<P> Earliest stages of chronology shown below (before neutrino decoupling) are an active area of research and based on ideas which are still speculative and subject to modification as scientific knowledge improves . </P> <P> "Time" column is based on extrapolation of observed metric expansion of space back in the past . For the earliest stages of chronology this extrapolation may be invalid . To give one example, eternal inflation theories propose that inflation lasts forever throughout most of the universe, making the notion of "N seconds since Big Bang" ill - defined . </P> <Table> <Tr> <Th> Epoch </Th> <Th> Time </Th> <Th> Redshift </Th> <Th> Temperature (Energy) </Th> <Th> Description </Th> </Tr> <Tr> <Td> Planck epoch </Td> <Td> <10 s </Td> <Td> </Td> <Td>> 10 K (> 10 GeV) </Td> <Td> The Planck scale is the scale beyond which current physical theories do not have predictive value . The Planck epoch is the time during which physics is assumed to have been dominated by quantum effects of gravity . </Td> </Tr> <Tr> <Td> Grand unification epoch </Td> <Td> <10 s </Td> <Td> </Td> <Td> (> 10 GeV) </Td> <Td> The three forces of the Standard Model are unified (assuming that nature is described by a Grand unification theory). </Td> </Tr> <Tr> <Td> Inflationary epoch, Electroweak epoch </Td> <Td> <10 s </Td> <Td> </Td> <Td> 10 K...10 K </Td> <Td> Cosmic inflation expands space by a factor of the order of 10 over a time of the order of 10 to 10 seconds . The universe is supercooled from about 10 down to 10 kelvins . The Strong Nuclear Force becomes distinct from the Electroweak Force . </Td> </Tr> <Tr> <Td> Quark epoch </Td> <Td> 10 s...10 s </Td> <Td> </Td> <Td>> 10 K (100 MeV) </Td> <Td> The forces of the Standard Model have separated, but energies are too high for quarks to coalesce into hadrons, instead forming a quark - gluon plasma . These are the highest energies directly observable in experiment in the Large Hadron Collider . </Td> </Tr> <Tr> <Td> Hadron epoch </Td> <Td> 10 s...1 s </Td> <Td> </Td> <Td>> 10 K </Td> <Td> Quarks are bound into hadrons . A slight matter - antimatter - asymmetry from the earlier phases (baryon asymmetry) results in an elimination of anti-hadrons . </Td> </Tr> <Tr> <Td> Neutrino decoupling </Td> <Td> 1 s </Td> <Td> </Td> <Td> 10 K (1 MeV) </Td> <Td> Neutrinos cease interacting with baryonic matter . The spherical volume of space which will become Observable universe is approximately 10 light - years in radius at this time . </Td> </Tr> <Tr> <Td> Lepton epoch </Td> <Td> 1 s...10 s </Td> <Td> </Td> <Td> 10 K...10 K </Td> <Td> Leptons and anti-leptons remain in thermal equilibrium . </Td> </Tr> <Tr> <Td> Big Bang nucleosynthesis </Td> <Td> 10 s...10 s </Td> <Td> </Td> <Td> 10 K...10 K (100 keV...1 keV) </Td> <Td> Protons and neutrons are bound into primordial atomic nuclei, hydrogen and helium - 4 . Small amounts of deuterium, helium - 3, and lithium - 7 are also synthesized . </Td> </Tr> <Tr> <Td> Photon epoch </Td> <Td> 10 s...1.2 × 10 s (380 ka) </Td> <Td> </Td> <Td> 10 K...4000 K </Td> <Td> The universe consists of a plasma of nuclei, electrons and photons; temperatures remain too high for the binding of electrons to nuclei . </Td> </Tr> <Tr> <Td> Recombination </Td> <Td> 380 ka </Td> <Td> 1100 </Td> <Td> 4000 K </Td> <Td> Electrons and atomic nuclei first become bound to form neutral atoms . Photons are no longer in thermal equilibrium with matter and the Universe first becomes transparent . Recombination lasts for about 100 ka, during which Universe is becoming more and more transparent to photons . The photons of the cosmic microwave background radiation originate at this time . The spherical volume of space which will become Observable universe is 42 million light - years in radius at this time . </Td> </Tr> <Tr> <Td> Dark Ages </Td> <Td> 380 ka...150 Ma </Td> <Td> 1100...20 </Td> <Td> 4000 K...60 K </Td> <Td> The time between recombination and the formation of the first stars . During this time, the only source of photons was hydrogen emitting radio waves at hydrogen line . Freely propagating CMB photons quickly (within ~ 500 ka) red - shifted to infrared, and Universe was devoid of visible light . </Td> </Tr> <Tr> <Td> Reionization </Td> <Td> 150 Ma...1 Ga </Td> <Td> 20...6 </Td> <Td> 60 K...19 K </Td> <Td> The most distant astronomical objects observable with telescopes date to this period; as of 2016, the most remote galaxy observed is GN - z11, at a redshift of 11.09 . The earliest "modern" Population III stars are formed in this period . </Td> </Tr> <Tr> <Td> Galaxy formation and evolution </Td> <Td> 1 Ga...10 Ga </Td> <Td> 6...0.4 </Td> <Td> 19 K...4 K </Td> <Td> Galaxies coalesce into "proto - clusters" from about 1 Ga (z = 6) and into Galaxy clusters beginning at 3 Gy (z = 2.1), and into superclusters from about 5 Gy (z = 1.2), see list of galaxy groups and clusters, list of superclusters . </Td> </Tr> <Tr> <Td> Present time </Td> <Td> 13.8 Ga </Td> <Td> 0 </Td> <Td> 2.7 K </Td> <Td> Farthest observable photons at this moment are CMB photons . They arrive from a sphere with the radius of 46 billion light - years . The spherical volume inside it is commonly referred to as Observable universe . </Td> </Tr> <Tr> <Th_colspan="5"> Alternative subdivisions of the chronology (overlapping several of the above periods) </Th> </Tr> <Tr> <Td> Matter - dominated era </Td> <Td> 47 ka...10 Ga </Td> <Td> 3600...0.4 </Td> <Td> 10 K...4 K </Td> <Td> During this time, the energy density of matter dominates both radiation density and dark energy, resulting in a decelerated metric expansion of space . </Td> </Tr> <Tr> <Td> Dark - energy - dominated era </Td> <Td>> 10 Ga </Td> <Td> <0.4 </Td> <Td> <4 K </Td> <Td> Matter density falls below dark energy density (vacuum energy), and expansion of space begins to accelerate . This time happens to correspond roughly to the time of the formation of the Solar System and the evolutionary history of life . </Td> </Tr> <Tr> <Td> Stelliferous Era </Td> <Td> 150 Ma...100 Ga </Td> <Td> 20...− 0.99 </Td> <Td> 60 K...0.03 K </Td> <Td> The time between the first formation of Population III stars until the cessation of star formation, leaving all stars in the form of degenerate remnants . </Td> </Tr> <Tr> <Td> Far future </Td> <Td>> 100 Ga </Td> <Td> <− 0.99 </Td> <Td> <0.1 K </Td> <Td> The Stelliferous Era will end as stars eventually die and fewer are born to replace them, leading to a darkening universe . Various theories suggest a number of subsequent possibilities . Assuming proton decay, matter may eventually evaporate into a Dark Era (heat death). Alternatively the universe may collapse in a Big Crunch . Alternative suggestions include a false vacuum catastrophe or a Big Rip as possible ends to the universe . </Td> </Tr> </Table> <Tr> <Th> Epoch </Th> <Th> Time </Th> <Th> Redshift </Th> <Th> Temperature (Energy) </Th> <Th> Description </Th> </Tr>

In the big bang which particles formed first