[meteorite-list] OT: Listening To Fermi

[JoshuaTreeMuseum]

Hi Richard;
That's an excellent argument for cancelling the silly SETI project.  The key 
word in your argument is "believe". You believe in the existence of exo-life 
without any supporting evidence, I don't. So we can agree to disagree.

If life never existed on Mars, I can't see it existing anywhere else. But, 
my beliefs are evidence based, I'll change them in a minute if someone will 
just show me the money.

-----------------------------------

Phil Whitmer


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Actually Phil, I'd disagree with that statement, even though I believe that 
the universe is filled to the brim with life, I think that intelligent life 
is exceedingly rare.

Personally I think that SETI is never going to find a signal, not because 
there is no life out there, but that the circumstances required to find a 
signal is exceedingly small. The analogy put forth by others in this thread 
of a child looking out a window for 32/1000ths of a second is a good one.

Use ourselves as an example. Radio technology on earth is barely a century 
old and we are already rapidly moving away from high powered transmitters to 
low powered devices for communications. Our most efficient long distance 
communications are already moving via fiber optics, so require no radio 
transmissions whatsoever.

Ask yourself what are/or were the most powerful transmitters used?
The answer is Early Warning defense radar systems. In fact at those 
frequencies Earth was brighter than the Sun. As the Cold War wound down, and 
the technology improved, lower power transmitters could do the same job. For 
about 40 years, Earth shined exceedingly brightly in microwaves, with a peak 
radiance about 1/3 through that period. So you can imagine a shell of 
microwaves 40 light years in thickness traveling out from our solar system, 
expanding at the speed of light. (I'm sure I'll be corrected here, but 
that's OK. I welcome it.)

Say a intelligent civilization, only a century behind us in technology 
(Almost statistically impossible) 50 light years away from us will develop 
the technology to detect radio waves of that frequency. Our microwaves from 
the early warning systems have been reaching them for more than a decade 
already, but they won't develop the technology to detect this radiation for 
another 30 years or so.

In other words, just as they gain the ability to detect our unintended 
signal to them just as it has completely passed them by. Even if they point 
their radio telescope directly at earth, they wouldn't hear us as our signal 
drops again below the background noise.

And so it goes planet after planet as the signal extends out into space in 
an ever expanding shell, growing ever weaker. If we continue our trend to 
become more radio silent in other frequencies too, our civilization could 
become radio dark again as far as the universe is concerned in the next 
hundred years or so.

Expand this problem by a more realistic estimate that civilizations become 
technologically capable thousands or millions of years apart, not mere 
decades apart...

Now reverse the situation. For SETI to work you have to be listening at the 
precise moment the signals are passing our region of space. Miss it by a 
century, a decade, a year, a day, and its too late. The signal is no longer 
detectable. It may literally take many millenia before the right combination 
of circumstances allow us to detect another civilization through just their 
radio communications, intended or otherwise.

Ironically, I think that SETI is an experiment that should not be abandoned, 
because you'll never know if there is a detectable signal if you don't look. 
I just think it will never yield a positive result. However, I do believe 
that the canceled Terrestrial Planet Finder mission had a much better chance 
to find habitable, and planets that have abundant life.