Searching for E.T.'s Laser

The search for extraterrestrial intelligence (SETI) has proceeded for the last few decades as a noble experiment among professional scientists and ardent amateurs—the latter even donating spare cycles on their desktop PCs to participate. It hypothesizes that it may take quite a long time to identify an intelligent signal from the cosmos; but if that should ever transpire, it would mark one of the greatest moments in the history of civilization, which would certainly justify all the tedious effort. In this month's feature "The New Search for E.T.", author Monte Ross updates us on the work of SETI scientists who are using new technology to search for signals from intelligent extraterrestrials who may have chosen to send their message via laser.

Ross , an IEEE Fellow and a pioneer in the use of laser communications, writes that using Frank Drake's famous equation for the probability of some intelligent beings existing in our galaxy we can deduce that the number is quite small, but it is not zero. (This is the very point comedians used to exaggerate when parodying the late astronomer Carl Sagan's use of the phrase "billions and billions of stars...".) In the Milky Way, if we were to assume that only one in a hundred million stars could be home to a planet with intelligent beings capable of advanced technology similar to our own, that would result in a prediction that there are about 1000 other civilizations that could be trying to contact us. He notes:

To date, though, radio astronomers have heard nothing. It's too soon to conclude that nobody's out there: maybe SETI researchers are just looking in the wrong place or in the wrong way. I believe they've made the latter mistake. No intelligent society would attempt to communicate with us over hundreds of light-years using radio waves when physics suggests other wavelengths would be the more intelligent choice.

Ross thinks the better tool for the job is a telescope known as a photon bucket. These lens-less devices search the heavens for optical signals using mirrors to scoop up raw photons, the way a wooden barrel collects rainwater. They also use multipixel photomultiplier tubes that convert the incoming photons into electrons, which then get amplified into an electrical signal that is fed into microprocessors for computer analysis. Such devices are now coming on line—sponsored by institutions such as Harvard University—in the hunt for the elusive signal from a real E.T. out there somewhere.

It might sound like looking for an atom from a needle in a mountain of haystacks, but the true believers remain undaunted. The greater the challenge, the more determination they muster to tackle it. And now, at least, they have an intriguing new tool in their hands to help them do the looking.


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