MADELINE BRAND, host:
This is DAY TO DAY. I'm Madeline Brand.
They could be out there. And a telescope sitting on a ridge outside Boston is looking for them: aliens. The telescope will soon begin scanning the sky, searching for laser signals from extra-terrestrials who want to say hello.
That they may send laser signals to do that is a new idea. Previously, scientists had assumed aliens would be sending radio signals.
NPR's DAVID KESTENBAUM reports.
DAVID KESTENBAUM reporting:
In the 1960s and '70s, researchers asked themselves: Now, what would I use if I were a space alien trying to send a message? Usually, the answer was some sort of radio transmission. Radio seemed easy and it could travel long distances in space.
Paul Horowitz is a physicist at Harvard. He says no one was really considering laser signals except for people like Charles Townes, who had just helped invent them. Towne's wrote a paper about it.
Professor PAUL HOROWITZ (Professor of Physics, Harvard University): I remember reading this and thinking, well, that's Charlie Townes, he's a laser guy. What do you expect? Back to my radio telescope, you know?
KESTENBAUM: Eventually, Horowitz came around. One thing that convinced him that aliens might be sending signals with lasers is that earthlings are now capable of it. If you take a big, modern laser and a mirror, it would make a pretty nice beacon.
Prof. HOROWITZ: So, we would send, or they would send--we're putting ourselves in their shoes, or whatever they wear on their feet, or whatever they have for feet--anyway, we would have this apparatus that was putting out these pulses perhaps 10 or 20 per second; each pulse powerful enough to be seen easily from a distant civilization.
KESTENBAUM: Lasers have a couple advantages: They produce a nice, focused beam, and for short amounts of time they can put out huge amounts of power, like a million billion watts.
Prof. HOROWITZ: That's something like a thousand times the total electric power output of the world.
KESTENBAUM: If we were to send out such a pulse, he says, it would appear 10,000 times brighter than our sun. Horowitz set up a small experiment to look for laser signals through an existing telescope, but it was like looking through a straw, he said.
So, now, he and his colleagues have built something better: A telescope and camera, specially designed to sweep across the entire northern sky. The search should take about 200 clear nights. They're testing the apparatus now.
Prof. HOROWITZ: The data that comes out of that every second is equivalent to the content of all books in print. Of course, we have the world's largest garbage can here, because we can't possibly store that kind of information. Even Google couldn't handle that. We throw it all out unless we see evidence of something that looks like an intentional laser flash coming from space.
CHARLES TOWNES (Nobel Prize winner; Inventor of the Laser): Well, I was pleased, of course.
KESTENBAUM: Nobel Prize winner, Charles Townes, who is happy people are finally doing what he suggested decades ago.
TOWNES: But, you know, we still have to hear that signal; we haven't heard a signal yet. If we can get a signal from some other civilization around some other star, that'll be a fantastic experience.
KESTENBAUM: Of course, it is possible that lasers are old hat for aliens now; that they've moved on to Z-rays or something. Townes says there is a lesson here.
TOWNES: You know, we get locked in on particular ways of thinking and we kind of neglect everything else. And this is one reason the laser took so long to be discovered. The laser could have been invented, oh, 30 years before I invented it, actually. We knew all the physics involved. And even when I started suggesting a laser, people said, oh, well, hmm, that's amusing, but, no, that's not likely to work.
KESTENBAUM: Silly humans.
David Kestenbaum, NPR News.
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