The History of the Universe

123 Pages·2016·2.314 MB·English

by  David H. Lyth (auth.)

David H. Lyth
The History
of the
Universe
Astronomers’ Universe
Moreinformationaboutthisseriesathttp://www.springer.com/series/6960
David H. Lyth
The History of the Universe
123
DavidH.Lyth
Physics
LancasterUniversity
Lancaster,UnitedKingdom
ISSN1614-659X ISSN2197-6651 (electronic)
Astronomers’Universe
ISBN978-3-319-22743-6 ISBN978-3-319-22744-3 (eBook)
DOI10.1007/978-3-319-22744-3
LibraryofCongressControlNumber:2015950857
SpringerChamHeidelbergNewYorkDordrechtLondon
©SpringerInternationalPublishingSwitzerland2016
Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof
thematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation,
broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionorinformation
storageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilarmethodology
nowknownorhereafterdeveloped.
Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublication
doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant
protectivelawsandregulationsandthereforefreeforgeneraluse.
Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationinthisbook
arebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishernortheauthorsor
theeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinorforany
errorsoromissionsthatmayhavebeenmade.
Coverillustration:CosmicTimelineIllustration.
Imagecredit:NASA/CXC/M.Weiss.Usedwithkindpermission.
Printedonacid-freepaper
Springer International Publishing AG Switzerland is part of Springer Science+Business Media
(www.springer.com)
Foreword
The way we view our world is changing dramatically. In the beginning of the
previouscentury,we did notevenknowthatother galaxiesexist;some prominent
astronomersthoughtthattheMilkyWaygalaxyisthewholeUniverse.Indeed,our
galaxyisincrediblylarge.Itconsistsofaboutahundredbillionstars,manyofwhich
haveplanetarysystems.Can we imagineanythingbiggerthanthat?Well, nowwe
knowthatthereareaboutahundredbillionofgalaxiesintheobservablepartofthe
Universe.
ForalongtimepeoplebelievedthattheUniverseisstatic.Indeed,whatelsecould
itbe?Whenwestudyphysicsatschool,ourteachersshowusathree-dimensional
referenceframewithaxeslabeledbyx,y,andzandexplainhowonecandescribe
motion of particles with respect to it. This suggests that space and time are just
a static set of coordinates. This picture was challenged by Albert Einstein in his
generaltheoryof relativity,butthe consequencesof this changewere so dramatic
that evenEinstein could notfully appreciate it. When a mathematicianAlexander
Friedmannsolved Einstein’s equationsand foundthat they describe an expanding
Universe,Einsteinatfirstthoughtthatthiswasamistake,andthenheattemptedto
modifyhisowntheoryinanefforttomaketheUniversestatic.
Later on, thanks to the observations made by Edwin Hubble, we learned that
galaxies move away from each other, and the theory of an expanding Universe
became universally accepted. Gradually it evolved into the theory of the hot Big
Bang,describingthecreationoftheUniverseasanexplosionfromthecosmological
singularity.TheUniversewassupposedtobehavelikeahugeballoffireexpanding
inalldirectionsandcoolingdown.Theechoofthisprimevalexplosionwascaptured
in1965andcalledtheCosmicMicrowaveBackgroundRadiation(CMB).Butwhere
wastheUniverseexpandingfrom?ThetheoryofthehotBigBangassumedthatthe
total number of elementary particles, which constitute all matter in the Universe,
didnotchangemuchsincethemomentofitscreation.Buthowcouldithappenthat
in the beginning there was no Universe and then suddenly all particles necessary
forcreationof billionsof galaxiesemergedfromnowhere?And notonlythat,but
thiswasdoneina rather“orderly”way:Densityofmatterin farremovedpartsof
v
vi Foreword
theworldispracticallythesame,asifthenewbornUniversewaspolishedwithan
incredibleaccuracybeforetheBigBangexplosion.
In the 1980s, the theory of the hot Big Bang was replaced by inflationary
theory. In the beginning, it looked like a science fiction story. According to this
theory, the newborn Universe was in an energetic vacuum-like state. Most of the
energy was contained in a special kind of matter called “scalar field.” Less than
a milligram of such matter is sufficient to create all matter in our Universe after
an explosive exponentially rapid expansion of space called inflation. This rapid
expansionstretchedallpreviouslyexistinginhomogeneitiesandmadetheUniverse
hugeandnearlyexactlyuniform.
Thiscouldseemobviouslywrong:Howcoulditbepossibletocreateeverything
from practically (or literally) nothing? What’s about energy conservation? Is it
possible for the Universe to expand so fast that its distant parts move away from
each other with the speed faster than the speed of light? As if to add insult to
injury, cosmologists proposed that galaxies were created due to amplification of
tinyquantumfluctuationsproducedduringinflation.Manypeopleobjected,saying
that nothing classical could be created from quantum. And yet, during the last
30yearsthistheoryhaspassednumeroustheoreticalconsistencychecks,andmany
of its predictions have been already confirmed by cosmological observations. It
is gradually becoming the leading cosmological paradigm for the description of
creationoftheUniverseandformationofitslarge-scalestructure.
Oneofthemostunexpectedconsequencesofinflationarytheoryisthatquantum
fluctuationsresponsibleforgalaxyformationssometimesmaybepowerfulenough
tocreatenewpartsofinflationaryUniverse,renderingtheUniverseasahugeeter-
nallygrowingself-reproducingfractal.InflationaryUniversebecomesamultiverse,
consistingofmanyexponentiallylargepartswithdifferentproperties.
Andeachofthesepartshasmanysecretswhichwearejustbeginningtouncover.
PreviouslywethoughtthattheUniverseisguidedbythefamousprinciple“whatyou
see is what you get.” But cosmologicalobservationshave shownthat we see only
about5%ofallmatterinourpartoftheUniverse.Approximately27%ofallmatter
isinaninvisiblestatecalleddarkmatter,and68%isinyetanotherinvisiblestate,
calleddarkenergy.
Recent progress in this area is so significant that following it is quite difficult.
Most of the new information is spread among thousands of scientific papers. It
is summarizedin some technicalbookswritten for cosmologistsactively working
inthefield.Twoofsuchbooks,CosmologicalInflationandLarge-ScaleStructure
and The PrimordialDensity Perturbation: Cosmology, Inflationand the Origin of
StructurebyDavidLythandAndrewLiddle,achievedtheirgoalbeautifully,helping
to educatea new generationof physicistsin all mattersrelated to cosmology.The
success of these books was not surprising: Both of their authors are prominent
scientists. David Lyth is one of the leading authorities in inflationary cosmology
andthetheoryofinflationaryperturbationsresponsibleforcreationofgalaxies.His
workscreatedanewlanguagewhichisoftenusedasabridgebetweentheoristsand
observers.
Foreword vii
The goalofthe bookby David LythThe History ofthe Universe is to describe
the new vision of the world in a simple, accessible, and reliable way. This is
not an easy task. One cannot achieve it without making many simplifications
which can easily produce a nice but blurry and imprecise image. That is why it
isespeciallyimportantto havea realexperttodothiswork.Astheauthorsaysin
thePreface,“theaccountofphysicsismeanttobeaccessibletoanybody.”However,
deep knowledge and understandingof the material as well as the experiencewith
presentingthismaterialinhisearlierbookshasallowedDavidLythtomakejustthe
rightamountofsimplificationtokeepthebookTheHistoryoftheUniversereadable
andunderstandablebyeveryone.Andyet the bookis veryaccurate,rigorous,and
informative; it provides a unique perspective, which, I believe, will make it very
usefulevenforthosewhoknowcosmologywell.
AndreiLinde

Preface
This book is about the history of the Universe, not only what happened but why
it happened. In other words, it is about cosmology which is actually a branch of
physics.
Ever since I first met them, I have been fascinated by physics and cosmology.
With physics that was when I was 11 years old and with cosmology when I was
43in1983.BeforeencounteringcosmologyIworkedonthetheoryofelementary
particles, whose collisions are observed at machines like the one at CERN in
Geneva. That turned out to be useful, because the collisions now observed in the
laboratoryhappenedalsointheearlyUniverse.
When I first encounteredcosmology,it had recently been suggested that all of
thestructureintheUniverseoriginatedasarandomquantumprocess,takingplace
at some very early time. The idea was both simple and remarkable,and I quickly
publishedsomeresearchonit.Thatwaseasierinthosedaysthanitisnowbecause
the subject had hardly any previous history and there were only a few relevant
papers.
More research followed, and along the way a couple of textbooks with my
colleague Andrew Liddle. Those are academic books aimed mostly at other
researchers. This book, by contrast, is intended to be accessible to everyone. As
we need physicsfor cosmology,a few chaptersof the book are devoted to it, and
morephysicsis introducedas we goalong.If youknowphysicsalready,youwill
beabletoskipsomeorallofthosebits.
I have many people to thank for questions that prompted the writing of this
book.Forinvaluablecommentsondraftsofthebookatvariousstages,IthankPhil
Furneaux, Brian Martin, Vince Higgs, my wife Margaret, and my brother Peter.
Finally,IamindebtedtopeopleinLancasterforhelpwiththefigures,inparticular
LingfeiWangwhosecontinuousattentionhasbeeninvaluable.
Lancaster,UK DavidH.Lyth
ix