alt Hacker News>>There are no material goods that can justify the material and energetic expense of any interstellar travel.
Material, no. but we know with absolute certainty that Earth will stop being habitable for humans at some point. So assuming any intelligent race, human descendent or otherwise, still exists on this planet, it will have to eventually move. It's just pure luck that we evolved when we did. But there are valid reasons for interstellar travel(other than you know, pure curiosity).
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Even if leaving the solar system, or whatever system a sentient race exists, were possible, going to war with another sentience in their home turf (which, remember, must first overcome the near impossible hurdles of getting there to begin with) is so unlikely it makes invasion fears absurd. I think the dark forest theory is groundless paranoia.
Scifi usually bypasses this by breaking the laws of physics, for the sake of storytelling.
It's a catch 22. If you want to preserve the Earth's biosphere or even biological humans, then you would need to move at least a ship the size of a small planetoid. That will support life for millenia that will be required for interstellar travel.
And if you can do that, then why bother with the interstellar travel? Just move to a higher orbit to survive the red giant stage. And then move closer to the stellar remnant, white dwarves will provide plenty of energy for trillions of years.
And if you manage to transcribe yourself into some kind of computing-based device, then why bother at all?
I wouldn't characterize it as "moving". Any excursion outside of the solar system will not be done by anything resembling a modern human, full stop. It may be plausible to send some sort of robot with some sort of nanomachine hoo-hah off in the direction of a nearby star, to seed life there. But no living human will ever leave the heliosphere.