And there is certainly in general no lack of radio signals that we receive from around our galaxy and beyond. But the point is that these signals typically seem to us quite random. And normally this has made us assume that they must in effect just be some kind of radio noise that is being produced by one of several simple physical processes.

But could it be that some of these signals instead come from extraterrestrial intelligence—and are in fact meaningful messages?

Ongoing communications between extraterrestrials seem likely to be localized to regions of space where they are needed, and therefore presumably not accessible to us. And even if some signals involved in such communications are broadcast, my guess is that they will exhibit essentially no detectable regularities. For any such regularity represents in a sense a redundancy or inefficiency that can be removed by the sender and receiver both using appropriate data compression.

But if there are beacons that are intended to be noticed even if one does not already know that they are there, then the signals these produce must necessarily have recognizable distinguishing features, and thus regularities that can be detected, at least by their potential users.

So perhaps the problem is just that the methods of perception and analysis that we as humans have are not powerful enough. And perhaps if we could only find the appropriate new method it would suddenly be clear that some of what we thought was random radio noise is actually the output of beacons set up by extraterrestrial intelligence.

For as we saw in Chapter 10 most of the methods of perception and analysis that we currently use can in general do little more than recognize repetition—and sometimes nesting. Yet in the course of this book we have seen a great many examples where data that appears to us quite random can in fact be produced by very simple underlying rules.

And although I somewhat doubt it, one could certainly imagine that if one were to show data like the center column of rule 30 or the digit sequence of π to an extraterrestrial then they would immediately be able to deduce simple rules that can produce these.

But even if at some point we were to find that some of the seemingly random radio noise that we detect can be generated by simple rules, what would this mean about extraterrestrial intelligence?