Nature timeline view • discuss • -13 — – -12 — – -11 — – -10 — – -9 — – -8 — – -7 — – -6 — – -5 — – -4 — – -3 — – -2 — – -1 — – 0 — cosmic expansion Earliest light cosmic speed-up Solar System water Single-celled life photosynthesis Multicellular life Land life Earliest gravity Dark energy Dark matter ← Earliest universe (−13.8) ← Earliest galaxy ← Earliest quasar ← Omega Centauri forms ← Andromeda Galaxy forms ← Milky Way Galaxy spiral arms form ← NGC 188 star cluster forms ← Alpha Centauri forms ← Earliest Earth (−4.54) ← Earliest life ← Earliest oxygen ← Atmospheric oxygen ← Earliest sexual reproduction ← Cambrian explosion ← Earliest humans L i f e P r i m o r d i a l Axis scale: billions of years. Also see: Human timeline and Life timeline