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UniverseEighthEditionRogerA.Freedman•WilliamJ.KaufmannIIICHAPTER26CosmologyChapter24and26onlinequizzesdueThursday12/9SkipChapter27FinalExam–Monday12/13,5:30-7:30PMThefinalwillcoverchapters23,24and26only,sameformatasExams1-3LastHW!Whatdoesitmeantosaytheuniverseisexpanding?A.Galaxiesaremovingthroughspaceawayfromeachother.B.Spaceisexpanding,carryinggalaxiesalongwithit.C.Allgalaxiesaremovingawayfromapointatthecenteroftheuniverse.D.Spaceisexpandingbutthegalaxiesarenotcarriedalongwithit,sotheseparationofgalaxiesdoesnotchange.E.Thegalaxiesareallgettinglarger.Q26.2Whatdoesitmeantosaytheuniverseisexpanding?A.Galaxiesaremovingthroughspaceawayfromeachother.B.Spaceisexpanding,carryinggalaxiesalongwithit.C.Allgalaxiesaremovingawayfromapointatthecenteroftheuniverse.D.Spaceisexpandingbutthegalaxiesarenotcarriedalongwithit,sotheseparationofgalaxiesdoesnotchange.E.Thegalaxiesareallgettinglarger.A26.2Galaxiesfurtherawayfromushavelargercosmologicalredshiftsthanthoseclosertous.Whatisthecosmologicalredshift?A.ADopplershiftinwhichthewavelengthofphotonsisincreasedduetothemotionofthegalaxiesawayfromusB.ADopplershiftinwhichthewavelengthofphotonsisdecreasedduetothemotionofthegalaxiesawayfromusC.PhotonstravelingthroughspacehavetheirwavelengthincreasedbecausethespacethroughwhichtheyaretravelingisexpandingD.PhotonstravelingthroughspacehavetheirwavelengthdecreasedbecausethespacethroughwhichtheyaretravelingisexpandingQ26.3Galaxiesfurtherawayfromushavelargercosmologicalredshiftsthanthoseclosertous.Whatisthecosmologicalredshift?A.ADopplershiftinwhichthewavelengthofphotonsisincreasedduetothemotionofthegalaxiesawayfromusB.ADopplershiftinwhichthewavelengthofphotonsisdecreasedduetothemotionofthegalaxiesawayfromusC.PhotonstravelingthroughspacehavetheirwavelengthincreasedbecausethespacethroughwhichtheyaretravelingisexpandingD.PhotonstravelingthroughspacehavetheirwavelengthdecreasedbecausethespacethroughwhichtheyaretravelingisexpandingA26.3WhichofthefollowingstatementsabouttheBigBangmodelofcosmologyarecorrect?A.Theuniversebeganasaninfinitelydensecosmicsingularity.B.TheBigBangcanbedescribedasthebeginningoftime.C.Thesizeoftheobservableuniverseisrelatedtotheageoftheuniverse.D.Duringthefirst10-43secondaftertheBigBang,theuniversewastoodensetobedescribedbytheknownlawsofphysics.E.Allofthesestatementsarecorrect.Q26.6WhichofthefollowingstatementsabouttheBigBangmodelofcosmologyarecorrect?A.Theuniversebeganasaninfinitelydensecosmicsingularity.B.TheBigBangcanbedescribedasthebeginningoftime.C.Thesizeoftheobservableuniverseisrelatedtotheageoftheuniverse.D.Duringthefirst10-43secondaftertheBigBang,theuniversewastoodensetobedescribedbytheknownlawsofphysics.E.Allofthesestatementsarecorrect.A26.6KeyIdeasTheExpansionoftheUniverse:TheHubblelawdescribesthecontinuingexpansionofspace.Theredshiftsthatweseefromdistantgalaxiesarecausedbythisexpansion,notbythemotionsofgalaxiesthroughspace.Theredshiftofadistantgalaxyisameasureofthescaleoftheuniverseatthetimethegalaxyemitteditslight.Itismeaninglesstospeakofanedgeorcentertotheuniverseorofwhatliesbeyondtheuniverse.TheCosmologicalPrinciple:Cosmologicaltheoriesarebasedontheideathatonlargescales,theuniverselooksthesameatalllocationsandineverydirection.KeyIdeasTheBigBang:TheuniversebeganasaninfinitelydensecosmicsingularitythatbeganitsexpansionintheeventcalledtheBigBang,whichcanbedescribedasthebeginningoftime.Theobservableuniverseextendsabout14billionlight-yearsineverydirectionfromtheEarth.Wecannotseeobjectsbeyondthisdistancebecauselightfromtheseobjectshasnothadenoughtimetoreachus.Duringthefirst10-43secondaftertheBigBang,theuniversewastoodensetobedescribedbytheknownlawsofphysics.KeyIdeasCosmicBackgroundRadiationandtheEvolutionoftheUniverse:Thecosmicmicrowavebackgroundradiation,correspondingtoradiationfromablackbodyatatemperatureofnearly3K,isthegreatlyredshiftedremnantofthehotuniverseasitexistedabout380,000yearsaftertheBigBang.Thebackgroundradiationwashotterandmoreintenseinthepast.Duringthefirst380,000yearsoftheuniverse,radiationandmatterformedanopaqueplasmacalledtheprimordialfireball.Whenthetemperatureoftheradiationfellbelow3000K,protonsandelectronscouldcombinetoformhydrogenatomsandtheuniversebecametransparent.Theabundanceofheliumintheuniverseisexplainedbythehightemperaturesinitsearlyhistory.KeyIdeasTheGeometryoftheUniverse:Thecurvatureoftheuniverseasawholedependsonhowthecombinedaveragemassdensity0comparestoacriticaldensityc.If0isgreaterthanc,thedensityparameter0hasavaluegreaterthan1,theuniverseisclosed,andspaceisspherical(withpositivecurvature).If0islessthanc,thedensityparameter0hasavaluelessthan1,theuniverseisopen,andspaceishyperbolic(withnegativecurvature).If0isequaltoc,thedensityparameter0isequalto1andspaceisflat(withzerocurvature).KeyIdeasCosmologicalParametersandDarkEnergy:Observationsoftemperaturevariationsinthecosmicmicrowavebackgroundindicatethattheuniverseisflatornearlyso,withacombinedaveragemassdensityequaltothecriticaldensity.Observationsofgalaxyclusterssuggestthattheaveragedensityofmatterintheu