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physical phenomena > event > era > Big Bang era > lepton era

lepton era
subject			fact

lepton era	is followed by nucleosynthetic era
	has duration 1 s
	is preceded by hadron era
	has start time 10-5 s after Big Bang
	has temperature 1010 K to 1012 K
	has definition 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).
	is a kind of Big Bang era
event	has synonym world point
	has time of occurrence