Age,Evolu+on,andSizeoftheCosmos
11.04.2016
Ma?hewSzydagis
1
LetThereBeaBigBang!
•  Let’sstartatthestart(13.82billionyears
ago).Buthowdoweknowtheageofthe
universetosuchhighprecisiontoday?
•  Variousindependentmethods
–  Differingmodelsofcosmicevolu+onmake
uniquepredic+onsforthepa?ernofthe
CosmicMicrowaveBackgroundRadia+on.
AmountofphotonredshiVcanvary
–  Cepheidvariablestars,TypeIasupernova
explosions,etc.allowustorobustly
es+matethevalueofHubble’sconstant.
Wecanthenreversetheexpansionofthe
universeonpaperwithmathema+cs
–  Densityover+me:infiniteatbeginning
–  Wecanfindtheoldeststarsanduse
knowledgeofstellarevolu+on(for
example,whitedwarfcooling)togeta
lowerboundwithinO(billion)yearsofthe
beginning(also,globularstarclusters)
•  Allagreewithintheuncertain+es,wow!!!
BrianPowell.ThisworkislicensedunderCrea%veCommons3.0
spaceplasma.tumblr.com
Credit:NASA,S.Charbinet
2
•  Popularsciencebook
WrinklesinTimeby
GeorgeSmootwasa
significantinfluence
upontheformand
styleoftoday’sslides
PhotoofG.SmootforJonBashor,LBNL
3
Origins
•  Thegreatunknown
•  Ablackhole,asingularity?
Naked(noeventhorizon)?
•  Zero-energyquantum
fluctua+on?
•  Apre-geometryoffoam-like
space-+mewhoselawsof
physicsarenotyetknown
•  Neednewphysicsto
describeandexplain
0seconds
Time
Temperature Infinity*
Infinity**
Energy
BlackHolesandTimeWarpsbyKipThorne
*UnitoftemperaturewillbeKelvin.Room
temperatureis~300K.Absolutezero(0K:
lowestpossible,nomo+on)is-273°C,-459°F
**Theunitofenergywillbeelectron-Volts(eV).
1eVistheamountofkine+cenergygainedby
anelectronexperiencinganelectricalpoten+al
ofexactly1Volt(V).Couchedinafamiliarterm,
1Calorie=4,184Joules(J)=2.611x1022eV
4
EndofQuantumGravityEpoch
10-43seconds
1032Kelvin
1028eV(Planck
energyscale)
•  Thestrongnuclear,weaknuclear,andelectromagne+c
forcesareunifiedintooneindis+nguishableforce.
•  ThisperiodisoVenreferredtoastheGrandUnifica+on
(Theory)orGUTEpoch.EndsaVer“Planck+me”(~5x10-44s)
•  Duringthisepoch,therelikelywasaveryrapid,accelera+ng
expansionoftheuniverse(thecosmicinfla+on).This
infla+onmadeouruniverseverylargeandflat,butalso
producedripplesinthespace+meitwascrea+ng.
5
EndofGUT/Infla+onaryEpoch
10-34s
1027K
1023eV
•  Thestrongforcebecomesdis+nctfromtheweakand
electromagne+cforces:endofgrandunifica+onofforces.
•  Theuniverseisaplasmaofquarks,gluons,electrons,
photons,neutrinos,andotherpar+cles.
•  Infla+onendsandtheexpandinguniversecoasts,gradually
slowingitsexpansionunderthepullofgravity.
•  At10-13s/1017K/1013eVenergyperpar+cleoftheLHC
(LargeHadronCollider)acceleratoratCERNinEurope
6
EndofElectroweak/QuarkEpoch
10-10s
1015K
1011eV
•  Electromagne+c&weakforcesseparate(10-12s)
•  Anexcessofonepartinabillion(athousand
million)ofma?eroveran+ma?erhasdeveloped.
•  Quarksareabletomergetoformprotonsand
neutrons:nolongerinquark-gluonplasma(10-5s)
•  Positronsfinishedannihila+ngtogammas(10-6s)
7
EndoftheNeutrinoEquilibrium
1second
1010K
106eV
•  Neutrinosdecouple(moreprecisely,0.2s)
•  AVerelectron-positronannihila+onresidual
electronsandcosmicbackgroundradia+onmain
ac+vecons+tuentsontheuniverse
•  Ra+oofneutronstoprotonsisnowfrozen
8
EndoftheLeptonEpoch
3minutes
109K
105eV
•  Protonsandneutronsareabletobindtogethertoformnucleisincetheir
bindingenergyisnowgreaterthanthecosmicbackgroundradia+on
energy,sothebackgroundoflight(photons)can’tbreakthemupanymore
•  Arapidsynthesisoflightnucleioccurs–firstdeuterium(heavyhydrogen:
oneprotonandoneneutron),thenheavierelements,primarilyheliumbut
uptolithium(threeprotonsandfourneutrons)nuclei.
•  About75%ofthenucleiarehydrogen(oneproton)and25%arehelium
(twoprotonsandtwoneutrons);onlyasma?eringareanotherelement.
Theheavierelementsarelaterformedbynuclearburninginstars.
9
EndofthePhotonEpoch
380,000years
3,000K/°Celsius
0.25eV
•  Ma?er(atoms)beginstodominateoverradia+on
(equaldensitypoint)at~1,000yearsaVertheBigBang
•  Ma?erandthecosmicbackgroundradia+ondecouple
aselectronsbindwithnucleitomakeneutralatoms.
•  Theuniversebecomestransparenttothecosmic
backgroundradia+on,makingitpossibleforCOBE,
WMAP,andPlanckspacecraVtomapthisepochoflast
sca?ering(alsogiventhenameofrecombina+on).
10
EndoftheStarlessEpoch
1billionyears
18K/-255°C
1.5e-3eV
•  Clustersofma?erhaveformedfromtheprimordialripplestoform
thefirststars,re-ionizingtheuniverseandbringingbackthenuclear
fusionprocesses;soonveryfirstgalac+cnuclei,quasars.
•  Intheinteriorofstars,theburningoftheprimordialhydrogenand
heliumnucleisynthesizestheheaviernucleisuchascarbon,nitrogen,
oxygen,andiron.Cloudsofhydrogencollapseduetogravity.
•  Elementsaredispersedbystellarwindsandsupernovaexplosions,
makingnewstars,planets,andlifepossible.Weareofstarmaterial
•  At~2-billion-yearmarkfirstproto-galaxies,galaxies,supernovae
11
Uptothecontemporaryera
13.8billionyears
2.725K/-270°C
2e-4eV
•  5billion:galaxyclusters,superclusterstakeshape.Heavyatoms
•  9.1billion:Oursolarsystemcondensedfromtheremnantsof
earlierstars.Chemicalprocesseshavelinkedatomstogetherto
formmoleculeslikeDNA,thencomplicatedsolidsandliquids.
•  ~10billion:firstlife-forms(onEarth)about4billionyearsagowow
•  NOW:Humankindhasemergedfromthedustofthestarsto
contemplatetheuniversesurroundingit--thinking,pondering…
~
12
TheSizeofOurUniverse
•  Thevisiblepartoftheuniverseis93billionlight-yearsin
diameter(spheredefinedbyhowfarlighthasbeenableto
travelsincethebeginning)
–  Wecandeterminethisbyageandexpansionrateandspeedof
light.Thenaïveanswerof13.8billionlight-yearswrongbecause
spaceexpandsfasterthanthespeedoflight
–  Thisdoesnotimplyuniverseisfiniteandspherical
•  En+reuniverseisatleast10trillionlight-years“across”but
maybeinfinite.Basedongeometrywearerightonthe
borderbetweenfinite(oppositeofgoingonforever–
havingaboundaryofsomekindwithcountablymany
galaxiesandstars)andinfinite
–  Occam’srazor:sameoutsidevisiblepartasinside.Samelaws
•  Wecannotnow(atleastnotasofyet!)haveadefini+ve
answeronthesizeofthetotaluniverse,whiletheremay
beothersuniversesbeyondit…
13