Human contact with alien civilizations may be more likely than we think. A recent NASA study estimated that there should be at least four habitable planets (and probably more) within about 32 light years of Earth—a cosmic stone’s throw away. Those planets could just now be receiving (albeit faintly) our television broadcasts of the 1989 inauguration of President George H.W. Bush. But would aliens understand those broadcasts? Would we understand aliens? Could we ever interpret their languages?
The 2016 movie “Arrival” portrayed scientists frantically scrambling to decode an alien language. Although the on-screen aliens communicated—and even thought—in a completely different way from humans, the hero played by Amy Adams of course eventually succeeded. But off-screen, alien language may be so, well, alien that we could never understand anything about it. How do we approach dealing with something so completely unknown that it may also be completely different from anything we might expect?
In fact, questions about the nature of possible alien languages are tractable. Language remains the lone thing that appears to separate humans from other animals on Earth. The comparison of human language with animal communication can help, should we ever frantically need to decode an alien signal. After all, aliens will have evolved their language on a planet that is, like Earth, also full of non-linguistic species. But what really is the difference between language and non-language?
As a first step, let us consider why we think that this essay is language but birdsong isn’t. Some birds sing incredibly complex and varied songs. The mockingbird, for instance, combines up to 100 different song types into long sequences that rarely repeat themselves. Can we really be sure that the birds aren’t speaking to each other? Or think of orcas (killer whales), which have a repertoire of more than 100 different calls. Might they be using their complex communication to talk?
These unanswered questions point us in the direction of how to decode alien language. Perhaps we could identify a telltale fingerprint of language—some kind of statistical test that would give an unequivocal sign that a particular signal from outer space was indeed an alien message and not just noise. Such a language test would also indicate whether pigeons are in fact talking about you behind your back: If their cooing passes the language test, that would indicate that they were truly saying something.
