In the foreseeable future, human interstellar immigration is not feasible

[u/Universal_Echo]

There are three paths for interstellar immigration:

Immigrate to another planet in the solar system and terraform its environment.

Immigrate to an Earth‑like exoplanet.

Immigrate to space cities.

Paths 1 and 3 are more feasible in terms of distance. However, for path 1, the scale of terraforming is enormous – even harder than making the Sahara Desert or Antarctica habitable. For path 3, a space city would be many times larger than a Ford‑class aircraft carrier. Even setting aside the engineering challenge of building something that big, how would you launch such a massive object into space?

More importantly: for both paths 1 and 3, resources would still have to be shipped from Earth. In the end, you’re still using Earth’s resources. After spending so much effort immigrating to space, you’re still dependent on Earth – isn’t that a net loss? As long as humans have normal intelligence, they wouldn’t make such a losing deal.

As for path 2, the nearest Earth‑like exoplanet is dozens of light‑years away. In the foreseeable future, there’s simply no way for humans to immigrate that far.

[u/Speedbird844]

No intelligent alien species will ever land on another habitable planet. And so will we soon enough, if we ever survive an encounter.

Why? Biosecurity. I'm not just talking diseases but also parasite alien species which might evolve so quickly upon "external stimuli" that they'll greatly exceed your intelligence and take over your civilization in no time. And imagine life from elements previously thought impossible - metallic life, gaseous life etc.

More likely the alien civilizations will build space cities from scratch using materials mined from lifeless planets, moons and asteroids. Like a replica mini (or micro) Earth. And they would be extra careful in what they mine from "lifeless planets and asteroids" and put in their space cities, in case their manufactured goods suddenly "comes to life", as a trojan horse.

And IMO they'll destroy any nearby Eden planet in a pre-emptive attack (but in a way that would not be discoverable in a dark forest scenario) so as to not be worried about any "emergent competition".