Here’s a thing. 90% of the galaxies in the universe have probably been scrubbed clean by gamma ray bursts. Most of the universe is hospitable only to bacteria. Now, that leaves something upwards of ten billion galaxies where that may not be true, which is still an awful lot. But they go further. It’s entirely possible, it seems, that complex life only has a better-than-even chance of forming on the edges of galaxies. The closer to the middle of the Milky Way you are, the more likely it is that you got microwaved before you did anything interesting.

The universe is close to fourteen billion years old. For the first five billion years, the whole universe was a gamma-ray oven. Nobody ever totally subscribes to the “we are the only intelligent life in the universe” theory, because the mathematics are entirely against it. It has long seemed to me, however, that the mathematics also suggest that we are the only intelligent life we will ever meet, because almost all of the universe before us is a blackened field.