episode705cosmology

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1、Episode705:CosmologyCosmologyisthestudyoftheorigins,historyandfutureoftheUniverse.ThecurrentlyfavouredmodelistheBigBang.SummaryDiscussion:Thehotbigbang.(10minutes)Discussion:HowoldistheUniverse?(10minutes)Studentquestions:TheageoftheUniverse.(20minutes)Discussion:Cosmicmicrowavebackground.(10

2、minutes)Discussion:ThefutureoftheUniverse.(10minutes)Studentquestions:Criticaldensity.(20minutes)Discussion:Missingmassanddarkenergy.(10minutes)Studentactivity:Olbers’paradox.(20minutes)Discussion:ThehotbigbangImaginerunningafilmoftheUniverse‘backwards’–allmatterandenergywereoriginallyinavery

3、,verydensestate.Allexplodedoutwards=theBigBang(FredHoylecoinedthisname,intendingittobederisive).WhathappenedbeforetheBigBang?Space-timewascreatedattheBigBang;somanycosmologistsarguethatthequestionhasnophysicalmeaning.Atthepresenttime(2005)theoverwhelmingweightofevidencefavourstheHotBigBangthe

4、ory.Thereare3independentpiecesofevidence:·theobservedexpansionoftheUniverse;·theCosmicMicrowaveBackground(CMB)radiation;·thecosmicrelativeabundanceofthelightelements(createdbytheBigBang,ratherthansubsequentlyinstarsorsupernovae).Discussion:HowoldistheUniverse?TAP704-3:Hubble’slawandtheageofth

5、eUniverseAsdiscussedabove,theHubbleconstantgivesusameansofestimatingtheageoftheUniverse.Itis~14billionyearsold.TAP705-1:The‘age’oftheUniverseThusthesizeofthevisibleUniverseissetbyhowfaralightbeamhastravelledsincetheBigBang=c´ageofUniverse=14´109lightyearsor1.3´1026m.Studentquestions:Theageoft

6、heUniverseStudentscanlookatanumberofestimatesoftheageoftheUniverse.21TAP705-2:CalculatingtheageoftheUniverseDiscussion:Cosmicmicrowavebackground(CMB)Spaceisfilledwiththecosmicmicrowavebackgroundradiation.ThisallowsanestimateofhowmuchtheUniversehasstretchedsinceitwasemitted.TAP705-4:Thecosmicm

7、icrowavebackgroundradiationDiscussion:ClosedUniverse–theBigCrunchFlatUniverse–expansionbutslowingOpenUniverse–continuedexpansionRadiusoftheUniverseTimesincetheBigBangThefutureoftheUniverseThisisatopicthatisstillthefocusofresearchanddebate.Ift