{"id":18519,"date":"2018-05-16T01:13:16","date_gmt":"2018-05-15T17:13:16","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/how-number-crunchers-could-help-crack-the-cosmological-mystery-of-dark-energy\/"},"modified":"2018-05-16T01:13:16","modified_gmt":"2018-05-15T17:13:16","slug":"how-number-crunchers-could-help-crack-the-cosmological-mystery-of-dark-energy","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/how-number-crunchers-could-help-crack-the-cosmological-mystery-of-dark-energy\/","title":{"rendered":"How number crunchers could help crack the cosmological mystery of dark energy"},"content":{"rendered":"<figure id=\"attachment_420073\" aria-describedby=\"caption-attachment-420073\" style=\"width: 630px\" class=\"wp-caption aligncenter\"><img fetchpriority=\"high\" decoding=\"async\" class=\"size-full-width wp-image-420073\" src=\"https:\/\/cdn.geekwire.com\/wp-content\/uploads\/2018\/05\/180515-perlmutter-630x422.jpg\" alt=\"Saul Perlmutter\" width=\"630\" height=\"422\" srcset=\"https:\/\/cdn.geekwire.com\/wp-content\/uploads\/2018\/05\/180515-perlmutter-630x422.jpg 630w, https:\/\/cdn.geekwire.com\/wp-content\/uploads\/2018\/05\/180515-perlmutter-768x514.jpg 768w, https:\/\/cdn.geekwire.com\/wp-content\/uploads\/2018\/05\/180515-perlmutter-1260x844.jpg 1260w\" sizes=\"(max-width: 630px) 100vw, 630px\"><figcaption data-nosnippet=\"\" id=\"caption-attachment-420073\" class=\"wp-caption-text\">Berkeley astrophysicist Saul Perlmutter discusses the implications of the universe\u2019s accelerating expansion at the University of Washington. (GeekWire Photo \/ Alan Boyle)<\/figcaption><\/figure>\n<p>Big data just might give astronomers a better grip on the answer to one of the biggest questions in physics: Exactly what\u2019s behind the mysterious acceleration in the expansion rate of the universe, also known as dark energy?<\/p>\n<p>And that means the number crunchers at the University of Washington\u2019s DIRAC Institute have their work cut out for them.<\/p>\n<p>The role of data analysis in resolving the mystery came to the fore on Monday evening during a talk given at the DIRAC Institute\u2019s first-ever open house on the UW campus. The speaker was none other than Berkeley astrophysicist Saul Perlmutter, who won a share of the Nobel Prize in physics in 2011 for finding the first evidence of dark energy.<\/p>\n<p>That first evidence came from years\u2019 worth of painstaking observations that were made for the Supernova Cosmology Project. Perlmutter and his colleagues scanned the skies, looking for a particular type of stellar explosion known as a Type 1A supernova. Such supernovae have a characteristic brightness and spectral signature, and can thus be used as \u201cstandard candles\u201d for judging how far away they are and how fast they\u2019re moving away from us.<\/p>\n<p>By correlating their distance (as measured by brightness) and their outward velocity (as measured by the Doppler shift in the wavelength of their starlight), the research team could see how the expansion rate of the universe has varied over the course of billions of years.<\/p>\n<p>The astronomers expected to find that the rate was either constant or slowing down&nbsp;\u2014 but they were gobsmacked to discover that the rate is speeding up. Perlmutter\u2019s group, and a rival group led by Johns Hopkins University\u2019s Adam Riess and Australian National University\u2019s Brian Schmidt, published their&nbsp; results simultaneously in 1998 and ended up sharing the Nobel three years later.<\/p>\n<p><iframe title=\"What is Dark Matter and Dark Energy?\" src=\"https:\/\/www.youtube.com\/embed\/QAa2O_8wBUQ?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen=\"\" data-ratio=\"0.5625\" data-width=\"800\" data-height=\"450\" style=\"display: block; margin: 0px; width: 800px; height: 450px;\"><\/iframe><\/p>\n<p>It didn\u2019t take long for theorists to come up with hypotheses to explain dark energy. Some of the hypotheses propose that it\u2019s a fundamental force that changes over time&nbsp;\u2014 a quality variously known as quintessence, or k-essence, or phantom energy.<\/p>\n<p>Others suggest it\u2019s simply a basic feature of empty space that has to be taken into account as a cosmological constant. That was an idea that Albert Einstein initially considered for his general theory of relativity, but later discarded.<\/p>\n<p>Or it could be that general relativity is wrong, even though the theory has passed every observational test since Einstein came up with the theory in 1915.<\/p>\n<p>\u201cThis is the kind of thing that scientists love,\u201d Perlmutter said. \u201cPhysicists live for finding the universe caught in the act of doing something completely bizarre.\u201d<\/p>\n<p>The problem is, there aren\u2019t yet enough supernova observations to determine which hypotheses stand a chance of being true, and which can be thrown out. Fortunately, more data is on the way.<\/p>\n<p>More than two dozen supernovae have been detected in extremely distant galaxy clusters, thanks to a Hubble Space Telescope observational campaign known as \u201cSee Change.\u201d So far, the details about the See Change supernovae have been \u201cblinded\u201d to ensure that the researchers don\u2019t skew their findings.<\/p>\n<p>\u201cIt\u2019s too easy to fool yourself if you let yourself see the results while you\u2019re still doing all the designing and testing,\u201d Perlmutter explained. \u201cI wish that more people understood why you don\u2019t look at things and assume you know the answer. It seems to me that\u2019s an important message for the political world as well.\u201d<\/p>\n<p>Perlmutter said the team is getting ready to unblind the results within the next month or so.<\/p>\n<p>The See Change data set and other analyses using existing data could help theorists fine-tune their hypotheses, but it won\u2019t be enough to start ruling out hypotheses. \u201cWe need the next generation of technology to do that,\u201d Perlmutter said.<\/p>\n<p>That\u2019s an opportunity for the DIRAC Institute, where \u201cDIRAC\u201d stands for Data Intensive Research in Astrophysics and Cosmology. \u201cIt\u2019s a great time to begin an institute like this,\u201d Perlmutter said.<\/p>\n<p>The institute\u2019s researchers are gearing up to analyze huge amounts of sky survey data from the Zwicky Transient Facility in California, and the Large Synoptic Survey Telescope in Chile. The ZTF project is just starting to get observations into the pipeline, and eventually it\u2019s expected to add 4 terabytes of data every night. The LSST, which is due to come online in the early 2020s, will produce about 20 terabytes\u2019 worth of imagery nightly.<\/p>\n<p>\u201cI think we should expect surprises with these new data sets,\u201d Perlmutter said.<\/p>\n<p><iframe title=\"DiRAC Institute Introduction\" src=\"https:\/\/player.vimeo.com\/video\/270004468?dnt=1&amp;app_id=122963\" frameborder=\"0\" allow=\"autoplay; fullscreen; picture-in-picture; clipboard-write; encrypted-media; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" data-ratio=\"0.5625\" data-width=\"800\" data-height=\"450\" style=\"display: block; margin: 0px; width: 800px; height: 450px;\"><\/iframe><\/p>\n<p>It\u2019s hard for anyone, even a Nobel-winning physicist, to anticipate what kind of surprises the universe will come up with. But Perlmutter hazarded a guess.<\/p>\n<p>One thing to look for is a cosmic transition that occurred about 5 billion years ago, when the universe\u2019s expansion rate started speeding up significantly.<\/p>\n<p>\u201cWe\u2019d love to see slight differences in how that happened, that would be the hallmarks of, let\u2019s say, a decaying field that\u2019s part of the explanation for why it\u2019s accelerating,\u201d Perlmutter said.<\/p>\n<p>\u201cAt this stage, when you ask the theorists, they don\u2019t give you much to go on. The differences in the theories are quite small, and then they also throw in 50 different theories that are all very similar to each other,\u201d he said. \u201cBut I think what we\u2019re hoping is, if you saw something that looked like some behavior that had to be explained \u2014 it would be fodder for an \u2018aha\u2019 moment.\u201d<\/p>\n<p>If the dark-energy mystery could be resolved, Perlmutter and his fellow physicists might feel more comfortable foreseeing the long-term future of the cosmos. Will it fizzle out into eternal darkness, which is currently the leading hypothesis? Or are there as-yet-undetected factors that will slow the universe to a halt, and then perhaps bring everything crashing back together in a reverse big bang?<\/p>\n<p>Perlmutter can\u2019t yet say whether even the ZTF and LSST observations will provide a rock-solid answer.<\/p>\n<p>\u201cBut I\u2019m not that disappointed,\u201d he said. \u201cI think a good mystery is almost as good as&nbsp;\u2014 well, maybe better than \u2014 a good answer.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Berkeley astrophysicist Saul Perlmutter discusses the implications of the universe\u2019s accelerating expansion at the University of Washington. (GeekWire Photo \/ Alan Boyle) Big data just might give astronomers a better grip on the answer to one of the biggest questions in physics: Exactly what\u2019s behind the mysterious acceleration in the expansion rate of the universe, [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[2050,4366,4570,5084,4368],"class_list":["post-18519","post","type-post","status-publish","format-standard","hentry","category-news","tag-cosmology","tag-dirac-institute","tag-physics","tag-supernova","tag-university-of-washington"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/18519"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=18519"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/18519\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=18519"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=18519"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=18519"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}