Aliens on the airwaves

It’s not just other humans we’re looking to communicate with. Radio provides some of the most interesting ways to potentially chat with alien life. But how would we go about broadcasting to ET? And how would know if he ever decided to phone home. Michael Garrett, Director of Jodrell Bank Centre for Astrophysics, told Chris Smith about why radio waves can be so useful...

Michael - Well, the nice thing about radio, and in fact one of your speakers just mentioned it - is that you only have to generate very low power waves to be able to communicate across the globe. So if you prepare to actually put a bit more power in your transmitter and you hook it up to, you know, a large antenna, like the Jodrell Bank telescope, then you can actually begin to send these signals, not just around the world, but you can actually send them through space. And indeed over a sort of large fraction of the galaxy. It doesn't cost very much which - as a Scotsman - that's always a good thing!

Chris - I wouldn't dare to say so Michael! But once you've made the signal, if it's in space already, does that mean it's going to propagate indefinitely? Because there's nothing - unless there's a star or some other entity in the way it's just going to go on forever until we pick it up.

迈克尔-没错。是的。和收音机非常好at that. As you go up to higher frequencies, even when you go into the near infrared and the optical, and even when you get to x-rays, then you get absorption by dust. So anything that's in the path of the electromagnetic signal will get absorbed. But radio would just go through everything. And that's one of the reasons we use it so prolifically here, you know, with wifi, for example, or mobile phones, is that radio waves can travel through windows. They can travel round corners, even go through walls etc.

克里斯-这就是你listening out for then? You're looking for radio waves originating from off-planet that might have some intelligence behind them?

Michael - Yeah. I mean, that's one of the things that we are interested in doing. The nice thing about a signal that's produced by technology - so a radio signal - is that it's really easy to see the difference between that kind of signal and a natural signal that's maybe being produced by a star or, or a planet or a galaxy. The technology usually produces very narrow band signals and you shift them in their amplitude or in their frequency, or you modulate them or you pulse them in some way. So it's really easy to be able to distinguish those from all the natural radiation that you see. And that's what we're looking for. We're looking for those signatures of technology, when we're looking at radio waves coming from space.

Chris - Isn't an inherent problem with this the scale that we're talking about, when one considers how big the universe is, how big just our own neck of the cosmic woods is. You know, our own galaxy is a hundred thousand light years across isn't it. So if there are aliens out there, then the signals that are traveling at the speed of light will have had to have been traveling to us for us to detect them for a really long time. So are they going to have to be really, really very advanced, way more advanced than we are, for example, in order to have made those signals to give them time to get to us?

Michael - They almost certainly are more advanced than we are. We've only been a sort of technical civilisation for say the last hundred years, if you define that as being when we started to use radio waves back in the time of Marconi. So we've only been doing that for about 120 years, and yes, the scale is a problem. The Milky Way is really, really big. And actually by comparison, the speed of the light is actually very, very slow. And then the other question is you may have many, many technical civilisations, but if they're only around for, you know, for maybe a few hundred years. Or they're only using radio for example for a few hundred years. Even if they're around for 10,000 years, again, it's the scale that gets you because 10,000 years is like a tiny amount of time compared to the age of the Milky way. So you could have civilisations, many of them just coming and going, but they never overlapped in time or in space.

Chris - Indeed, you're sort of sticking a pin in the bubble of "is there life out there" with these sorts of sentiments, aren't you? But as Jill Tarter from NASA once said to me, it's too cheap not to do this sort of project and go looking, isn't it? Have we actually ever picked up anything that might be aliens though?

迈克尔,我不这么认为。有几个interesting signals recently actually reported in December. There's a very interesting signal. But it looks as though that's going to be sort of local radio frequency interference, now that the data have been properly analysed. So I don't think we've really had a good example of a signal. But as you say, you know, we can do all sorts of sort of normal astronomy. And in parallel to the astronomy, we can siphon off the signals and we can be looking also for that technological signature that we think we would find with a radio wave that's produced by technology. So we can do our standard astronomy, but at the same time, we can siphon off the data and think about this question. Because for me, I don't think there's a more important question out there than, "are we alone?" Are there other intelligent civilisations out there like us? So I think it's really a cheap way of answering a really important question.

Chris - And what constitutes to you, intelligent life or evidence of intelligent life? Are we sort of looking for the alien equivalent of The Naked Scientists radio programme? Is that what you're looking for?

Michael - Well, it could be that yeah, but it could be all sorts of things. For example, it could be radar systems that perhaps other civilisations are using for their aircraft or for tracking missiles. So it doesn't have to be sort of radio shows per se. We are using radio for all sorts of different types of things. We use them in our mobile systems. We use them in wifi. You know, we're completely surrounded here by radio waves and those radio waves are actually moving off planet. We have the Star Link system that's going to provide wifi from orbit. We have spacecraft that are moving out into the solar system and beyond the solar system. So sort of that radio halo and all that radio activity, we might expect to find that with another technical civilisation. We certainly want to look for that.

Chris - If you were pushed to give an answer to this next question, how likely do you think it is in the next 50 years that we're going to find evidence of alien communications?

Michael - Yeah, I think we've never been in a better position to do it. We are now doing systematic surveys with the best possible equipment. And that's been funded through the breakthrough listen programme that Yuri Milner and Julia Milner have been funding. So we are really doing proper surveys now. I don't know about 50 years, but I wouldn't be surprised if something turns up in the next 10 years, and I think it's definitely worth a couple of quid.