Early universe Chronology of the universe

1 universe

1.1 supersymmetry breaking (speculative)
1.2 electroweak symmetry breaking , quark epoch
1.3 hadron epoch
1.4 lepton epoch
1.5 photon epoch

1.5.1 nucleosynthesis
1.5.2 matter domination


1.6 recombination
1.7 dark ages

1.7.1 habitable epoch

early universe

after cosmic inflation ends, universe filled quark–gluon plasma. point onwards physics of universe better understood, , energies involved in quark epoch directly amenable experiment.

supersymmetry breaking (speculative)

if supersymmetry property of our universe, must broken @ energy no lower 1 tev, electroweak symmetry scale. masses of particles , superpartners no longer equal, explain why no superpartners of known particles have ever been observed.

electroweak symmetry breaking , quark epoch

between 10 second , 10 second after big bang

as universe s temperature falls below high energy level, believed higgs field spontaneously acquires vacuum expectation value, breaks electroweak gauge symmetry. has 2 related effects:

at end of epoch, fundamental interactions of gravitation, electromagnetism, strong interaction , weak interaction have taken present forms, , fundamental particles have mass, temperature of universe still high allow quarks bind form hadrons.

hadron epoch

between 10 second , 1 second after big bang

the quark–gluon plasma composes universe cools until hadrons, including baryons such protons , neutrons, can form. @ approximately 1 second after big bang neutrinos decouple , begin traveling freely through space. cosmic neutrino background, while unlikely ever observed in detail since neutrino energies low, analogous cosmic microwave background emitted later. (see above regarding quark–gluon plasma, under string theory epoch.) however, there strong indirect evidence cosmic neutrino background exists, both big bang nucleosynthesis predictions of helium abundance, , anisotropies in cosmic microwave background.

lepton epoch

between 1 second , 10 seconds after big bang

the majority of hadrons , anti-hadrons annihilate each other @ end of hadron epoch, leaving leptons , anti-leptons dominating mass of universe. approximately 10 seconds after big bang temperature of universe falls point @ new lepton/anti-lepton pairs no longer created , leptons , anti-leptons eliminated in annihilation reactions, leaving small residue of leptons.

photon epoch

between 10 seconds , 380,000 years after big bang

after leptons , anti-leptons annihilated @ end of lepton epoch energy of universe dominated photons. these photons still interacting charged protons, electrons , (eventually) nuclei, , continue next 380,000 years.

nucleosynthesis

between 3 minutes , 20 minutes after big bang

during photon epoch temperature of universe falls point atomic nuclei can begin form. protons (hydrogen ions) , neutrons begin combine atomic nuclei in process of nuclear fusion. free neutrons combine protons form deuterium. deuterium rapidly fuses helium-4. nucleosynthesis lasts seventeen minutes, since temperature , density of universe has fallen point nuclear fusion cannot continue. time, neutrons have been incorporated helium nuclei. leaves 3 times more hydrogen helium-4 (by mass) , trace quantities of other light nuclei.

matter domination

70,000 years after big bang

at time, densities of non-relativistic matter (atomic nuclei) , relativistic radiation (photons) equal. jeans length, determines smallest structures can form (due competition between gravitational attraction , pressure effects), begins fall , perturbations, instead of being wiped out free-streaming radiation, can begin grow in amplitude.

according lambda-cdm model, @ stage, cold dark matter dominates, paving way gravitational collapse amplify tiny inhomogeneities left cosmic inflation, making dense regions denser , rarefied regions more rarefied. however, because present theories nature of dark matter inconclusive, there yet no consensus origin @ earlier times, exist baryonic matter.

recombination

ca. 377,000 years after big bang



9 year wmap data (2012) shows cosmic microwave background radiation variations throughout universe our perspective, though actual variations smoother diagram suggests.

hydrogen , helium atoms begin form density of universe falls. thought have occurred 377,000 years after big bang. hydrogen , helium @ beginning ionized, i.e., no electrons bound nuclei, (containing positively charged protons) therefore electrically charged (+1 , +2 respectively). universe cools down, electrons captured ions, forming electrically neutral atoms. process relatively fast (and faster helium hydrogen), , known recombination. @ end of recombination, of protons in universe bound in neutral atoms. therefore, photons mean free path becomes infinite , photons can travel freely (see thomson scattering): universe has become transparent. cosmic event referred decoupling.

the photons present @ time of decoupling same photons see in cosmic microwave background (cmb) radiation, after being cooled expansion of universe. around same time, existing pressure waves within electron-baryon plasma — known baryon acoustic oscillations — became embedded in distribution of matter condensed, giving rise slight preference in distribution of large scale objects. therefore, cosmic microwave background picture of universe @ end of epoch including tiny fluctuations generated during inflation (see diagram), , spread of objects such galaxies in universe indication of scale , size of universe developed on time.

dark ages

ca. around 380 thousand – 150 million years after big bang, dark ages. ended around 1 billion years after big bang

before decoupling occurred, of photons in universe interacting electrons , protons in photon-baryon fluid. universe opaque or foggy result. there light not light can observe through telescopes - since then, has been red-shifted visible red (corresponding ~3000 k) radio waves in microwave range (corresponding temperature of 3 k). baryonic matter in universe consisted of ionized plasma, , became neutral when gained free electrons during recombination , thereby releasing photons, creating cmb. when photons released (or decoupled) universe became transparent. @ point, additional radiation emitted 21 cm spin line of neutral hydrogen. there observational effort underway detect faint radiation, in principle more powerful tool cosmic microwave background studying universe.

the dark ages thought have been present around 380 thousand 150 million years after big bang. transitioned , ended around 1 billion years after big bang. october 2010 discovery of udfy-38135539, first observed galaxy have existed during following reionization epoch, gives window these times. galaxy earliest in period observed , distant galaxy ever observed on record of leiden university s richard j. bouwens , garth d. illingsworth uc observatories/lick observatory. found galaxy udfj-39546284 @ time 480 million years after big bang or halfway through cosmic dark ages @ distance of 13.2 billion light-years. more recently, udfy-38135539, egsy8p7 , gn-z11 galaxies found around 380–550 million years after big bang , @ distance of around 13.4 billion light-years.

habitable epoch

ca. 10-17 million years after big bang

the dark ages span period during temperature of cosmic background radiation cooled 4000 k down 60 k. background temperature between 373 k , 273 k, allowing possibility of liquid water, during period of 6.6 million years, 10 17 million after big bang (redshift 137–100). loeb (2014) speculated primitive life might in principle have appeared during window, called habitable epoch of universe .