Why Would Aliens Want the Earth?

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay

Basic Assumptions

If an incoming alien race has faster than light travel, teleportation, reactionless drives, direct conversion of matter to energy, anti-gravity, or other staple science fiction technologies, all bets are off. We have no idea what they'd be able to do because we have no idea how those technologies could even be possible, given our understanding of the laws of physics. And if you're about to pooh-pooh that as impossibly myopic, why not first prove you know anything about the laws of physics? Say, explain how Trojan orbits work, in detail, as in, do the math. Or explain how Maxwell's Equations lead to radio.

We can assume that any race capable of crossing interstellar space will be able to do anything we can do or even remotely contemplate doing. On the other hand, space travel won't be trivial, even for them. Traveling between ships in their fleet will probably be easy out there in zero gravity, but getting to speeds capable of crossing space in a reasonable time, and slowing down once they reach their destination, will take serious effort. Any civilization capable of crossing interstellar space will probably be able to travel freely between planets, but it will still take a lot of energy and time. Landing on massive planets, and getting off again, will also be a significant effort. Terraforming planets will likewise take a lot of effort and, even more important, time.

If Earth-like planets are extremely rare and we just happen to be on one that the aliens need, well, sucks to be us. On the other hand, if earth-like planets are at all common, the odds are very much against one of them having an intelligent civilization. If humans last 5 million years, that will be less than 1/1000 of the age of the earth. The odds of aliens coming here during our window of existence are about 1/1000.

So we'd have to assume that any extra-solar visitors come to our solar system for a specific reason, which might be to colonize, gather resources, or explore. (Or possibly, as in Arthur C. Clarke's Rama novels, simply to use the Sun for a trajectory change.) We should pretty much assume that they are ahead of us technologically in just about everything. Anything we have on the drawing boards, they can do.

They certainly will have technology for observing planets around other stars, since we ourselves have begun to do it. If they have telescopes millions of kilometers apart flying in formation with their ships, they can combine the images to obtain the effective resolution of a telescope millions of kilometers in diameter. We already have conceptual ideas for doing this. So quite likely they would have pretty good images of all the planets in our solar system.

If they pick up our radio and television signals, they'd probably know that there is at least that level of technology in our solar system. Most likely they'd pick up only the carrier wave, with the actual signal information too weak to pick out. Then again, in zero gravity, there would be nothing to stop them from building a radio dish kilometers across. We have to assume they are at least as good at cryptography as we are, so if they could pick up the information, they would likely be able to decipher it.


In the unlikely event they simply come here blind because they just picked a G-class star at random and didn't do any reconnaissance on the way in, it's very likely that they wouldn't lightly pack up and go to another star, since interstellar travel will be resource and time intensive. And, of course, if they know what's here, then they came here for a specific reason. But if their primary goal is resources, and they can travel easily between planets, there are much better sources than the Earth.

If they come to our solar system to gather extraterrestrial resources, earth might be irrelevant to them, just like us going into the woods to pick berries is irrelevant to some bird nesting in a nearby tree. We are very unlikely to be a threat, or even a nuisance. Aww, isn't that cute? We have itty-bitty nucwear weapons. They can travel between planets and we can't go beyond earth orbit. They could strip-mine Mars and we'd be able to do little more than watch. We might launch robotic missions to watch them, and maybe pick up some useful ideas, assuming the aliens allow them to get close.

We are also unlikely to have anything cultural or technological that they need. Iron and steel? With nickel-iron asteroids for the taking? Electronics? They probably maxed out Moore's Law ages ago. Some of our cultural artifacts and art works may be of interest.

So Who Needs Earth?

There are a few reasons why extraterrestrial visitors might come specifically to Earth apart from curiosity or exchanging greetings:

Encounter Scenarios

They Come and Go

They come into the solar system, harvest a few comets and metal rich asteroids, suck hydrocarbons out of the Gas Giants, unfurl giant solar arrays to replenish their energy storage, and leave without contacting us at all. If this had happened even in 1900, we probably would have not even noticed it, but today we would. We'd certainly know we weren't alone, but on the other hand we'd be more alone than ever, since there are races that travel among the stars and don't even consider us worth contacting.

We are Superior

Forget this. They came here. We can't go there. They will likely be ahead of us in everything. the only exception might be a District 9 scenario, where a small alien contingent arrives, either as refugees or because they had a catastrophic failure of their ship.

We're OK, They're OK (Star Trek)

The best of all possible universes. But we'll still be grossly inferior to them in technology. But they'll treat us nice, and maybe let us share their stuff. That may not be a good thing (see Culture Shock, below).

War of the Worlds (or V, or the Borg)

We're food, raw material, or an impediment. Maybe we can make ourselves enough of a nuisance that they leave us alone if we stay out of their way. On the other hand, with our industrial base gone, we're back to rocks and sharp sticks pretty soon, and what kind of a fight can we put up then?

We might make a good ad hoc food source, especially as a way of exterminating us, but we'd be lousy as a continuing source of food. We escape, attack our handlers, and grow slowly. As opposed to cows, who are dumb, docile, fast growing and capable of eating grass.

Watership Down

Watership Down was a 1972 novel by Richard Adams about a colony of rabbits that had to find a new home. It begins with a vision of bulldozers tearing up the field the rabbits lived in. The humans didn't hate the rabbits, or even care about them. They were just in the way.
    I consider this the most likely scenario. They come to Earth because they want copper and aluminum, and they need open space to set up facilities to fabricate things for their ships, and why build a huge enclosed dome on the Moon when Earth already has a comfortable working environment? So they see our copper mines and strip them out. They detect other hydrothermal ores forming underground and dig them out, as well. And they don't care that it's Yellowstone National Park. Maybe they'll realize we already have a lot of refined copper and root it out of our cities, just like the Spanish plundered New World silver. They don't hate us, and they may even try to avoid gratuitous harm, but in comparison to them, we're about as smart as a Labrador retriever, and we just don't rate on their scale. Some of them might study us as exercises in exobiology, but their children can write things more advanced than Hamletand make up songs more elaborate than anything by Beethoven. Our art will interest them less than the cheapest tourist trinket impresses us. They won't go out of their way to hurt us, because advanced beings don't unnecessarily mistreat lower life forms (although kids will step on bugs), but if they want something, they'll take it. If they want to clear Florida to build a solar power array, or use Iowa to grow some crop important to them, they'll do it. We'll just have to move, just like the bunny rabbits did.

Culture Shock

Maybe benevolent aliens won't be such a good thing after all. Even when advanced civilizations have encountered primitive ones on earth peacefully, the results have generally been rough on the primitive civilization.

For openers, what's the point of research when the aliens already have the answer to any question we might ever ask? We could easily become passive users of their knowledge.

Then there's the impact on our beliefs. If they have indisputably been around for millions of years, that pretty much demolishes a recent creation, right? Or maybe not. It's very likely we'd see the rise of powerful movements denouncing the aliens as liars or hoaxers and demanding an end to contact with them. What if they've had a peaceful, benign, just civilization for hundreds of thousands of years, superior to us in every way, and have never, ever had the concept of a god? What if they have an extremely dogmatic religion, especially one that meshes with some of our more dogmatic creeds? What if they have rigid sex roles, or rigid social classes, or practice slavery? What if they have no limits on sexual behavior whatsoever?

Finally, some humans will certainly interact more closely with the aliens than others. If the aliens aren't careful, they can create such an economic disparity that humanity ends up becoming a wholly owned subsidiary of Aliens, Inc. Even on earth, anthropologists have noted there are clearly defined zones of influence around outposts of advanced civilizations. Some humans would be almost wholly assimilated. Others would find that proximity to alien knowledge gives them powerful advantages over less favored humans, either in trade or in the use of force.

That assumes that the aliens are benign or at least neutral. If they're here to exploit us or at least get what they want without regard for us, then things will get a whole lot nastier. Because there will certainly be humans who will work for whatever rewards the aliens offer. They'll strip-mine Chicago for the metals, in exchange for power or sex. Or they'll act as overseers to keep the rest of us in line.

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Created 13 January 1998, Last Update 11 January 2020