Professor Michael Rowan-Robinson is an astrophysicist at Imperial College, London. Professor Rowan-Robinson believes that the only place to find intelligent civilisation in the Galaxy is here on Earth. If it did exist elsewhere, we'd know about it by now.

Is there anyone else out there in the Universe?
I take the view that we’re perhaps alone in our galaxy, that we are the only civilisation with advanced technology and this is somewhat unusual amongst my astronomical colleagues - most of them take the view that life is common throughout the galaxy and that intelligent life is common.

Could you explain why you are sceptical, with reference to the Drake equation?
Well the Drake equation, which was invented by Frank Drake in 1952 in fact, is meant to be a way of trying to estimate how many intelligent civilisations are out there now as we speak, and so it has a number of factors, some of which are astronomical, some of which biological, which you multiply together to get the number of civilisations. So the kind of factors are first of all you need a star like the Sun and can’t be too different from the Sun otherwise it wouldn’t be suitable for us. Second factor is it’s got to be a single star, it must have a planetary system and probably it needs a planet like Jupiter to deflect asteroids, or most asteroids, away from the region of the Earth. Then the next factor is you have to have a planet like the Earth, more or less the same, could be a bit bigger, a bit smaller, bit nearer in so it would be a bit hotter, it could be a bit further away, so it would be slightly cooler, but not very much. And so those are the astronomical factors, you put them together and you find that the number of planets like the Earth that are formed per year is about one thousandth of a terrestrial planet is formed in our galaxy per year.

Now there are the other factors, the biological factors and so on. So the first one is the probability that life will evolve, life will form on a planet like Earth. So, given that bacteria emerge very quickly in history of the Earth, that might be 1, the probability might be 1. The next factor is the probability that life will evolve to an intelligent, technologically civilised creature like ourselves: now, the optimists, those that believe that they are everywhere believe that factor is also 1, but I think that a lot of the biologists are very sceptical of that, there seem to be so many lucky chances that seem to have let to our evolution that that factor could be a lot less than 1. But let’s assume it’s 1 for the moment. And then the final factor is how long a technological civilisation lasts. Now, if it lasts 1000 years, say, put down 1000th per year, multiply by 1000 , you end up with one civilisation like us in our galaxy, and we’re it.

What's the Fermi paradox? How does that support your argument?
The Fermi paradox was put forward by Enrico Fermi, a famous physicist around 1950, and basically it’s in the form of a question – Where are they? Basically he was arguing that if there are technological civilisations pervading the galaxy then they would be here by now. And there is an additional part of that argument, which is that our Sun is going to die in a few billion years, and if we’re still around, and we’ve had a few billion years of technology, we’re bound to start thinking about moving to another planet, we’ll know where the other planets are and we’ll send out expeditions, it seems to me inevitable. And it only takes about a million years for a civilisation to spread through the whole galaxy in this way, just using technology not that different from what we have today. So I personally think that the Fermi paradox is a rather strong argument for saying that we are actually alone.

Tell us about SETI (Search for Extraterrestrial Intelligence). Does the failure of SETI to give any results tell us that there's nothing out there? Now what do you have to assume to make it worthwhile to listen for a signal?
Well, you have to assume that intelligent life is pervasive in the galaxy, that it’s abundant, you have to assume that they’re pretty much like us, you know, that they’re not immensely more sophisticated than us, because you wouldn’t imagine that they would signal to us if they were. And you have to assume that they’re not interested in space travel, in travelling. So for some reason they are not trying to colonise the galaxy, they’re not trying to escape from their star, they’re just interested in chatting to us. And so the idea is they’re sending out signals. In fact, the idea that inspires the SETI enthusiasts is that there’s a kind of galactic club of civilisations who are talking to each other and if only we could get on the right frequency we could join in the chatline, that is the sort of concept.

Well, my own view is that it’s unlikely to be successful because as I said I think that probably we are alone and it’s interesting that although there’s been a lot of work on SETI over the last 20/30 years, with ever-increasing sophistication in searches, they obviously haven’t detected anything, otherwise we’d have heard about it.

I could’ve accepted that civilisations are pervasive, that for some reason the evolution to intelligent life is a simple matter, there are many civilisations, but if so I believe the SETI programme would have been successful by now. I think the fact that the galaxy is so silent in terms of intelligent signals is telling us something, and it fits in with the fact that they haven’t come here in spaceships either.

What about the idea that intelligent alien civilisations wouldn't want to communicate with us?
Some people like to suggest that they are there, but they stay hidden from us. And there could be 2 reasons why they would do that – one is they’ve already investigated us and decided that we’re so unpleasant that we’re in quarantine, they do not wish to allow us to join the galactic club so they make sure that we’re not aware of them. Another is that they regard us as we regard ants. I mean, we look down at an ant’s colony, it’s extremely clever and sophisticated, there they are waving their feelers at each other and we see communicating, so they have some kind of a society and so on.

Nevertheless, we don’t think ants represent somebody we could have a conversation with. And so maybe they are so advanced that we are not worth having a conversation with. That’s possible, but as I say, if there are civilisations that are so advanced, and they’re everywhere, I think that they would be interested in our real estate and they would just come and step on us, like we step on ants.

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