Some people seem to think that quantum* entanglement* will allow faster than light communication;
however it seems that no useful information can be sent faster than light by this method, although entanglement/teleportation might improve the amount and quality of information which can be sent by *classical channels- *
that is to say at light speed.
Yes, basically what is known as quantum teleportation utilizes the non-loclaity of quantum entanglement. I’d be careful about your phrasing tho’ as ‘communication’ usually means (and certainly in this context) the sending of information, which as you say, is something quantum teleportaion/enetanglemnt cannot do FTL.
I can see no way that quantum teleportation can improve the quality of information sent as it requires a classical communication channel (you could even send the iformation by post if you so wished), infact all quantum teleportation does is sidestep the so-called ‘no clones theorum’ of quantum mechanics which was once thought an obstacle to teleportation.
If i understand you correctly, you think that it is likely that we are the only intelligent species currently existing? Despite what i was saying about Von Neumann probes i actually think the opposite.
The only thing we definately know is that any given solar system has a non-zero probability of developing intelligent life. Given that however, i would argue that the best working assumption we should take is that that probability is as high as allowed by what we know. For example, if we know that the probability of life for a solar system is either 0.005 or 0.01, we should assume 0.01 until evidence points otherwise as that assumption means that our existence is less improbable. Kind of the same principle as if you have a choice between two theories - one that says we’re the centre of the universe, and the other that says we’re just another unimportant star amongst many others. If both theories are equally supported by evidence you go with the one that doesn’t assign us a special place in the universe. Similarly, if you have a choice between life being staggeringly improbable and our existence being a fluke, or life being fairly common and us being just another life bearing planet among many others you go for the second.
Of course that doesn’t prove a thing. But i think that until we have evidence otherwise, we should assume intelligent life is common, as that means we’re not special.
However, it doesn’t quite work that way for existance due to the anthropic principle. The chances of at least 1 sentient species arising is exactly 1 no matter what the actual chances of life evolving is since sentience is a neccesary pre-condition to the asking of the question “Are we alone”. Thus, the fact that we exist does not tell us anything at all about what the likelyhood is that life could have arisen.
Really fun interactive place to put your own numbers into the** Drake Equation ** yourself – which is what we are talking about here.
http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html
I guess I am a Star Trek/Star Wars baby: I believe that there is an abundance of life in the universe – but I know it is a belief & only very loosely more than a WAG.
Having said that
I guess one thing to amplify Haj touched on regarding the OP: Life has existed on earth for +/-4billion years, “Intelligent life” has existed (depending on your definition – maybe homo halibis the first in the homo genus?) for 2.5 million or circa 250,000 for moderns (red herring alert).
We have been a detectable civilization for circa 80 years, we have been seriously searching for ET for less than 40 years. So, although Life has been here for 4.5 billion years, Earth has only been able to answer the Vulcans or Wookies for 40. Are you positive beyond all doubt humankind will be here and searching in 150 years? Any odds against that absolutely for sure happening need to be weighed in too. That is a big factor to consider.
We are looking for them; it is of little consequence in the Search for Extraterrestial Intelligence how long humanity survives;
what is important is how long have their civilisations existed for, and are they transmitting on wavelengths we can detect, at power levels we can detect?
If only one in a thousand civilisations lasts for millions of years, we would see that civilisation (if it were in range). In fact it is very likely that every detectable civilisation will be much older than humanity, if they are there at all.
SF worldbuilding at
http://www.orionsarm.com/main.html
SentientBeing What is a gamma ray sweep?
— I feel obliged to point out that we didn’t have the capability of doing any of that just a couple of hundred years ago, and within a thousand years we will likely no longer be doing any of that any more (either because we’ve moved on to better technology or we’ve managed to remove ourselves from the food chain). That makes this a pretty small window to be looking through.
I disagree. Canals are not cutting edge technology - few if any would be built now - but that doesn’t mean they aren’t still in use. Similarly even if the aliens switch to cable, I suspect that they would still find some use for radio waves, if not for communication then for something else. Resources tend to be used.
I disagree. Although, I would not rule out the possibility of the existence or nonexistence of alien technological civilizations, I would think that we could put some sort of bounds on the question. We have a lack of evidence from conventional astronomers. We have the SETI data. We have not spotted any Dyson spheres. Then there’s the Fermi paradox: given the ease of interstellar transport (over thousands of years, not decades) why haven’t we come across any aliens or alien probes? (Outside of Area 51, of course.) I agree that characterizations should be made with a great deal of hedging, however.
The possibility that technological life is self-extinguishing would tend to lower the probability of concurrent intelligent life in the galaxy.
I tend to agree with Stephen Jay Gould, who points out in his book “Wonderful LIfe” that there appears to have been a gap of more than 2 billion years between the first signs of life on Earth and the first evidence of multicellular life on Earth. Two billions years is a very long time, even in evolutionary terms. Given the speed with which life arose, Gould’s guess is that life is pretty commonplace in the universe – just about anyplace that’ll support liquid water might well support life. But most of those planets likely have as their highest form of life algal mats – perhaps all of them. Getting cells to subsume themselves into a metaorganism may be more of a problem than is generally realized.
I disagree. The trouble is that, because of the anthropic principle, we’d end up making the exact same observations either way. So there’s no a priori reason to assume we’re not special.
For the same reason, the so-called doomsday argument is invalid. See below.
Let’s apply the principle to human population growth. It is possible that humanity will colonize the galaxy and grow in numbers to trillions and trillions, if not more. If that is the case, it was a highly unlikely event that you would be born while humanity occupies just one planet and numbers less than 10 billion. On the assumption that you do not occupy a special place in human history, it is thus far more likely that human population has peaked. The end of the world is nigh. Have a nice day 
Apologies for my clumsy syntax, I meant a sweep with a powerful gigahertz beam (ie. in the gamma ray part of the EM spectrum), which the Areciebo radio telescope could detect from pretty much anywhere in the galaxy.
We cannot hear anything from anywhere in the galaxy, even though the technological level required to emit a galaxy-wide audible signal is roughly that of producing an H-bomb. Perhaps the two facts are not unrelated.
Indeed, but even if these resources are for some reason not used at all (which itself seems rather unlikely - nobody will be a vintage radio ham or make their own TV set just for giggles?), then they would still doubtless be able to detect our almighty racket. There would then have to be some kind of colossal conspiracy to ensure nobody sent us anything in return.
And even if such a conspiracy could survive, they could not prevent those leaks from way back in their technological infancy. The fact that we cannot hear anything at all, even from 50,000 years ago, bodes ill I fear.
Ahh, but how long have we neen sending out that “almighty racket”? Halve that interval to give them the time to send the same type of signal back to us and you’ve limited your visibility window substantially. That logic doesn’t work with any civilization more than 100 light-years away.
Not at the signal strength that it would take for us to be able to detect it, no. Correct me if I’m wrong here, but I’m under the impression that the SETI folks have stated that if another civilization was generating signals at the strength levels that we are currently capable of doing then we’d be currently unable to detect them.
Ahh, but (see above comment) we’re currently unable to detect any signals that would be inadvertantly sent at the signal strength they’d normally be broadcast at.
Past thread. We could detect radio signals at 5 LY, military radar at 50 LY and GHz beams at 100,000 LY
[sub](Just as I specified originally.
Difficult to communicate with another planet? Hah.)[/sub]
Fair enough. I can see your point. I still personally believe though that intelligent life must at least be not that rare (imprecise terms i know!). It just seems to me that as we have learnt more about the world around us, the more we’ve realised how insignificant we are in relation to the universe. Suddenly learning that we are the only intelligent species existing would somehow go against this pattern. I know its not a logical argument, but those are my thoughts, anyway.
Oh and BTW regarding the Doomsday argument, i’ve heard of it before but i’m not particularly knowledgable about it. Couldn’t an argument against it be that our birth is not distributed randomly in time because the future is uncertain, or does it require more subtle arguments?
Thanks for the link. I will cheerfully concede the point that it is reasonable to assume that there has been no civilization transmitting military-grade radar within 50 light-years of us during the last 50 years.
Note, though, that our galaxy is 100,000 light-years in diameter, so a 50-light-year sphere represents a pretty tiny segment of it. Less than a billionth of it, I think.
Note also that inlike situation with the radar beams, the GHz beams that you’re referring to are assumed to be directional rather than broadcast. I’m assuming that the dispersion of such a directional beam would have to be pretty tight to get detectability at any appreciable distance out of it. Given that, the odds of anyone who is “sweeping” the skies with such a broadcast from a distance of, say, a quarter-of-a-galaxy away targeting our specific area any time within the last hundred years would be infinitely small.
And, as Q.E.D. mentioned in that linked thread, we’re assuming that the other folks are using the same technology that we are. As he put it “just a step up from beating on freaking drums”.
(Note to self: try to remember the difference between radius and diameter.) Ahh, maybe we should make that “about a billionth” :o
I am not sure we aren’t arguing the same point, but it is of the utmost consequence to the OP (paraphrased): Give me good reasons why ET isn’t there.
I say based on 4.5 billion years of life on Earth we have been able to seek and respond for 40. It really isn’t a stretch to say that in real cosmic time there will be no difference between the development of technology to seek and speak to ET and the technology to destroy the seeker and speaker. Given our example, it isn’t insane to think that we aren’t 100% sure that the search will last more than a few short centuries. If that is a real pattern, (and Drake [& you seem to] says it is possible) then that may affect ET and the chance to find him, (which the thread kind of moved into). It seems you object to me using us as an example … but given the likely development of relevant technologies that doesn’t seem outlandish to me.
Just to respond to a few disparate points made by people:
Broken Column said:
I’m not sure whether you mean our universe will end some day or whether you mean our planet will end but it doesn’t matter which of these you mean because in either case you could be wrong. First of all let’s take the scenario of our planet:
I assume that, by this, you are referring to the fact that in 5 billion years time our sun will inevitably expand and swallow the earth before shrinking to become a red dwarf?
There is nothing inevitable about this at all. Yes, this is what happens to stars when they reach a certain age but there is one factor that makes our sun different from all the other stars in the known universe - us. We are observing the expansion of our sun and this means that we could therefore put a stop to it. In principle we already know what needs to be done - we just have to remove material from the sun and cast it off into space. We need to regulate the sun to stop it getting too big.
This sounds like a tall order but remember we’ve got 5 billion years to figure out how to do it. We have already sent a probe to Mercury in 1973 that orbited the planet and could withstand the heat of a Mercury day. Mariner 10 is still, to this day, orbiting the sun although it’s components have probably now been blown out by solar radiation.
So we already know, in principle, what needs to be done and we’ve got 5 billion years to figure out a way to do it.
The second thing you might have meant was that our universe would end. Well again, not necessarily. It’s possible that the nearer we get to the endpoint of the universe the slower time goes, so that we never actually reach the end. The last second of the universe will last for infinity and, during that last second, our knowledge will grow exponentially. David Deutsch is an eminent physicist, read his book The Fabric of Reaity for more info.
Deutsch also covers quantum computers which have been mentioned in this thread.
MC Master of Ceremonies said:
Quantum computers are nothing to do with travelling faster than light (for that, you need superstring theory, M theory etc). The point about quantum computers is that they can perform some calculations many times faster than ordinary computers, in particular factorisation. There is no quick way to factorise a number. Suppose you take a random long number:
6354976546595698637623476
There is no way to find the factors of that number (two numbers which multiply together to give that result) apart from doing it the long way. Quantum computers do it in no time. The reason suggested by Deutsch ( and in fact Deutsch suggests that this is the only explanation) is that quantum computers must be using parallel universes.
An ordinary computer has to work it out over time performing one calculation at a time. Therefore, fast as modern computers are, they would still take hundreds of years to factor the number I gave above ie computers move through time in a linear fashion - forwards.
Quantum computers, on the other hand, spread out their calculations over many universes. So rather than moving forwards through time they spread the work out sideways, over many universes. An ordinary computer may take a thousand seconds to do something whereas a quantum computer will just spread the calculation out over a thousand universes and therefore come up with the answer in one second.
This may all sound very sci-fi but as far as we can work out, this is what seems to be happening.
This is David Deutsch’s homepage, his book is well worth a read.
We are going to need much bigger detectors if we want to find civilisations comparable to our own; we would be undetectable more than 50 ly away without much bigger telescopes.
A hi-tech, long-lived civilisation might be expected to have spread outand covered part of the galaxy by now; but the high powered narrow beam transmissions such a civilisation might be expected to use would be difficult to detect unless we were in the line of sight…
perhaps we would pick up a transmission between an interstellar ship and the home (or destination) planet- but only briefly.
This might explain such transient phenomena as the ‘Wow!’ signal from 1977.
Not always. Didn’t we sometimes assume we’d find life, probably intellegant life, on mars, moon, etc? Then we discovered our liquid-water plaent was rare in the solar system.
Personally, I like this kind of ‘meta’ common sense argument. Just maybe not in this case…