How will we communicate with aliens?

Humans have always looked up at the stars and wondered whether we might be sharing this universe with other forms of intelligent life. One is St Andrews University’s John Elliott, who coordinates for the newly-launched SETI Post-Detection Hub - that’s the Search for ExtraTerrestrial Intelligence. He told James why we need to have a plan in place for when the inevitable “close encounter” occurs in the future…

John - The post detection hub is, when we've discovered something, whether it's a distant signal or even an artefact - a myriad of scenarios - it's the bit where people say "what next?" And we are the "what next." We need to coordinate all the different disciplines, all the different scientific endeavours together, such as we have a framework, a methodology, by which we then know whatever scenario it is, we have a plan on how to deal with it.

James - I'm sure you get bombarded with movie references, but what springs to mind when you talk about this coordinated effort is Close Encounters of the Third Kind, when they're receiving those light and audio signals and the team of government led officials are there, furiously typing away, trying to crack what the communications are.

John - The whole point of the plan is that we'd have forethought in what we need to do and we'd have done many years of research to plan this. The scenarios you mention in films often are, "Well, let's get the codebreakers involved." No! An analogy is, in the Second World War, with the enigma code, we were cracking a German code. Now, we knew it was German. Alright, it was encoded, but we knew what the source language was and we knew we had to try and translate it into something we understood. We're dealing with the unknown. Everything I've created; mathematical models, algorithms, all the dirty stuff that's underneath it, all has to deal with how can we make sense of something we know nothing about in the first place.

James - Probably difficult to get my head around just the basic principles you have to start from, but could you give me an idea? Obviously it's going to depend on what sort of communication we get for you to then be able to do something with it. What sort of eventualities have you prepared for so far?

John - If we receive something, just say like a binary bit stream - loads of ones and zeros - if you looked at billions of these coming in, no one could make sense of it, and if it had no resemblance to any human languages we particularly know you couldn't translate it into something. It wasn't like making up your own Rosetta Stone. I've devised algorithms that slide along it at variable windows - it's pattern finding. Once you can find patterns, no matter where they are - because fundamentally the speaker has to make it comprehensible to the hearer - so whatever communication system's being used it has to have that sort of underlying structure. If there is an information type structure in there which would flag up intelligence, you already know that you've got something special, and you build up and try and piece it together like a jigsaw as best you can.

James - It feels like as a species, people are coming round much more to the idea - as the scale of the universe becomes more apparent to the layman when they see images from the James Webb telescope, better science communication from astronomers, etc. - there's almost a building consensus that intelligent life is a firm possibility.

John - What's happened more recently is we've been discovering more and more of these Exoplanets around distant stars. So what we call exoplanets, we're finding thousands of them. In fact, we're finding them really around every other star. And if you think about just our own galaxy having at least 200 billion stars in it, we're talking then the same sort of numbers for planets out there. In fact, if you had multiple planets around most systems, you may be going towards a trillion planets in our own galaxy. That's just our galaxy. There's 125 billion in the observable universe. To think there's no life out there - I think there's probably even microbial life in our own solar system. But intelligent life, within a thousand light years of where we are, we've probably got at least a handful, if not more potential intelligent civilizations sitting out there.