Originally posted by Rajk999
I disagree that anything should stop humans on Earth from attempting to contact other life in the universe.
It will probably be a LOOONG search. Thing is, we humans now have the capability of hearing OURSELVES from the other side of the galaxy, our radio telescopes are that sensitive but so far nothing of intelligent nature coming our way.
The problem could be this: Here we are in a nice cozy galactic neighborhood with literally billions of stars within 100,000 light years or so. Now it may be that high tech civilizations have a certain life span, for whatever reason, they start out spewing radio waves and maybe THZ and IR and visible laser signals into space.
We have done that for say 100 years or so.
So now OUR signals are contained in a sphere with a radius of 100 light years, a sphere 200 light years across so there is no getting around the fact that anyone within 100 light years with stuff as sensitive as ours will hear US.
So suppose someone out there 100 light years away hears our signals and decides to answer, HI THERE, WE ARE THE KLUTES, WE LIVE ON THE PLANET KLUTE AND IT LOOKS LIKE THIS, followed by cutsey pics of their home land.
But of course we don't hear that signal at all till the year 2117 and we send a reply, they don't hear it till our year 2217 and we go HI BACK, YOU LIKE MUSIC? and we send some Frank Sinatra...
They send back, Great stuff! now its 2317 and so forth.
Now that might be barely possible
But suppose that projected civilization is not 100 light years away but 10,000 light years away.
So our growing sphere of radio wave, that wavefront is proceeding slowly through the galaxy and 10,000 years later a civilization is there able to pick up our signals and answers. but this time the answer comes to us in the year 22,017. A bit of a stretch to think that we would even HAVE a technical civilization that far in the future or even if humanity would exist then. Now jump that forward, suppose that civilization is not 10,000 light years way but 100,000 light years away.
So 100,000 years from now, they have gone from cave men to advanced civilization like Earthy's and they now pick up our signals which have been traveling 100,000 years.
They go, WOW, we are not alone. Send back a signal of their own, they have not much idea how far away we are but they send their stuff anyway.
Now 200,000 years have gone by on Earth. What will we be THAT far in the future?
Now suppose we and say just for grins, a general rule of civilizations is they seldom last 10,000 years. So suppose there is a civilization that is 30,000 light years away.
Our wave front reaches them 30,000 years later but their civilization has long gone from hi tech to low tech maybe back to hi tech three or four times, and we catch them on a down cycle.
Then they get high tech back say 10,000 years later. So OUR civilization goes bonkers at say 5000 years from now and we maybe don't perish but are pushed back to era's like ancient Greece or such, no tech to speak of, certainly had forgotten radio and the like.
So our wavefront goes by, 5,000 years of it, their civilization has their ups and downs and our 5000 year long signal dies down and continues on it's way through the galaxy but THAT civilization that had a chance to hear our signals now has not the capability of listening in so it's like 2 ships passing by in the night, neither one knowing about the other even though they might have been the best of friends if they knew each other.
THAT is the problem of finding aliens.
Another thing, suppose our civilization grows to the extent that we stop for whatever reason, to send out radio waves, suppose we realize we are polluting the galaxy or some such or we simply grow past the need for radio and now we modulate neutrino beams, whatever, now the wavefront is say only 200 light years deep, it goes by, that 200 year wide signal path, goes by a lot of civilizations in the wrong stage of their existence to hear us so another set of ships passing in the night.
The gist of that: if we hope to really speak with aliens, they bloody well better be within 100 light years or so, preferably TEN light years away.
But we have already sussed out most of the local neighborhood a few hundred light years out with nothing heard.
So to me, it's a great effort and radio telescopy will gain a lot from the effort in terms of much better and more sensitive receivers with much narrowerer bandwidth detection and modulation and demodulation schemes, I don't hold out much hope for actual aliens to be heard in OUR neighborhood. Maybe we will get a hit from something all the way cross the galaxy but though nice, that would definitely be a one way transmission, but maybe they would know that and start transmitting the encycopedia Galactica like Carl Sagan suggests....
Calling All Aliens
25 May '17 00:02
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