Are we alone in the universe? Astronomer Seth Shostak has dedicated his career to trying to find out, with . Shostak talked to Barry DiGregorio about why he’s sure that intelligent aliens exist, the powerful new telescope that will help in the hunt, and what he would do if he detected a signal from ET
Why do you think intelligent extraterrestrials exist?
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To believe that they don’t exist requires positing that what’s happened on Earth is some sort of miracle. I find that premise a tougher sell than to think that intelligence is a fairly frequent development in a 14-billion-year-old cosmos.
When did you decide that the search for alien intelligence would be your career goal?
I have a photo of the moment. In it I am reading a book that had just come out by I. S. Shklovskii and Carl Sagan called Intelligent Life In The Universe, while noting down some data on galaxies. That was in 1967.
Was that a “eureka” moment?
Sort of. At that moment it occurred to me that the radio-telescope antennas I was using to study galaxies could also be used to see if we have cosmic company out there. It’s hard to think of any project of greater potential significance. And hey, there have been 10,000 generations of people before me who were interested in intelligent life in the sky, but who couldn’t do an experiment. How nice to be alive when that’s finally possible.
What does searching for alien intelligence involve?
We look for certain types of signals – ones that we can detect with straightforward equipment here on Earth. That means radio and visible light. For radio, most of the searches are trying to find very narrow-band signal components, as these are the hallmarks of deliberate transmissions. In the optical, we hunt for sudden bursts of photons from alien lasers.
There are also a few searches for alien artefacts, like interstellar rockets and Dyson spheres – hypothetical shells built around stars by advanced civilisations to capture energy – but these efforts have been limited.
How can you tell you’re looking for the right thing?
The only way to be sure that we’re using the right strategy is to find something! But on the basis of the physics we know, electromagnetic radiation – which is just another way of saying radio and light – is the fastest and least energetically expensive way to send information across interstellar distances. So it looks good, at least on paper.
What do you say to Stephen Wolfram’s assertion in New Scientist that SETI is groping in the dark with no idea what to grope for?
It’s easy to suggest that we’re doing the wrong thing and, until we find a signal, there is always the possibility that such a suggestion has merit. I judge alternative SETI approaches on the basis of whether they can be tested by experiment, either now or in the foreseeable future. If a hypothesis is proposed without the ability to use it to direct a search, then it’s like telling Christopher Columbus that he should swap his ships for jet aircraft. Not helpful.
We have searched for alien life for 50 years and found nothing. Isn’t that long enough?
It might seem so, but in fact we’ve only examined fewer than 1000 nearby star systems – at least, over a wide frequency range and with high sensitivity. That’s an insignificant sample of galactic real estate. Thanks to the march of technology, this fraction will increase by three orders of magnitude over the next three decades. At that point, maybe it would make sense to discuss whether we should throw in the towel, assuming there’s still no joy.
How will the new help SETI?
We can use ATA constantly for searching, rather than relying on someone else’s antenna. It also allows scrutiny of more than one star system at a time and it’s designed to be able to keep up with the feverish advance of digital electronics. When you add these factors together, you get an instrument that’s much faster at sifting the galaxy for signals. So if there’s a broadcast to be heard, this new telescope may allow us to hear it far sooner than previous approaches.
If we detect alien intelligence, is there any possibility of then communicating with it?
There’s a possibility, although conversation is going to be poky. They’ll probably be at least hundreds of light years distant, and the chances that we’ll understand anything of their message, assuming there is one, are slight. That’s just my prejudice, of course. We’ll have to wait and see if it’s justified.
Couldn’t it be dangerous to find, and possibly return, extraterrestrial messages?
I think this is truly unlikely, given both the physical and cultural distance that would separate us from them. If I were suddenly in touch with termites in Nepal, my first thought would not be to go to that far-off locale and destroy both them and their habitat.
What do you say to people who think that aliens have already reached us, via UFOs and suchlike?
I say: “Don’t tell me about the thousands of sightings every year. Just tell me what you think is the very best case, the one that will make it into the refereed journals of astrobiology.” I’m still awaiting a satisfying response to that request.
Why will the ATA focus on our galaxy’s central region rather than that contain some of the most ancient stars in our galaxy?
Globular clusters have their problems. They are very old stars, so chances are that they don’t have many planets – they formed so early in the history of the universe that there weren’t a lot of heavy elements around to build rocky planets like Earth. And many globular clusters are really far away, so any signals would be very weak.
The centre of the galaxy is the one unique spot in our galaxy. If you are going to leave a transmitter beaming out a signal, putting it at the centre of the galaxy means you can be confident that everybody in the galaxy will look there sooner or later.
More than 300 planets have been found orbiting in other solar systems in our galaxy. Wouldn’t these exoplanets make good targets for a SETI search?
We are looking at all the stars that have planets for one of the first projects with the ATA. Most of the planets found so far are not appealing as habitats for life. But even if you found 100 Earth-like planets that were thought to have life because oxygen was detected in their atmospheres, it might not mean anything. Two billion years ago the Earth had atmospheric oxygen but no intelligent life to send a signal out. We have only developed the ability to detect signals within the last 50 years. The point is that you need lots of Earth-like worlds if you want to find a signal.
“You need lots of Earth-like worlds if you want to find a signal”
What would you do if, today, you detected a signal which indicated extraterrestrial intelligence?
Log in to my calendar and delete all meetings and obligations for the next three months. And I’d probably stock up on Valium.
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Profile
Seth Shostak has been interested in aliens since childhood. He holds a PhD in radio astronomy from the California Institute of Technology and worked for 10 years at the Kapteyn Astronomical Institute in Groningen, the Netherlands. For the last 20 years, he has been a radio astronomer at the Search for Extraterrestrial Intelligence (SETI) Institute in Mountain View, California. His latest book, Confessions of an Alien Hunter, is out next year.
