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

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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/02/25/galaxy.planets.kepler/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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  • #2
russ_watters
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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.
 
  • #3
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It could be they're making completely wrong assumptions about what we would find intelligible.
 
  • #4
epenguin
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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?
 
  • #5
epenguin
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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.
 
  • #6
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They communicate telepathically, I hear them constantly and it is very annoying :)
 
  • #7
mgb_phys
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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.
 
  • #8
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.
 
  • #9
mgb_phys
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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?
 
  • #10
turbo
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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.
 
  • #11
HallsofIvy
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They communicate telepathically, I hear them constantly and it is very annoying :)
Have you tried wearing an aluminum foil beanie?
 
  • #12
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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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  • #13
Vanadium 50
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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....
 
  • #14
epenguin
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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.
 
  • #15
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I hope this is a light hearted reply, or come on...

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

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.

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?? :smile:

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... :uhh:
 
  • #16
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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.
 
  • #17
mgb_phys
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Only tin foil works. And you can't get tin any more - only aluminum. That's why "they" made us switch you know....
I don't wear a tinfoil hat any more since I heard that the CIA own Alcoa.
 
  • #18
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Scientific American had an article about this in July 2000. http://www.sciam.com/article.cfm?id=where-are-they [Broken]

Or read http://en.wikipedia.org/wiki/Fermi_paradox

Not being a digital subscriber it's been nearly nine years since I read the article but as I recall, it mentioned that as the SETI program has been in operation since the 60s, if there are other advanced civilizations in our galaxy, there is about a 50% chance we would have detected them by now.
 
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  • #19
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What we consider to be intelligent may turn out to not be a very advantageous evolutionary trait.

Civilizations that do transmit do not do so for very long. Maybe they destroy themselves. Maybe they use other means to exchange information. RF is very energy inefficient.

We have not had the technology to send or receive in RF for very long. If there were a technical civilization only 75 light years away and they received a signal from us and immediately sent one back, there still would not have been enough time for us to receive the reply. This is practically in our own backyard, and we would not know this species existed. If technical civilizations can be mostly ruled out of existing in our galaxy, it must be under the assumption that all technical species transmit in RF for hundreds of thousands of years. In my opinion that is a difficult assumption to accept.

Although I do think that it is a possibility for many civilizations to exist in our galaxy alone, I don't see any reason to assume that they would all be around at the exact same time in history. The entire lifetime of our species can be measured in hundreds of thousands of years, the galaxy in thousands of millions. There may only be a window of about 200 years that civilizations transmit in RF, in a galaxy so large that it takes 100,000 years for the signal to go from one end to the other. Imagine a thin shelled sphere propagating outwards from earth at the speed of light. The 200 light year band could pass right over intelligent species that have not yet developed the requisite technology to detect it. Or the RF band could be 10,000 light years away from a technical civilization that could detect it, but will not exist when the signal finally arrives. If in the far future we ever discover evidence of technical civilizations, I think it will be an endeavor that highly favors archeology over inter-species diplomacy. We could very well be the only technical species in the galaxy - right now.:bugeye:
 
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  • #20
You should hear what Nuclear Physicist Stanton Friedman has to say about SETI.
 
  • #21
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RF technology is not really the issue nor is the time since its development. The essence of the Fermi paradox is that any civilization that achieves interstellar travel should be able to colonize the galaxy in a geologically short time. If there are as many intelligent civilizations as has been suggested, where are they? From the Wikipedia reference above...

The Fermi paradox can be asked in two ways. The first is, "Why are no aliens or their artifacts physically here?" If interstellar travel is possible, even the "slow" kind nearly within the reach of Earth technology, then it would only take from 5 million to 50 million years to colonize the galaxy.[5] This is a relatively small amount of time on a geological scale, let alone a cosmological one. Since there are many stars older than the sun, or since intelligent life might have evolved earlier elsewhere, the question then becomes why the galaxy has not been colonized already. Even if colonization is impractical or undesirable to all alien civilizations, large scale exploration of the galaxy is still possible; the means of exploration and theoretical probes involved are discussed extensively below. However, no signs of either colonization or exploration have been generally acknowledged.
 
  • #22
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RF technology is not really the issue nor is the time since its development. The essence of the Fermi paradox is that any civilization that achieves interstellar travel should be able to colonize the galaxy in a geologically short time. If there are as many intelligent civilizations as has been suggested, where are they? From the Wikipedia reference above...

The Fermi paradox can be asked in two ways. The first is, "Why are no aliens or their artifacts physically here?" If interstellar travel is possible, even the "slow" kind nearly within the reach of Earth technology, then it would only take from 5 million to 50 million years to colonize the galaxy.[5] This is a relatively small amount of time on a geological scale, let alone a cosmological one. Since there are many stars older than the sun, or since intelligent life might have evolved earlier elsewhere, the question then becomes why the galaxy has not been colonized already. Even if colonization is impractical or undesirable to all alien civilizations, large scale exploration of the galaxy is still possible; the means of exploration and theoretical probes involved are discussed extensively below. However, no signs of either colonization or exploration have been generally acknowledged.

Who is to say they didn't? Maybe we are a colony of a species that seeded other stars and didn't have FTL travel. Maybe they did it and aren't around anymore since it would have been a long, long time ago, in a solar system far, far away. We could colonize the galaxy without ever leaving the solar system and without FTL.
 
  • #23
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However, no signs of either colonization or exploration have been generally acknowledged.

Actually, many believers assert that we are part of a constellation of colonies, that humans did not originate on earth, which, they say, explains why all reported ET's are more or less humanoid. They would simply say the fact it's not generally acknowledged we're being visited doesn't mean we aren't.
 
  • #24
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One problem with the Fermi paradox is that it states that the Earth is typical, it isn't. We have an extremely large moon and it is probably extremely rare for an Earthlike planet to have a moon like ours. The question is does the moon offer us enough protection to account for lifes existence long enough to be technological or conversely does the lack of a large moon inhibit intelligent life from evolving.
 
  • #25
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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/02/25/galaxy.planets.kepler/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.
Cool thread. Lots of good answers imho. How long would it take for a signal from the nearest Earthlike planet to get to us? Would you expect any degradation or dissipation of the signal? And I'm also interested in the answer to your question regarding what the Earth would be like without our Moon.

It also might be that the probabilities are more along the lines of, say, one Earthlike planet (with Moon, assuming it's necessary) per galaxy, or per 10 galaxies, or 100 ... . Who knows? We don't know how big our Universe is, do we? Also, an almost identical solar system with an almost identical Earthlike planet wouldn't necessarily produce intelligence on the order of ours. In fact, I think, probably not.

So, my guess is that the probability of intelligent life (humanlike or higher) in the universe is extremely low.
 

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