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L07_2020-01-31_More-BB-Evidence_Inflation.pdf - Recall:...

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1Recall: Cosmological PrincipalWe don’t reside in a special place within theUniverse;Everyone should see the Universe lookingabout the same as we see it.IsotropicUniverse looks the same no matter inwhich direction you lookHomogeneousUniverse is about the same everywhere1. Darkness of the night sky isevidence for the Big Bang12
2Olbers’sParadox(an analogy):Looking from within aforest that is…1) very large(~infinite)2) well established(~unchanging)3) everywherethe same…then our view willalways intersect with apart of a tree, nomatter where we lookOlbers’sParadoxIf universe were1) infinite2) unchanging3) everywherethe same…then, stars wouldcompletely coverthe nightsky, making it everywhere as bright as the Sun!34
3But if theforest isevolving(#of trees isincreasing ordying out)…then theremay not becompleteblockage ofour view.Night sky isdark becausethe universechanges withtime.Because lighttravels at afinite speed,looking outinto spacelets us seeback to atime whenthere werefewer stars56
4What have we learned?Why is the darkness of the night skyevidence for the Big Bang?If the universe were eternal, unchanging, andeverywhere the same, the entire night skywould be covered with starsThe night sky is dark because we can see backto a time when there were no stars2. The abundances of elements addsfurther support to the Big Bang theory78
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Term
Fall
Professor
buckbym
Tags
Dark Energy, Dark Matter, General Relativity, Big Bang, Cosmic microwave background radiation

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