THE FERMI PARADOX STATES THAT

The Fermi Paradox states that if intelligent life occurs with relative frequency, then there should already be extraterrestrials visiting Earth. Others (like Ian Crawford in his July 2002 Scientific American article) have quantified this statesment by considering the age of the galaxy (~14 billion years), how quickly life moves from origin to intelligence (4 billion years for us), and how quickly a civilization could colonize the galaxy. Crawford figures a people capable of traveling at 10% the speed of light could fill the galaxy with colonies spaced 10 light-years apart in 50 million years assuming it takes 5000 for each new colony to send out colony ships of its own (here’s a figure showing the same assuming it takes 500 instead of 5000 years). 50 million years is nothing in galactic terms, so any such civilization should have already swung by our end of the galaxy and seen that Earth is a fine little patch of real estate. The fact that there aren’t any aliens here now suggests that intelligence is a very rare, and that we may be the only example.

There are all manner of attacks against the Fermi Paradox, including the difficulty of interstellar space travel and the anthropocentrist fallacy of imposing human (or perhaps just Western) expansionist inclinations on an alien civilization. This was the topic of discussion for my tutorial meeting this week, and my partner Paul Crittenden made a particularly interesting refutation: you can avoid all the issues of anthropocentrism and look at the question with some conservative scrutiny if you assume that the most powerful force motivating any species to leave its home planet would be the imminent demise of that planet. Self-preservation isn’t an assumption based on anthropocentrism, so one would assume that the prospect of imminent extinction would motivate anyone to hightail it to the nearest good-looking star. If you accept this as the baseline motive for colonization, then a civilization capable of expanding throughout the galaxy would in fact only be moving from planet to planet. The sprawling graph in that figure would instead be a segmented line. Or it would just be a point that moves in time.

This is actually quite a reasonable assumption, since colonization would be incredibly expensive, and I can think of few things that would justify it. Exploration and curiosity won’t cut it, since assuming ET holds these values in high esteem is just as dangerous as assuming them to be greedy and resource-hungry like we are. And our greed has yet to outweigh the costs of prospecting in our own solar system , making that assumption even less adequate. Paul’s point is the only safe assumption, and if we take it to heart, then maybe ETI shouldn’t necessarily be here by now, and may just be struggling to get by on a single little rock somewhere, just like us.