the underlying assumptions rig the debate

cavediver, you seem to have some confusion between the concept of theories and terms and an observed process. It's true that you need to learn some things, such as what is a photon or what polarization means, in order to know what the observations are in the experiments, but there is a process in these experiments of a photon being sent out through a medium or slit, etc, etc,....and that can be described in English.Now, the interpretation of what we observe may indeed require more depth, but at the same time, you seem to be the one constantly avoiding discussing the issue while hurling insults.Edited by randman, : No reason given.

Hadn't read this yet....so at least there is some substantive response. Good. As sidenote, does this mean you rule out transverse waves as possible since they do travel backwards in time if the theory is true?It seems that if you are correct and that it is such a hard and fast rule that this sort of thing is impossible, that the transverse wave theory should be viewed as some sort of joke, eh?Edited by randman, : No reason given.

In the quantum eraser experiments, the polarization filters are set up and the interference pattern disappears (the idea being we could then obtain information about the path, right?).But when we scramble that with a third filter, the interference pattern reappars (the idea being it does so in response to not being able to be measured).What is your idea or explanation for this?

From our vantage point is the wave-function extended over segments of time? In other words, when we see a photon at different points of it's trajectory, are you saying that the wave-function occupies those different points simultaneously?Edited by randman, : No reason given.

So you accept that it is reasonable to assert non-observed backwards in time waves, but that these waves cannot EVER affect the wave-function, being after all from the future and there is nothing in the future that can affect a wave funtion, as you stated so emphatically.And you don't see any inconsistencies with your statements here?Edited by randman, : No reason given.

Percy, your appeal to science fiction or stuff like that is strange on a several points. First off, it is factually wrong as there is fiction in both books and movies related to time travel and things like this. In fact, there is a ton of it.Secondly, the issue of fiction has no place in a scientific discussion.Third, you act as though transverse wave theory and the many-worlds theory don't exist. Transverse waves are causality backwards in time, but theorized in a manner to preserve the time-line on a macro-level. Many-worlds deals with an evolving multiverse continually being spun off (all possible realities coexist).The more mainstream theories deal with photons in these experiments upon observation taking on more particle-like behaviour, and in fact experiments do demonstrate this with the photon's path prior to the observation affected. This is incontrovertible. You are just not understanding the experiments, though it appears PaulK did.The simple fact is in the delayed-choice experiments, the delayed-choice is a delayed-observation/measurement. What it shows is that the photon acts as a particle, going through one hole or the other, rather than a wave, when it is observed, and this is amazingly true even if the particle goes through one path prior to the observation. That is why language is sometimes used as if the photon "knows" what is going to happen to it, and so knows to be particle-like.There are a lot of theories to explain why this occurs, and no one is disputing that, but you and some others seem to be disputing that it even occurs at all, as if the experiments are not real or something, and imo, that is wrong.There is a reason language is used to suggest the photon seems to know in advance, and the most logical assumption and the actual thing we observe (however you want to reinterpret it) is that a later event on the photon's trajectory affects it's path before it got there.This is really what Wheeler's original thought experiment dealing with a photon from billions of years away was about. He theorized that the photon's path would be based on how we decide to observe it. Wheeler's solution to the issue was to claim the photon had never really travelled at all until we observe it, but existed in an undefined and unreal state of possibilities.There are other ways to look at it, but these experiments were designed to test that idea, and they showed that indeed the way we observe, and even whether we have the ability to observe affects the photon's behaviour. If we can know it's path, it travels in one path only. If that information is scrambled and we cannot know it's path, it travels more wave-like in superposition. That can be seen with the interference pattern appearing when we have no way to know the path, and disappearing when we do have a way even if delayed to after the fact.This is why Anton Zellinger theorizes that elementary particles as he calls them contain a bit of information. Once that information is able to be detected, then the collapse occurs and the bit is spent.Imo, you don't seem to have a basic grasp of the discussion as evidenced by your comment on FTL communication which is an interesting debate, but not that germane to this particular discussion. You ought to take some time to look at these experiments. Read what Zellinger thinks is going on and some of his work. Read Wheeler's views. See what the Chaio group thinks (some curious comments by them), etc,...Edited by randman, : No reason given.

So backwards in time waves "obery causality"?Clearly, the future can affect the past in your view if you think transverse waves can flow back and affect earlier times. Seems like a reversal here from your earlier claims?Now on the topic of the wave-function being a 4-D function, are you claiming that the wave function spans more than one moment in time in respect to it's surroundings?

How is the past not materially affected? If the past takes on discrete form as a result of present observation, then it is materially affected. I assume materially refers to material and not in the legal sense.Now, it may well be true these affects are very small at any given point in time, but adding up all points in time since this works, the effects can add up. Remember that the macroscopic world consists of the quantum world. Why not? You admit that some parts of the past are indeterminate, or are determined later by events in the present. So should we assume these changes cannot affect the past? Your logic makes no sense. Causing an indeterminate area to be determined is by definition a change. So? How is that relevant at all to the fact that the delayed-choice still affects the wave function as if the choice was not delayed; that the photon still travels one route and does so before the choice? Everyone is entitled to their faith, but that doesn't make it a correct scientific argument.

Care to prove or substantiate that? That is your assumption, and that's the point here.Moreover, this gets more complicated as "consistent with all past observations" is not really a well-defined concept, is it? The quantum eraser experiments have proven that "determined" states can be undone, despite physicists thinking otherwise for decades. A collapse of the wave function to particle-like path and behaviour can be reversed, correct?So there are not determined states that cannot be changed. I have given a hard example backed by experiments where information can be erased, and so a determined path undone. Have you got anything to back up your claim that it cannot be?Why not be openminded here and consider the possibility, or better yet, the likelihood that indeed the past is not determined, but can be affected, but those affects are small at any given point in time, but multiplied over all points in time, they add up. I think you and Percy as well are mixing up thread topics. I have talked about the role of consciousness on other threads, but it matters not a whit for the scope of this discussion, except perhaps if we get into the idea of the It from Bit. But whether it is a mechanical process (that can potentially be observed) or not, the issue is quite simply that the collapse of the wave function to a particle-like path occurs even when the measurement on the trajectory occurs afterwards. http://www.physik.fu-berlin.de/...ikationen/RevModPhys99.pdfNote that the criterion is whether information is available to know whether the particle took one path or the other. If this knowable based on the current events in the apparatus, the photon travels as a particle, but if not, as a wave.The germane point to this discussion is that even if part of the apparatus that can indicate whether a wave or particle passes through is placed at the end of the process, the result is the same. The photon takes a particle path, and this confirms some aspects of Wheeler's delayed-choice thought experiments, right? That a present event can have a determinative affect on the past. The pathway of the photon BEFORE the measurement is affected if the measurement is such that information can be conveyed.Note Zeilinger's comment on the mascroscopic world (same link). Edited by randman, : No reason given.

cavediver, so we are back to your typical approach, eh? Resort to claims of authority and refuse to substantiate your points, substituting your resume for argument.The problem is that you suggest all scientists agree with you here when clearly that is not the case. You also dodged the issue of whether in your view a 4-D wave-function operates over several points of time simultaneously. If that is your stance, I can see why you don't want to go there. You would then by definition be agreeing with me.On having all this down-pat, no, I don't claim that. At the same time, the little bit I have gleaned is pretty straightforward although understanding the correct interpretation is dicey. You though, seem to be denying the actual events observed in experiments, and do so in a rude manner without ever getting into the details, and just say, you don't understand it, but each time I question you about details, you are forced to admit those details.Maybe you just don't like the implications of these experiments. Einstein didn't like some of the implications either, whether true ot not, but not liking the implications due to your theology is not the same as a scientific argument.If we can know about which path the photon took in the experiments, then it behaves like a particle, correct?If we cannot know, then it behaves like a wave, correct?This is true even if the way we can know which path it takes occurs after the path has been taken, correct?So however you want to describe it, the simple fact is from our vantage point, the event to determine what we can know even when occuring after the photon travels, results in the same thing; particle-like behaviour.I realize you may have all sorts of ways to talk about this, as do many physicists; some like Wheeler resolve it by stating the photon doesn't really exist as a wave or particle until observed or measured, but regardless, the path BEFORE THE MEASUREMENT in it's trajectory is affected somehow.Btw, for the lurkers, one of the solutions often presented (by men such as Wheeler) and often rejected by others is as follows: 410 error - Gone Note the way some, and perhaps PaulK on this thread is one, gets around the appearance of "reality changes depending on how we measure it" is to deny reality altogether as separate from the observer and other factors. My point is that this is a conundrum because the experiments appear to show delayed-choice affecting past reality, and in one sense, there is no question that occurs. The question is whether we have a good enough handle on what reality and the past actually consists of, imo.

That's correct. You are stating your position (an assumption) without any substantiation. The experiment has nothing to do with "erasing information that might produce a contradiction" as far as I can tell. The experiment is about a simple observation that overturned previous beliefs. If the potential to know the path is there, the photon takes on path, but that information can be erased by removing the ability to determine what path the photon took. If we cannot know what path the photon took, then the photon takes all the available paths.That's what the experiment is showing. It doesn't explain this coorelation between potential knowledge and the wave-function, but it does demonstrate it. Zeilinger offers a theory to explain it, however.But regardless, I don't see where you come up with the past observations thing. How is that not hard evidence of what I am talking about, PaulK. There is clearly a definite change in what the photon does, behaving more like a particle or more like a wave. It is affected, right? As was the idea that the quantum eraser was totally impossible, but we see that was not the case, don't we?

Whose mistaken assumption are you talking about? Certainly not mine. In fact, you coming around to this point (from my vantage point) helps bring my point home. Here we have a system that manifests 2 or more discrete forms in the material universe over long distances and considering GR, irrespective of time, correct?So the waveform occupies and works in a manner irrespective of space and time in some sense, correct?Now here is the crux of this debate....if we conduct an action at the end of a photon's path that can determine which path the photon took, does it act particle-like and take one path or does it behave like a wave and take all potential paths?I submit that the photon takes on path like a particle, and as such, the action at the end of it's path affects which path the particle took before it ever got to the end of it's path. I further submit that this is not randman's idea but a simple, observed fact for which some reason you guys don't want to come clean and admit to.Now, I realize there are lots of different interpretations, but I think there needs to be some agreement that the photon behaves like a particle and takes on path if that is knowable, even if the way to determine which path it took occurs at the end of the process and after the path has occured.Edited by randman, : No reason given.

Percy, the problem with your bare assertions "that no one agrees with you Edited by randman, : No reason given.

Percy, the problem with your bare assertions "that no one agrees with you

Percy, I can't seem to fix this in reply mode to you so I am trying here.
Percy, the problem with your bare assertions "that no one agrees with you (randman)" is that basically that's all it is, and when someone does agree with one aspect of a point, such as PaulK stating an undeterminative aspect of the past does become determinate, you jump and try to explain that away. Imo, you are offering no substance at all on this thread. Please substantiate your claims. Specifically:In the delayed-choice and other experiments, does the ability to know which path a photon took coorealate to whether it travels on one path as a particle or on all possible paths as a wave?Does this collapsing to one path occur even when the means to determine what path the photon took occurs in a delayed fashion after the photon has already taken it's path?Just answer those 2 questions please, and substantiate your answers with references to actual experiments or quotes from someone analyzing those experiments.