Big Bang Theory states that a substance of which the universe was once in a singular state.This condition is determined by infinite density and temperature of the substance.At some point in time the universe emerged from the big bang of the particles of matter in the singular state.Since the universe is continuously expanded and cooled.
first big bang theory was called "dynamic evolving model."The term "big bang" was first used by Fred Hoyle in 1949.After the publication of works F.Hoyla, this definition has become widespread.
According to the big bang theory the universe is constantly expanding.The moment when this process started, it is considered the birth of the universe.Presumably this occurred at about 13.7
7 billion years ago.In the first instant of the big bang all the matter was a hot mixture of particles and antiparticles photons.Antiparticles encountered particles and converted into photons, which instantly turned into a particle and antiparticle.This process is gradually subsided, due to the cooling of the universe.Particles and antiparticles began to disappear, because the transformation into photons can occur at any temperature and decay into the antiparticles and particles only at high.
development of the universe is divided into the following age: hadron, leptons, photons, and the star.Hadron era - a period of the beginning of the universe.At this stage, the universe consisted of elementary particles - hadrons.After a millionth of a second after the birth of the universe the temperature dropped, and the materialization of particles stopped.Most never show such a nuclear force, as in the hadron era.The duration of the hadron era was one ten-thousandth of a second.
Leptonic hadron era followed.It began with the collapse of the last Andronov and ended after a few seconds.At this time, I stopped the materialization of electrons and positrons.It is beginning of the neutrino particle.The whole universe is filled with a huge number of neutrinos.
After lepton era came the era of the photon.The most important part of the universe after the lepton era become photons.Since the universe is constantly expanding, the density of photons and particles decreased.The rest energy of the expansion of the universe does not change the energy of photons decreases during expansion.Prevalence of photons over other particles decreases, and gradually disappeared.It ended photon era and the period of the big bang.
After the photon era, a period reign of particles - a stellar era.It continues to this day.Compared to previous eras, the era of stellar evolution seems slow.The reason for this - low temperature and density.