Timeline of the universe
This is a brief history of the universe, providing a general overview and a timeline to understand our place in it. Time is measured in billion years, and you may want to check my post How to imagine 1 billion years? first.
| Time bln.y. | Event Description |
|---|---|
| < 13.8 | Before the Big Bang. We have no observational evidence of what came before. Time itself may have begun at the Big Bang, making the question meaningless. Any speculation about "before" is highly uncertain. |
| - 13.8 | The Big Bang - the leading cosmological model explaining the origin and evolution of the universe. The universe began as a tiny, hot, and dense point and suddenly started expanding. Space, time, and everything we observe began to grow and evolve. |
| - 13.6 | Formation of the Milky Way - the galaxy that includes our Solar System. |
| - 4.6 | Formation of the Solar System begins. Age and cosmological history |
| - 4.5 | Formation of Earth begins. |
| - 4.1 | Possible emergence of the earliest life forms on Earth. Earliest known life forms |
| - 3.5 | Confirmed earliest life forms on Earth. Earliest known life forms |
| - 2.4 | Great Oxidation Event - oxygen levels rise, enabling complex life to evolve but causing the extinction of anaerobic organisms. |
| - 2.1 | Earliest known multicellular life appears. Francevillian biota |
| - 1.5 | Earliest fungi appear. Evolution of fungi |
| - 0.6 | Earliest animals appear. Otavia |
| 0 | Present day - we are here today |
| + 0.6 | COâ‚‚ levels drop too low for most plants to survive. Some adapt, but eventually, all plants die. Without plants, animals also go extinct. Future of Earth |
| + 1 | The Sun becomes hotter, causing the oceans to evaporate. With no water, life ends, and Earth becomes a dead, motionless planet without weather, earthquakes, or a carbon cycle. Future of Earth |
| + 4.5 | Andromeda–Milky Way collision - the two galaxies merge. Earth will likely survive, but the Solar System may move to a different position in the galaxy. |
| + 7.5 | Earth is likely absorbed by the Sun as it enters its red giant phase. Future of Earth |
| + 8 | The Sun becomes a carbon–oxygen white dwarf, retaining about 54% of its current mass. A white dwarf is extremely dense - packing a Sun-like mass into an Earth-sized volume. Timeline of the far future |
| + 22 | Estimated time until the end of the universe in a Big Rip scenario. Timeline of the far future |
Some thoughts and reflections
It took 14 billion years for the universe to bring us to this moment, and in 22 billion years, everything may come to an end. The Big Rip is like an absolute zero of existence, meaning things could effectively stop much sooner. In a way, we are somewhere in the middle of this grand process.
Life appeared surprisingly early on Earth, but its evolution took an incredibly long time - about 4 billion years. Perhaps life doesn't always need that long, but looking at our own history, it seems like a fragile, risky process. It might have never evolved at all, or started too late, leaving too little time before the Sun makes Earth uninhabitable.
There would be a great irony if humanity itself ended life on Earth, or if we set evolution back millions of years - losing life a chance to leave Earth before it becomes uninhabitable. It's a delicate balance, and we are standing right on the edge.