Hunt for Intelligent Aliens Focuses on Faint Laser Flashes


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Message boards : SETI@home Science : Hunt for Intelligent Aliens Focuses on Faint Laser Flashes

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rolo1
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Message 1409311 - Posted: 29 Aug 2013, 13:20:21 UTC

http://www.space.com/22448-alien-life-search-laser-signals.html

"They show that current detector technology can detect individual photons and process their arrival times to sense the expected faint illumination from even a distant alien transmitter," said astronomer Geoffrey Marcy at the University of California, Berkeley, who did not take part in this study. "The key now is to implement their SETI technique on a large telescope having a mirror of diameter 1 to 3 meters (3 to 10 feet) to begin searching for periodic laser transmissions."

Interesting...
Will we be crunching for laser signals soon too??

Sorry if this has been posted somewhere else.

Rolo
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Message 1409496 - Posted: 29 Aug 2013, 19:59:36 UTC

Lasers are so narrowly focused that I suppose they would have to be aimed with such precision that probably doesn't exist. I've never seen reports on how much a laser beam spreads over very long distances.
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Message 1409503 - Posted: 29 Aug 2013, 20:20:34 UTC - in response to Message 1409496.

There would be significant beam divergence over interstellar distances.

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Message 1409870 - Posted: 30 Aug 2013, 17:52:17 UTC

Assuming something close to optical wavelengths, and a laser beam with a minimum diameter of 10 meters, as was done in the article, the divergence of the beam should be about 70 million kilometers at one hundred light years, and 700 million at 1000 light years, supposing my calculations are approximately correct. Neither would appear to require extraordinarily precise aiming to encounter our planet.

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Message 1409887 - Posted: 30 Aug 2013, 18:54:15 UTC - in response to Message 1409870.

Assuming something close to optical wavelengths, and a laser beam with a minimum diameter of 10 meters, as was done in the article, the divergence of the beam should be about 70 million kilometers at one hundred light years, and 700 million at 1000 light years, supposing my calculations are approximately correct. Neither would appear to require extraordinarily precise aiming to encounter our planet.

The diameter of Earth's orbit around the Sun is ~299.2 million kilometers (2 AU). Someone sending such a laser beam to us needs to know precisely where the Sun will be in a hundred or thousand years, both in angular measure and distance, and knowing where Earth will be in its orbit would improve chances of reception.

Our knowledge of star systems at those kinds of distances is not yet accurate enough to send such a beam, but we can hope a more mature civilization has gathered and refined enough measurements...
Joe

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Message 1410124 - Posted: 31 Aug 2013, 15:00:58 UTC

A 700 million km wide beam would easily encompass the Earth if merely aimed at the predicted position of the Sun, 1000 years in the future. A 70 million km wide beam, if aimed at the position of the Sun 100 years in the future would cover about 15 percent of Earth's orbit immediately. One adjacent beam to either side of the first one would cover the entire orbit of the Earth.

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Message 1410379 - Posted: 1 Sep 2013, 9:08:36 UTC - in response to Message 1410124.

They wouldn't know where to send it. They wouldn't know we are here. It would have to be a slewed beam that hits us by chance.

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Message 1410422 - Posted: 1 Sep 2013, 12:55:36 UTC

It seems to me that the chances of us detecting a laser signal are much lower than those of finding a radio signal. Of course finding any evidence of a laser would almost certainly have to point toward an intelligent origin.
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Message 1410430 - Posted: 1 Sep 2013, 14:10:10 UTC
Last modified: 1 Sep 2013, 14:45:52 UTC

First-- a correction to my last post. A 70 million km wide laser beam would require two beam widths on either side of one pointing directly at the predicted position of the Sun, for a total of five, in order to cover all possible positions of our planet, in its orbit. Since laser beam width is inversely proportional to its rate of divergence, selecting a beam, somewhat narrower at the outset would cause a single beam to diverge in such a way as to cover the entire habitable zone around a star, at once.
It seems likely that an advanced civilization would know not only the locations of extrasolar planets likely to be suitable for life, but also which planets showed spectroscopic evidence of such life, in the constituents of their atmospheres. We ourselves have already begun to do the first, and will soon be able to make a start at doing the second.

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Message 1411039 - Posted: 3 Sep 2013, 13:25:57 UTC

Does all sound promising though.

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Message 1411382 - Posted: 4 Sep 2013, 14:23:38 UTC

+1
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