Chronology of the universe

The sequence of major physical events in cosmic history, from the universe’s hot, dense early state to its present expansion and structure.

Big Bang: The early hot, dense state from which the observable universe has expanded and evolved. It marks the beginning of the timeline’s well-supported physical account.
Planck epoch: The earliest interval in cosmic history, when quantum-gravity effects are expected to dominate. It marks the limit of current physical theories near the timeline’s beginning.
Cosmic age: The elapsed time since the universe’s early hot, dense state, estimated at about 13.8 billion years. It gives the timeline its measured overall duration.
Dark matter: Matter inferred from gravity that emits, absorbs, and reflects little or no light. Its gravitational influence helped cosmic structures grow, though its identity remains unknown.
Cosmic inflation: A proposed brief period of extremely rapid expansion in the universe’s earliest moments. It may explain the large-scale uniformity and initial density variations that shaped later events.
Dark Ages (cosmology): The period after recombination and before the first luminous stars formed. It fills the long interval between the cosmic microwave background and the first stars.
Cosmic distance ladder: A sequence of methods for measuring distances to increasingly remote astronomical objects. Distance measurements help reconstruct expansion and place observations in cosmic time.
Dark energy: The name for the unknown cause of the universe’s observed accelerated expansion. It dominates the late-time expansion and shapes predictions for cosmic history’s future.
Big Bang nucleosynthesis: The formation of light atomic nuclei during the universe’s first minutes. It set the primordial abundances of hydrogen, helium, and other light elements.
Cosmic dawn: The era when the first stars and galaxies began to emit light. It ended the universe’s extended dark period and began reionization.

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ChronologyBroader topic: It extends chronological reconstruction from cosmic origins to the present.