Timeline

## **Key**

Collaborators on Project Alternis may add to this page to include events. The beginning of the *Common Era*, the time known as modern well-recorded history, is defined to begin with the first human space probe launch, as this event kickstarted almost every event which came after. For cosmological events prior to recorded history such as the formaiton of planets, the *AC* (After Creation) date system is used.

**AC**: After Creation

**BCE**: Before Common Era

**CE**: Common Era

## **Primordial History**

**0 AC**
The beginning of time. The universe emerges from timelessness in an event known simply as "Creation".

**~70,000 AC**
Matter now predominates over radiation in the total energy makeup of the universe
**379,000 AC**
Hydrogen and Helium nuclei capture electrons in Recombination, allowing light to travel unfettered and creating the cosmic microwave background.
The Universal Dark Ages begin as the afterglow of Creation fades.
**10-17 million AC**
Cosmic background temperatures descend to habitable temperatures, triggering the Temperate epoch. During this time, rogue planets supporting life may have existed.
**~100 million AC**
The first star shines, beginning the reionization epoch and bringing new light to the universe.
Shortly afterwards, the first large black holes are formed, possibly forming the seeds of the supermassive black holes now found at the centers of galaxies.
**~600 million AC**
The first galaxies fully coalesce around supermassive black holes formed by now-dead Population III stars.
**~1 billion AC**
Reionization ends as most of the universe's neutral Hydrogen is now ionized by stellar radiation.
The Milky Way's disk is fully formed.
**~4 billion AC**
Earliest population I stars form, the earliest cousins of Sol.
### After Timeline Fork

**9.1 billion AC / 4.63 billion BCE**
Sol begins to collapse from a molecular cloud.
**TIMELINE FORK OF PROJECT ALTERNIS**: Subtle differences in the makeup of the Solar Nebula result in a differently arranged solar system on a large-scale display of the butterfly effect.
Planets begin to form in the nascent Solar System, including the large worlds of Savis, Crius, and Caelus. These worlds begin disturbing the surrounding material, restricting the formation of further supermassive planets.
**4.57-4.50 billion BCE**
Sol's core ignites, blasting away remaining gas from the protoplanetary disk and arresting the growth of Savis, Crius, and Caelus.
The great migration of Savis towards the asteroid belt is arrested early by a mean motion resonance with its neighbor Crius, allowing the planet Phaeton to form in the midst of the belt and preserving a much more substantial fraction of its original mass.
Caelus moves far outward, being kicked onto an elliptical orbit and disrupting the inner Kuiper Belt.
Earth, Theia, Venus, Mars, and Mercury form from the remaining rocky debris in the inner solar system.
Theia is captured in orbit of Earth alongside its likely former moon Klein.
Simud is likely captured from the asteroid belt.
**4.11 billion BCE**
Life evolves on Venus.
**3.8 billion BCE**
Venusian life is transplantd to Earth and Theia via panspermia.
Life evolves beneath the icy shells of Europa and Enceladus, possibly spreading between them via panspermia.
**970 million BCE**
Theian life shows the first signs of multicellularity and cooperation, and continues evolving over the intervening years
**712 million BCE**
Theia enters a *snowball phase*, where the vast majority of its oceans and surface freeze over, due to its relatively small size and difficulty retaining internal heat. Earth follows soon after.
**544 million BCE**
Earth enters the Great Proliferation, where biodiversity abruptly exploded. This was likely due to the evolutionary stressors placed on life forms by the Snowball Earth period.
**443 million BCE**
Nakaran supernova triggers enormous mass extinctions on life-bearing worlds in the Solar System. Theia's slow-burn evolution allows much of the primordial life beneath the seas to escape destruction.
Venusian life finally dies as its atmosphere thickens under a runaway greenhouse effect.