--- On Mon, 7/19/10, Jed Rothwell <jedrothw...@gmail.com> wrote:
> Hmmm . . . What about up-links to geosynchronous TV and telcom > satellites. Or, if a civilization expands beyond one planet (but not > interstellar), what about interplanetary communications? I don't have any data on hand about those systems, but it'd be interesting to look into. The satellite broadcasts themselves are going to be aimed down here, so those originating in space (minus something which might bounce off the atmosphere) wouldn't likely factor in. Whatever we send up to them, might be a different matter. The Voyager probes with 22W transmitters can reach here from >40 AU. I wonder how much further the Earth transmissions TO them can reach out to? > I think the best prospect would be to eavesdrop on an interstellar > civilization. Might be, but given that our communications technologies are becoming more compressed and efficient, we might not know what we're listening to. For instance, I recently constructed a vacuum tube radio from scratch. Coils let it cover everything from LW to SW. There are plenty of data transmissions on the SW bands which are barely understandable. In the higher frequencies, where even neater tricks can be done, the situation gets more interesting. If we eavesdrop, the best me might get is a brief flash of 'some noise' which looks tantalizingly like an artificial broadcast, but never repeats. There have been hundreds of these, the most famous being the '77 WOW signal that the Big Ear picked up. I think it would be fascinating if it turned out that the '77 signal was something artificial, maybe a burst transmission of planetary data that a probe had gathered. Maybe it was their version of Neil Armstrong, setting foot on a new world. (I still can't get over the fact that they bulldozed the Big Ear to make a golf course. Apologies to Bluto Blutarsky, but... "They took the scope! The whole f*****g scope!!!") ... And again, this all assumes 'they' are using radio. > >The fact that no intelligible broadcast could be detected from a > >distance of more than ~1/3 light-year is interesting; there could be > >something as close as Alpha Centauri, and we might never know about it. > Goodness! That's sobering. That's assuming they have approximately the > same technology as we do. It puts CETI in perspective; we have not > checked much yet. - Jed I'm working out some simple, 'crunchy' calculations on how they might fare with a bigger receiver aperture. It does make one think. The galaxy has 400 billion suns, and we can't even detect technology around the nearest one, even if it is there. In some ways, it seems a little scary. In other ways, it's sort of comforting to be able to go outside, look up, and know that there are still plenty of places for the stellar cartographers to write, "Here be dragons." What can I say, I love the unknown. --Kyle
