the underlying assumptions rig the debate

Then you need an actual quote in order to show this. This is all you provided from Message 150: That's not a quote. I'd be the last to claim a perfect memory, but I've seen one of the lectures where he says this (I'm sure he said it many times), and he said it very early in the lecture before he'd gotten to any details.I'm not trying to give you a hard time. I just think your claims should have better correspondence with the actual situation within science. Maybe one day we'll uncover convincing evidence of causality violations, but it hasn't happened yet, and to claim that it has is just plain wrong.--Percy

I guess I should add that even if he said it in the context of the 2-slit experiment, it still can't be construed that Feynman accepted causality violations as experimentally established.If causality violation had been demonstrated experimentally, then you would be able to find sites all over the net saying things like, "The experiment that first established causality violation was...etc...".It should tell you something that the best you can do is find quotes about something else and claim that they're about causality violation.--Percy

You are confusing issues here. You guys brought up superluminality, and that is indeed an area of research that is contested, but how a photon behaves in these experiments is a different issue. First off, QM predicted the behaviour, and repeated tests verify it. The behaviour indicates that if you can determine what path (in the past be definition) that a photon takes, then it takes (in the past) a single path (from our vantage point at a minimum).However, if you cannot tell which path (by definition in the past) a photon took, then the photon takes all possible paths (from our vantage point).So how you decide to measure determines the past in these experiments. That's something you need to understand because it's not really contested.There are ways though for physicists to interpret this to get around seeming backwards in time causality (even though some advance backwards in time causality with transverse waves), and one way is to claim the photon only appears to take one path but actually takes all possible paths. The Many-Worlds and Many-Minds interpretations do that, as well as perhaps some others such as claiming what we measure and see is not reality but merely phenomena associated with reality, which cannot be directly observed (Hologram and other approaches).But regardless, from a human perspective, how you question the photon and what can be known from the photon does determine whether in the observable world we live in, exactly what the photon did in the past. If you can know if it took a single path in the past, then in the past it takes a single path (even if it took all paths at one time, as shown in the quantum eraser experiment). if you cannot know, then the photon acts like a wave and the interference pattern appears.I strongly suggest before you keep bashing me that you take some time to get a handle on what is actually observed in these experiments.

And why did he not accept causality violations? You need to learn a bit more about the interpretations that avoid this somewhat obvious conclusion and also realize that some like Wheeler do talk about causality in a different way (in other words violating causality). Others like even PaulK here from his reading, presumably picked up from scientists, get around this by saying the past was indeterminate and so try to get around it that way.Iblis seemed to be saying that the photon still takes all possible paths even though it appears to only take one path when we can determine that path. Imo, this is sort of the same thing as I am saying since the universe we live in as human beings would have a multitude of pasts, that appear or disappear depending on our observations.Another way around the obvious causality from the present towards the past is similar, and to claim that not only do all pasts exist in superposition as possibles, but all exist as real (the Many-Worlds) and so one might try to get around the causality issue that way.The more mainstream way around it, advanced by Borh, was to deny physical manifestations are real. Under that scenario, all we can ask about reality is the phenomena, never dealing directly with the reality at all.But once again, however you want to spin this, the bottom line is the past we can measure or have experiences, etc,....is determined in part by the present knowledge we can have of it. You can find plenty of ways to say it is not the present having a causitive effect on the past, but in human terms, the past can and does change as demonstrated by these experiments.

cavediver, I think you are confusing the human concept of transfer with the concept of transferring some physical energy or something. Let's take your example as poor as it is and you acknowledge that. The big deal is that you instantly know the state of the other particle billions of light-years away, and the knowledge of that situation may well have been transferred from the box you have in front of you, but using this principle you can know something instantly about a box a billion light-years away.I think this process can be manipulated to convey information. Certainly, information was conveyed when the box was opened, wasn't it? You can say, yea, but scientifically no superluminal transfer occurred. Well, in this instance, I say so what?If you can devise a way to know something about something in a distant place, well, I think there is a potential to manipulate that process.The truth is information is transferred over space and time instantly all the time. Heck, when I read a history book, I am getting information about the past.But none of this really relates to the OP anyway.

Superluminality was merely mentioned in passing as part of an explanation from Iblis in Message 41 about how entanglement really works, and only to say superluminality isn't possible. It was one sentence in a long post. It was you who later went off and found a paper from ORNL which you then offered as proof that we had our heads in the sand regarding superluminality. Now you're acting as if you knew it hadn't achieved wide acceptance all along: No kidding! The proper understanding isn't contested, but you don't have the proper understanding. How you measure doesn't determine the past, but it does determine what happens and what you end up seeing and measuring. Physicists don't have to do this because they interpret the experimental results correctly within the framework of quantum theory. You, on the other hand, have drawn a conclusion completely contrary to quantum theory simply because you've fallen in love with the idea of the present changing the past. Yeah, sorry about you feeling bashed, not intentional. My suggestion to you is to try understand the consensus view better, even if you don't accept it. You might find it has more to recommend it than you think, even if it doesn't support your hoped for transformation-of-the-past capability. Maybe you're right and one day we'll figure out that this is indeed possible, but there's very little in our current understanding of quantum behavior to indicate this.--Percy

I going to assume you're mischaracterizing PaulK's views and that he doesn't actually believe that obvious evidence of causality violations is gotten around by excuses about indeterminancy. This is just your caricature of his views.Your misunderstanding in this regard is one of the reasons why Iblis mentioned information in regard to entanglement at one point. PaulK wasn't saying that scientists make an excuse. He was making a very real point about information. He was explaining to you that what you think is changing in the past is actually information you never really had. What you are saying is by no stretch of the imagination anything like "sort of the same thing" as what Iblis is saying. That would be like saying being right is sort of the same thing as being wrong.The correct view described by Iblis is that once observed, the "all paths" possibilities decohere into a single possibility, the one observed. This represents possibilities going away.Your incorrect view holds that somehow some action in the present creates new possibilities in the past, and beyond that, you believe that this is the accepted view of mainstream science and that everyone else here just refuses to understand it. If I were you I'd look for a more likely theory than that you're right and everyone else is wrong.--Percy

NO NO NO NO NO NO NO!!!!You've completely missed Cavediver's point. It isn't that this is a poor example of entanglement. It's that this isn't an example of entanglement at all! Not even close! In fact, it's misleading. This is almost too funny! Not only can entanglement not be used for superluminal communication, Cavediver's example of an incorrect analog for entanglement most certainly cannot be used for superluminal communication. There is nothing in entanglement that allows you to know anything about a distant place. You can't even know if the distant particle has even be measured. All you can do is measure your particle and know that if and when they measure theirs, it will have the opposite spin. Omigod! It only gets better!There are some interesting thought experiments you can think through to help you understand entanglement. For example, you give one entangled particle to a close friend who is traveling to a distant destination across the galaxy. You both have the same hobby of building ships in a bottle, but you won't be able to pursue this together while he's gone. Usually one of you makes the masts, sails and rigging while the other makes the main body of the ship, and you decide who does what by a random flip of a coin.Your friend will be pretty busy on the way out and will only have time for ship-building on the way back, so you decide to use the entangled particles as a coin flip. When your friend reaches his destination he'll check the spin of his particle, and if it is positive spin then he'll build the masts, sails and rigging, and if it is negative spin he'll build the ship's body. You, here on earth, will check your particle, which will have opposite spin, and then you will also know which to portion to build.So off he goes, you both check your particles a few years later when he arrives (he knows when he arrives, all you can do is check your particle according to his ETA), and you both begin building your respective parts of the ship. Then a few years after that he returns and lo and behold, you find that you've both built complementary parts of the ship, and as part of that night's celebration you assemble them and insert them in the bottle as a symbol of your long and enduring friendship.Why is this not FTL communication?--Percy

From Randman's link: Edited by PaulK, : Provide reason for edit here.m

First off, you ought to reread what PaulK stated before assuming I am mischaracterizing his statements. This what he said: You go on to say something that shows you have not understood my argument here: It doesn't matter what "you" know or don't know, or whether you ever had information or not. What matters, at least as it seems from these experiments, is what can be known at any point in time. So if one can know what path the photon already took, the photon will have taken a single path. If one cannot tell which path a photon takes, it takes all possible paths. This is shown in that when we change the test so we can know, the interference pattern disappears such that the photon travels as a particle, and when we change the measurement so there is no way to tell, the interference pattern reemerges so that photon took, in the past, all possible paths.Clearly then, the path the photon takes or took is determined by our approach to questioning it. Zeilinger points this out in suggesting that perhaps the photon is an "elementary particle" containing a bit of information, and when that information cannot be known, the bit is not spent and so the particle is superposition, but when it can be known, the particle's bit is spent, and so only one path is taken. Whether you agree with him, understanding why he advances a more developed version of Wheeler's It from Bit concept helps to understand the experiments. In other words, he is trying to solve a problem. Maybe if you consider his solution, you will see the problem I am talking about here.So let's take this further, along the path of a photon then, it may hit a spot due to circumstances that there is a means of registering the photon's path and so at that point, the photon in the past will have taken a single path. But later down the road, the means to determine which path the photon took could be erased or lost, and so the photon then, over the same stretch of space in the past, will have travelled in superposition and not a single path. In that manner, the past that we deal with does indeed demonstrably change.Whether someone knows about the path or not is not really germane to the discussion. In fact, the person that measures the photon when they can tell what it did will see the photon having taken only one path, and another person measuring the same photon but without the means even in principle of knowing from measurement what path the photon took, will see the same past as having shown the particle travel as a wave.Now you can debate how to solve this dilemna all you want, but pretending the dilemna isn't there is not a good argument, and that seems to be what you are doing. And the quantum eraser experiment shows that this decoherence is not permanent. That's a key point you are missing here.

That's correct, but you have to realize that "our information changes" includes the information about what constitutes the past.

This is a contradiction. You admit you can know what a particle's spin is on the other side of the universe; hence you can know something about a distant place. I am not ignorant one or the group of ignorant folks that claimed no respectable scientists were devoting resources to working on superluminality. You are in that group. The problem with me mocking you, as you try to do with me, is you are so ignorant and your side so stubborn that proving you wrong is like talking to a brick wall.Similarly, you fail to realize harnessing the principle of entanglement is in it's infancy. You assume that such and such cannot be done, and ridicule that, but in reality, there are scientists working to see if it can be done all the time. A few years ago, Hawkings said time travel was impossible, and now says that though unlikely, it is possible.Why do you think he said that, Percy? You think he's an ignorant fool as well since after all breaking the time barrier in this manner would constitute a total violation of the physical principles you claim cannot occur.Right now, we don't really understand fully the mechanism of entanglement and so it is foolish to say that this mechanism cannot be used for such and such. The truth is entanglement suggests there is a deeper structure within the universe that we presently are aware of. Cavediver himself has speculated along the lines of thinking in terms of a hologram right here on this thread. If that's the case, figuring out how the underlying reality generates this hologram could do a lot of things.Zeilinger stated that entanglement appears to work outside space and time. You think he is saying if it works outside space and time that he really believes it can never be used to do some things people say cannot be done? I don't. I am not sure if he would openly state that yet, but just mentioning it appears to involve a process outside space and time already says much the same thing as I am saying.Lastly, what does superluminality have to do with my arguments in the OP?Edited by randman, : No reason given.

Randman, this was my f'ing profession. I used to teach this stuff (Advanced Quantum Mechanics) at the f'ing University of Cambridge to the gradutaes.. got it??? I'm starting to get a little pissed that some layman has the nerve to start telling me what I'm confusing...The rest of your post is the funniest stuff I've read yet. You have to back away and realise just how out of your depth you really are, before you make an even bigger ass of yourself.I've had enough... anyone else?

Yeah, I just wet myself reading Randman's reply It's at this point that I realise I am not only wasting my time, but my life is actually slipping away before my eyes... I may have to bow out for a while

You know darn well the issues I am bringing up are real, but all you do is scoff and throw mud, refusing to engage any of these issues with substance, imo.For example, I posted Zeilinger's statement that he considered the criterion for whether a photon behaved like a wave or particle to be what we could know, not the measurement itself, about the wave-function. That, on it's own, is an incredibly far-reaching comment clearly demonstrable in these experiments with or without any math being involved at all.Your comment?Nada, but derision. Well, I really don't care if it WAS your "f'ing profession". It IS his profession and I consider his statements much more significant than your BS derision about, hey, it's because you don't know the math, etc, etc,....especially when these are optical experiments done with apparatus, not simply math experiments.I throw a baseball through a window, and you can tell me I don't understand it all day long because I don't know the math behind the velocity, wind speed, curve, gravity, etc,..., but pretending I don't know the ball went through the window is ludicrous. Same with these experiments. Whatever labels you want to apply and whether or not what we observe is real or a holographic projection or whatever, the experiments do show a set of observed details.Most I have read indicate they believe the experiments do show that you measure the photon one way and it will show it behaved as a particle, and measure the other, and it will show it behaved as a wave. I think you know that, but just don't want to admit it.Next time you want to argue based on your resume, why don't you at least address the points that have been raised.Edited by randman, : No reason given.Edited by randman, : spelling and to place emphasis via quotation marks and caps