--- 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
