Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site topaz.ARPA Path: utzoo!linus!philabs!cmcl2!seismo!columbia!topaz!milne From: milne@uci-icse Newsgroups: net.sf-lovers Subject: Re: visible civilization Message-ID: <3076@topaz.ARPA> Date: Fri, 2-Aug-85 21:49:04 EDT Article-I.D.: topaz.3076 Posted: Fri Aug 2 21:49:04 1985 Date-Received: Sun, 4-Aug-85 05:57:04 EDT Sender: daemon@topaz.ARPA Organization: Rutgers Univ., New Brunswick, N.J. Lines: 36 From: Alastair Milne >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> I'm told that the Earth is the brightest radio source in this region of the galaxy, so finding it shouldn't be too hard if you have radio telescopes. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< I'm certainly no expert, but if Earth is brighter than the Sun, in any band, I'll be very surprised. You might double check with your source, if you can; also about competition with Jupiter, and possibly Saturn. There is also the problem of the angular distance of Earth from the Sun, especially from very distant (ie much more than Alpha Centauri) stars. I've neither the time nor the inclination to go through the math, but I suspect it would be difficult, perhaps extremely so, to resolve Earth's signals from the Sun's. And remember, as I said in my first posting, to pick up any of Earth's signals at all other than natural ones (and I don't know whether there are any) you have to be within about 50 or 60 light years. I'm sure no such signals were generated anywhere on Earth more than 60 years ago, or perhaps 70, when the first crude recordings were done. And at 70 light years' radius, those signals, weak as they were to start with, must have attenuated miserably. So I would place 70 light years as the maximum radius at which Earth could be detected by radio telescopes, if it could be so detected at all. Alastair PS. Thanks for keeping the discussion going. This is rather interesting.