How we’ll talk to alien life
The SETI Institute's Seth Shostak reveals all
The Search for Extraterrestrial Intelligence (SETI) is one of the most exciting
topics in all of astronomy, but what are the different ways we might receive messages from ET – and what language could we use to strike up a
conversation? We caught up with leading SETI researcher Seth Shostak
Can you tell us a little about your background and how you first got involved in the SETI field?
I’m the senior astronomer and also an Institute fellow here at the SETI Institute. I’ve been here for about 24 years, so it’s the longest job I’ve ever had. I got here kind of accidentally – I studied radio astronomy and spent quite a bit of time studying galaxies with radio telescopes, including 13 years in Holland. I wasn’t doing SETI at the time, but I was certainly interested in it, as it’s the same technology that we were using to study galaxies; it’s just radio astronomy but with a slightly different kind of receiver and obviously a different goal.
After I moved back to the US in 1988 to work with one of my brothers on a software startup that unfortunately failed, I was without a job for about a year. Thankfully, some people here at the SETI Institute, which happens to be located in the same town where I was living [Mountain View, California], heard that I was here, and they simply rang me up and asked if I wanted a job. That was at the time when there was some NASA funding for SETI, so there was more money around!
When most people think of SETI they think of big radio dishes pointing towards the sky, and as you say, your own background is in radio astronomy. Is that the only realistic way that we might receive signals from extraterrestrials?
Radio’s certainly not the only game in town, but I think what’s actually being done in SETI is always rather restricted by money and resources. You have to make something of a bet and decide what it is you’re going to do given whatever money you have. So far that’s largely been radio SETI, but there’s no doubt there are other ways to look for things.
For instance, both the University of California at Berkeley and we here at the SETI Institute are building equipment that will look for laser flashes. There’s been some work in that field for 20 or 30 years, but not much has been done – no one’s systematically searched the sky for flashing laser beacons. For example, if tonight some spotlight went off in the Orion constellation for a microsecond – a green flash or something like that – it probably wouldn’t be seen. Those sorts of signals could be happening all over the place all the time, but we wouldn’t know. So it’s a ripe area for investigation and it’s time we started looking.
But I guess 90 per cent of the effort is still going to radio SETI. The advantage of radio, of course, is that you can broadcast it. If you have a big laser then you have to decide exactly where you’re going to point it, but with radio, you can send it across a broader swath of the sky. Of course if aliens were being thrifty, they could also target the radio transmissions, which is to say aim them in a tighter beam. But perhaps if lasers had been invented before radio, then maybe 90 per cent of today’s effort would be dedicated to optical SETI – there’s definitely a historical component there.
There seems to have been a surge of interest in the possibility of detecting artificial structures built by alien civilisations. What do you think are the possibilities for that kind of discovery, and how would it compare to deliberate signals?
Artefacts have advantages and disadvantages – the advantage is that if you build something big, you don’t have to aim it at anybody; you don’t have to deliberately get the attention of somebody else, they might just trip across it. We might be able to find something even though a distant civilisation had no intention of getting discovered. Artefacts are also long-lasting – if you’re sending a signal you have to hope that someone’s looking in the right direction at the right time.
The disadvantage is that an artefact probably isn’t going to be very useful for signalling. Of course if you’re talking about aliens with the technology to build a Dyson sphere, then they’d have the ability to send signals, but that depends on their intentions.
As far as sending actual bits of information, then you’d probably rely on optical or radio signals. Optical signals such as laser beams could send more bits per second than radio, but they have their own problems – they might be absorbed or scattered by the interstellar medium, depending on what the wavelength is.
Are there any other hypothetical ways of sending actual messages that don’t rely on light or radio?
Some people have suggested neutrinos as a way of communicating. I’ve never been very keen on the idea – they’re very expensive to produce in terms of energy, and so far as we know they’re very hard to detect. Having said that, maybe they’re only hard to detect for us, and the big advantage is that neutrinos go everywhere – they pass straight through the Earth.
In terms of how much data you could send, there was a paper a good few years ago that pointed out, if your goal is to send the maximum number of bits per second, then the best way of doing that is to load up a bunch of thumb drives, put them in a rocket and send them somewhere. It would obviously take a long time and you have to know where the rocket’s going, but you could argue that some of that also applies to other SETI methods…
People write me all the time talking about gravitational waves, but I’m not sure. Gravitational waves are very hard to produce and hard to detect and I can’t see any real advantage over neutrinos. You can’t encode a lot of bits of information by colliding a pair of neutron stars together!
When we’re talking about sending messages, we naturally fall into terminology that we use when talking about signals on Earth – do those terms really make sense when talking about communicating with alien civilisations?
Well some people would say that talking about binary and bits as an encoding scheme is maybe too anthropocentric, but I don’t think so. With
The Allen Telescope Array (ATA) conducts a simultaneous search for extraterrestrial intelligence (SETI)
The SETI Institute and the University of California at Berkeley are developing Optical SETI – a search for laser pulses from distant aliens