Hannah Devlin: Why are we searching for radio waves from aliens? Couldn’t aliens have a completely different means of communication?
Jill Tarter: We evolved on a planet that is illuminated by the Sun. We developed sensory receptors that are sensitive to electromagnetic radiation that happen to peak at 5,500 Angstroms, where the Sun peaks. Radio is just long light — it’s not very hard to get from sensing light to sensing radio. If you’re trying to attract the attention of an emerging technology — and we’re about the youngest technology in the galaxy that could have any chance of having an interstellar conversation — you would probably use something that’s simple and attention-getting.

HD: Radio or optical signals would take hundreds or thousands of years to reach us. How would we converse with the aliens?
JT: The same way you have a conversation with Shakespeare or the ancient Greeks or Romans. It’s one way — you don’t get a chance to ask questions, but you can still learn a lot. You could probably say hello back, but you would never know if they heard you or not. That is probably the model for interstellar discourse.

HD: Do you think we will ever actually meet ET?
JT: Carl Sagan suggested that they’d teach us how to build a vehicle to travel there. It’s a fanciful scenario, but it might be what happens. On the other hand, it seems silly to put vast energy requirements into sending macroscopic wet biology when you can just send information. When we talk about interstellar travel, we have a very limited view and always assume that it’s going to be Battlestar Galactica boldly going, as opposed to nanobots, or other kinds of small energy-efficient ways of exploring.

HD: Will our first contact be their first contact too?
JT: We don’t know if there are other technologies out there, that’s the question that we’re trying to answer, but if there are then they’re older than we are and have greater capabilities than we do. This is just on the basis that we’re a 100-year-old technology in a 10 billion-year-old galaxy. We’re just now able to try this game. It’s overwhelmingly improbable that our first contact with them will also be their first contact with anyone. They’ve done this before — we’ll simply follow their lead.

HD: Do you ever have doubts about SETI?
JT: I could be totally wrong about everything. But we could also do nothing and I think that’s pretty silly. We have this question and we have some tools that we can use. It would be foolish not to use them. Columbus didn’t wait for a 747. He used the tools he had and they turned out to be marginally adequate.

Jill Tarter is an American astronomer and director of the Centre for SETI Research in California