13.787 ± 0.020 BYA (Billion Years Ago)
Planck Epoch (The Singularity)
Time = 0 to 10⁻⁴³ seconds. The universe is at infinite density and temperature. General relativity breaks down. All fundamental forces are unified.
10⁻³⁶ to 10⁻³² Seconds
Cosmic Inflation
Space expands exponentially by a factor of 10²⁶. The universe smooths out, explaining the horizon problem.
380,000 Years
Recombination & The CMB
Temperature drops to 3000K. Electrons bind to nuclei (Hydrogen/Helium). Photons decouple, creating the Cosmic Microwave Background radiation—the first light.
400 Million Years
Reionization (First Stars)
Population III stars form from primordial hydrogen. They are massive, luminous, and short-lived, synthesizing the first heavy elements.
9.2 BYA (4.6 Billion Years Ago)
Solar Nebula Collapse
A giant molecular cloud fragment collapses. 99.8% of mass forms the Sun; the remaining 0.2% forms the protoplanetary disk.
4.503 BYA
Theia Impact (Moon Formation)
A Mars-sized protoplanet (Theia) strikes the proto-Earth at an oblique angle. Debris forms the Moon. Earth's axis tilts, creating seasons.
4.1 - 3.8 BYA
Late Heavy Bombardment
Migration of Jupiter and Saturn scatters planetesimals, pockmarking the inner planets and delivering water/organics to Earth.