This thread is the fliip side of this onein Great Debates. I’m opening mine here because the question is essentially idle.
Alien invasions are perhaps the commonest trope in science fiction. But, honestly, the whole idea makes no sense to me, at least in terms of aliens from other star systems. They’d have evolved under such different circumstances that it seems horriby unlikely that they’d have any use for any terrestrial life form as food. Mining Earth for its resources similarly makes little sense; there is little raw material here that you couldn’t get elsewhere in the solar system with less trouble. I can’t believe it’s because Earth girls are easy. So why would aliens ever invade?
It’s sort of like the Anthropic Principle of Fiction: conflict makes for interesting stories. I just assume there are millions of untold (and unwritten) stories about peacful alien visitors, but the fact that you’re only seeing ones that by definition made it into the media skews the view of the popular conception of a putative alien encounter.
So it’s quite possible that most people think aliens would not invade violently yet there be mostly stories about alien invasions.
I don’t mean in fiction. Perhaps I should have written a longer OP.
Stipulate that extraterrestrial intelligences exists and evolved completely independently of life on Earth. Stipulate further that such aliens have FTL tech. Why would they ever invade Earth?
More importantly if they did invade why would a species advanced enough to travel at light speed not prepare for Earth’s common cold, protection against water which covers 70% of our surface or count down their attack with an obvious radio signal.
Your question assumes that invading aliens are enough like humans to make their motives comprehensible to us.
In Steel Beach, John Varley touches lightly upon “The Invaders.” They are a race from the stars that come to the Earth and exterminate all humans and eradicate all human artifacts in a matter of days. Nothing humans do has any detectible effect on them, and in fact, no human that survives (because they happened to be off-planet at the time) has ever so much as *seen *an Invader.
The motives of a sufficiently alien race would be just that: alien. Are ants capable of understanding the motivation of a little boy that kicks over their mound?
They’ve set out across the universe at sublight speed in a generation ship, because their homeworld is dying. Ship’s systems are starting to fail, and Earth is the only habitable planet reachable. (Niven/Pournelle’s Footfall is a variant of this theme; the invaders were a splinter group expelled from a larger fleet, and Earth was the only place they could go). Other than that, if we’re limited to sublight travel, it’s hard to see how a conflict for resources could develop.
With FTL travel, the possibilities open up. Conceivably Earth could be a source for some valuable luxury good. Perhaps an alien analogue to heroin can only be distilled from human spinal fluid. Our uranium might be valuable for alien artwork.
One could also postulate an Ineffable Cultural Imperative. Perhaps they have a religion that they are compelled to impose on other life forms. Perhaps they are Diggers and Levelers, who feel obliged to eliminate our income inequalities.
They’ve been picking up our television signals and are really pissed that Pushing Daisies may be cancelled while other “reality” crap shows just keeps going and going.
Having been beaten to the ‘aliens do alien things because they’re freaking aliens’ line of reasoning, I think the biggest reason would be territory – Earth-like (i.e. life supporting) planets might be rare, and the aliens might not have much qualms about forcibly acquiring new rental space for their own species.
I think the easiest reason would just be sraight out conquest. But even that assumes they think anything like us.
A more fascinating question, to me, at least: If we ran across an alien civilization, would we conquer (thinks of the black man, thinks of all of the non-white nations across the earth that have been subjugated) or would we try to work with them?
I cynically think it would depend on their level of technology.
Here’s one. Human beings and their culture may be nothing much to the bug-eyed monsters, and there may be no strictly physical resources here on Earth that are worth bothering about, but…
Just how common are life-bearing worlds? We’ve got a biosphere going here, a reasonably diverse one, and maybe the aliens just want to have a careful look through it to see what’s tasty, what could revolutionize their manufacturing processes, what might help to cure their equivalent to cancer. No earth species is likely to have evolved in exactly the same way, with the same way on any other place in the reachable universe. (Assuming that there’s some kind of intergalactic limit on FTL.)
Of course, this means that they’d probably be very careful about how much of the jungles and forests they’d blast with their cannons. Cities are presumably okay.
