<Radio Transcript – April 9, 1984>
Bob Maywood: In our final interview with astrophysicists Katherine Collins and Stephen Appleton we take a voyage into the unknown, a talk about the possibility of living on other worlds and – the million dollar question – whether we’re all alone in this Universe.
So I guess Dr Collins, the first question for you – do you think we’ll ever leave our home planet and colonise the galaxies?
Katherine Collins: We’re going to have to. Not just yet, but in about 4 billion years the sun will swell and engulf the world, so we’d better be gone by then. Whether we can reach other galaxies… that’s more difficult. You have to get your head around the sheer distances involved. You can’t move faster than light, and it takes light over four years to get here from Proxima Centauri, our closest neighboring star – and that’s travelling at nearly two hundred thousand miles each second. If you were travelling at the same speed as Apollo when it went to the moon, it’d take you nearly a million years. Galaxies, let’s see, well Andromeda is two and a half million light years away. That’s a long flight! So I’d say it’s a tall order, but then four billion years is a long time to figure that one out.
BM: And what about other life – what about someone reaching us? Isn’t it possible that an alien race with some kind of advanced science might be able to cross those distances?
Stephen Appleton: No.
SA: It’s entirely possible that life exists out there, but intelligent life is a completely different thing.
KC: There’s a famous problem called Fermi’s Paradox. It basically says that the Universe is so big, it’s hard to believe that intelligent life hasn’t evolved someone out there. Assuming they have, then like us they’d probably try and find other life, and they’d also be emitting signals – our radio and TV signals are already out there and expanding – so why haven’t we heard from them?
SA: Because they don’t exist…
KC: Right, but that’s the paradox – it’s inconceivable in a near infinite volume, statistically speaking, that they don’t. But this is where you have to factor in time. When we look at the universe, we’re looking back in time, right? So they may exist, but we may never hear them because their signals haven’t reached us yet.
SA: So for argument’s sake, if there are little green men –
KC: Or women.
SA: Or women, right, or women, broadcasting from Andromeda tonight, we wouldn’t get the signal for another two and a half million years.
KC: Actually, it’s a bit more complicated than that, but you get the idea.