Tim O’Brien is a Professor of Astrophysics and an Associate Director of Jodrell Bank Centre for Astrophysics at The University of Manchester. Tim’s research concentrates on the study of exploding stars using telescopes around the world and in space, working across the spectrum from radio waves to X-rays.
In this TEDxOldham talk Tim discusses the latest science behind the search for alien life.
Tim O’Brien – TEDx Talk Transcript
Thanks very much.
I’m going to ask you a sort of interesting question, which is: where are all the aliens?
I’m a scientist, not crazy, but I actually think maybe there are aliens around, and I want to convince you that this is a worthwhile scientific question to ask.
But I think, first of all, we need to appreciate how big space is. The best answer that I ever heard was in the Hitchhiker’s Guide to the Galaxy, Douglas Adams that space was big, very big, extremely big. We really don’t know how big it is.
Let’s get a little chance to understand that. This is the sun, even occasionally spotted from here in Manchester. But the sun is about 150 million kilometers away, which is a bit hard to imagine. The earth is about 12,000 kilometers across.
So, 150 million kilometers is a large distance. One of the things we tend to do is, we think about how long would it take to get to somewhere if we traveled at a certain speed. So in this case, the fastest we can travel is the speed of light. So, that’s about 300,000 kilometers every second and at that speed, you’d get to the sun in about eight minutes.
So in fact, when you look at the sun, that light has taken eight minutes to reach you, which is, you know, the sort of length of time – you’re here listening to a part of all of these talks – is not too long.
But space is obviously bigger than that. If you go out into our Milky Way galaxy, our Milky Way galaxy has many suns, may stars, hundreds of billions of stars. So, if we shared all the stars out between all the people on the earth, we’d all get about 50 each, basically, is that sort of number of stars in our Milky Way galaxy, and the nearest another star to the sun, that light that took eight minutes to reach us from the sun.
It’s on its way now, when I started talking, some lights set off from the sun and then it’ll get here about halfway through this talk. And, if that light sort of passed by the earth, we’d waited for that light to get to the nearest another star, we’ll be sitting here listening to my talk for about four years.
So probably, not the best thing to be doing. So huge, vast distances between the stars. And, across the whole of our Milky Way galaxy, that light would take 100,000 years to cross it with those hundreds of millions of stars within it.
Actually, that picture is a galaxy. It’s not our galaxy. It’s the nearest big spiral galaxy to our own. It’s called the Andromeda galaxy. So, it’s the nearest other big, large galaxy like the Milky Way. The light from those stars that you see in that picture, you can actually see this if you know where to look, you can actually see the center of this galaxy just with an unaided eye, you don’t need a telescope. A little fuzzy blob.
That light you can see from the center of that galaxy takes 2.5 million years to reach us. So, you see back in time 2.5 million years when you look at a galaxy like this. So space is big and this is just the nearest another galaxy.
If we’re talking about life, we’re asking the question about where are the Aliens? We need to probably ask where are the planets? We only know of one example of life so far, life here on this planet.
So, we know that there are many stars. We can see them shining in the night sky but it’s very hard to see the planets.
So, do these hundreds of millions of stars have planets orbiting them?
They do. And we’re living in a very special time at the moment, actually, where 20 years or so ago, we found the first planet orbiting another star like the sun. And I looked up what the number was yesterday, and the number now is 1,642 confirmed planets orbiting another stars. So, that’s just the ones we’ve found.
By extrapolating that to all the stars in our Milky Way… we know that there are billions and billions of planets in our Milky Way. Virtually, every star that you see in the night sky will be orbited by planets.
Of course, you could ask the question: Do those planets have life on them? And one of the key things there is, whether they’re too close to their star. Would they be too hot? So, for example, liquid water is something we think is key to life here on earth, the only example of life we have.
So, if you’re too close to your sun, it’d be too hot; that water would evaporate. If you were too far from your star, from your sun, then you would actually find that that water would freeze. You wouldn’t have the liquid water, we think it would be essential for all the biochemistry to go on that keep us, allows us to be alive, allows us to have life on earth.
Again, looking at what we’ve found in our Milky Way alone with these, 1.5 thousand confirmed planets so far, we know there must be billions of so-called habitable planets, just in our Milky Way galaxy. Not in the Andromeda galaxy the one I’ve shown you this another galaxy. And not in the hundred billion other galaxies that we can see in the observable universe.
Just in our own, there must be billions of habitable planets, potentially habitable planets. In other words, ones that are not too close to their star, not too hot; not too far away, not too cold so they’ve got liquid water.
Now, have aliens visited earth?
Who thinks aliens have visited the earth? Oh, nobody’s daring to put their hands up. OK, there’s quite a lot of people around the planet who do believe aliens visit the earth and visit the earth all the time and indeed claim to have met them.
But I don’t think there’s actually much good evidence for that. But, it’s sort of an interesting question, might they’ve done – you know, we’ve only been around for… Well, modern humans have not been around for that long at all, in terms of the history of the planet, just a few hundred thousand years.
So, might aliens have visited the earth at some point? Well, here’s an interesting sort of thing to think about. And it’s something we might do in the future, which is to send out a fleet of what are called von Neumann Probes. They’re space probes that you send off and they go out to search around other stars to see what they can find around other stars.
We’ve just discussed the fact that these stars are very far away, even light takes four years to reach just the nearest another star. We can’t make things travel at the speed of light, the fastest spacecraft travels at something like 60,000 km an hour or that sort of speed, a small fraction of the speed of light.
So, imagine sending out one of these space probes traveling at… that’s a fraction of the speed of light. That’s the sort of speed we can send things out at the moment. It would take it, you know, maybe 50,000 – 100,000 years to reach the nearest another star.
But when it gets there, what it does is it self-replicates. So, it gets there, and maybe along the way it gathers material from the stuff between the stars maybe, when it gets to a planet around one of those stars, it gathers more material and it builds a copy of itself.
And then, actually, those spacecrafts set off again and they head off in different directions and they go to the next another stars. And when they get there, each of those self-replicates and sets off again. This sounds a bit like science fiction, but, in fact, it’s possible to imagine that we’ll be able to do this in the not-too-distant future.