In an excerpt from a book of essays by scientists discussing the search for extraterrestrial life, an astrobiologist wonders why aliens would even bother with Earth.
To make the point, he runs through a list of common sci-fi alien invasion movie plots. Like when the monsters come to Earth looking for slaves. Or lunch.
Alien races enslaving each other is a common trope of many science fiction universes. While enslavement of defeated enemies or other vulnerable populations has regrettably been a common feature of our history on Earth, it’s hard to see why a species with the capability of voyaging between the stars, and therefore having already demonstrated the mastery of a highly advanced level of machinery and of marshaling energy resources, would have any need for slaves. Constructing robots, or other forms of automation or mechanization, would be a far more effective solution for labor — people are feeble in comparison, harder to fix, and need to be fed.
Maybe they will arrive looking to steal the Earth’s water or other raw materials.
The problem with this supposition is that there are loads of far better sources of water in space… you’d have access to a far greater amount of water in the icy moons and cometary halo of the outer solar system. You’d also find it much more practical to operate in deep space, rather than trying to suck up the oceans against the gravitational pull of the planet Earth. And as with the water, it’s hard to see why aliens would bother extracting material against the gravity of the Earth when the asteroids are composed of the same basic rocky stuff.
Of course the process of just getting here in the first place is a major physics problem. Instead of sending bulky, fragile life forms, our first extraterrestrial visitors would more likely be “sentient robots as emissaries”.
Although alien invasion films like “Independence Day” often do huge box office,1 thought exercises like this that address the science (and pseudo-science) behind them are actually more fun. I even enjoy it when people like Neil deGrasse Tyson take a science poop all over big sci-fi movies.
But then, I’m strange. Possibly alien?