Martha Adams wrote:

"Matt Giwer" wrote in message
g.com...
mike3 wrote:
I was wondering: How do we know it would even be possible to receive
the signals from aliens even if they did exist and did send out radio?
Considering we have a galaxy full of stars blasting out far more
intense radio signals than any ground-based transmitter could.
Wouldn't it be like trying to listen for a fly buzzing on the other
end of a stadium, with 50,000 screaming fans in between you and it?
How do sonars hear a submarine miles away in the midst of all the
noise in the ocean?
You listen for a particular frequency while filtering out _all_ the
other frequencies. If the signal is greater than the noise in that
very narrow band you hear it. Further, you can integrate that
frequency over time. Noise in that band will average out to zero while
the frequency will increase with time.
Using your example how do you hear your friend sitting next to you in
a stadium in the midst of all the noise in a stadium? You can also
talk in a loud factory and there the trick is not to shout but to
speak normally and distinctly. The ear is very good at picking out the
frequencies of interest.
The only requirement is to have frequencies of interest louder than
the noise at those same frequencies. The broadband noise level
(stadium noise) is not important. The entire radio/TV spectrum has a
huge noise level broadband. But by tuning to just a narrow range of
frequencies you can pick one station out of all the stations and all
the noise.
In practice, SETI is looking at the "water hole" frequency which is
particularly quiet over very long distances. It is assumed anyone
sending knows that also and chooses that frequency so as to be heard.
That assumption does not apply unless there is a deliberate attempt to
communicate. I am not aware of any reasoning which can lead to a
second frequency to monitor so after that one frequency it is a crap
shoot.

That's the long answer. The short answer is the question relies upon total
ignorance concerning its topic. There used to be rational and informed
people posting here, but mostly rubbish lately. How come?

At one time there were also people here who answered the questions of
novices. I waited a day and then replied. As expected my reply generated
responses to me rather than different style answers to the questioner. Why is
that?

Whether or not we choose to remember it, we were all novices at one time. As
the questioner did not hint at his background a response touching on several
different factors was given in hopes of finding common ground upon which to
build a more useful answer.

When there was regular discussion on the problems of the S@H follies there
were technical discussions. Now that S@H has had its lunch eaten by a more
general program and that program works smoothly there is little to discuss and
thus very few technical discussions get started.

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