Recently during a conversation about the possibility of intelligent life on other worlds someone suggested that the silence SETI has experienced is conclusive proof that there is none. Otherwise, the argument went, something would have already been detected. How srong of an argument is this? I for one think it's weak.
The_Fire
Unimpressed Female
Note; This is based on my memory, so I suggest checking out the SETI webpage , but that argument can be considered flawed due to the following reasons:
1: SETI is only listening to a narrow spectre of frequences. They filter out things they consider "background noise". While the specific frequencies are selected from a somewhat educated guess on where an alien transmission may be, this means they could be listning to the wrong thing. Or that a signal in the "Background noise" doesn't get recorded at all.
2: It is possible that a more advanced civlisation have already started using some sort of alternate communications which means they are no longer emitting radiowaves and that their old stuff have already passed us.
3: Due to distance, it's possible that "their" transmission haven't reached us yet. Our first transmission have barely reached the next starsystems yet.
There are probably more reasons, but those are the ones I get of the top of my head.
1: SETI is only listening to a narrow spectre of frequences. They filter out things they consider "background noise". While the specific frequencies are selected from a somewhat educated guess on where an alien transmission may be, this means they could be listning to the wrong thing. Or that a signal in the "Background noise" doesn't get recorded at all.
2: It is possible that a more advanced civlisation have already started using some sort of alternate communications which means they are no longer emitting radiowaves and that their old stuff have already passed us.
3: Due to distance, it's possible that "their" transmission haven't reached us yet. Our first transmission have barely reached the next starsystems yet.
There are probably more reasons, but those are the ones I get of the top of my head.
Yes, I agree! Also, many of the civilizations might not have the technology we possess. We have to remember that during most of human history we were unable to emit any radio waves. That we are able to now is a consequence of our specific history. So maybe, just maybe we are the only ones who have achieved this? Unlikely though it may seem it might just be so-well, it isn't an impossibility.
On the other hand, we might really be alone in terms of being the only material creatures with intelligence, or perhaps the only creatures period. That too is unlikely in view of the vastness of the universe but also not an impossibility.
In any case, as you said, the present silence isn't sufficient to justify a definite conclusion.
BTW
Since I am not an atheist I am not basing my speculations on evolution as I am certain most of those who will respond to this thread will.
On the other hand, we might really be alone in terms of being the only material creatures with intelligence, or perhaps the only creatures period. That too is unlikely in view of the vastness of the universe but also not an impossibility.
In any case, as you said, the present silence isn't sufficient to justify a definite conclusion.
BTW
Since I am not an atheist I am not basing my speculations on evolution as I am certain most of those who will respond to this thread will.
NobbyNobbs
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Two more reasons:
4) SETI can only inspect one very small section of sky at a time. it's possible that while they are facing north, the signals are coming from the south.
5) The logical fallacy inherent in the argument: lack of evidence is not evidence of non-existence.
4) SETI can only inspect one very small section of sky at a time. it's possible that while they are facing north, the signals are coming from the south.
5) The logical fallacy inherent in the argument: lack of evidence is not evidence of non-existence.
my_wan
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If there were dozens of technological civilizations we are capable of detecting it is highly unlikely we would have found any of them yet given the time we have been searching. Due to the distance if we ever do find one it means by definition that they are thousands if not hundreds of thousands of years ahead of us technological. Given the time spans and our recent technological emergence the odds are vastly in favor of them being at least hundreds of thousands of years ahead of us regardless.
So long as we remain tied to this planet our extinction is assured in the long run. Regardless of our environmental effects or lack of it.
So long as we remain tied to this planet our extinction is assured in the long run. Regardless of our environmental effects or lack of it.
BenBurch
Gatekeeper of The Left
Why do we assume that these ET civilizations would be using radio at all? They might use lasers for everything, or use such tight RF beams that there is little chance of one of them pointing at earth.
Arkan_Wolfshade
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It is extremly weak, in that "abscence of evidence is not evidence of abscence".
sphenisc
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However evidence of absence is evidence of absence.
And 52 terabytes is evidence.
http://www.astrobio.net/news/article710.html
Jimbo07
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The Allen Telescope Array may help. It has a wide field of view and a wider frequency band.
Even a few years of silence from ATA won't be strong evidence of absence.
However, like any good science, searchers should at least be prepared that there really is no one out there! It's a question of how many generations worth of data will be convincing. I'm sure some already are. There aren't any Martians, but it's still illuminating to explore there...
I once read a Sci Fi short story where only one other "intelligent" space-faring race was found. Result? War! The "This town isn't big enough for both of us" scenario. But in this case, ironically, the universe wasn't big enough. Weird!
my_wan
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Very true. I would also suspect that for broader transmissions they would use spread spectrum. If this is the case then unless you know exactly which set of frequencies to listen to it would sound like normal background noise. This remains true even if you listen on a broad enough range of frequencies to be getting their whole range of frequencies. If some kind of encryption was encoded between a pair of sets of frequencies then even prior knowledge of the frequency sets would sound like static.
There is also the possibility of even more advanced stuff. If something roughly akin to Quantum encryption was used then the very act of trying to listen would mean there is no signal to listen to. They could also know that you tried.
The speed of light limitation would remain an issue for communication as well as for the home planet waiting on the ship to reach its' destination. That is assuming such a race would even be dependent on any given planet (which I doubt). The light speed issue is no issue at all from the ships point of view. From the ship perspective it can essentially get from anywhere to anywhere as fast as they want to. If they travel very far at these speeds we might actually catch up to them technologically.
Personally I think SETIs only chance would be to find a race that only fairly recently gained technological status. Similar to our technological status. The laws of physics indicate that early technologies would be fairly consistent across all races. As technology progresses the way a races technology is expressed can increasingly vary, within certain very broad parameters.
Jimbo07
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That, or light speed isn't even a problem. Maybe they communicate by spacefolded micro-wormholes (or to quote Fry, "Magic. Got it.").
Maybe they are life-forms made of some exotic substance (or to quote Homer, "Silli foam.").
The point is, anything beyond what we are capable of detecting is sheer speculation and not a good justification for resources spent (or not) on SETI.
I agree, as our communications technology progresses, it may be more reasonable to speculate on what is happening in those media...
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roger
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SETI has examined something like 1 hundreth trillionith of the available search space. If I'm looking for my keys,and I am not sure if they are in my house or not, I don't examine a few molecules at the entrance, shrug, and conclude that the keys are not here.
ETA: yes, that's a silly analogy, don't bother pointing out the logical fallacy contained within, and focus on the size of the search space left unexplored.
ETA: yes, that's a silly analogy, don't bother pointing out the logical fallacy contained within, and focus on the size of the search space left unexplored.
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Arkan_Wolfshade
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But if the total possible data that could be collected for analysis is 520 or 5200 TB, then 52 TB of not finding anything is not significant.
Diagoras
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And what if the closest intelligent life form is in a galaxy 4 billion light years away? SETI is looking at stars within our galaxy; if they find nothing around our neighborhood, that doesn't mean there isn't any intelligent life out there anywhere. If it's really, really, really far away, maybe they just don't have any reason to send an extremely powerful signal our way announcing their existence, and even if they tried we're not looking for it, assuming it's had enough time to travel here for us to detect it. At this point, it seems unlikely we'd notice an intelligent civilization in another galaxy, unless they exploded a whole bunch of supernovae in a pattern that spelled out "Hi, we're aliens" in their alien language.
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Jimbo07
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Here's a nice response to some potential criticisms of SETI:
No Tax Dollars Spent!
Of course, this response won't appeal to people who are not predisposed to exploratory pursuits (Everest climbers, for example, really anger someone close to me).
No Tax Dollars Spent!
Of course, this response won't appeal to people who are not predisposed to exploratory pursuits (Everest climbers, for example, really anger someone close to me).
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BenBurch
Gatekeeper of The Left
Data waterfalling and redundancy in a digital stream are nearly as unrecognizable as an encrypted stream, and likely to be used between civilizations that already know each other, or deep space assets of a single race.
my_wan
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I know that Robertson-Walker manifolds allow the spacial and temporal components to vary independently but personally I doubt that very seriously, at least not without producing the same relativistic effects as standard high speed travel. That's leading off topic though so start a new thread if you want to call me on it.
Perhaps something like this;
http://www.space.com/scienceastronomy/070814_plasma_life.html
Yes I agree. Most anything more advanced would likely not be targetable by SETI even if we understood the technology well anyway. That was my point in the broad (technically reasonable) examples I used. I do feel like we understand enough now to understand at least very broadly the individual components of such an advanced technology, with only a few caveats.
I can identify dozens of communication schemes that are physically if not technologically possible. The number of protocols that can be used with each of those technologies expands the possibilities exponentially. We can't even be sure they wouldn't use different technologies and/or protocols to transmit different components of the same message. So I disagree in that I think it is reasonable to speculate about those technologies now. However, such speculation now or after we develop similar technologies is likely not to be of any use to a SETI program.
Sorry for nit picking but I've thought quiet a bit about it. Your points were very reasonable.