A logical paradox in searching for ET ?

[Just thinking]

An article I read recently examined possibilities as to why there are no extraterrestrials making themselves known to us. Its theme centered around a galaxy (ours) that in all likelihood should be full of life --- yet we see nothing, and addressed those issues. But one thing it didn't mention is what I think might be a logical paradox in searching for ET --- or at least in the means for searching for it.

When it comes to trying to make extraterrestrial contact, we basically have 2 means of approach. One (Plan A) is to send out into space a variety of signals and spacecraft identifying ourselves. Signals are cheap (relatively) --- but are they really going to do the job? If you really want to get our presence known I think you need to send out thousands of self replicating robot probes in all directions. This is very expensive --- and we do not yet have the technology. But even if we did, it would still eat up a tremendous amount of energy, effort and cost with no guaranteed results.

The other choice (Plan B) is to sit back and wait for them to contact us --- this includes SETI and various other programs that search for intelligent signals. This is very cheap to do, even though it would still require a good deal of effort and time --- but still with no guaranteed results.

Now, for the paradox: Logically, if we assume that other ET civilizations are as logical as us, then they too would be left with these two basic choices. If we think of choosing Plan A, then there is no reason for us to believe ET would behave any differently, as they will be contacting us and we needn't be spending such a great deal of resources for naught. (Let ET use the energy.) If, however this leads us to then choose Plan B, we should feel that ET would also come to the same conclusion --- the result being no one sends out any ships. It seems that no matter which choice you think of making, you keep coming back to the choice that does little or nothing in making your presence known. In other words, you don't have a choice.

The only way I see of the paradox no longer existing, is if somehow sending out robot ships becomes economically feasible --- but can that ever be the case?

[GreedyAlgorithm]

Simple. Assume all races will choose plan C, which is flip a giant coin and execute plan A on heads, plan B on tails.

I'm not sure Kant understood mixed strategies. ;)

[SphereGuy]

Except we've been sending out signals for decades in the form of radio and television programs.

[drkitten]

When it comes to trying to make extraterrestrial contact, we basically have 2 means of approach. One (Plan A) is to send out into space a variety of signals and spacecraft identifying ourselves. Signals are cheap (relatively) --- but are they really going to do the job? If you really want to get our presence known I think you need to send out thousands of self replicating robot probes in all directions. This is very expensive --- and we do not yet have the technology.

The only way I see of the paradox no longer existing, is if somehow sending out robot ships becomes economically feasible --- but can that ever be the case?

You've answered your own question. When self-replicating robot technology becomes practical (at the moment, it's not even possible), it will be practical to send out large numbers of identifying spacecraft.

But beyond that, there is no paradox. We're doing both plan A and plan B right now.

[jnelso99]

Except we've been sending out signals for decades in the form of radio and television programs.

APOD had a cool image of the Milky Way a few weeks ago:

http://antwrp.gsfc.nasa.gov/apod/ap080606.html

If we had been sending out radio signals in one form or another for 100 years (probably an overestimation, but the math is easier), then on the full-size APOD image (2048x2048), our radio presence would be a circle about three pixels in diameter. There are probably hundreds of stars and planets in that area, but what are the realistic odds that either they are capable of picking up the signals, or that some other being just happens to pass this way at just the right time? (I know - that last one is pretty much the plot of that NG Star Trek movie...)

[rocketdodger]

You've answered your own question. When self-replicating robot technology becomes practical (at the moment, it's not even possible), it will be practical to send out large numbers of identifying spacecraft.

But beyond that, there is no paradox. We're doing both plan A and plan B right now.

Anyone read "Spin?"

[casebro]

And with the doppler effect, signals lower in frequency as distance grows. plus the strength also drops at a cube root of distance. So just how far out are our signals decipherable? same three pixels?

[ravdin]

Except we've been sending out signals for decades in the form of radio and television programs.

That's true, but we haven't been announcing our presence for very long... only about 70 years. It doesn't seem far fetched to me that even if the universe is teeming with life forms, we could be the only species within a 100 light year radius to have developed the technology to broadcast radio waves into space.

I also think that it's probably extremely rare (if not unique) to our planet that we have developed the technology so recently. It might be some time before we attract the notice of a more advanced civilization and get a signal back, if they even chose to do so.

[Loss Leader]

As others have said, the supressed premise is that our current behavior won't accidentally alert ETs and vice-versa.

We're now inside a signal bubble at least 140 light years across, with a volume of 360,000 cubic light years. Over the next twelve months, it will grow by 15,000 cubic light years.

Eventually, somebody's going to see us.

[madurobob]

As others have said, the supressed premise is that our current behavior won't accidentally alert ETs and vice-versa.

We're now inside a signal bubble at least 140 light years across, with a volume of 360,000 cubic light years. Over the next twelve months, it will grow by 15,000 cubic light years.

Eventually, somebody's going to see us.

While thats true, the quality of the signal deteriorates almost to the level of background noise not much further out than our own solar system. As far away as the next solar system it is not discernible from background noise with equipment similar to what we have on Earth today. So, they would have the be very advanced aliens looking for a specific signal.

[RecoveringYuppy]

While thats true, the quality of the signal deteriorates almost to the level of background noise not much further out than our own solar system. As far away as the next solar system it is not discernible from background noise with equipment similar to what we have on Earth today. So, they would have the be very advanced aliens looking for a specific signal.
The Arecibo Message (http://en.wikipedia.org/wiki/Arecibo_message) has a chance of being noticed. Of course, the densest region of targets is going to take 25,000 years to reach. And they may only have about an hour to notice it.

[Loss Leader]

As far away as the next solar system it is not discernible from background noise with equipment similar to what we have on Earth today. So, they would have the be very advanced aliens looking for a specific signal.


How advanced? The equipment we have on Earth today has been frozen at its current level of technology for how long?

An alien civilization would need maybe fifty years on us, at most, to have a huge, orbiting, radio telescope array a couple hundred miles across. It doesn't seem like a very difficult technological hurdle.

[Merko]

We haven't had this technology for very long. What will happen next?

Maybe such an advanced society simply isn't sustainable, economically, environmentally, or socially, and we'll go extinct within a few thousand years.

Maybe we'll grow paranoid and start encrypting all our radio signals to look like background noise if you don't have the proper sync code, so that no evil alien civilisation will notice us.

Maybe we will find a technology that is vastly superior to radio, and we'll never even think about listening to radio frequencies.

Maybe our technological progress will be followed by a social development that will make us uninterested in other civilisations.

Maybe we will gain the understanding that it is, after all, so ridiculously unlikely that there will be another advanced civilisation within hearing distance, that we won't even bother looking for them anymore.

Maybe we will become so advanced that we cannot figure out how it comes that this nearby civilisation that we have found, doesn't manage to detect and respond to our signals, even though they follow a universally valid and very beautiful pattern that every intelligent being should instantly recognise.

[CapelDodger]

Plan A ... If you really want to get our presence known I think you need to send out thousands of self replicating robot probes in all directions. This is very expensive --- and we do not yet have the technology. But even if we did, it would still eat up a tremendous amount of energy, effort and cost with no guaranteed results.

Given the technology (and this isn't something we're going to be doing very soon) the "self-replicating" feature does reduce the cost substantially. If you send out, say, four self-replicating systems, and they each produce a continuing stream, it doesn't take many generations to cover the galaxy.

This kind of technology may well be developed for in-system purposes, so the big hold-up, IMO, would be the motivation. Nobody's likely to see any results in their own lifetimes (let alone their scientific or political career-spans) so there's no great pressure to actually get the thing off the ground (so to speak). Even a Jupiter probe can be easily slotted into a scientific career-span, but inter-stellar? Not so much.

[CapelDodger]

An alien civilization would need maybe fifty years on us, at most, to have a huge, orbiting, radio telescope array a couple hundred miles across. It doesn't seem like a very difficult technological hurdle.

Indeed. The question is, why build it? SETI as we know it exists because it can piggy-back on mainstream research and associated technology. It's unlikely to ever become a big project in itself. For us.

Might there be an alien civilisation that is enough like ours to be able to build space-based radio-telescopes et cetera, but different enough to actually do it? I think you'd have to run out of most other things you can do before you'd actually get around to doing it.

[CapelDodger]

The Arecibo Message (http://en.wikipedia.org/wiki/Arecibo_message) has a chance of being noticed. Of course, the densest region of targets is going to take 25,000 years to reach. And they may only have about an hour to notice it.

Quite, but there's a certain nobility to it all the same, don't you think? Whatever happens next, we didn't come and go without at least one shout of "We were here!". I very much doubt we're the first to do it . There could be millions of such shouts out there, never dying but red-shifting away :).

[Just thinking]

Thanks for all the responses.

To those that say we've been sending out signals for over 100 years, I think there are several possible snags. We really aren't doing it in a concerted effort to signal anyone out there --- we're simply relying on our signal to just leak out to them. Besides, we're just one spec in the sky to them --- we should try and broaden out signal's origin, no? Of course, this would take much more effort and cost (and time) than we have ever done. Plus, you want to cover the sky --- or as much as possible with good, clean strong signals. Again, I see this as being quite expensive (right now, to us). But if we do think this as the best logical cost-effective plan, then ET should also. Yet we aren't getting anything. Why?

To those that suggest sending out only a few robot probes that will eventually cover the galaxy, I think that's too small a number --- you're depending on a huge success rate (at least in the beginning). But if you're right, then why haven't we seen any? Surely the galaxy is old enough for a single advanced civilization to give that a go. Also, if that's correct, then ET will conclude that they should just wait for one (which should have well arrived by now) --- hey, it should work. Result, they don't send any.

I'm wondering if there is a name for this logical paradox. If not, I claim it as the Paradox of Group Involvement. It's where you have a group of isolated individuals that decide to choose between 2 choices, one of which will benefit them much more than the other. The problem is, once one sees which choice is better, any other one will do the same. This results in a situation where that given choice then becomes the lesser benefit -- to everyone. Of course, deciding then to make the other choice as your decision (from the start) you realize that it will by default be of little benefit, so no one chooses it. In the end, you cannot make the better choice.

[The Man]

An article I read recently examined possibilities as to why there are no extraterrestrials making themselves known to us. ?


Because they choose not to? Just because I choose not answer my phone does not mean that I am not home.

Except we've been sending out signals for decades in the form of radio and television programs.


Given the content of most radio and TV programs (including commercials), would you really want to let the originators of such know that you are home (like in the 1985 movie “Explores”). The next thing you know you’d be getting all these signals offering to refinance your planet or saying that your planet’s warranty has expired.



Ming: Pathetic Earthlings. Hurling your bodies out into the void - without the slightest inkling of who or what is out here. If you had known anything about the true nature of the universe - anything at all - you would have hidden from it in terror.

1980 “Flash Gordon”



If you really want to get our presence known I think you need to send out thousands of self replicating robot probes in all directions.


Isn’t that how the “Borg” and the “Replicators” got started?

No wonder no one wants to talk to us.

[drkitten]

I'm wondering if there is a name for this logical paradox.

I suggest "nonexistent."

The paradox as you frame it is very similar to the Prisoner's Dilemma. But given both the possibility of mixed strategies and the simple fact that technological prowess makes the symmetry you propose ludicrous, the ET problem is not at all paradoxical.

[Loss Leader]

Well, let's just rephrase it. Al wants to talk to Betty. He can go to Betty's house or he can stay home and wait for Betty to come to him. Betty wants to talk to Al. She can stay home and wait for him or go over to his house. There are no other possibilities and neither has any way to get information about the other.

In that case, there's a 50% chance that the two will meet and a 50% chance they won't. There is no choice that mitigates the potential losses, even at the cost of a lower potential gain.

Each should just flip a coin. It doesn't matter which choice they pick. Nothing can help their odds.

[gdnp]

I agree that this is a false dilemma. We are given two choices, when in fact there are many other choices, and the choices are not mutually exclusive. For example, sending out robots designed to send messages to many stars would be more efficient than visiting each star individually.

The "self replicating robots" is not practical on several grounds. Robots don't "grow", especially out of stardust. The energy needed to accelerate the robot to near-light speed would be tremendous. The distances that need to be covered are immense. Even if the robot could beam a message back instead of make the return trip, we would be waiting for decades even to reach the nearest suitable stars. Beaming messages directly at said stars would be a whole lot simpler.

[Just thinking]

Well, let's just rephrase it. ... Each should just flip a coin. It doesn't matter which choice they pick. Nothing can help their odds.

But we are talking here of many people wanting to talk to everyone else. Being just one, and using your analogy of coin flipping, I think it would be damn near impossible that all will choose to stay at home and wait. Therefore, I can bet on someone contacting me --- so I stay home and wait. Problem is ... each individual can come to that identical conclusion.

[Just thinking]

I agree that this is a false dilemma. We are given two choices, when in fact there are many other choices, and the choices are not mutually exclusive. For example, sending out robots designed to send messages to many stars would be more efficient than visiting each star individually.

Yes ... so if ET comes to this conclusion (and I see no reason as to why he shouldn't) all we need do is wait for him to contact us. But then, ET will reason that he can just wait too --- why should he expend all the energy, time and costs? You see, once you reason that it's best to send out probes, you can reason that ET will do the same, so each side waits for the other.

The "self replicating robots" is not practical on several grounds. Robots don't "grow", especially out of stardust. The energy needed to accelerate the robot to near-light speed would be tremendous. The distances that need to be covered are immense. Even if the robot could beam a message back instead of make the return trip, we would be waiting for decades even to reach the nearest suitable stars. Beaming messages directly at said stars would be a whole lot simpler.

Not grow like us ... replicate by landing on a planet that will allow it to develop and exploit the planet's resources to send out more probes like itself. This of course requires very advanced artificial intelligence ... which we at present don't posses.

[technoextreme]

An article I read recently examined possibilities as to why there are no extraterrestrials making themselves known to us. Its theme centered around a galaxy (ours) that in all likelihood should be full of life --- yet we see nothing, and addressed those issues.
You know my statistics textbook dealt with this on the first page of the book. This is nothing more than faulty woo logic because all in all you are making a wild guess as to the likely hood of life on other planets.

[Just thinking]

You know my statistics textbook dealt with this on the first page of the book. This is nothing more than faulty woo logic because all in all you are making a wild guess as to the likely hood of life on other planets.

Well, of course that's true in that the assumption is that there are other planets with advanced life (advanced beyond us) out there. But a wild guess can cut both ways ... it can be way too high a probability or way too low as well. Regardless, my question in the OP is to discuss the possible paradox in the methods of ever finding ET, and deciding which course of action to best pursue.

[Just thinking]

I suggest "nonexistent."

The paradox as you frame it is very similar to the Prisoner's Dilemma. But given both the possibility of mixed strategies and the simple fact that technological prowess makes the symmetry you propose ludicrous, the ET problem is not at all paradoxical.

I don't think it's exactly the same, although there are similarities. My paradox involves a course of action that once derived, becomes unnecessary due to the fact that one then realizes others will choose the same course of action, so what's the point? It's the more you're drawn to a given conclusion (Plan A), the more that conclusion becomes useless. Making you go back to the alternate choice (Plan B). The only symmetry I am assuming is that logical thinking is universal, and that we here on Earth have no special form of logic that works differently elsewhere.

[Just thinking]

You've answered your own question. When self-replicating robot technology becomes practical (at the moment, it's not even possible), it will be practical to send out large numbers of identifying spacecraft.

Now hold on, there. Can it ever be practical? Perhaps one day we will have the technology for self replicating probes, but will it ever be cost effective? I think we now have the technology to go to Mars, but at what cost? And how often? How about a base on the Moon?

But beyond that, there is no paradox. We're doing both plan A and plan B right now.

I think that's quite a bit of wishful thinking, on both parts.

[gdnp]

It is still not a paradox. The most logical way to contact a civilization would be a radio message. We can both beam messages to likely stars and listen for other messages beamed to us.

The technology necessary for producing a self-replicating robot is daunting, to say the least. Think of the steps:

1) create robot
2) launch into space
3) accelerate to near-light speed
4) navigate to suitable planet over years-decades-centuries, before you run out of power or a critical part breaks
5) land on planet
6) starting just from yourself, find suitable ore to mine and smelt into metal to make more robots. Produce a microchip factory. Produce a rocket factory. Produce fuel to launch rockets with new robots and accelerate them to near-light speed.
7) repeat as necessary
8) once you find life, transmit a message back to earth, or make the return trip, only to discover that the sun burned out a few billion years ago.

[Vorpal]

Maybe we'll grow paranoid and start encrypting all our radio signals to look like background noise if you don't have the proper sync code, so that no evil alien civilisation will notice us.
We're are already doing it, but not for reasons of paranoia. Digital modulation methods generally do make the signal look like background noise unless you know the particulars of the encoding method, and this is even more so for spread-spectrum digital methods. We won't be sending signals recognizable as such for much longer, and even out total combined output power is completely unremarkable compared to other noisy radio sources in the sky.

[Just thinking]

It is still not a paradox. The most logical way to contact a civilization would be a radio message. We can both beam messages to likely stars and listen for other messages beamed to us.

Most cost effective, probably. Most logical? If that's the case, don't you think we should have discovered something by now? After all, won't everyone (everyone that wishes to communicate) be doing it? Isn't the galaxy old enough for there to be someone's signal for us to receive?

It's not that I'm disagreeing with you ... I'm just questioning the method's effectiveness.

[gdnp]

Most cost effective, probably. Most logical? If that's the case, don't you think we should have discovered something by now? After all, won't everyone (everyone that wishes to communicate) be doing it? Isn't the galaxy old enough for there to be someone's signal for us to receive?

It's not that I'm disagreeing with you ... I'm just questioning the method's effectiveness.

Clearly, the method has not yielded positive results yet. It still remains the only feasible method. We can't produce self-replicating robots, and sending nor can we accelerate probes to the relativistic speeds necessary to reach other star systems that might support life. Until such technology exists, the question is moot. The best we can do is to continue calling, and continue listening.

And continue building better phones.

The question is whether it is worth the effort. I think it is. The proof of extraterrestrial life would force a shift in human consciousness. No longer could we claim to be unique, and claims of being "special" or "God's chosen people" would be highly suspect. And think of the debates it would engender. What if we discovered unmistakable evidence of an intelligent civilization 10 light years away. What greeting would we send them, knowing it would be 20 or more years until we got a reply?

It would also give the truthers something to do once they have tired of "debunking" the 9/11 attacks. An Atheist conspiracy to shake our trust in God would be a popular theme, I imagine.

[quarky]

We should hide as long as possible. The aliens are not good people. They are looking for places like ours, just as we would be, should we ever achieve that ability.

[gdnp]

We should hide as long as possible. The aliens are not good people. They are looking for places like ours, just as we would be, should we ever achieve that ability.

I agree that if they exist that they are probably looking for places like ours. Your suggestion that they are doing this with bad intent is (obviously) unsupported and frankly implausible. The distances involved are so immense the probability of ever physically visiting another alien civilization is virtually nonexistent. So what harm can they do from a distance? Beam alien porn at us?

[wollery]

And with the doppler effect, signals lower in frequency as distance grows. plus the strength also drops at a cube root of distance. So just how far out are our signals decipherable? same three pixels?No.

Doppler effect is not relative to distance on interstellar scales, only on cosmological scales, and the signal strength drops as the square root of the distance (it divides out over the surface of the sphere, not the volume of it).

[casebro]

Okay, then how far out are our signals decipherable?

In light years, pixels, or furlongs, whatever?

[RecoveringYuppy]

Depends on the receiver. An unfocused antenna probably wouldn't be able to notice us anywhere outside our own solar system. But a large enough, well focused enough antenna could notice from anywhere in the galaxy (at least once our signals reach them). But they'd have to get around to looking right at us.

[Molinaro]

Well, let's just rephrase it. Al wants to talk to Betty. He can go to Betty's house or he can stay home and wait for Betty to come to him. Betty wants to talk to Al. She can stay home and wait for him or go over to his house. There are no other possibilities and neither has any way to get information about the other.

In that case, there's a 50% chance that the two will meet and a 50% chance they won't. There is no choice that mitigates the potential losses, even at the cost of a lower potential gain.

Each should just flip a coin. It doesn't matter which choice they pick. Nothing can help their odds.

That presumes equal difficulty, due to equal technological advancement.

Current SETI efforts are not looking to see passive signals from civilizations as advanced as us. We could just barely detect our own passive signals at the distance of Proxima Centauri.

We are looking for much more powerfull, directed signals, from a far more advanced civilization.

The supposed paradox does not apply.

[JoeTheJuggler]

Its theme centered around a galaxy (ours) that in all likelihood should be full of life --- yet we see nothing, and addressed those issues.
Why is "full of life" likely? That's pretty much the question to be answered--how prevalent is life that leads at least to intelligence capable of coming up with radio technology.

Does anyone have any information that leads to the conclusion that a galaxy full of this sort of life is very likely?

That's true, but we haven't been announcing our presence for very long... only about 70 years. It doesn't seem far fetched to me that even if the universe is teeming with life forms, we could be the only species within a 100 light year radius to have developed the technology to broadcast radio waves into space.
Yes. Time is a pretty big deal.

And let's not forget that in our only small sample (our solar system) we know of one planet teeming with life and no other compelling evidence for any kind of life at all.

Even on the one planet teeming with life, it's not really a 1 out of 1 probability that you'll find intelligence capable radio technology if you consider time. The earth has been around for some 4 billion years plus, but as ravdin points out, we've only been broadcasting for around 70 years. As far as we no, there has been no other civilization on Earth with radio technology.

That's not what I'd call evidence for a high probability (the "in all likelihood" of the OP) of any two such civilizations being close enough for a long enough time to receive each other's signals.

[bokonon]

Doppler effect is not relative to distance on interstellar scales, only on cosmological scales
I don't think the Doppler effect for electromagnetic signals really depends on distance at all. As with the train's horn, it depends on whether the source is moving relative to the receiver, and if so, how fast and which way. We've detected binary stars because the light from them is both red-shifted and blue-shifted, depending on whether the body emitting the light is moving away from us or toward us. Light from other galaxies has been red-shifted by the expansion of space during the billions of years the light has been in transit. If space had not been expanding, and the galaxies had not been moving relative to the earth when the light was emitted, we'd expect to see the atomic spectra in the same frequencies in which they appear in the laboratory (perhaps slightly shifted by the movement of the earth as it received the light). While distance can be deduced from the shift, the shift is not strictly a function of distance.

[bokonon]

Why is "full of life" likely? That's pretty much the question to be answered--how prevalent is life that leads at least to intelligence capable of coming up with radio technology.
It doesn't seem very likely to me at all. The more I learn about the series of happy accidents that seem to have led to intelligent life on this planet, the more I think the "billions and billions" which Sagan popularized when I was a kid is still probably a couple of orders of magnitude too small.

I'm fairly sure life has developed elsewhere in the galaxy, but have no confidence at all that organisms capable of sending and receiving radio signals over interstellar distances exist anywhere but here.

[gdnp]

I'm fairly sure life has developed elsewhere in the galaxy, but have no confidence at all that organisms capable of sending and receiving radio signals over interstellar distances exist anywhere but here.

Or at least anywhere near enough that we could communicate. It doesn't help much if there is intelligent life in the galaxies billions of light years away. We will never contact them either way, unless the physics is wrong and FTL communication is possible.

[bokonon]

When it comes to trying to make extraterrestrial contact, we basically have 2 means of approach. One (Plan A) is to send out into space a variety of signals and spacecraft identifying ourselves. Signals are cheap (relatively) --- but are they really going to do the job? If you really want to get our presence known I think you need to send out thousands of self replicating robot probes in all directions. This is very expensive --- and we do not yet have the technology. But even if we did, it would still eat up a tremendous amount of energy, effort and cost with no guaranteed results.
And no discernible benefit. Even if one of those probes did miraculously make it to a distant planet with intelligent life, managed a soft landing on a solid surface where it would be discovered by one of the intelligent life forms, popped out a flag and played "The Star-Spangled Banner," what good would that do us?

Even assuming that an advanced civilization capable of interstellar travel is benign (perhaps because they managed not to blast themselves back into their stone age before they developed the capability of interstellar travel), it still seems like signals would be the best way to contact them. Interstellar communication is feasible today; interstellar travel may never be. Voyager will take 73,000 years to travel as far as Proxima Centauri (assuming it was headed that way, which it isn't). Assuming everything goes perfectly, 150,000 years to exchange information with our closest possible neighbors via probe doesn't seem very promising.

Now, for the paradox: Logically, if we assume that other ET civilizations are as logical as us, then they too would be left with these two basic choices. If we think of choosing Plan A, then there is no reason for us to believe ET would behave any differently, as they will be contacting us and we needn't be spending such a great deal of resources for naught. (Let ET use the energy.) If, however this leads us to then choose Plan B, we should feel that ET would also come to the same conclusion --- the result being no one sends out any ships. It seems that no matter which choice you think of making, you keep coming back to the choice that does little or nothing in making your presence known. In other words, you don't have a choice.
Nonsense. It's fairly cheap to generate a signal, so there's nothing to stop you from shouting out to the universe at the same time you're listening. If I'm wandering in a dark forest, and I think my situation would benefit from a little human companionship, I'll shout at the same time I'm listening for the shouts of others. I don't reason "Well, if there was anybody else out here, they'd be shouting themselves," because maybe they wouldn't.

There are questions about whether you SHOULD be shouting. Maybe your shouts will only attract bears. Maybe there really isn't anyone else out there, and all your shouting will be a waste of time.

I think the most likely reason we haven't heard from a more advanced civilization is that there isn't one in our galaxy. The next most likely reason is that they don't feel the need to communicate. The third most likely reason is that they are communicating, but it still looks like background noise to us.

Personally, if I wanted to communicate with extraterrestrials, I'd send directional signals to stars within 100 light years. Any more than that, and the chances are you'll only be wasting the extraterrestrials' time, as even if they receive and decode our signal, and send a message back, in 200 years time it's questionable whether anyone on earth will still remember to listen.

ETA: According to this site (http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980123d.html), there are approximately 14,600 stars within 100 light years of us, though it says most of them are too dim to detect. Perhaps the James Webb Space Telescope, scheduled for launch in 2011, can help to fill in our knowledge of them.

[The Man]

It doesn't seem very likely to me at all. The more I learn about the series of happy accidents that seem to have led to intelligent life on this planet, the more I think the "billions and billions" which Sagan popularized when I was a kid is still probably a couple of orders of magnitude too small.

I'm fairly sure life has developed elsewhere in the galaxy, but have no confidence at all that organisms capable of sending and receiving radio signals over interstellar distances exist anywhere but here.

Even if there was something that could raise your confidence that organisms capable of sending and receiving radio signals over interstellar distances exist anywhere but here, that would still leave us with the problem of how many of those organisms would be interested in contacting or being contacted by other life forms. Even within our own human history isolationism and protectionism were sometimes the cultural norm. It would not be far fetched to suppose other societies capable of sending and receiving radio signals over interstellar distances with absolutely no desire to do so for contacting or being contacted by other societies. Also in a cross species aspect we certainly have more examples of such closed societies (particularly in inserts) and others where consumption is more the cross species (or even same species) norm then communication. Certainly with increased intelligence one would hope for an increased desire to learn and communicate (even with other species) but there is nothing to conclusively demonstrate that. The OP seems to take us as an example of what an ET would logically do or would come to the same conclusion as us. Conversely if we actually look at what we have done in our history, what species currently do as closed societies and in consuming each other, there seems to be far more equally logical alternatives.

[gdnp]

I think the flaw in your reasoning here is that human societies have been isolationist in the past because of limited resources and the fear that the outside society will either steal your stuff or at least overturn the status quo. It doesn't take a rocket scientist to figure out that we have nothing worth taking that is worth the cost in time and resources of getting here and back. If the upside in terms of knowledge exchange and understanding of our origins remains and the downside of worrying about invasion is eliminated, why not? It's a pretty basic question: who else is out there? Any culture with the curiosity to have invented radio would want to know.

It's like discussing something with someone over the internet. You can exchange information, to the benefit of both people, without worrying that the other guy is going to drink all your beer or hit on your girlfriend.

[bokonon]

While I agree that there's no danger of invasion, I don't think "upset the status quo" is a reason that can be so easily dismissed. That's part of the reason North Korea wants to limit knowledge of the outside world inside its borders. I could see how a culture might exist that would prefer to believe it was unique in the universe, rather than go looking for evidence that it was not.

[quarky]

Funny stuff.

When one hears the standard reason for why we need to go out into the universe; why it is our destiny...its always about some sort of exploitation.

its because we've ruined our planet; because we need resources; because we've overpopulated.

From the alien perspective, we aren't about good news.

Is it illogical to consider that other "intelligent" life-forms, should they exist, would have similar motives?

They will come here and eat our hearts while they beat.
Don't let this happen.

vote "NO" on contacting intelligent life in the universe!

[bokonon]

When one hears the standard reason for why we need to go out into the universe; why it is our destiny...its always about some sort of exploitation.

its because we've ruined our planet; because we need resources; because we've overpopulated.
Yeah, I think that "standard reason" is being proposed mostly by people who haven't thought it through with an understanding of the engineering effort that would be required.

If our technology ever advances to the point that it is possible to exploit extraterrestrial resources, I can't imagine we'd ever need to leave the solar system to do so. We could chop Venus up into tiny pieces and smelt it all, and still have 7 planets left.

The only other "resource" we have is location. We're a habitable planet, whereas we know most others aren't. But that's us -- there's no guarantee that any beings from another star system would find our range of temperatures, or the mix in our atmosphere, habitable, even if they could purge the planet of all existing life to guard against a "War of the Worlds" fiasco.

I don't think there's anything to worry about on that account, even if every star we can see has a planet with intelligent life orbiting it.

[The Man]

I think the flaw in your reasoning here is that human societies have been isolationist in the past because of limited resources and the fear that the outside society will either steal your stuff or at least overturn the status quo. It doesn't take a rocket scientist to figure out that we have nothing worth taking that is worth the cost in time and resources of getting here and back. If the upside in terms of knowledge exchange and understanding of our origins remains and the downside of worrying about invasion is eliminated, why not? It's a pretty basic question: who else is out there? Any culture with the curiosity to have invented radio would want to know.

It's like discussing something with someone over the internet. You can exchange information, to the benefit of both people, without worrying that the other guy is going to drink all your beer or hit on your girlfriend.

Well that might be a flaw in my reasoning if that was my reasoning or the reasoning of all of those isolationist human societies. Who says it is us that are the isolationist or the ones worried about invasion? Clearly we have been sending probes and signals as well as listening. Some societal structures are very rigid and simply not interested in outside influences.

If someone had grow up right next door to you, then eventual broke into your house, drank all your beer kidnapped your girlfriend and killed your dog, you might start wandering about the guy down the street who is always waving at and calling to you when you are out cutting your grass.

I hope you at least take some safety measures when talking on the internet and have some kind of firewall software. There is nothing on my computer worth stealing but that doesn’t stop people from trying to gain access. Some people just like to see what they can get away with or use my computer for their own purposes.

I think the flaw in your reasoning of the flaw in my reasoning is assuming these our my or perhaps what I might think should be our concerns and not what I am trying to express as the possible concerns, lack of interest or specific distain for other societal contact that some possible extro-socitiy might have about communicating with us. A lot of our history of isolationistic societies was due to the belief that they were superior and others were just “barbarians”.

[gdnp]

Funny stuff.

When one hears the standard reason for why we need to go out into the universe; why it is our destiny...its always about some sort of exploitation.

its because we've ruined our planet; because we need resources; because we've overpopulated.
Nope. It's for knowledge. Once the scientists have discovered all the elements and subatomic particles, synthesized all the chemicals, created all the computers, modeled all the weather, studied all the DNA, what are they going to do? say "that's all there is", or look for someone else to talk to.

From the alien perspective, we aren't about good news.

Is it illogical to consider that other "intelligent" life-forms, should they exist, would have similar motives?

They will come here and eat our hearts while they beat.
The probability that alien metabolism and human metabolism are similar enough that we would be palatable to them, much less tasty enough to be worth the trip, is so remote that it is a non-issue. If they could get here. Which they can't.
Don't let this happen.

vote "NO" on contacting intelligent life in the universe!


You've been watching too many sci-fi movies. It would be better to worry about the resurrected dinosaurs a la Jurassic park. That at least is theoretically feasible.

[The Man]

From the alien perspective, we aren't about good news.

Is it illogical to consider that other "intelligent" life-forms, should they exist, would have similar motives?


No more illogical then it is to consider that they might have different motives then we might consider.




They will come here and eat our hearts while they beat.
Don't let this happen.

vote "NO" on contacting intelligent life in the universe!


That is a key element particularly in a society that controls information or chooses to limit possible outside influence, similar to what bokonon remarked about North Korea. External threats can be a very unifying and motivating tool, as President Regan often remarked.


http://www.geocities.com/Area51/Shadowlands/6583/et063.html

December 4th, 1985:
While addressing a group of high school students in Fallston Maryland..." I couldn't help but say to Gorbachev, just think how easy his task and mine might be...if suddenly there was a threat to this world from some other species from another planet outside in the universe. We'd forget all the little local differences ....between our countries....and find out once and for all that we really are all human."

September 21st, 1987:
Before the United Nations General Assembly: " In our obsession with antagonisms of the moment," said Reagan, "we often forget how much unites all the members of humanity. Perhaps we need some outside, universal threat to make us recognize this common bond. I occasionally think how quickly our differences worldwide would vanish if we were facing an alien threat from outside this world. And yet, I ask you," he went on, "is not an alien threat already among us ? What could be more alien to universal aspirations of our peoples than war and the threat of war?"

May 5th, 1988:
As President Reagan leaves the White House on the way to Chicago. Talking about the importance of frankness; for a desire for peaceful solutions and wars he goes on to say..."But, I've often wondered what if all of us in the world discovered that we were threatened by an outer--a power from another planet." Reagan said. "Wouldn't we all of a sudden find that we didn't have any differences between us at all, we were all human beings, citizens of the world and wouldn't we come together to fight that particular threat?" The president said.


From that aspect the “beating heart eating alien” threat can be both powerful and useful despite its abundant lack of credibility, as gdnp remarked. However in a controlled society “credibility” is just what that society says it is and wouldn’t you know that those “beating heart eating aliens” always get the people who doubt their existence first. I guess they find the skeptics heart the tastiest of them all and you do not even want to think about their “skeptic brain sucking” pets, that just draws them to you.

[Just thinking]

And no discernible benefit. Even if one of those probes did miraculously make it to a distant planet with intelligent life, managed a soft landing on a solid surface where it would be discovered by one of the intelligent life forms, popped out a flag and played "The Star-Spangled Banner," what good would that do us?

The probes can be of many different varieties. Each can be a beacon sending out concentrated signals in multiple directions, thus in a relatively short time (if able to get to 0.1c) broadening our radio footprint. Of course there is also the hope in one actually being intercepted --- but that is, I agree, unlikely.

Even assuming that an advanced civilization capable of interstellar travel is benign (perhaps because they managed not to blast themselves back into their stone age before they developed the capability of interstellar travel), it still seems like signals would be the best way to contact them. Interstellar communication is feasible today; interstellar travel may never be. Voyager will take 73,000 years to travel as far as Proxima Centauri (assuming it was headed that way, which it isn't). Assuming everything goes perfectly, 150,000 years to exchange information with our closest possible neighbors via probe doesn't seem very promising.

Yes ... but how is it best done? From a single point in the galactic sky?

Nonsense. It's fairly cheap to generate a signal, so there's nothing to stop you from shouting out to the universe at the same time you're listening. If I'm wandering in a dark forest, and I think my situation would benefit from a little human companionship, I'll shout at the same time I'm listening for the shouts of others. I don't reason "Well, if there was anybody else out here, they'd be shouting themselves," because maybe they wouldn't.

If it's so cheap, why aren't we doing it? Anyway, I think (as mentioned above) sending from a single location can make the effort almost useless. As for the forest analogy, if you really wanted to improve your efforts, wouldn't you leave markers of some sort along your path indicating your presence, hoping someone might stumble upon them. You can leave information about where you're headed and why you might need their help. Shouting from a single location might work --- but if you really wanted to make your presence known you might choose instead to use a small controlled burn (smoke signal). Also, if others are out there wanting to be noticed, they would in all likelihood use a similar method, knowing that merely shouting from a single point is almost futile.

There are questions about whether you SHOULD be shouting. Maybe your shouts will only attract bears. Maybe there really isn't anyone else out there, and all your shouting will be a waste of time. I think the most likely reason we haven't heard from a more advanced civilization is that there isn't one in our galaxy. The next most likely reason is that they don't feel the need to communicate. The third most likely reason is that they are communicating, but it still looks like background noise to us.

Unfortunately, I tend to agree with your first reason --- assuming the next reason for everyone out there is a bit of a stretch in that I think we want to communicate --- or at least many of us do. So I don't think it too unreasonable in believing some of them think like us. As for the third reason, that may be very hard to determine. I would hope that those wishing to communicate are making a much better effort than we presently are doing.

[gdnp]

If it's so cheap, why aren't we doing it? Anyway, I think (as mentioned above) sending from a single location can make the effort almost useless. As for the forest analogy, if you really wanted to improve your efforts, wouldn't you leave markers of some sort along your path indicating your presence, hoping someone might stumble upon them. You can leave information about where you're headed and why you might need their help. Shouting from a single location might work --- but if you really wanted to make your presence known you might choose instead to use a small controlled burn (smoke signal). Also, if others are out there wanting to be noticed, they would in all likelihood use a similar method, knowing that merely shouting from a single point is almost futile.

The problem is that we live in a forest 1000 miles across and given current technology it would take us 1000 years to get to the next tree. Well, really it's more like a desert than a forest. So the idea of wanting to shout from different locations is just not practical. More practical would be to use a megaphone to shout at particular potential "oases".

[Just thinking]

So the idea of wanting to shout from different locations is just not practical.

So you're coming to the same conclusion (in a sense) that I came to --- sending out probes is costly, both in energy and resources. And by whatever logical path we use to arrive at using that method, one can argue that ET would arrive there as well. And if ET's doing it, why should we? But I think he's not ... because we're not, nor are we likely to do so. Perhaps ever. So where does that leave us (and ET)? Doomed to just sit back and occasionally send out restricted signals (in direction, duration and strength) in hopes of ever receiving same? Putting our ears to narrow sections of the sky listening for that faint hint of a brief signal that could be missed if we blink?

More practical would be to use a megaphone to shout at particular potential "oases".

Do we sit at what ET might consider an oasis?

[bokonon]

The probes can be of many different varieties. Each can be a beacon sending out concentrated signals in multiple directions, thus in a relatively short time (if able to get to 0.1c) broadening our radio footprint. Of course there is also the hope in one actually being intercepted --- but that is, I agree, unlikely.
I admit, I hadn't considered the idea of broadcasting probes to expand our footprint, but having considered it, I still don't think it's a good idea.

As mentioned, Voyager 1, the fastest probe we've created to date, having traveled for over 30 years, is less than 1 light day from Earth. It cost millions to launch. Even though it's nuclear-powered, and has exceeded its expected lifespan, it's expected to run out of broadcasting power within the next decade. Even if we could design cheap probes with power sources that would be capable of broadcasting for the tens of thousands of years required to reach the next nearest star, it wouldn't significantly expand our footprint, as we could have sent pure signals to the same locations tens of thousands of years earlier. Radio signals travel at light speed, and consume negligible energy leaving the earth's (and the sun's) gravity well. Probes are unlikely ever to match those design specs.

Yes ... but how is it best done? From a single point in the galactic sky?
Yes, unless the objective is to confuse the aliens into launching their heart-seeking fleets in the direction of our probes rather than the direction of our hearts.

If it's so cheap, why aren't we doing it?
Generating enough power to keep the "signal to noise" ratio high enough over interstellar distances is extremely cheap compared to shooting probes at the same stars, but it still requires a substantial investment. I suspect the reason we aren't doing it is the one I gave earlier -- there's no discernible benefit. I'm sure sooner or later it will be done "just because we can," but I'm still pessimistic about the prospect of ever getting an answer to our message in a bottle.