One of the fun things about grad school in science or engineering is getting a bunch of highly technically educated people together to go see a movie. Like “Battle: Los Angeles.” If you want to see a movie with Marines being very Marine-y and some big gasoline explosions, go see this movie. If you want to see cool aliens, awesome technology, and innovative ideas, then, uh…don’t.
I’m not going to do a general review of “Battle: LA,” nor a general critique of the science. (I will leave the latter up to Ryan, and I’m sure if he does such a critique it will be a fantastic read.) I will say that I liked how the aliens basically use guns and jets/rockets instead of inexplicable hover-things and energy blasters, and I liked that the reason the aliens are unstoppable at first is not because of their tech but because our soldiers don’t understand how to fight them. (Of course, the usual video-game rules of technology apply: three bazillion M-16 rounds fired into an alien aren’t enough to kill it; but do one quick alien autopsy in the field and suddenly all our guns work with full effectiveness!)
It’s the premise of the movie I want to poke at. The whole reason the aliens are attacking Earth is to claim our resources. Sound familiar? In a brief glimpse of a TV news program, Professor Greybeard explains (scientists, get your cringes ready!):
The aliens must be attacking us for our resources. Specifically, our water. 70% of Earth’s surface is covered with water, and the chemical composition of our water is unique in the solar system: it is in liquid form.
(I paraphrased from what I could recall.)
This is both factually inaccurate and a ridiculous premise for an alien invasion, for three reasons:
- The Earth’s water has exactly the same chemical composition as water anywhere else in the Solar System: two hydrogens stuck to an oxygen. And, in fact, water is one of the most common molecules in the Solar System – nay, universe!
- The Earth is not the only place in the Solar System where liquid water exists: scientists are about as sure as scientists can be that there is liquid water under the crusts of Europa and Enceladus, and possibly Ganymede and Titan as well.
- Water (liquid or ice) is available in many places throughout the Solar System, and as it turns out, the water on Earth’s surface is one of the hardest places to get at it, if your starting point is space.
Now, I will have to explain #3 a bit. My point relates to the depth of the Earth’s gravity well: in the words of xkcd, the reason “why it took a huge rocket to get to the Moon but only a small one to get back.” If aliens wanted to take our resources, presumably they want to do so because they need those resources for something. And since this alien civilization apparently makes a living moving from planet to planet (or star system to star system), they are going to have to move these resources or their products off of the planets they were harvested from. That means, for every kilogram of water the aliens pump out of Earth’s oceans, they need to produce spacecraft, rockets, and fuel to get the water up into space again. Think of how big the Space Shuttle is, and how much fuel we load it full of, just to get school-bus-sized Space Station modules into orbit. Contrast that with the tiny Lunar Module ascent rocket from the Apollo days.
Clearly, there must be a better way to get water off of planets. So, without further ado, the Quantum Rocketry Guide for Successful Star System Invasion and Resource Extraction for Nomadic Species: Continue reading Quantum Rocketry Guide: Star System Invasion!