the underlying assumptions rig the debate

Note: PaulK, please supply the link for people reading.So in your view, what is the criteria for whether we see the photon travel in superposition, taking all paths, or whether we see the photon travel on only one path?I think before we go any further, we need to establish this first, and then we can assess when such instances occur with that criteria or not. For example, you state: But you offer no reason as to why. What is the criteria here? So then you are admitting that the past path is determined by a present event in some instances? Percy thinks you can't possibly believe that, even though you have stated it repeatedly.One problem with your belief here in indeterminacy of the superposition is that it creates an interference pattern in the here and now. Do you think prior to observation that the photon's path is not real, as some think such as Wheeler, or do you think the photon's path changes as a result of observation?

I suggest that you check the title of this subthread again. It is about Zeilinger's views, not mine. I support my assertions with direct quotes from Zeilinger as I should.As I understand Zeilinger's views the statements follow from his ideas on the relationship between QM and information theory. And according to Zeilinger the collapse is a consequence of gaining more information through pbservation. Do I have to keep repeating these quotes ?The link, BTW is the one you provided earlier in the thread. I do not have it handy since I downloaded the paper at the time and I refer to my local copy when necessary.

So PaulK, are you are admitting that the past path is determined by a present event in some instances?Or are you just saying Zeilinger believes that?What is your position here?Edited by randman, : No reason given.

One problem though you keep ignoring is that information can change back again.I think you are also failing to realize that regardless of whether Zeilinger's theory in connecting QM to information theory is correct and regardless of whether your reading of him is correct, he is still stating that the past path of the photon is determined by the present. That is still the past being determined by the present, at least in the universe people live in.Now, you have made the argument, and did so before quoting Zeilinger, that this does not change the past because the past is indeterminate, but the path when in superposition does reveal an interference pattern, right? So it has real world effects.How do you resolve this?I will come back to Zeilinger and information exchanges later, but I think you don't realize that either way, the past path is determined by the present, and so we see the past in some sense being shaped by the present in QM.

Well, I give you Werner Heisenberg, and yes, it is all over the Net. http://www.physicsnow.net/history/heisenberg/p08c.htm Page not found | American Institute of PhysicsThis last quote is sort of interesting from a human perspective as well. Edited by randman, : No reason given.

I'll keep it short and simple. I am not convinced that the past can be materially affected by future events. (Which I beleive is what Percy is referring to - you've clouded the issue enough times)..

But is the past path of the photon determined by the present, or not?"Future events", btw, is less clear than talking about the present affecting the past. I think concerning this question, we should be precise.So your answer....?Edited by randman, : No reason given.

That's horribly ambiguous.

quote:

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One problem though you keep ignoring is that information can change back again.

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You mean that Zeilinger is "ignoring" it. But can it "change back" ?
(Why do I keep having to point out that it is Zeilinger's views we are discussing here ?) [quote] Now, you have made the argument, and did so before quoting Zeilinger, that this does not change the past because the past is indeterminate, but the path when in superposition does reveal an interference pattern, right? So it has real world effects.
[/quot]And we get an interference effect BECAUSE the path is indeterminate. If the path the photon followed had any material effect then we wouldn't get the interference pattern.And I notice that you're clouding the issue again. The major point is whether the sort of changes proposed in your OP can happen.

I've given my answer.d

Seems like you are dodging, and the reason is that to state that the past is not affected by future events could be interpreted to mean that once the past is determined, it is not affected by future events.Clearly, these men are stating the past "becomes" real based on present events. So why not make your position clear?Do you believe that, or not?Also, reviewing and thinking about Zeilinger's theory, I think he does believe that once the Bit of information is spent, even if not observed by a conscious observer, that the photon remains in the collapsed state, but I am not sure how he reconciles that with the quantum eraser experiment and think this is a logical error because along it's path in the quantum eraser experiment, the photon though unmeasured by people could have been measured and we know from earlier experiments that it would have showed a collapsed state, right?So the simple fact is that at that point in time, the photon was acting more particle-like than wave-like and if measured, it would have shown no interference pattern. I assume you agree with that, but claim the path wasn't real or something, and if that is the case, then the fixing of the photon's path you refer to would only occur upon actual measurement, not whether it could be measured, and that is a major contradiction in your stance.Moreover, this sort of reminds me of the superluminal tangent, though more germane to this discussion than that. I quoted Zeilinger along with Mandel, Wheeler and others to show that they all agreed the past takes on definite form as a result of the way we measure it in the present. To this point, you have not really made it clear whether you agree with that or not, imo.Do you agree, or disagree with that?

What do you mean by indeterminate? The interference pattern shows a real interaction of wave-like propogation. It is real, and in our universe, correct? And it has measurable effects, right?Just because it is in superposition as a wave does not mean it isn't within our universe as real.

It's not ambigious at all. The way we measure a photon determines it's path, period, and that includes the path the photon already took.What don't you understand about that?If you want to say, like Wheeler and others, that the photon never took a path in the past until observed in the present, fine, but it still means the past is formed by the present.

I mean that there is no definite path that the photon follows. THe photon is "smeared" accross all the possible paths, with the energy distributed according to the probability of those paths. That's why we see an interference pattern.i.e. we get an interference pattern because the path is indeterminate

Being "smeared" or however you want to describe it across all possible paths or in a wave-like manner is not the same as indeterminate. It's a determined path. It's just not a single path.To be "indeterminate", it would have taken no path at all, but merely exists as a potential to take all paths, and there would be no interference pattern as nothing would have occured.There are those like Wheeler that say the photon's path is indeterminate until observation, but once it is determined by measurement that the photon behaved like a wave, it is determined.I think you confused this a little.