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Big Bang era
subject			fact

Big Bang era	is a kind of era
	has definition A theoretical era postulated to have occurred after the Big Bang. They are in order : Planck era hadron era inflation era lepton era nucleosynthetic era radiation era matter era
	has start time relative to the Big Bang
	has temperature
	is preceded by
	is followed by
era	has duration
event	has synonym world point
	has time of occurrence

Kinds of Big Bang era :

• Big bang crossover effect (3 facts) - The epoch during the radiation era when the universe switched from being radiation-dominated to being matter-dominated.
• hadron era (9 facts) (hadron barrier) - The Big Bang era when the Universe was matter-dominated, containing many hadrons in equilibrium with the radiation field and when kT ≈ m_π. The hadron era ended when the characteristic photon energy fell below the rest mass of a pion or π-meson (270 electron masses), and very few hadrons remained (about one hadron for every 10⁸ photons)., The Big Bang era during which quantum and general-relativistic effects are expected to modify each other in an unknown way.
• inflation era (7 facts) - The idea that, when it was a fraction of a second old, the universe expanded dramatically. If inflation is correct, then the mass density of the universe (Ω) should be 1.0, if there is no cosmological constant; if there is a cosmological constant and inflation is correct, the sum of Ω and the cosmological constant (λ) should be 1.0., Big Bang era in which the spacetime continuum underwent an intense period of exponential expansion, in response to the separation of the strong nuclear force from the electroweak force. This idea solves the flatness and horizon problems., Big Bang era in which the universe is driven into exponential expansion by the repulsive gravitational field created by a false vacuum. The inflation would end with the decay of the false vacuum. Although the inflation would occur in far less than a second, it could account for the "bang" of the big bang theory, it could explain the origin of essentially all the matter in the observed universe, and it can solve the horizon problem and the flatness problem. It could also generate the density perturbations that would later become the seeds for galaxy formation., Big Bang era in which universe undergoes a brief burst of enormous expansion., Big Bang era in which the infant universe went through a brief period of extremely rapid (exponential) expansion, after which it settled back into the more leisurely rate of expansion of the standard model. The period of rapid expansion began and ended when the universe was still much less than a second old, yet it provides a physical explanation for the flatness and horizon puzzles. The inflationary universe model also suggests that the universe is vastly larger than the portion of it that is visible to us. (See exponential expansion.)
• lepton era (7 facts) - The Big Bang era when the temperature had dropped to about 10¹² K and when the Universe consisted mainly of leptons and photons. It lasted until the temperature fell below 10¹⁰ K. At this stage, the characteristic photon energy fell below the rest mass energy of an electron, and the abundance of electron-positron pairs fell by many orders of magnitude. Only one electron survived for every 10⁸ photons. The universe was subsequently radiation-dominated (substantial numbers of neutrinos were also present, but they did not interact directly with the matter or the radiation).
• matter era (14 facts) (recombination era, decoupling era) - The Big Bang era when the temperature had dropped to 3000 K, at which time the recombination of hydrogen became possible. The plasma of free electrons and nuclei condensed to form a neutral gas. Matter and radiation consequently decouple from one another because no further scattering of the radiation occurs., Separation of classes of particles from regular interaction with one another, as in the decoupling of photons from particles of matter that produced the cosmic background radiation., The rapid transition from an ionized state at a redshift of 1000, when the blackbody radiation is scattered by the free electrons, to an unionized state, when the matter is predominantly in the form of hydrogen atoms that do not scatter the radiation appreciably. Radiation subsequently does not interact with matter unless the matter becomes reionized at a later epoch by radiation from quasars or forming galaxies., The epoch at t ≈ 10¹³ s after the big bang (T ≈ 3000 K) when matter and radiation decoupled., The era some 3 × 10⁵ years after the Big Bang when the cosmic blackbody radiation was last scattered by the matter. At this era, at a redshift of about 1,000 and a temperature of about 3,000 K, the protons and electrons combined to form hydrogen atoms, which are effectively transparent to the radiation., A cosmic epoch during which the matter content of the Universe ceased to be ionized. This led to a decrease in the optical depth of the Universe, and the photons of radiation (which we now observe as the cosmic microwave background) became able to travel large distances without interacting with matter., The release of photons from constant collisions with massive particles as the universe expanded and its matter density diminished. See decoupling.
• nucleosynthetic era (6 facts) - The Big Bang era when neutrons were produced and helium and deuterium were synthesized. At t = 200 sec, nucleosynthesis began rather abruptly and virtually all deuterium was synthesized to helium.
• Planck era (6 facts) - The Big Bang era, prior to which Einstein's theory of gravitation breaks down and a quantized theory of gravity is needed. Density was so high that gravitational force acted as strongly as the other fundamental forces on the sub-atomic scale.
• radiation era (7 facts) - The Big Bang era when the temperature had dropped to 10⁹K and the rate of electron-positron pair annihilation exceeded the rate of their production, leaving radiation the dominant constituent of the universe.