Adhering to natural laws and physics as much as possible
, what could cause Venus to go from a habitable planet to its current state, and how long would it take from the apocalyptic event to achieve the current state?
In this scenario, human life evolved on Venus, the apocalyptic event took place, and humans moved to earth. Events after that do not matter and do not need to line up with actual human history.
Venus Pre Apocalypse
- Chemical composition same or similar to earth
- Able to support human life
- Hosts Type 1 civilization
- Can be man made
- Can be natural
- Can be both
- Can be neither
After TBD amount of time post Apocalypse
- Venus is how it is now
- What would slow the rotation of the planet?
- What would cause the drastic chemical change to acidic atmosphere?
Does not have to be perfectly scientific, but reasonably realistic. Type 1 Civilization-esque level of technology and “science” allowed.
Or a predecessor that could micro evolve to live in the similar chemical composition of earth. If different, please outline said differences.
Space-faring but not yet colonizing. See this SE answer for plausible reasons for delayed space travel.
What political landscape would be in place and/or cause such an event?
Nothing is out of the question so long as it resolves into the current state of the solar system
If you are clever enough to think of what that might possibly be. I’m not.