SETI: Astronomy as a Contact Sport - A Conversation with Jill Tarter

Howard Burton

• Editorial: Ideas Roadshow
• Año: 2021
• ISBN:
  9781771701150
• Categoría: Physical Sciences
• Categoría: Astronomy & Astrophysics

This book is based on an in-depth conversation between Howard Burton and Jill Tarter, Chair Emeritus for SETI Research at SETI Institute and Former Director of the Center for SETI Research. Astronomer Jill Tarter has spent the majority of her professional life driving forward the science and technology of the Search for Extraterrestrial Intelligence, rigorously scanning the sky for the signs of some signal sent to us from outer space. This wide-ranging conversation explores the history of the scientific search for extraterrestrial intelligence, what the present state is of our quest for signals from other planets, what those signals might look like and how we can interpret them, and how SETI research has a surprisingly positive effect on other technologies. This carefully-edited book includes an introduction, Searching for "What Is", and questions for discussion at the end of each chapter: I. Introducing SETI - The benefits of not growing up II. A Sense of Scale - Getting the big pictureIII. Detection - Examining the detailsIV. Suddenly Relevant - Scientific serendipity and holding up a mirrorV. Reaching Out - GloballyAbout Ideas Roadshow Conversations: This book is part of a series of 100 Ideas Roadshow Conversations. Presented in an accessible, conversational format, Ideas Roadshow books not only explore frontline academic research featuring world-leading researchers but also reveal the inspirations and personal journeys behind the research.

The Conversation

I. Introducing SETI

The benefits of not growing up

JT: Welcome to the Allen Telescopic Array. Not like your father’s radio telescope.

HB: No, not at all. And thanks so much for inviting me up here. So SETI: the search for extraterrestrial intelligence.

I should clarify—and I do this at my own peril because I may very well be cutting our readership in half or perhaps more—that this has absolutely nothing to do with alien abduction. This search has absolutely nothing to do with Roswell or with any other tales you might have heard of aliens in your backyard. This is serious scientific research.

JT: Right, this is the real deal.

HB: This is the real deal. And I’d like to throw it over to you now and ask what this is all about. What is SETI? Where did it start? And how did you become involved?

JT: Well, SETI is an acronym: Search for Extraterrestrial Intelligence. But having said that, I also have to say that’s a misnomer, that we don’t know how to find intelligence. I assume you’re intelligent because you’ve come to visit me. But figuring out intelligence at a distance is something we can’t do. So we use a proxy, we use technology as a proxy for intelligence. What we’re trying to do is use the tools of the astronomer—radio telescopes in this case, optical telescopes in other sites—to try to figure out if we can see evidence that someone out there is using some kind of technology that we can sense over the enormous distances between the stars.

HB: Sending us a message, giving us a beacon of a sort.

JT: That’s right. Generating a signal that doesn’t look like astrophysics, doesn’t look like Mother Nature, but looks like something that was engineered.

HB: So, what kind of a signal would that be? Give us a broad-based description of the sorts of signals that we would be looking for, these non-natural signals.

JT: Well, consider something in the optical range: how about a flash, a bright, bright flash of light, which lasts less than a billionth of a second. We don’t know of any astronomical sources that can do that. But lasers can. So if someone out there takes a laser and combines it with a big telescope, they can focus the laser and send out a pulse with all sorts of information encoded in it and it will arrive at our telescopes looking nothing like Mother Nature. And we’ll notice it, if you build detectors that can count photons fast enough to realize that you just got a whole lot of photons in one nanosecond.

That’s optical SETI and that didn’t start until roughly the year 2000 because the research community couldn’t afford the receiver technology. The technology existed before—it was being used by the military—but scientists couldn’t afford it.

Now we can, so we’re doing optical SETI too. Historically SETI has used radio searches to look for signals that are compressed in frequency. The optical signals are compressed in time, a billionth of a second or less. In radio SETI we’re looking for signals that have a lot of power: just sort of one channel on the radio dial.

HB: Just like when you’d listen to the radio yourself, you’re looking at a particular frequency, you’re tuned to a particular frequency. So the idea is that anybody who wants to communicate with us would also be sending something tuned to some unique frequency.

JT: Right, because nature doesn’t do that. Nature is emitting signals from lots and lots of atoms or molecules that are moving relative to one another. So even if each atom emits a particular frequency, that emission is spread out in the frequency domain because of the relative motion.

On the other hand, using technology, we can send and receive very narrow band signals. That’s one thing and that’s traditionally what we’ve looked for. We’re beginning to be able to use the correlator technology and the imaging technology here at the Allen Telescope Array to look for signals that have a lot of encoded information. We look for signals that have a repetitive cycle to them, even if we don’t know how to decode them. Again, it’s the sort of thing that nature doesn’t do.

There are all kinds of different signals you could look for and the more computer power we have to throw at this problem, the wider we can make our net, but this idea of a single tone—sort of a dial tone, if you wish—an attention-getting signal, still remains a valid one. And that’s what we’re looking for.

HB: Because that’s essentially what we would do if we were in the business—and perhaps we will be at some point—if we were in the business of beaming out a signal to other people to let them know exactly where we are and what we are thinking. We would do something presumably similar to this.

JT: Well, we might do that; and I think we would and if we ever grow up as a civilization that may be in our future, to start transmitting. But if you’re going to transmit with some effect, you’ve got to be talking about 10,000-year or 15,000-year plans and we’re barely able to get two-year plans done…

HB: Or even two-month plans.

JT: Right. So that’s in our future.

HB: Let me just back up for a moment and ask you to back up and tell us a little bit more of the history of how SETI came to be. You mentioned before that SETI started with radio telescopes, but perhaps you can give us a little bit of history as to how SETI came to be what it is now and how you personally got involved, because I think that’s a wonderful story.

JT: Well, SETI as a scientific discipline started in 1959 with the publication of a paper in the journal Nature by Giuseppe Cocconi and Phil Morrison; associated with the hydrogen atom because it’s the most abundant element in the universe. So that paper was the scientific birth of SETI.

Meanwhile, Frank Drake, who was working at the National Radio Astronomy Observatory in Green Bank, West Virginia, had been thinking independently about SETI and he had been planning on a search in 1960. He kind of got scooped when this paper came out.

HB: Really? I didn’t realize that.

JT: Oh, yeah. It was all done in secret until this paper came out; and then they were a little bit upset that somebody had beaten them to the punch.

HB: Sure. By months.

JT: Yes, by months. But anyway, in the spring of 1960 at Green Bank, Frank used the Tatel Telescope to listen for signals from two nearby stars, Tau Ceti and Epsilon Eridani. That was called Project Ozma and it was the first radio search. He was doing exactly the sort of thing we’re doing now: looking for these narrow band signals.

He could do it only one channel at a time, we now do hundreds of millions of channels at a time because technology has improved. But that was the first observational program; and since 1960, there have been 120, 125 projects that I’ve been able to find in the literature and document.

It seems like a lot: more than fifty years. People say, “Well, if you’ve looked for fifty years and you haven’t found anything, there must be nothing out there.” They just haven’t got much of a concept about how vast the cosmos is, how large this cosmic haystack that we’re trying to search is and how many different dimensions—all of these different ways that signals could be generated that we haven’t yet searched for. So it’s a daunting undertaking, but it’s really fun to be part of an exponential technology. Things are growing so fast and we can do so much more today t...