--- On Sat, 7/17/10, mix...@bigpond.com <mix...@bigpond.com> wrote: > To put this in perspective, in order to pick up 1 > micro-Watt in total from our > 10 MW transmitter, the dish would have to have a radius of > 6 million km. > BTW the *closest* star to Sol is 4 ly away, not one.
1uW is a lot of power, at least to a radio receiver. I'm pretty sure my homebrew regen set will beat this. My flame radio would probably detect it as well, even as badly received as that project was. If Wikipedia is to be believed, and several other places, including NASA themselves confirm it, the Galileo probe's 20W transmitter produced a signal which, upon reaching the DSN dish, had a power of about 1x10^-21W. The dynamics are far different from broadcast TV, of course, but the situation isn't so terribly bad for listening. Really, I wouldn't expect to find intelligent life around Alpha Centauri. The dynamics of the system are somewhat of a mess. I think we need to look a little further away. Beta CVn is probably one of the most interesting, and not too far away by cosmic standards. Zeta Tucanae, 18 Scorpii could be candidates. I don't know if any of these were recently determined to be spectroscopic binaries. Of course this could be narrowing things too much. M-type stars are the most common, and if we assume a life system using ammonia or some other cryofluid as a thalassogen, things are more interesting. Going a little more off topic, Stephen Gillett's book "World Building" gives some alternative possible biosystems. He's a little too pessimistic as far as technology goes. For instance, the world he calls "Clorox" has an atmosphere loaded with free chlorine gas. The suggestion that a lack of fire, and rapid corrosion of steel (the steel would rapidly corrode, and you couldn't smelt it in the first place) would stymie technological development seems sort of short sighted given intelligence. Intelligence finds a way, I believe. Hell, simply coating the transformer steel in rubber or plastic (maybe on a chlorine world they have PVC trees) would stop the corrosion. The challenges presented to the inhabitants of that world might actually spur development and innovation. --Kyle