korean, ul#menu-science-portuguese, ul#menu-science-spanish { background-color: #f8f8f8; padding: 8%; } #nav_menu-17 { background-color: #f8f8f8; padding: 8%; } #nav_menu-17 h3 { margin-bottom: 0; } /* PAGES */ h1.entry-title { font-size: 4.8rem; margin-bottom: 6%; text-align: left; } div.photo-summary img { margin-bottom: 4%; } /* FULL-WIDTH */ .full-width .content { padding-right: 0px; font-size: 1.8rem; font-family: open-sans, sans-serif; } .full-width h1.entry-title { padding-left: 0px; } /* MISC */ .institute { font-weight: bold; color: #099; } hr { border-bottom: 1px solid #ddd; } /* EXTERNAL LINKS */ a.ext:after, .ext a:after, h3.ext:after { content: ''; display: inline-block; /* float: right; */ margin-left: 10px; width: 12px; height: 12px; background-image: url(/wp-content/uploads/sites/8/2018/06/ext-1.png); background-size: 24px 12px; background-repeat: no-repeat; background-position: -12px 0; } a.ext.white:after, .ext.white a:after, a.ext:hover:after, .ext a:hover:after { background-position:0 0; } .home-middle .ext:after, .entry-title-link.ext:after { content: ''; display: inline-block; width: 12px; height: 12px; background-image: url(images/ext.png); background-size:24px 12px; background-repeat:no-repeat; background-position:-12px 0; margin-left:8px; float:none; } /* ---- Flex Gallery ---- */ .children { display: flex; flex-flow: row wrap; justify-content: space-around; min-height: 200px; } .child { flex: 0 0 auto; list-style-type: none; width: 30%; padding: 25px; border: solid 1px #ddd; font-size: 1.6rem; } .child a { background-color: #fff; display: block; padding: 0; background-repeat: no-repeat; background-size: contain; background-position: center top; color: #333333; text-decoration: none; text-align: center; position: relative; } .child h3 { text-decoration: none; text-align: center; font-size: 2.3rem; font-weight: 600; /* letter-spacing: 3px; */ color: #fff; line-height: 0; margin-bottom: 0; } /* ---- FOOTER ---- */ .social-links img { height: 40px; padding-right: 20px; } a.footer-button { color: white; padding: 16px; text-align: center; text-decoration: none; display: inline-block; font-size: 16px; margin: 4px 30px 30px 0px; cursor: pointer; border-radius: 8px; border: 1px solid #fff; } .site-footer { display: none; } .footer-widgets a { text-decoration: none; display: inline; } footer .footer-social { margin: 36px 0 24px 0; padding: 0; font-size: 30px; text-align: center; } .copyright { font-size: 70%; padding-top: 20px; } .wp-caption-text { margin-top: 8px; }</style></head> <body class="page-template-default page page-id-12 custom-header header-image content-sidebar genesis-breadcrumbs-hidden genesis-footer-widgets-visible" itemscope itemtype="https://schema.org/WebPage"><div class="site-container"><ul class="genesis-skip-link"><li><a href="#genesis-content" class="screen-reader-shortcut"> Skip to main content</a></li><li><a href="#genesis-sidebar-primary" class="screen-reader-shortcut"> Skip to primary sidebar</a></li><li><a href="#genesis-footer-widgets" class="screen-reader-shortcut"> Skip to footer</a></li></ul><header class="site-header" itemscope itemtype="https://schema.org/WPHeader"><div class="wrap"><div class="title-area"><p class="site-title" itemprop="headline"><a href="https://www.desi.lbl.gov/">Dark Energy Spectroscopic Instrument (DESI)</a></p></div><div class="widget-area header-widget-area"><section id="nav_menu-20" class="widget widget_nav_menu"><div class="widget-wrap"><nav class="nav-header" itemscope itemtype="https://schema.org/SiteNavigationElement"><ul id="menu-main-navigation" class="menu genesis-nav-menu js-superfish"><li id="menu-item-59" class="menu-item menu-item-type-post_type menu-item-object-page current-menu-ancestor current-menu-parent 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system</span></a></li> <li id="menu-item-93" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-93"><a href="https://www.desi.lbl.gov/data-systems/" itemprop="url"><span itemprop="name">data systems</span></a></li> <li id="menu-item-91" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-has-children menu-item-91"><a href="https://www.desi.lbl.gov/bringing-desi-to-life/" itemprop="url"><span itemprop="name">bringing DESI to life</span></a> <ul class="sub-menu"> <li id="menu-item-212" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-212"><a href="https://www.desi.lbl.gov/bringing-desi-to-life/commissioning-instrument/" itemprop="url"><span itemprop="name">commissioning Instrument</span></a></li> <li id="menu-item-213" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-213"><a href="https://www.desi.lbl.gov/bringing-desi-to-life/protodesi/" itemprop="url"><span 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itemscope itemtype="https://schema.org/CreativeWork"><div class="entry-content" itemprop="text"><p data-wp-editing="1"><a href="https://www.desi.lbl.gov/es/redshifts-and-distance-spanish"><img decoding="async" class="alignleft" src="https://www.desi.lbl.gov/wp-content/uploads/sites/8/2019/12/spanish-1-e1576602273893.png" width="50" height="50" /></a><a href="https://www.desi.lbl.gov/fr/redshifts-and-distance-french"><img decoding="async" class="alignleft" src="https://www.desi.lbl.gov/wp-content/uploads/sites/8/2020/03/france-512-e1585601646579.png" width="50" height="50" /></a><a href="//www.desi.lbl.gov/kr/redshifts-and-distance-korean"><img loading="lazy" decoding="async" class="alignleft" src="https://www.desi.lbl.gov/wp-content/uploads/sites/8/2020/09/Korean_flag.png" width="70" height="50" /></a><a href="https://www.desi.lbl.gov/zh/redshifts-and-distance-chinese"><img loading="lazy" decoding="async" class="alignleft" src="https://www.desi.lbl.gov/wp-content/uploads/sites/8/2021/01/chinese-1-e1612247124782.png" width="50" height="50" /></a><a href="https://www.desi.lbl.gov/ka/redshifts-and-distance-georgian"><img loading="lazy" decoding="async" class="alignleft" src="https://www.desi.lbl.gov/wp-content/uploads/sites/8/2021/02/geo-flag-e1613113476346.png" width="50" height="50" /></a><a href="https://www.desi.lbl.gov/pt/redshifts-and-distance-portuguese"><img loading="lazy" decoding="async" class="alignleft" src="https://www.desi.lbl.gov/wp-content/uploads/sites/8/2021/03/pt-br-e1615507733955.png" width="50" height="50" /></a><a href="https://www.desi.lbl.gov/de/redshifts-and-distance-german"><img loading="lazy" decoding="async" class="alignleft" src="https://www.desi.lbl.gov/wp-content/uploads/sites/8/2021/07/de-flag-e1627535531831.png" alt="" width="50" height="50" /></a><a href="https://www.desi.lbl.gov/ca/redshifts-and-distance-catalan"><img loading="lazy" decoding="async" class="alignleft" src="https://www.desi.lbl.gov/wp-content/uploads/sites/8/2021/08/3253480-catalonia-icon-flag_106770-e1629935057530.png" width="50" height="50" /></a><a href="https://www.desi.lbl.gov/it/redshifts-and-distance-italian"><img loading="lazy" decoding="async" class="alignleft" src="https://www.desi.lbl.gov/wp-content/uploads/sites/8/2021/12/flag_italy-600x600.png" width="50" height="50" /></a></p> <p><a href="/wp-content/uploads/sites/8/2018/06/sunset-observatory.jpg"><img loading="lazy" decoding="async" class="size-large wp-image-362 alignnone" src="https://www.desi.lbl.gov/wp-content/uploads/sites/8/2018/06/sunset-observatory-1024x768.jpg" alt="" width="1024" height="768" srcset="https://www.desi.lbl.gov/wp-content/uploads/sites/8/2018/06/sunset-observatory-1024x768.jpg 1024w, https://www.desi.lbl.gov/wp-content/uploads/sites/8/2018/06/sunset-observatory-600x450.jpg 600w, https://www.desi.lbl.gov/wp-content/uploads/sites/8/2018/06/sunset-observatory-768x576.jpg 768w, https://www.desi.lbl.gov/wp-content/uploads/sites/8/2018/06/sunset-observatory-300x225.jpg 300w" sizes="auto, (max-width: 1024px) 100vw, 1024px" /></a></p> <p class="lead">In an expanding Universe, light waves get stretched, increasing their wavelength and shifting them to become more and more red (“redshift”).</p> <p>This is equivalent to the Doppler shift of an object moving away from us, so we often describe this as the recessional velocity. The redshift can be measured by taking the light of the object and spreading it into a rainbow to measure the amount of light at each separate wavelength. Because we know the chemical fingerprint of elements in galaxies, which includes elements such as hydrogen and oxygen, we know that they emit light at certain wavelengths. In the observed spectra—the range of observed wavelengths of light—we measure the light at redder wavelengths and measure the amount of the redshift.</p> <p>Importantly, the further the galaxy is from us, the greater the redshift and the larger the inferred recessional velocity. For nearby objects, this is the famous Hubble law: Velocity is proportional to distance. However, as one looks back to galaxies at much earlier periods of time, the relationship between distance and redshift becomes more complicated. This is directly related to the expansion history of the universe. If the universe has more matter in it then the expansion slows down over time, and high-redshift objects appear closer. Conversely, if the dark energy is causing the expansion to accelerate, then the high-redshift objects appear further away. It was the detection of this effect in the brightness of high-redshift supernovae that led to the discovery of dark energy and earned the 2011 Nobel Prize in physics. And it is this detailed relationship of distance and redshift that is the primary science driver for DESI.</p> <p style="text-align: right"><strong><a href="/mapping-the-universe/">mapping the universe »</a></strong></p> </div></article></main><aside class="sidebar sidebar-primary widget-area" role="complementary" aria-label="Primary Sidebar" itemscope itemtype="https://schema.org/WPSideBar" id="genesis-sidebar-primary"><h2 class="genesis-sidebar-title screen-reader-text">Primary Sidebar</h2><section id="nav_menu-49" class="widget widget_nav_menu"><div class="widget-wrap"><div class="menu-science-english-container"><ul id="menu-science-english" class="menu"><li id="menu-item-406" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-406"><a href="https://www.desi.lbl.gov/science/" itemprop="url">science overview</a></li> <li id="menu-item-228" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-228"><a href="https://www.desi.lbl.gov/cosmology-and-dark-energy/" itemprop="url">cosmology and dark energy</a></li> <li id="menu-item-230" class="menu-item menu-item-type-post_type menu-item-object-page current-menu-item page_item page-item-12 current_page_item menu-item-230"><a href="https://www.desi.lbl.gov/redshifts-and-distance/" aria-current="page" itemprop="url">redshifts and distance</a></li> <li id="menu-item-229" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-229"><a href="https://www.desi.lbl.gov/mapping-the-universe/" itemprop="url">mapping the universe</a></li> <li id="menu-item-231" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-231"><a href="https://www.desi.lbl.gov/the-desi-science-mission/" itemprop="url">the DESI science mission</a></li> <li id="menu-item-232" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-232"><a href="https://www.desi.lbl.gov/the-desi-survey/" itemprop="url">the DESI survey</a></li> <li id="menu-item-233" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-233"><a href="https://www.desi.lbl.gov/imaging-surveys/" itemprop="url">imaging surveys</a></li> </ul></div></div></section> </aside></div></div><div class="footer-widgets" id="genesis-footer-widgets"><h2 class="genesis-sidebar-title screen-reader-text">Footer</h2><div class="wrap"><div class="widget-area footer-widgets-1 footer-widget-area"><section id="custom_html-4" class="widget_text widget widget_custom_html"><div class="widget_text widget-wrap"><div class="textwidget custom-html-widget"><div> <p> <a href="https://desi.lbl.gov/trac/login" class="footer-button">TEAM LOGIN</a></p> <p class="social-links"> <a class="twitter" href="https://twitter.com/desisurvey" target="_blank"><img src="/wp-content/uploads/sites/8/2018/06/twitter-icon@05x.png" alt="twitter"></a>   <a class="item2 ir" href="https://www.instagram.com/desisurvey/?hl=en" target="_blank"><img src="/wp-content/uploads/sites/8/2018/06/instagram-icon@05x.png" alt="instagram"></a>   <a class="item3 ir" href="https://www.facebook.com/DESI-Survey-2104105159914082/?modal=admin_todo_tour" target="_blank"><img src="/wp-content/uploads/sites/8/2018/06/facebook-icon@05x.png" alt="facebook"></a> </p> </div> <p class="copyright"> Copyright © 2018 Dark Energy Spectroscopic Instrument [DESI] </p></div></div></section> </div></div></div><footer class="site-footer" itemscope itemtype="https://schema.org/WPFooter"><div class="wrap"><p>Copyright © 2025 · <a href="http://my.studiopress.com/themes/parallax/">Parallax Pro DESI</a> on <a href="https://www.studiopress.com/">Genesis Framework</a> · <a href="https://wordpress.org/">WordPress</a> · <a href="https://www.desi.lbl.gov/wp-login.php">Log in</a></p></div></footer></div><script type="text/javascript" src="https://www.desi.lbl.gov/wp-includes/js/hoverIntent.min.js?ver=1.10.2" id="hoverIntent-js"></script> <script type="text/javascript" src="https://www.desi.lbl.gov/wp-content/themes/genesis/lib/js/menu/superfish.min.js?ver=1.7.10" id="superfish-js"></script> <script type="text/javascript" src="https://www.desi.lbl.gov/wp-content/themes/genesis/lib/js/menu/superfish.args.min.js?ver=3.4.0" id="superfish-args-js"></script> <script type="text/javascript" src="https://www.desi.lbl.gov/wp-content/themes/genesis/lib/js/skip-links.min.js?ver=3.4.0" id="skip-links-js"></script> <script type="text/javascript" id="parallax-responsive-menu-js-extra"> /* <![CDATA[ */ var genesis_responsive_menu = {"mainMenu":"Menu","subMenu":"Submenu","menuClasses":{"combine":[".nav-header",".nav-primary"]}}; 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