Re: A of E author in alien light signal detection project

Don Klipstein wrote...

In article <pan.2006.05.16.06.58.04.837327@xxxxxxxxxxx>,
Rich Grise wrote:

I seriously doubt if anyone who has the power to communicate between
star systems would use electromagnetic radiation to do it. What's the
status on gravity waves these days? How about quantum black holes? ;-)

Well, I could comment a bit on gravity waves vs. lasers.

Consider wavelength, and how that limits narrowness of a beam.

If I wanted to be noticed by someone on a planet 30 lightyears away,
I would get the biggest Nd:YAG ("YAG") laser that I could get and fire
it through a large telescope.

Let's see what happens if I get a 25 megawatt peak pulse YAG laser
(1064 nm) and fire it out a telescope whose objective is 3 meters in
diameter. I try Google and find 25 MW YAG lasers have been made, and
Earth's biggest telescope is about 5 meters last time I checked ...

Don, you can review Paul's take on the numbers at his oseti website.
http://seti.harvard.edu/oseti/ and http://seti.harvard.edu/oseti/allsky/

One working assumption, IIRC, is the transmitting end employs at least
MJ pulses, with a Keck-size telescope (10 meters). This would allow
detection to a 1000 light-year range, if the telescope is aimed at us
(the transmitted beam would spread out to the orbit of Jupiter). Some
calculations in a 1998 paper, http://seti.harvard.edu/oseti/tech.pdf
and a 1999 paper, http://seti.harvard.edu/oseti/bioast99_paper.pdf

One of Paul's students, Andrew Howard, has used the new all-sky oseti
telescope to take a quick look at a few million stars, a factoid he's
including in his PhD thesis-defense lecture, Thursday the 18th.


--
Thanks,
- Win
.

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