[Take] binary, base 2 numbers. The I Ching, from ancient China, kind of uses those—and there are places where they’d been kind of invented a long time ago, but really nobody cared until modern times, as computers and the whole wave of technology that makes good use of binary numbers. Would the aliens care about binary numbers? Well, if you’d gone back 500 years in human mathematical history and you’d been talking with [François] Vieta, the inventor of algebra, about binary numbers, he wouldn’t have had a clue, probably. And yet, today, binary numbers look to be fundamental, simple, it’s-obvious type aspects of mathematics. That’s an example of a historical accident… I think that the challenge in all these cases with alien intelligence of any kind is there’s a big computational universe of possible things you can compute about out there, and the particular ones that one has sampled are very dependent on the detailed history of a civilization.