- The Washington Times - Monday, February 11, 2002

The Internet, ever a democratizing influence, has put the quest for extraterrestrial intelligence on your desktop. You too can look for little green men. And it's effortless. You can do it in your spare time. All you have to do is go to setiathome.ssl.berkeley.edu/ and download a screen saver.
It works like this. If there is life among the stars, think some astronomers, it might be trying to signal us, or signal somebody, and we might be able to pick up the radio signals. This assumes that space aliens communicate by radio. A gigantic radio telescope in Arecibo, Puerto Rico, picks up vast amounts of radio noise, but doesn't have the disposable computer power to search through it for signs of intelligence. Mostly it's used by astronomers for other things.
A group at Berkeley, Calif., had a bright idea, one that many others have had and occasionally used. What if, they asked, we hooked together huge numbers of personal computers everywhere, via the Internet, and let them analyze chunks of data in their spare time?
Good idea, but how do you do it? There are various ways. The SETI at Home folk decided to use a mathematically clever screen saver. When you go to lunch, or to sleep, or maybe get lost among acres of cubicles and can't find yours, the screen saver pops up and, with it, the mathematical-analysis software.It grinds away madly on the radio data (which it gets from Berkeley when you are on the Internet.) When you touch a key, having found your cubicle, it instantly stops and the computer is yours again.When it has finished, it sends the results to Berkeley by Internet. The idea is to find pulsed or communicationslike signals.
Slick. I'll bet a lot of theses come out of it.
More than three million computers have participated so far.There are versions of the screen saver for UNIX, Windows and Macs.
Exactly how much computing power this produces is hard to say, but "a whole bunch" is a good approximation.According to SETI at Home, "The most powerful computer, IBM's White, is rated at 12 TeraFLOPS and costs $110 million. SETI at Home currently gets about 15 TeraFLOPS and has cost $500,000 so far." A TeraFLOPS is one trillion floating-point operations per second.You could balance your checkbook really fast with that.
The mathematics of searching is complicated, but the ideas aren't very.For example, a serious problem is distinguishing very weak signals coming from deep space from the abundant radio interference produced by us: radio stations, airplanes, satellites, electric motors, what have you.
However, certain things make it easier to filter out interference.In particular, the radio telescope is fixed to the Earth, which means that the receive-beam sweeps across the sky as the Earth turns.A source among the stars produces a 12-second signal that rises in strength as the target moves into the beam and falls as it moves back out. Most terrestrial interferences are steady.This and other sorts of calculations, such as doing fast-Fourier transforms, are what your little desktop box will do.Afterward, it may think memos are boring.
The whole search relies on various assumptions that don't necessarily make much sense.Radio is awfully slow for interstellar conversation.If an alien or bunch of them were five light-years away, which isn't very far at all, 10 years would pass before they could get an answer to a signal.It just wouldn't work for romance: After very little cooing back and forth, you'd be on Social Security.
And aliens, I'd think, would be unlikely to be trying to communicate with us. Humans have had radio for only a century or so, so nobody beyond a hundred light-years should know we exist. We're probably the technological equivalent of headhunters eating grubs.
Thing is, we have to look for green men by radio because we don't know any other way.Radio waves travel at the speed of light, which is the theoretical maximum at which anything can travel just now anyway and so radio is the only way we have for hunting for other intelligence. (Except maybe for going to Roswell and waiting for flying saucers to crash. They seem to have maintenance problem. But the Air Force hides the remains.)
The people doing this are perfectly aware of the objections.Assuredly, they are very bright, a characteristic of astrophysicists, and it's hard to think of anything more fun for graduate students to work on.However, it's cheap and, well, what if they found something?

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