> Presume there are only 1 billion people left on Earth when we decide it's time to go
The scenario that leads to have only 1B left from where we're at would entail such a catastrophic meltdown of society that even building a rocket would likely not be feasible, let alone anything significant for a human exode.
Think about it, you're fighting against something that killed 7B people, be it the end of fossil fuels, climate change, a massive and deadly pandemic, a war or another type of catastrophe. There are probably global food shortage, areas that can't be lived in anymore. The global supply chain doesn't exist anymore, and government is much more localized, very different. Being down to 1B is probably not the bottom line of your decline, 1B people is still a lot. Your priorities are based on survival, you're trying to figure out how to grow enough food, gather enough water. You don't have enough reserve capacity that you can spare it on projects like building a lot of rockets and colonizing another planet.
Rockets are a thing of complex societies with abondant energy ; not a last minute effort to preserve the human race.
The scenario that leads to have only 1B left from where we're at would entail such a catastrophic meltdown of society that even building a rocket would likely not be feasible, let alone anything significant for a human exode.
Think about it, you're fighting against something that killed 7B people, be it the end of fossil fuels, climate change, a massive and deadly pandemic, a war or another type of catastrophe. There are probably global food shortage, areas that can't be lived in anymore. The global supply chain doesn't exist anymore, and government is much more localized, very different. Being down to 1B is probably not the bottom line of your decline, 1B people is still a lot. Your priorities are based on survival, you're trying to figure out how to grow enough food, gather enough water. You don't have enough reserve capacity that you can spare it on projects like building a lot of rockets and colonizing another planet.
Rockets are a thing of complex societies with abondant energy ; not a last minute effort to preserve the human race.