Copernicus and Darwin taught us that we are not the centre of the universe. But fifty years have passed since we began listening for life in the cosmos. A billion radio channels have scanned the sky. No extra terrestrial intelligence has been found. Is it once again time to think we may be alone, and to reassess what it is to be human?

Maggie Aderin-Pocock is research fellow in UCL Department of Science and Technology Studies and an Honorary Research Associate in UCL Department of Physics and Astronomy. Since 2014, she has co-presented the long-running astronomy TV programme The Sky at Night.

Here she speaks to the IAI about the probability of finding intelligent life elsewhere in the universe, and what it would mean for mankind if we do.

The Drake equation posits that, given the vast number of galaxies and stars and possible habitable planets, there has to be intelligent life somewhere. But despite our best efforts to look, we still haven’t found any. Is this a problem?

No, I don’t think it is a problem at all, because unfortunately the probability is against us. If you look at the Drake equation and put various numbers in, after a number of experts, we come up with the possibility of five intelligent civilisations in the whole of the galaxy. The galaxy is very, very large and, even travelling as fast as we can with modern technology, to go and visit our next-door neighbour’s star, would be a journey of 76,000 years. If there is intelligent life out there, how are we going to find it? There are about 200 billion stars in our galaxy, so it’s really like looking for a needle in a haystack or a drop in the ocean.

It was generally agreed in the debate that we’d all like the idea of being able to find other intelligent species. But as Stephen Hawking has pointed out, in our own history when two civilisations meet, the less advanced one almost always get the worst deal. For example, the Spanish coming to the Americas.

That is judging the extraterrestrial on our own turf. This is the problem. We only have one example of life, and that’s us. Man’s inhumanity to man is pretty grim. So based purely on the history of own actions, yes I think it could be pretty scary. But it depends on the type of intelligence. You do hope that if they can manage interstellar travel, then they’ll be operating on a higher intellectual plane than we are at the moment. I’m ever the optimist.

If there are other species they will have evolved along the same lines as us, they will have been subject to the laws of natural selection. Will they not therefore show certain aggressive traits?

Again, this is too presumptuous that they’ll be exactly like us or that they will have evolved in the same way. Evolution is only one way to develop. That’s the problem – we only have one example on which to base our suppositions. But I’m always hopeful.

In my mind’s eye, I look at planet Earth and I can see no resolution for our wars. But if something external changed, maybe we met with an act of force, suddenly we would unite, we would stop quarrelling, we’d stop looking at our differences and we’d see ourselves as human or we’d see ourselves as a global society. My ideal scenario is that the aliens come and say, “okay we’re taking over”, and we pull resources in response and we work together for the first time in our history.

Let’s say that we found fossilised evidence of bacteria living in water molecules on Mars. What would be the significance?

If we found bacteria on Mars, it would mean life could live somewhere else other than Earth, and that would be pretty mind-blowing. At the moment we can only find life on Earth and we don’t know if it even exists anywhere else. If we find it on Mars, even if it is not intelligent, I think it would be a game changer. That’s a 100% increase, which is pretty good going.

Is it fair to argue that the search for intelligence is an anthropocentric search in the sense that we are only looking for intelligence because we think of ourselves as intelligent? What is it about intelligence that’s so important?

We need to be careful with the Drake equation because it is about civilisation rather than intelligence, and civilisation is a very, very narrow term within the Drake equation. Humans have only been civilised for, say, 50 or 60 years in that respect. When we think of aliens we think of little green men with antennae and an extra eye, but it’s very limited conception of intelligent life. There’s one idea that we keep on going to Mars and looking for life, while there are these dots that are looking back at us. Each time they keep still – maybe that’s life on Mars. The point is that we might not even recognise life or intelligence as we see it, so that makes it a lot more challenging.

How do you think we’d react to discovering that we were alone in the universe?

Firstly, the problem is that discovering a negative is very hard. It’s like proving there’s no God. How do you go about doing that? How do you go about proving that in the galaxy there’s no life? I can’t see how you could ever prove that.

From the very beginning we looked up at the night sky and wondered. I think in some ways you could compare it to God: did we create God or did God create man? It’s almost like that – a need for another entity out there so that we are not alone. It could be God, it could be aliens, but somehow I don’t think we want to be alone. As I say, I don’t see how we could ever prove that there aren’t any aliens out there.

There seems to be a view that science’s role is not merely to demystify the world but also to remove man from the centre of the universe.

I don’t see that as science’s role at all. It’s just that as we get more and more information, we feel that that’s the way the evidence is pointing. But that’s not science’s role, and I think we have enough evidence out there to tell us straight that we’re insignificant. That’s what evidence gives us. The fact that when we think of aliens, we think of them as very human like, or very earth-like, shows us that we still have that instinct. Scientists still have that instinct. It’s not our goal in life to show our insignificance; it’s just that the evidence has given us that.

You’ve stressed the need to stop thinking about possible life in the universe on human terms. But is it possible to remove ourselves completely from the equation? Might the search for life be a way of looking at ourselves anew?

The Drake equation and the search for intelligent life both encourage us to look introspectively, and I think that’s a good thing. When artificial intelligence comes along, by looking at ourselves we can define what intelligence actually is. That’s a very useful thing for us to do. But I don’t think the ultimate goal is to understand ourselves. The ultimate goal is to find something out there – and part of that process is understanding ourselves better as well.