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Optical SETI


  12:55:04 am, by Nimble   , 526 words  
Categories: Thoughts, Science

Optical SETI

The Planetary Society sponsors an odd variety of space activities, like the Earth Dials and the Huygens microphone that let us hear the sounds of Titan. Their solar sail program suffered a major setback last year when the Volna launch vehicle failed while carrying their solar sail vehicle, the Cosmos I.

They're just about ready on their Optical SETI Search program. We've seen a lot about radio-based SETI, popularized by the movie Contact, and the distributed computing project by Berkeley, SETI@Home.

For those of you unfamiliar with the term, SETI is the Search for Extra-Terrestrial Intelligence. It's a search far in the heavens for signs of communication. No UFOs, no aliens in Roswell.

The idea being that if intelligence arose here, it may have arisen elsewhere. We simply do not know the odds of that, despite things like the Drake Equation. It's like a lottery winner trying to figure out what the odds are that they won, without hardly any benefit of knowing how the odds came to be.

We've found more than 150 exoplanets, which makes the "are there planets out there?" question (which we didn't know for sure until recently) answerable in the positive. That said, a SETI search, even if there's intelligent life out there, doesn't stand much of a chance of finding anything. Why might that be?

We're looking for a strong signal. Our own strongest signals went out with radar and television in the mid-20th century. Now our signals are getting more complicated, to pack more information in, and the energy output per signal is dropping with better technology. Aliens couldn't even hope to see our early TV broadcasts much outside the solar system. What are the chances that if we've done this in less than 100 years, that we could even look out on the sky and hope to get an accidental signal?

Whatever we see on this search will actually have had to be directed at us; it's not going to be an accidental intercept. Some being far away would have had to say "let's send a signal - there - with lots of power in a tight beam". We've hardly sent out any of that kind of signal ourselves - one of the signals was sent via the Arecibo to the M13 cluster, some 21,000 light years away. Oh good! Wake me up when the message arrives!

On top of that, we've been presuming radio will be the medium. Or at least, that's all we've had resources for. This Optical SETI project will look for optical laser messages. Once again, fat chance unless this exactly matches with the desires of some extraterrestrial life. Who's to say that we won't discover a more interesting way to send information when the quantum revolution comes? If radio and optical are passé elsewhere, it would be like sitting on an island without a radio - you could be inundated with radio waves, but you wouldn't have a clue (braces-used-as-antennae notwithstanding :) )

So I wish them good luck, but it really will have to be that :) Certainly increases the chance of finding an actual laser beam directed at us up from zero percent to extremely small percent, anyhow :)

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