February 6, 1998
What kind of thing would make us sure we had detected extraterrestrial intelligence? What about receiving the digits of pi?
Well, that’s a tough one, for two reasons. First, how would we know that there was a complicated intentional intelligence generating those digits? You see, I’ve found some very simple systems that generate things like the digits of pi. Systems so simple that we could easily imagine they’d occur naturally, without intentional intelligence. So even if we found the digits of pi, we’d have a hard time being sure that the thing that produced them was something like us—a really complicated, evolved, learning thing—rather than just something like a piece of fluid.
Then there’s a whole other problem: how would we know that we were receiving the digits of pi? You see, the digits of pi seem effectively random for essentially all purposes. And we certainly don’t have any idea how to build some kind of analyzer that would systematically detect the digits as nonrandom. Well, the obvious question is: are there in fact radio signals that could be the digits of pi coming from around the galaxy? The answer is definitely yes. If you point a radio telescope in almost any direction, you’ll hear “radio noise”. Maybe it’s all thermal emission from hot gas, but maybe—just maybe—there are the digits of pi out there. We don’t right now have any way to know for sure.