V,
>From http://www.faqs.org/faqs/astronomy/faq/part6/section-12.html
I did some calculations (assumes I did the arithmetic right) for a dish with an
aperture of 10,000 meters. Such a structure could be conceivably constructed in
space, using either one massive construct, or arrays of smaller ones linked
together. I don't know if there would be a detriment in using multiple ones or
not, so lets just assume our aliens are using a single, huge dish with an
efficiency of 50%, as per the paper, and we'll leave the SNR at 25 as well.
FM radio reaches out to about 0.008 ly. No one's listening to Canned Heat or
Johnny Cash.
UHF picture reaches 0.001 ly. "I Love Lucy" and "Welcome Back Kotter" are out.
UHF carrier reaches 10.06 ly. "Oh sh----"
Assuming technology has progressed farther than our own (not an unlikely
assumption if our aliens have the space program necessary to build a 10km
diameter radiotelescope in deep space), someone could easily be listening to us
from Tau Ceti. They might not know what we're saying, or who we are, but they
could get the hint that there is a technological civilization somewhere around
that dim yellow star in their sky.
If they are curious enough, maybe they would come by and see us some time.
--Kyle
