We could just build giant bomb shelters. It’s cheaper, holds more people, and doesn’t require nearly the investment in a completely closed ecosystem. But that ain’t sexy.
If you want something that uniquely requires leaving the planet for somewhere you have truck in literally everything except rocks, you’re pretty much limited to the sun becoming a red giant. That and gamma ray bursts. That’s pretty much it.
If you want something that uniquely requires leaving the planet for somewhere you have truck in literally everything except rocks, you’re pretty much limited to the sun becoming a red giant. That and gamma ray bursts. That’s pretty much it.