Astronomy & Space Science · AST-686
Particle Epochs of the Early Universe: Foundations
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Overview
Core model: Particle Epochs of the Early Universe
As the early universe expanded and cooled, the particle species and interactions in thermal equilibrium changed. Cosmologists describe this evolution in epochs associated with high-energy symmetries, quarks and gluons, hadron formation, leptons, neutrino decoupling, and later nucleosynthesis.
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- 01The Big Bang — SummaryOpen source ↗
OpenStax Astronomy 2e · Mar 9, 2022
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Particle physics experiments constrain relevant reactions, while primordial abundances, the CMB, and the cosmic neutrino background predicted by the model encode consequences of early thermal history.
supported · checked Sep 22, 2026Expansion reduces temperature and density, while interaction rates determine whether particle populations remain in equilibrium.
supported · checked Sep 22, 2026As the early universe expanded and cooled, the particle species and interactions in thermal equilibrium changed.
supported · checked Sep 22, 2026