## If they are out there why don't we hear them?

Just saw an article that there is new speculation based on discovered planets around other suns that there could be earthlike planets around all the stars that are similar to ours (not news to me, I would have bet money on that before we ever discovered the first planet). Also that there could be life on many of them. If there is life it could be intelligent.

http://www.cnn.com/2009/TECH/space/0...ler/index.html

Assuming for the sake of argument that there are hundreds or even thousands of intelligent civilizations in our galaxy, why haven't we heard them? What are the possible explanations for the silence?

In another thread I asked how far away would we be able to detect a civilization that is emitting signals exactly like we are emitting ignoring the travel time issue. It seems from the posts there that we should be able to detect emissions like ours from almost anywhere in the galaxy so detection isn't the obvious problem.
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 Mentor The coming digital changeover holds a potential answer to that question: There is a very narrow window of history when a civilization transmits enough power to have a reasonable chance of being heard from dozens of light years away. Once we switch to all digital communications, the power requirements and output drop substantially.
 It could be they're making completely wrong assumptions about what we would find intelligible.

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## If they are out there why don't we hear them?

 Quote by russ_watters The coming digital changeover holds a potential answer to that question: There is a very narrow window of history when a civilization transmits enough power to have a reasonable chance of being heard from dozens of light years away. Once we switch to all digital communications, the power requirements and output drop substantially.
Has the switch over last 2 or 3 decades from relatively few high-powered transmission to lower powered but many more ones now decreased or increased the total power?
 Recognitions: Gold Member One consideration I sometimes think is their ethics: whereas we 150 years ago contacting a different civilisation (apart from less noble motives) had no doubt we were doing our duty and benefiting them in drawing them into ours, now we are more likely on contacting a people in Brazilia or New Guinea to think the ethical thing is to leave them alone and that it is better for them not to know anything of us.
 Recognitions: Gold Member They communicate telepathically, I hear them constantly and it is very annoying :)

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 Quote by epenguin Has the switch over last 2 or 3 decades from relatively few high-powered transmission to lower powered but many more ones now decreased or increased the total power?
Probably not but it has decreased the detectability. Lots of compressed data streams on a broadband spectrum in microwave is a lot harder to pick out than a repeating TV signal at a single VHF frequency.
 Its possible they have developed far more advanced ways of communication and us monitoring radio frequencies is not going to be able to detect the methods they use. Or it could be possible they have not yet developed advanced technology yet. Who really knows.

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 Quote by subliminal Its possible they have developed far more advanced ways of communication and us monitoring radio frequencies is not going to be able to detect the methods they use.
Aliens have cable?
 Recognitions: Gold Member Once a distribution system is in place (LANs, Internet backbone, fiber optics, DSL over copper pairs) it would be impossible for any aliens to know that we're chattering away, transferring huge amounts of data, etc. Apart from broadcast entertainment (over-the-air TV and radio) much of our society has gone radio-quiet. It is not unreasonable to believe that an alien civilization that has developed communications over EM channels would also soon develop methods of communication that are comparable to ours (low-power distributed networks) eventually.

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 Quote by dilletante They communicate telepathically, I hear them constantly and it is very annoying :)
Have you tried wearing an aluminum foil beanie?
 I think there are a couple of possible explanations. I don't believe that of the millions of stars in billions of galaxies that this planet is the only one that supports carbon based life (the only kind there is) or that it is the only planet that can. So there should be plenty of life out there. There isn't only one of anything with the possible exception of the universe. One explanation which isn't a pleasant thought is that almost all technological civilizations destroy themselves within a short time of being able to transmit RF. This would leave a small window of detection available for any of those civilizations. We are headed down this road and will be damn lucky if we are still high tech 200 years from now. I personally give it very low odds. We are assaulting our future viability on virtually every possible front. Another is that an intelligent society might not be anything like us. If their society were more like ants or bees than us they wouldn't be emitting RF even though they could. They would also be more likely not to destroy themselves. They could also be an extremely timid species that didn't evolve from carnivores like we did, which is part of our problem. They would be scared to advertise their presence because of racial fear of being eaten. Taking it to the other extreme, they could be a species of extreme carnivores. Where they don't advertise their presence the better to pounce on an unaware prey and hide from other carnivores such as themselves. Another possibility is that it's rare to have metal on an earthlike planet. I don't know if this is likely. Another is that no civilization lasts long enough to protect itself from being squashed by system debris or is too stupid to, like us. There is an asteroid or comet heading for us right now, the only question is when will it get here. My personal favorite is that all technological civilizations eventually create a supercollider of sufficient power that it destroys them. ;)

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 Quote by HallsofIvy Have you tried wearing an aluminum foil beanie?
Only tin foil works. And you can't get tin any more - only aluminum. That's why "they" made us switch you know....

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 Quote by nottheone My personal favorite is that all technological civilizations eventually create a supercollider of sufficient power that it destroys them. ;)
The good news is that to make one that destroys the Universe takes at least 5 billion years.

I hope this is a light hearted reply, or come on...

 Quote by nottheone carbon based life (the only kind there is) or that it is the only planet that can.
I had a feeling silicon based life forms were also probable

 Quote by nottheone There isn't only one of anything with the possible exception of the universe.
Is there only one universe? That may still be up for debate, but I think they're heading towards something with a few more than one.

 Quote by nottheone One explanation which isn't a pleasant thought is that almost all technological civilizations destroy themselves within a short time of being able to transmit RF.
You know of other technically advanced civilizations that discovered RF and then destroyed themselves and you're keeping that information from us??

 Quote by nottheone Another is that no civilization lasts long enough to protect itself from being squashed by system debris or is too stupid to, like us. There is an asteroid or comet heading for us right now, the only question is when will it get here.
You sure know of a lot of other civilizations that have had untimely ends...
 If you read my post carefully you will see that those are POSSIBILITIES for why we don't hear them. I have no certain knowledge of any of this and I didn't claim to. I would bet anything that all life is carbon based though. As far as carbon based life goes if we ever find life elsewhere it will be carbon based for a lot of reasons. Nature only makes things as complex as necessary. Carbon based life is only possible because of the ability of carbon to create thousands of compounds. Complexity is a requirement of life, more so for intelligent life. If nature could have made us simply she would have. From Wikianswers: "It is estimated that the human body may contain over two million proteins, coded for by only 20,000 - 25,000 genes. We have http://wiki.answers.com/Q/l on just over a million proteins, taken mainly from http://wiki.answers.com/Q/l found in the ~100 genomes which have been fully sequenced as of 2007. Proteins are long molecular chains made from the 20 basic building blocks of life, amino acids. The longest known protein, titin, also known as connectin, contains 26,926 amino acids. Titin is found in muscle and contributes to its passive stiffness. Because the 20 amino acids can be connected up in arbitrary sequences, the total space of possible proteins is exponential, with a value of approximately 2050,000, a tremendous number" No other element other than carbon is capable of doing this as far as I know.

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