Say astronomers discover a brown dwarf, rogue super-Jupiter, or other massive object on a dangerous path toward our solar system. Calculations show that this flyby would seriously disrupt all the planets’ orbits, including Earth’s.
Not being an astrophysicist, I imagine three outcomes. Earth is thrown out of the Sun’s orbit; it’s thrown into a collision course with the Sun; or our orbit is made more elliptical, but stable.
Is there anything humans could do to prevent this, or at least minimize the problem?
Could we use nuclear power to alter our own orbit? Could we sacrifice another planet somehow to save ourselves? With detailed calculations, can we preemptively do anything to stay where we are afterward?
The likely increase of asteroid and comet impacts is another issue.
(And yes, I have read Fritz Leiber’s “A Pail of Air.”)
Okay, try this thought: Suppose we had a case where the Earth was going to be destroyed or nearly so, and we knew it, and couldn’t do much about it, BUT . . .
It’s going to happen about, say, 80 to 100 (or more) years in the future. (Or, sooner, but conditions for life on Earth won’t get too horribly bad until about then.)
So WE are not going to die in a ball of fire or freeze or other such horrible death. It’s our great-grandchildren, mostly not born yet, who will do that. How might we save them?
How about a global mass sterilization project (not necessarily voluntary) so the current generation will quietly, relatively peacefully, die out, without producing that future doomed generation? Would you buy into that?
As for the OP’s situation, we’d be screwed. Assuming the planet wasn’t annihilated, I suppose a few humans could keep living in nuclear-powered refuges while the atmosphere froze around them, like in the SF stories. We have that level of tech. But I don’t consider it really likely this would work, long-term, going by the example of Biosphere 2
If it was going to happen 80 to 100 years in the future, we might be able to build generation ships and travel to another solar system. Or we might not. Who knows?
Given a thousand years to work with (for the development of the technology and to implement the process, combined), we might be able to change our orbit. A hundred years, though, it would depend on a breakthrough, the discovery (and implementation) of some new science not even hinted at by anything we know, and those are never reliable (that is, we can depend on the fact that we’ll have some breakthroughs, but we can’t depend on what they’re going to be).
We had that discussion earlier. Ain’t no way we’re building a generation ship in that timescale.
There’s reasonable hope that some vestige of humanity could survive. Civilization’s buggered, but we might build a new one in a few thousand years, once the meagre handful of survivors of either the ice age or the desertification get their act together. There’s still flint to knap, after all.
80-to-100 years? Plenty of time for a Deus ex Machina. Why, there’s probably a scientist on a planet that’s about to explode putting his infant son in a spacecraft right now…