The first line of this article goes “A group of American aerospace engineers have written a book on how to defend the earth against alien invasion.” I have to ask… why would an alien race bother?

Many science fiction stories use an alien invasion as their main premise, but how likely is that, really? Even if we postulate that intelligent species are a dime a dozen in this corner of the galaxy, why would any alien race decide to move in on Earth?

When you strip away all of the nonsense and rhetoric around war, humans have always fought either for resources (usually land), or out of fear, rational or otherwise, that someone else was going to attack them. (Certain leaders might have encouraged that fear for their own reasons — an external enemy is a proven way to rally people behind even an unpopular leader, as the aftermath of the World Trade Center attacks demonstrated all too well — but it was the populace’s fear that allowed George W. Bush to take the US to war.)

Think about it. If an alien race has achieved a level of space travel that would allow them to visit Earth at all, then they could also visit any other planet in this solar system that they want. They’ve got the physical resources of an entire solar system to call on, at the very least, and all the energy of the star in the center of it. With those and their technology, they could presumably make just about anything they need or desire. So we don’t have anything they’d want, and could be no threat to them. Why would they bother even glancing at Earth, let alone spend the time to invade us?

The only scenario that I could see as (possibly) viable is one where they’re invading specifically because we’re here — that for some reason, human meat is a delicacy to them. (If you try to tell me that they want us for our brains, I’ll laugh in your face.) But since they would have to have evolved in a different solar system entirely, we’d probably poison them outright, and if not, I’m sure we’d all taste like chicken.

Sorry guys, your paranoid fantasies just don’t wash, even for an armchair-scientist geek.