Re: OT: Aliens in the heavans (was Re: seti@home)
Tom Cook writes:
> Actually electromagnetic radiation falls off inversely with distance,...
Field intensity is inversely proportional to distance. Power density is
inversly proportional to the square of distance (and power is, of course,
what we can actually detect).
> ...since no-one has yet devised an antenna which radiates very
> well in all directions...
That's completely irrelevant.
> The direction of propagation is perpendicular to the direction of motion
> of the exciting charges (aren't they exciting? ;-) and so the wave
> propagates in the horizontal plane (assuming that your antenna is
> oriented that way.
The radiation propagates in all directions (though the intensity varies
around the antenna patern). I think you are confounding polarization and
propagation.
> I agree with you (except about wave energy density); I believe a 1 MW RF
> plane radiator is very difficult to demodulate with our technology from
> the edge of our solar system,...
Just the other day NASA received a response to a signal that they sent to
Pioneer 10. It is 22 light-hours out and has a low-gain antenna and a
transmitter power of a few watts.
--
John Hasler
john@dhh.gt.org
Dancing Horse Hill
Elmwood, Wisconsin
Reply to: