Spooky action & FTL communication

[Quasi-stellar Guy]

I was listening to a podcast the other day and they talked about the issue of Special Relativity vs. Quantum mechanics - where Relativity being the one that is showing noticeable cracks. They mentioned in passing that even with the phenomenon of entanglement, you could not use it for FTL communication... but they never went into 'why?'

How do you square spooky-action-at-a-distance while still keeping "C" as the absolute speed limit?? :confused:

[m74z00219]

well, when two particles are entangled, you could measure the spin of one (say you measure spin-up), then you would instantly know the spin of the particle it's entangled with (spin-down).

Despite you affecting the distant particle instantly, you can't use it for communication because you cannot choose the spin state of the particle in your lab.

If you could, a scientist with the distant particle could constantly pass it though a Stern-Gerlach apparatus and obtain messages.


Um, hope that helps some.

[Ken G]

It's the difference between what you can know yourself, versus what you can ever tell someone else.

[Quasi-stellar Guy]

... you can't use it for communication because you cannot choose the spin state of the particle in your lab.Ah! So that is the key! Thank you!

[m74z00219]

It's the difference between what you can know yourself, versus what you can ever tell someone else.

Not necessarily, more like it would take N years to tell someone with the other particle N light-years away what you got and therefore, what s/he's got.

[cjameshuff]

Not necessarily, more like it would take N years to tell someone with the other particle N light-years away what you got and therefore, what s/he's got.

Which is what makes it useful for encryption. Each side gets half of a set of entangled pairs. You receive an encrypted message via radio, laser, or a note scribbled on a napkin, and the fact that you did so tells you that the other party read their half of the entangled pairs and encrypted the message using the result. You read your pair, figure out what their result was and hence what they encrypted the message with, and can now decrypt it. Somebody who didn't receive an entangled particle can't decrypt it without having to use a brute force approach.

[astromark]

big words do not impress me. In fact. I live in a very confused state of utter entanglement and constant confusion. This thread thus far has done little to help.
quantum physics and particle entanglement and even string theories might mean some things to some of you... not this fellow. Confusion rains supreme.
I have followed the writings of Mr Hawking and find the logic of his thinking compelling. He has mentioned this very argument in his attempt to explain the possible explanations for and of this universe.. Am I wondering of topic,? . . Yes. Its hard not to when so much has been said and so little is explained.
Faster than light communication is and will most probably never be possible.. but is there and can there be things that are happening faster than C. Yes. Take the expansion rate of the universe as one. I will wait for the Large Hadron Collider to be tested and run.... answers will be expected for the bucks spent... Will this answer your question,? No. It must likely will not. Can it be answered. Maybe not. Some things are so vague and unclear its little wonder we are not all mad. I might be. Is it madness to ask of things we do not know,? Oh dear me, it might be.... LOl ;)I do not see an answer to this question, and think one will not be forthcoming any day soon. This does not for a moment imply that it is wrong or should not be sought. The search is the quest we seek. The answer is not.

[Grey]

well, when two particles are entangled, you could measure the spin of one (say you measure spin-up), then you would instantly know the spin of the particle it's entangled with (spin-down).

Despite you affecting the distant particle instantly, you can't use it for communication because you cannot choose the spin state of the particle in your lab.

If you could, a scientist with the distant particle could constantly pass it though a Stern-Gerlach apparatus and obtain messages.Also, it's important to remember just what the "spooky" part of this is. It's not that the two entangled particles always have opposite values if you measure the same property (say, spin in the x-direction). That could be satisfied easily if you just assume that the two particles really have opposite values of spin in the x-direction, which are set when they are created in an entangled state, and you just don't know what those values are yet. That could be explained entirely with a classical model with the particles having real (though unknown until measured) properties. The thing that's weird is what happens when you measure certain different things (maybe one person measures the spin in one direction, and the other observer measures spin in a direction offset by 45 degrees from that one). What you find out then is that quantum mechanics predicts (and experiment bears out) that the correlation between the two measurements is better than it should be if you assume that the particles no longer interact or change their spin values once they've been sent on their merry way, and that the choice one observer makes about what angle to set his Stern-Gerlach apparatus doesn't have any effect on what results the other observer sees.

You still can't use this to communicate, since the results individually are random, but entanglement isn't just a classical case where two results are linked but not yet known because they haven't been measured. If it were that simple, there wouldn't be so much interest in it.

[dhd40]

....The thing that's weird is what happens when you measure certain different things (maybe one person measures the spin in one direction, and the other observer measures spin in a direction offset by 45 degrees from that one). What you find out then is that quantum mechanics predicts (and experiment bears out) that the correlation between the two measurements is better than it should be if you assume that the particles no longer interact or change their spin values once they've been sent on their merry way, and that the choice one observer makes about what angle to set his Stern-Gerlach apparatus doesn't have any effect on what results the other observer sees. ...

(my bold)
Do you have to make the choice about that angle before the entangled particles are sent out, or could you chose (at least theoretically) the angle after the emission of the entangled particles?

If the answer is "before" then the particles might have lurked :)

[Grey]

(my bold)
Do you have to make the choice about that angle before the entangled particles are sent out, or could you chose (at least theoretically) the angle after the emission of the entangled particles?

If the answer is "before" then the particles might have lurked :)You can do either. You get the same results regardless of when you make the choice for how to set the two detectors. In the idealized thought experiment version, you'd have your two detectors placed a few light days apart, so that you could make the choices manually in a leisurely manner, and be completely confident that nothing you do in either lab should affect what measurement results are obtained in the other. And in fact some of the experiments have at least set things up so that the detector settings are chosen at random and switched rapidly enough (with the detectors placed far enough away from the source of entangled particles) that for any given pair, the settings of the detector are only determined after those particles have been emitted. Pretty much everyone agrees that if you could actually set up the more idealized version, you'd get the same results that have been seen in the experiments we've actually done.

[Ken G]

What you find out then is that quantum mechanics predicts (and experiment bears out) that the correlation between the two measurements is better than it should be if you assume that the particles no longer interact or change their spin values once they've been sent on their merry way, and that the choice one observer makes about what angle to set his Stern-Gerlach apparatus doesn't have any effect on what results the other observer sees.While this is all true, and an important point to make, it should also be pointed out that there is an alternative way of looking at the situation that never invokes the word "effect", and which in my opinion goes a long way toward demystifying the "spooky" aspects. Basically, the spooky action at a distance part comes from the picture that a particle "has" a spin, that spin somehow represents information that is carried by the particle itself. If you instead think of spin as a concept in your own mind, then there simply is no "action" that passes between entangled particles. The whole business is about information that is extracted from the reality, and it is true that no other objective observer's reality can contradict it, but the information need not be carried by and accompany the individual particles. It is all very much about the way we manipulate information when we conceptualize our reality, and information is in our head (it is what we use to obtain constraints that reality must obey). Reality's sole constraint is that two people's information must not contradict each other-- but it is not necessary to imagine (though we are welcome to imagine if we so choose) that reality cares one whit for our information beyond that simple constraint. Entanglement is about higher-order extraction and manipulation of that information, and yes it is very surprising and subtle in just the ways being described here, but there is no need to imply that what happens to one particle affects the other in any way at all. That all comes from the desire to imagine that information is carried by the particles, so one must choose one's poison when deciding what bizarre aspects of reality we should cling to when forced to let go of some prejudice.

In other words, when we make the connection between our information and the reality, we always have a choice: we can picture the simplest structures for encoding that information into the reality, which is to imagine that the particles themselves carry the information, as though reality was a kind of "answer man" that knows all things all the time even when not asked, but then we must imagine that information can somehow be instantly updated based on events for distant particles. Or, we can simply imagine that the information is encoded in more complex structures that are manipulated by physicists making predictions (this is exactly how quantum mechanics uses information), and reality only provides answers as it is asked for them-- it "carries" no information at all, but there is an energy cost for extracting information. In this latter view, the sole constraint reality must obey for physics to work is that reality must not give out contradictory information.

[Disinfo Agent]

But isn't it still strange that what's in the mind of one observer should correlate with what's in the mind of another, in that way? Either you have faraway particles behaving in unison, or you have faraway minds perceiving reality in unison. Aren't both possibilities equally surprising?

[Ken G]

Yes, it is very surprising indeed that reality supports a concept of "objectivity". I have no idea why it does that, but surely this fact is the very basis of the concept of "reality". My point is merely that the deep issue here, in my view, is that reality abhors contradiction-- not that reality can instantly transport physical effects between two distant particles (which makes little sense in view of the relativity of the very concept of instantaneity). I think the bottom line here is that reality must "think" very differently than we do, so we should recognize that "spooky action at a distance" is really just a kind of band-aid to help us cope with that.

[Grey]

But isn't it still strange that what's in the mind of one observer should correlate with what's in the mind of another, in that way? Either you have faraway particles behaving in unison, or you have faraway minds perceiving reality in unison. Aren't both possibilities equally surprising?Ken and I have gone around in circles on this a number of times. He holds a view that seems at odds with how most of the physics community views the issue (though he's pretty convinced that it's everybody else that doesn't really understand what's going on). I've given up on trying to persuade him otherwise, my skills at debate and explanation are not sufficient for the task, sadly.

He's right, though, in that the most commonly accepted solution to the dilemma is to acknowledge that the attributes that we measure for various particles cannot be considered localized to the particles (Einstein would have hated this solution). Ken G balks for some reason at calling such a universe nonlocal, even though it is clearly not local. I think that you're correct that the result is equally surprisingly however we look at it.

Ken G has pointed out that in order to see the surprising correlation, you have to communicate your results to each other by some "normal" means, but I was previously unable to get him to acknowledge the difference between a correlation which is present prior to that local method of communication, and only verified by such communication, and a correlation that takes place because of some local communication.

[Ken G]

Ken and I have gone around in circles on this a number of times. He holds a view that seems at odds with how most of the physics community views the issue (though he's pretty convinced that it's everybody else that doesn't really understand what's going on). Actually, that is itself one of the things we don't agree on-- I maintain that nothing I said above is anything less than simple fact, and is contradicted by zero theoretical argument or experimental data. If you feel that any of that is untrue, you should give specifics, rather than making unsubstantiated claims. Isn't that what you require of any ATM argument?

Ken G balks for some reason at calling such a universe nonlocal, even though it is clearly not local.I think if you read my statements just above more carefully, you will see clearly that what I "balk" at is the use of the word effect to describe the constraints that allow quantum mechanics to successfully describe entanglement. Indeed, I point to nothing other than quantum mechanics itself-- quantum mechanics tells us what will happen in these experiments, without ever invoking the concept of an effect. So if quantum mechanics doesn't need that concept, and quantum mechanics fully succeeds at every prediction we can make on the subject, then why do you feel the need to add it? That is the real source of the disagreement, I regret I have failed to make that clear before.

Ken G has pointed out that in order to see the surprising correlation, you have to communicate your results to each other by some "normal" means, but I was previously unable to get him to acknowledge the difference between a correlation which is present prior to that local method of communication, and only verified by such communication, and a correlation that takes place because of some local communication.What do you mean, exactly, by a correlation that is "present prior to" its determination? Does a particle have a velocity before I measure it? You are simply making the most common of all errors in dealing with quantum mechanical quantities, you are projecting it onto a classical concept prior to when that is actually necessary to do. A correlation is a correlation, it does not have a "time", it is a bit of information, and it exists when it exists. You would claim the correlation existed before the measurements were compared, and I say your words add philosophy where none is required, and the philosophy creates difficulties, so why use it? It is not necessary to use either one of the claims you compared, that the correlation existed before the measurements were compared, nor that it was created by the comparison. It is only necessary to say that a correlation is a correlation, and look at its own definition-- the correlation was calculated by the comparison. Same with all the concepts used in quantum mechanics. You simply add a lot of unnecessary baggage that is not present in the physics itself, and then worry about the problems that baggage has added. I say, look to yourself as the source of the conundrum, whenever that situation occurs.

[dhd40]

You can do either. You get the same results regardless of when you make the choice for how to set the two detectors. In the idealized thought experiment version, you'd have your two detectors placed a few light days apart, so that you could make the choices manually in a leisurely manner, and be completely confident that nothing you do in either lab should affect what measurement results are obtained in the other. And in fact some of the experiments have at least set things up so that the detector settings are chosen at random and switched rapidly enough (with the detectors placed far enough away from the source of entangled particles) that for any given pair, the settings of the detector are only determined after those particles have been emitted. Pretty much everyone agrees that if you could actually set up the more idealized version, you'd get the same results that have been seen in the experiments we've actually done.

Thanks, that clarifies my question very much

[dhd40]

...

Indeed, I point to nothing other than quantum mechanics itself-- quantum mechanics tells us what will happen in these experiments, without ever invoking the concept of an effect. So if quantum mechanics doesn't need that concept, and quantum mechanics fully succeeds at every prediction we can make on the subject, then why do you feel the need to add it? ...



If I understand this correctly it means: don´t care about any effects/explanations (quantum mechanics doesn´t "explain"), don´t try to understand the WHY (quantum mechanics doesn´t tell us anything about the WHY)

But this, exactly, is the very weird situation. You see all the perfect predictions of QM, but you (I) don´t know the WHY. The weirdness seems to be a result of philosophical (or psychological, or learned ?) barriers in our brain.

I don´t feel much better than astromark :sad:

[Ken G]

If I understand this correctly it means: don´t care about any effects/explanations (quantum mechanics doesn´t "explain"), don´t try to understand the WHY (quantum mechanics doesn´t tell us anything about the WHY)
What I actually mean is that quantum mechanics is the best path we have to use when wondering about the "why", even if we never get as far as we might like, because it least it places us on the firm footing of being able to predict outcomes (even if only statistically). There is a long history of people trying to leave quantum mechanics to get to "why", and the results are categorically pretty awful. Even the Bohm-deBroglie description is little more than window dressing built on top of quantum mechanics, adding essentially nothing to it, and not getting any closer to the "why"s.

But this, exactly, is the very weird situation. You see all the perfect predictions of QM, but you (I) don´t know the WHY. The weirdness seems to be a result of philosophical (or psychological, or learned ?) barriers in our brain.
I don't think we ever know the "why", even in situations that are absolutely mundane. Instead, we merely become so familiar with some phenomenon, we stop asking why, and forget that we stopped asking. Take gravity (please). Babies are fascinated by gravity, they can't get enough of watching it work. But we stop dropping things at some point, because we have become absolutely sure what will happen. This is extreme familiarity, but at what point do we understand why things fall? We make predictive theories about it that succeed, but we never get to the why, we just learn to stop asking why. Then you get into a new area, like quantum entanglement, and you are the baby once again asking why. Perhaps it is sad that we stop asking why after giving up on trying to understand why, but it is just human nature. The point is, we should never mistake familiarity for understanding.

[dhd40]

...
I don't think we ever know the "why", even in situations that are absolutely mundane. Instead, we merely become so familiar with some phenomenon, we stop asking why, and forget that we stopped asking. ... We make predictive theories about it that succeed, but we never get to the why, we just learn to stop asking why. ...

Interesting views. The more I think about it, the more I get convinced you´re right.
Which doesn´t calm down my sadness, au contraire ...

[Ken G]

Well, it is not my goal to contribute to anyone's sadness, but rather to find the root of that sadness and question it. I think the root of the sadness is that you've been sold a bit of a "tall tale" about what science is capable of doing, but once we understand what it is actually capable of, we can content ourselves with making the most of that recognition. We are basically very smart apes, and the whole idea that we know things about the universe on scales of an atom, or a galaxy, is astonishing. That is something to revel it, I would say-- we should not feel sad that we encounter fundamental limits in our ability to know what is "really" going on around us, we should be amazed how deeply and profoundly we need to penetrate that basic fabric before we encounter those limitations.

[peteshimmon]

Just when I think I have a working popular
explanation of this subject, along comes
Ken to say we still dont get it:) Well
no matter. You know I will come running (or
hobbling) when a neat experiment shows the
theory clearly.

In the meantime my own working picture. All
the Universe is happening in an instant! From
beginning to end! Elementary particles dont
know time, it is just one interaction after
another! This includes our existance. We
exist in the ghostly space between
interactions. So...no spooky communication
between particles! There is no time:)

[a1call]

*-Could this spooky action in a distance explain the apparent non-"relativity" of rotating frames of reference? In other words, could apparent absoluteness of direction for all that there is be an entanglement state inherited from the moment of the "creation/"big-bang?

Is it correct to say there are no absolute directions in space but all matter share one set of directions just because they are entangled?

*-In 1899 the astronomer Karl Schwarzschild pointed out an observation about double stars. [1] The motion of two stars orbiting each other is planar, the two orbits of the stars of the system lie in a plane.
...
Schwarzschild pointed out that that was invariably seen: the direction of the angular momentum of all observed double star systems remains fixed with respect to the direction of the angular momentum of the Solar system. The logical inference is that just like gyroscopes, the angular momentum of all celestial bodies is angular momentum with respect to a universal inertial space.


Source (http://en.wikipedia.org/wiki/Inertial_space)


If there was an observer on one of the entangled particles wouldn't he/she/it make a very similar statement (to the quoted text) about the other particle/s it was entangled with. Could these random synced rotations be an observation/indication of relativistic "rotational" frames of reference?

[Disinfo Agent]

I think if you read my statements just above more carefully, you will see clearly that what I "balk" at is the use of the word effect to describe the constraints that allow quantum mechanics to successfully describe entanglement. Indeed, I point to nothing other than quantum mechanics itself-- quantum mechanics tells us what will happen in these experiments, without ever invoking the concept of an effect. So if quantum mechanics doesn't need that concept, and quantum mechanics fully succeeds at every prediction we can make on the subject, then why do you feel the need to add it? That is the real source of the disagreement, I regret I have failed to make that clear before.

[...]

What do you mean, exactly, by a correlation that is "present prior to" its determination? Does a particle have a velocity before I measure it? You are simply making the most common of all errors in dealing with quantum mechanical quantities, you are projecting it onto a classical concept prior to when that is actually necessary to do. A correlation is a correlation, it does not have a "time", it is a bit of information, and it exists when it exists. You would claim the correlation existed before the measurements were compared, and I say your words add philosophy where none is required, and the philosophy creates difficulties, so why use it? It is not necessary to use either one of the claims you compared, that the correlation existed before the measurements were compared, nor that it was created by the comparison. It is only necessary to say that a correlation is a correlation, and look at its own definition-- the correlation was calculated by the comparison. Same with all the concepts used in quantum mechanics. You simply add a lot of unnecessary baggage that is not present in the physics itself, and then worry about the problems that baggage has added. I say, look to yourself as the source of the conundrum, whenever that situation occurs.I think the problem that people have with terms like "effect", "influence", "communication", "determine", "action at a distance", or even "correlation", is that many of them suggest a causal link between the two observations. People tend to interpret quantum entanglement as the result of one observation instantly causing/changing the result of the other observation. This is a possible interpretation of quantum mechanics (http://en.wikipedia.org/wiki/Interpretation_of_quantum_mechanics), but perhaps not the only one. Hence, I believe, Ken's reservations.

Now, interpreting these words as indications of causality is actually an error (except for "action at a distance"), but I see how the terminology can sound confusing. On the other hand, "quantum entanglement" by itself sounds a bit obscure. Perhaps we could temporarily use a different term to help us think about this phenomenon with a minimal of preconceived notions. How about "quantum synchronicity"? The two observations in quantum entanglement don't necessarily affect each other at the moment of observation, but they are synchronised in the sense that they obey common patterns of symmetry, like swimmers in a synchronised swimming routine (http://en.wikipedia.org/wiki/Synchronised_swimming). :)

Then the question becomes: why and how are the observations "synchronised"? Why don't they just fluctuate independently "at random", like dust under Brownian motion?...

[Grey]

Actually, that is itself one of the things we don't agree on-- I maintain that nothing I said above is anything less than simple fact, and is contradicted by zero theoretical argument or experimental data. If you feel that any of that is untrue, you should give specifics, rather than making unsubstantiated claims. Isn't that what you require of any ATM argument?Sure. You stated specifically here (http://www.bautforum.com/space-astronomy-questions-answers/70918-blinkin-cat-again-schrodinger-question.html#post1184510) that your answer was "somewhat nonstandard", but that you still think you're right. You've made similar statements a couple other times in our other discussions, that you think a large number of people in the physics community don't understand entanglement right. For example, you've commented that Bell's theorem is irrelevant, but I think most physicists view it as a fairly significant result. And that's all I said, that you acknowledge that your view isn't necessarily the standard one, but that you still think you're right. So who's on the ATM side of things here? :)

I think if you read my statements just above more carefully, you will see clearly that what I "balk" at is the use of the word effect to describe the constraints that allow quantum mechanics to successfully describe entanglement. Indeed, I point to nothing other than quantum mechanics itself-- quantum mechanics tells us what will happen in these experiments, without ever invoking the concept of an effect. So if quantum mechanics doesn't need that concept, and quantum mechanics fully succeeds at every prediction we can make on the subject, then why do you feel the need to add it? That is the real source of the disagreement, I regret I have failed to make that clear before.I don't think quantum mechanics ever has much of a "cause and effect" in the way we often think of it. We tend to use potentials rather than applied forces, for example. And most predictions that we make up and up statistical in nature. So we know that a given particle might be measured (say) 50% spin up or 50% spin down. We measure, and find it to be spin down. We have no notion of what caused that specific particle to be spin down rather than spin up, or even if it's meaningful to discuss that. If there is some underlying mechanism that causes such things, it seems very likely that it might be forever inaccessible to us, hidden behind quantum randomness. And you have specifically objected to describing things as nonlocal, even though you've agreed that they are not local. For example, here (http://www.bautforum.com/science-technology/69542-disproof-conscious-collapse-interpretation-qm-3.html#post1164653) you're stating that reality is "holistic" and neither local nor nonlocal. Except that as far as I can tell, you use the term "holistic" to refer to a subset of what every other physicist would use "nonlocal" to describe, but you don't like the word nonlocal.

What do you mean, exactly, by a correlation that is "present prior to" its determination? Does a particle have a velocity before I measure it? You are simply making the most common of all errors in dealing with quantum mechanical quantities, you are projecting it onto a classical concept prior to when that is actually necessary to do. A correlation is a correlation, it does not have a "time", it is a bit of information, and it exists when it exists. You would claim the correlation existed before the measurements were compared, and I say your words add philosophy where none is required, and the philosophy creates difficulties, so why use it? It is not necessary to use either one of the claims you compared, that the correlation existed before the measurements were compared, nor that it was created by the comparison. It is only necessary to say that a correlation is a correlation, and look at its own definition-- the correlation was calculated by the comparison. Same with all the concepts used in quantum mechanics. You simply add a lot of unnecessary baggage that is not present in the physics itself, and then worry about the problems that baggage has added. I say, look to yourself as the source of the conundrum, whenever that situation occurs.Suppose Xavier and Yvette write down some values (in each case, a string of Y's and N's in some specific order), and seal them in envelopes. At this point, we have no idea whether those series are correlated in any way, since we have no idea what method Xavier and Yvette used to pick those particluar strings. Maybe they just made them up at random, in which case they're presumably not correlated at all. Maybe they wrote down whether the stock market fell each day during the last month, in which case they'll be 100% correlated (and they'll both show a depressingly large number of Y's...). Now, here's the question I'd ask you. Does the correlation (if any) between these two lists already exist now, when they've been written down and sealed, or does that correlation exist only when they mail them both to me, and I open them up and look at the lists, and check to see if any correlation exists. I would maintain that, once the lists are written down, any lack of knowledge about the lists is just classical ignorance and has nothing to do with quantum uncertainty about the results: the correlation is there or is not there, we just don't know about it yet. This is the same way that a coin tossed in a sealed box is not an example of quantum indeterminacy: as far as quantum theory in concerned, a coin like this is definitely either heads or tails, even though we don't know it yet, and this is very different from a particle whose spin may be up or down, but that is not established yet because we haven't measured it.

[Ken G]

I think the problem that people have with terms like "effect", "influence", "communication", "determine", "action at a distance", or even "correlation", is that many of them suggest a causal link between the two observations. People tend to interpret quantum entanglement as the result of one observation instantly causing/changing the result of the other observation. This is a possible interpretation of quantum mechanics (http://en.wikipedia.org/wiki/Interpretation_of_quantum_mechanics), but perhaps not the only one. Hence, I believe, Ken's reservations.Right, that's exactly the issue I'm having with the standard language that gets used, unnecessarily, to describe entanglement. Such language merely furthers the misconceptions that trying to apply classical thinking hampers us with. It is fine to show why classical thinking doesn't work, which is partly what it is used for and was used for above, but it shouldn't be used as our description of what is happening-- expressly because it is not suitably divorced from that very same classical thinking that caused the problems in the first place.
How about "quantum synchronicity"? The two observations in quantum entanglement don't necessarily affect each other at the moment of observation, but they are synchronised in the sense that they obey common patterns of symmetry, like swimmers in a synchronised swimming routine (http://en.wikipedia.org/wiki/Synchronised_swimming). I'd have no objection to those terms, but then I don't object to "entanglement" either. It is the causality implications that bother me, as you point out, so any words that avoid those connotations would suit me fine.

Then the question becomes: why and how are the observations "synchronised"? Why don't they just fluctuate independently "at random", like dust under Brownian motion?...Yes, why does nature avoid contradictions, and what rules does it permit itself to follow in the pursuit of avoiding contradictions? Personally, I expect that even causality is purely a notion of our intellect, and is merely a shadow of some deeper and more natural principle that we have yet to glean. Hence, when normal notions about causality create awkwardnesses in our descriptions, we should not simply tolerate that in a bow to how our intelligence works, but instead we should recognize that as an entry point toward gleaning those deeper principles.

[Ken G]

Sure. You stated specifically here (http://www.bautforum.com/space-astronomy-questions-answers/70918-blinkin-cat-again-schrodinger-question.html#post1184510) that your answer was "somewhat nonstandard", but that you still think you're right. I'm well aware that I am objecting to the normal language that gets used, that hardly qualifies as being "at odds" with what other people are saying. The same is true when I point out that nothing in the Big Bang theory requires us to state categorically that "space is expanding", even though my pointing out our options there is indeed a nonstandard thing to do. Surely you can recognize the difference between pointing out weaknesses in the dogmatic adherence to a certain view, versus being at odds with that view? And yes, of course I do think I am correct in what I am pointing out-- it would be rather foolish of me to point it out if I did not think it correct to do so.


You've made similar statements a couple other times in our other discussions, that you think a large number of people in the physics community don't understand entanglement right.But that's perfectly obvious. I can find in a quick Google search many examples of people incorrectly explaining entanglement on seemingly knowledgable websites. And surely you recall that thread where I had to point out the misconceptions certain people had about when it was still possible to alter the wavefunction of a photon propagating through a complicated apparatus? But aren't you taking us a bit off topic with this line of questioning?

I don't think quantum mechanics ever has much of a "cause and effect" in the way we often think of it.I agree-- so we need to take that lesson and avoid causal language whenever possible. To me, an "effect" is causal language.

And you have specifically objected to describing things as nonlocal, even though you've agreed that they are not local. For example, here (http://www.bautforum.com/science-technology/69542-disproof-conscious-collapse-interpretation-qm-3.html#post1164653) you're stating that reality is "holistic" and neither local nor nonlocal. Again, that is because the way you mean nonlocal is not simply "different from local", which would make it logically impossible to be neither local nor nonlocal. Your way of using "nonlocal" is always in regard to nonlocal effects, ergo my objections to it.

Now, here's the question I'd ask you. Does the correlation (if any) between these two lists already exist now, when they've been written down and sealed, or does that correlation exist only when they mail them both to me, and I open them up and look at the lists, and check to see if any correlation exists. You are asking me a philosophical question, and I will give you a philosophical answer. We can get away with imagining the correlation exists whenever we want to imagine that-- as long as we do indeed get away with it. When we don't get away with it, we have made a mistake we need to correct. But formally, a correlation exists when its own definition says it exists-- the rest is philosophy. The lesson of quantum mechanics is very much a story of when we do, and when we do not, get away with certain ways of picturing reality. We need to take that lesson to heart.

I would maintain that, once the lists are written down, any lack of knowledge about the lists is just classical ignorance and has nothing to do with quantum uncertainty about the results: the correlation is there or is not there, we just don't know about it yet.But all that really means is you cannot think of a situation where you would not get away with your philosophy. I can't either-- that's a situation where you can get away with it, expressly because there is no phase information stored in that scenario. But entanglement is just not like that, there is phase information. What's more, there is not even a way to unambiguously determine "when" those lists were written down, as they are in acausally connected reference frames.

[Disinfo Agent]

I agree-- so we need to take that lesson and avoid causal language whenever possible. To me, an "effect" is causal language.I can't help pointing out that in certain areas of statistics (I'm thinking of multivariate analysis, and the design and analysis of experiments), the word "effect" doesn't necessarily imply a causal link. Even though effects are usually sought with the ultimate goal of establishing a causal link, the fact that "variable X has an effect on variable Y" does not by itself imply that either of them causes the other. This is an instance of the old adage that correlation does not imply causation.

[dhd40]

... I think the root of the sadness is that you've been sold a bit of a "tall tale" about what science is capable of doing ....

Well, actually it´s the other way round. I don´t expect science to be capable of explaining everything. I would be satisfied to know that we will never find out the "truth" because of .... (insert whatever you like) ... The sadness is to be told that we´ll never find the "truth", that there´s zero chance to find it (e.g. Bell´s theorem, no hidden variables, etc), in principle, no matter how intelligent we might be.
That´s the real sadness. Telling me that mankind will never be intelligent enough to find the truth behind everything isn´t a problem. But telling me that this will be impossible forever, independently of how sophisticated mankind´s intelligence ever develops, that´s ... sad


We are basically very smart apes, and the whole idea that we know things about the universe on scales of an atom, or a galaxy, is astonishing.
Yes, yes, yes, ...

-- we should not feel sad that we encounter fundamental limits in our ability to know what is "really" going on around us

I would agree if someone would tell me that it´s a matter of OUR limited ability to know what´s really going on around us. But, as I said above, it doesn´t seem to depend on this limited ability, it seems to be a fundamental principle, and that´s ... well ... sad

[dhd40]

Just when I think I have a working popular
explanation of this subject, along comes
Ken to say we still dont get it:)

Hopefully :)

In the meantime my own working picture. All
the Universe is happening in an instant! From
beginning to end! ....

Which makes me wonder whether all the Universe is one and only one wave function. No joke, I mean it!

[Ken G]

Even though effects are usually sought with the ultimate goal of establishing a causal link, the fact that "variable X has an effect on variable Y" does not by itself imply that either of them causes the other. This is an instance of the old adage that correlation does not imply causation.I can't speak to the literature you are talking about, but I would find that a pretty strange use of the word "effect". For example, in the spirit of "correlation does not imply causation", we might say the number of people using umbrellas on a given day correlates strongly with whether or not it rained that day. Would the statisticians of which you speak then say, "variable 'use of umbrellas' has an effect on variable 'whether or not it rains'"?

[Ken G]

Telling me that mankind will never be intelligent enough to find the truth behind everything isn´t a problem. But telling me that this will be impossible forever, independently of how sophisticated mankind´s intelligence ever develops, that´s ... sadBut perhaps the role of intelligence is to go in another direction than to find that truth-- maybe intelligence is understanding what intelligence is capable of doing. For example, was it not intelligent for Godel to prove that the algegra on real numbers is either incomplete or inconsistent? I wouldn't say it is sad that this is true of the reals, I would say it's amazing that our intelligence can let us know this is true of the reals.
I would agree if someone would tell me that it´s a matter of OUR limited ability to know what´s really going on around us. But, as I said above, it doesn´t seem to depend on this limited ability, it seems to be a fundamental principle, and that´s ... well ... sadNo "fundamental principle" is separable from our intelligence. Some superintelligent alien species might be taking an entirely different tack, that resembles ours in not even the least way.

[dhd40]

...
Some superintelligent alien species might be taking an entirely different tack, that resembles ours in not even the least way.

Agreed. But even then they will not be able to overcome Bell´s theorem (if my layman´s understanding of this is correct)

[Ken G]

I agree, we have no reason to think they can overcome the limitations of quantum mechanics (say, the uncertainty principle), but they might use a different approach that simply never encounters it. They might, if we allow ourselves the most far-fetched example, predict outcomes not with physical laws, but instead by peeking into a machine that sees the future as it actually will be. We don't know that technology is impossible, we just don't know how you'd do it. But if someone had that technology, they would not need equations or variables of any kind to make predictions, and they would not encounter Bell's theorem at all. Maybe the machine would only work on simple systems, like quantum mechanics does, and there would then be no logical contradictions.

[dhd40]

... They might, if we allow ourselves the most far-fetched example, predict outcomes not with physical laws ...
Outcomes of experiments? Maybe, e.g. "perfect" simulation techniques. Well, "perfect" would not be easy to define :think:

... but instead by peeking into a machine that sees the future as it actually will be. ...
(my bold)
Here I disagree. This would be something like a time machine, enabling silly grandfather paradoxes, etc.

Seeing the future as it actually will be must be horrific.
But besides that, wouldn´t that imply FTL communication? The future, however far away, would be visible with a twinkle in one's eye

[Ken G]

Here I disagree. This would be something like a time machine, enabling silly grandfather paradoxes, etc. No, seeing the future involves no paradoxes. Indeed, it was once thought that Newtonian physics could "see into the future", i.e., make fully deterministic predictions. There was never any problem with "changing" the future, because the Newtonian prediction was always predicated on certain assumptions, such that if they were changed, so would be the prediction. My "see into the future" machine would be no different. No paradoxes, just a few philosophical difficulties around naive concepts of free will and so forth.

Seeing the future as it actually will be must be horrific.There is a terrific book by John Gardner called "Jason and Medeia", in which he has a character who is an Oracle, who has just this problem. The Oracle sees the future as it will be, but it's even worse than a conditional future, it's the absolute future. So his whole life is infused with a complete sense of pointlessness and boredom, like watching a movie for the 100th time by the time events actually unfold as he foresaw them. Even his death unfolds as a completely boring event for him. Apparently, he could not help but peek into that "machine".

But besides that, wouldn´t that imply FTL communication? The future, however far away, would be visible with a twinkle in one's eye
The future could be restricted to be within one's own causal horizon-- perhaps the machine would not be able to see futures outside that horizon. Or perhaps it could only see outside that horizon-- and note there would never be any way to communicate what you saw to anyone outside your horizon. None of this contradicts relativity, because even if we take relativity as being correct, it merely constrains what can affect other things; it imposes no constraints on making predictions. It is merely a scheme for making predictions, it holds no sway over other schemes for doing the same. Same for quantum mechanics-- it comes complete with its own limitations. Any theory which does not contradict quantum mechanics is also unfettered by quantum mechanics.

[dhd40]

....
There is a terrific book by John Gardner called "Jason and Medeia", in which he has a character who is an Oracle, who has just this problem. The Oracle sees the future as it will be, but it's even worse than a conditional future, it's the absolute future. So his whole life is infused with a complete sense of pointlessness and boredom, like watching a movie for the 100th time by the time events actually unfold as he foresaw them. Even his death unfolds as a completely boring event for him. Apparently, he could not help but peek into that "machine".

As I said: horrific :mad:

The future could be restricted to be within one's own causal horizon-- ...
I would have expected "future" to be infinite by definition (each/every event beyond now ?)

BTW: What´s the difference between "each" and "every"?

[Ken G]

I would have expected "future" to be infinite by definition (each/every event beyond now ?)
Our future causal horizon is infinite, in principle.

BTW: What´s the difference between "each" and "every"?
Not much but I'm not sure what this is in reference to.

[dhd40]

Not much but I'm not sure what this is in reference to.

Sorry, I was just wondering about the correct wording in

I would have expected "future" to be infinite by definition (each/every event beyond now ?)

[Ken G]

Oh I see, that slipped by. Yes, I think "each and every" is legalise for "each," or "every", sort of like "for all intents and purposes"!