Assuming that human messages actually reach their target, what would earthlings and aliens talk about? The obvious subject to focus on is mathematics; its basic concepts are often assumed to be universal. Any intelligent species might have an interest in natural numbers (1, 2, 3 and so on) as well as things such as pi. But moving beyond that to wider conversation would be far harder. Scientists have worked on “self-interpreting” languages— written in a way that aims to teach the reader the language as they go—which might make the next steps possible.
Is there any reason to think alien communication systems would share the two key design features of human language, words and grammar? A word like “book” is a symbol for all objects that exhibit bookish qualities; would aliens also employ symbols, rather than having separate names for every object in their world? Mr Oberhaus adduces arguments that they might. Whatever type of society they inhabit, alien life-forms would have limited time and energy, as people do. It is efficient to use symbols. Similarly, human grammar allows a vast number of sentences to be made from a finite number of rules. Any resource-constrained Moon-man might develop such grammar, too.
Even if all such hurdles were overcome, however, distance would still be a problem. Human children learn their first language by listening, trying it out and getting instant feedback. This give-and- take allows them to use fluent sentences by the age of four. In 2015 the first known exoplanet at a “goldilocks” distance from its star (not too near and not too far), and with water, was discovered 110 light-years away. A message sent today would arrive in 2129; its reply, in 2239. The kinds of exchanges depicted in sci-fi films would take lifetimes.
The awesome challenges of communicating across the galaxy mean that some think it not worth the effort—to say nothing of a political question raised by Mr Oberhaus: “Who speaks for Earth?” But pondering these obstacles raises another thought, not about aliens but what humanity has in common. Linguists argue about whether languages share universal features or are unique products of local cultures; whatever the answer, the world’s 7,000-odd tongues are vastly closer to one another than anything to be found out there.