Thank you for that. I think you are wisely keeping your options open. Of course Smolin argues the case that evolution of physics is a necessity to get where we are. With evolution of life we can see roughly how a progression can start from very simple chemical life forms to the more complex animals and plants we are familiar with. If cosmic evolution requires baby universes from the beginning then the starting point is already very complex and selective. Simple universes would not have babies so how did things get going? This would be more a question for Wheeler or Smolin I suppose.
The Tao of It and Bit by Cristinel Stoica
Cristi
Why do you want to presume there are any 'mysteries' . Might it just be that the QM view of how physical existence occurs is incorrect. For example, in your para on delayed initial conditions: "Classically, the state of the universe at any
moment of time is determined by the initial conditions. This is prohibited in quantum
mechanics, because we can only ask whether the system is in a small subset of possible states. It is not possible, even in principle, to know the complete state".
Really? So how does existence occur in this context, how can there be a number of possible existent states at the same time, and what does not occur, but exists, so that its complete state can never be known?
"The observer asks questions, and the universe gives yes/no answers. But the answers
always define at least a possible solution".
Not so. What happened has already happened. And indeed, unless you have an answer to the above, it has happened definitely. Whether or not we have the ability to discern that is irrelevant to the physical circumstance, as to is the act of observing/measuring/etc.
Now the Global consistency principle is interesting, in so far as iot is an allusion to what really happens. That is, it is another one of those mechanisms I spoke of which attempts to counteract the consequences of the flaw in the presumption as to how physical existence occurs. Note: "they have to behave well at infinity (otherwise they can't have physical reality).
It would be a lot easier to just re-visit what has been denigrated as 'classical' and realise that to have existence and difference, physical existence must be a sequence of discrete definitive physically existent states of whatever comprises it. That gives you the 'essence' of what QM thinks it is addressing, but without the impossible presumption that physical existence involves some form of indefiniteness, and the attendant rationalisations that then have to be invoked to keep the theory 'on track'.
Paul
I fully agree. In fact, looking at what we know so far in fundamental physics, I don't see too much room for evolution of the laws. At most some constants that are reset at the next big bang, but how many constants really are obtained from symmetry breaking, and can be expected to be actually variable? Of course, if we want to save the idea of evolving laws, we can appeal to the string landscape, and imagine that, when passing in the baby universe, the Calabi-Yau manifold can change. But I don't know if this can go anywhere.
Paul,
You said:
"Why do you want to presume there are any 'mysteries' . Might it just be that the QM view of how physical existence occurs is incorrect."
Do you think that QM was invented by some guys to look cool, and that there was no need for it?
You think that "what happened has already happened". Think at the Mach-Zehnder interferometer. A photons encounters the first beam splitter. What will the state of the photon be immediately after it left the first beam splitter? Is the photon traveling along one arm of the interferometer, or the other? Or is it traveling along both arms? If "what happened has already happened", one should be able to say what happened at this point. But one cannot say this, unless we know what will happen at the other end of the interferometer, where it is decided whether to leave or to remove the second beam splitter. How do you explain this?
Best,
Cristi
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Cristi
"Do you think that QM was invented by some guys to look cool, and that there was no need for it?"
No. As I said, it was developed because the actual circumstance was not fully understood, so that got 'relegated' to classical, and the new concepts took over.
And here, in the next paragraph, is an example of that process: "You think that "what happened has already happened". Yes. And I do not need to look at Max-Zehnder, or anybody else to say that, just consider the irrefutable generic physical facts. The photon, or indeed anything else which has physical presence, must be in some physically existent state at any given time, otherwise how is it physically existent? There is a fundamental contradiction in the stance. On the one hand discrete definitive states are presumed, otherwise there would be nothing to consider, but then they are imbued with some form of indefiniteness, which means they cannot be what they are being considered to be in the first place.
"If "what happened has already happened", one should be able to say what happened at this point." Only if we understood all the circumstances of the previous physically existent state in the sequence. Whether we can explain/differentiate something is irrelevant to whether it occurred or not. And the simple fact is that discrete physically existent states cannot be identified by experimentation. The degree of alteration and duration involved is vanishingly small. What is happening here is that at the conceptual level of 'objects' we are deeming physical existence on the basis of superficial physical characteristics. We even, assert that the 'object' persists in existence but has changed, which is a contradiction. We even know this is not the case. We know any given 'object' involves difference, ie alteration, but we do not take that to its logical conclusion, ie it is physically a sequence of discrete definitive physically existent states. And when we consider its reality, we are really considering one of those, although we are actually unable to differentiate them.
Now, QM is positively trying to consider reality at the existential level. And part of the problem is that we are still only identifying parts or amalgams of states. But it was thought necessary, wrongly, that to do so rested on a new presumption about how physical existence occurred, which can be summed up as involving some form of non-definitiveness (relativity has the same problem). Which it does not, obviously, because otherwise there could not be existence and difference. The immediate questions in that situation are, so what exists, and what becomes what? Because if nothing else, we know there is physical existence independently of the mechanisms whereby we are aware of it, and we know that if we compare such inputs there is difference. Something (definitive) has happened (definitive), and something else (definive) then happened (definitive), etc.
Which brings me back to the main point. Observation, or any form of sensing, involves the receipt of physical input. Receipt, ie it exists independently and if the right mechanism is in the line of travel it will be received. The brick wall behind you received similar light, it just cannot then process it. What happens subsequently is irrelevant to the physical circumstance, because that involves the development of a perception as to what was received, and is subsequent. To receive something, means that that something has already occurred. So the concept that observation, etc, has an effect on the physical circumstance is nonsense. That alone kills any physical theory which invokes observational intervention stone dead. However, just in case(!), what is physically received is not what physically occurred anyway, but a physically existent representation of it, eg light. At most one can say that its physically existent form ceased to exist on the interaction of receipt (just as it does with a brick). Again what existed up to that point did so. The act of measuring which is often not differentiated from the act of observation, just involves the selection of a time at which observation is deemed to have occurred, and a reference to enable comparison in order to identify difference.
The real lesson here is that we should have adhered to basic rules about physical existence (and understood them in the first place), and not have overturned them when confronted by problems/occurrences when trying to consider it at its elementary level. When I was young television broadcasting was prone to problems, so often a message would be shown which said, 'please do not adjust your set we are having problems with the transmission'.
Paul
Paul,
If "what happened has already happened", then what happens with the photon, after it leaves the first beam splitter?
Is there an answer to this, which is compatible to "what happened has already happened"? If yes, what is the answer? If no, then I am free to search it in other place.
Best regards,
Cristi
Hi Cristi,
Nice essay, easy enough to read that even I can understand it (I am not a physicist).
I agree with your global consistency principle, I have an example of how it could be implemented.
In my essay (Definetely It from Bit !) the Universe is a succession of 2D layers of information (like rings around an onion). We (and our surrounding world) are just information moving up the layers at the speed of light. In relation to each layer, the inner layers represent the past and the outer layers represent the future. Each layer can evolve separately but they must always form a "coherent" storyline. (there are as many "presents" as there are layers).
If I am correct, then the consecutive layers (ie: the complete information sphere) could be what you call "the solution (it) which combines consistently all the pieces of the puzzle (the yes/no bits at different points and moments of time)"
Cheers,
Patrick
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Cristinel,
Could you please comment on [/link:http://arxiv.org/pdf/1007.3977v1.pdf] B Gaasbeek (2010) [/link] Demystifying the Delayed Choice Experiments, arXiv:1007.3977v1 [quant-ph] 22 Jul 2010
Your delayed initial conditions are intriguing to me who did not yet deal with that matter. Did you get support?
Best regards,
Eckard
Cristi,
I must take exception to your statement that "The main mystery of quantum mechanics is contained in Wheeler's delayed choice experiment."
Last September, in the discussion of my essay for the previous FQXI essay contest, I pointed out that the delayed choice experiment, was not merely badly designed, but badly conceived. The telescopes block the path from a slit just as surely as if the slit had been closed. It thereby precludes any possibility for this apparatus to produce an "interference pattern".
It is not the case that "the past is determined by our choice", rather it is "the path is determined by our choice".
Consequently, Wheeler threw the baby out with the bath water.
Rob McEachern
Hi Patrick,
Interesting the onion layers idea. I look forward into reading your essay.
Thank you for the feedback. I made extra effort to reach a broader audience.
Best regards,
Cristi
Robert,
The path decribes a history, does it not?
Tom
Dear Robert,
I think you have a keen eye for telescopes and optics. Delayed choice experiments, not at galactic scale, but at lab scale, were performed, and the delay was ensured. The experiment confirmed the theoretical prediction.
Wheeler proposes the delayed choice experiment with the Mach-Zehnder interferometer, and also the one with a telescope and galaxy. I think that the one with telescope and galaxy is an exaggeration, done for explanatory reason. Something like Brian Greene's Quantum Cafe, or Gamow's books with Mr. Tompkins, where quantum or relativistic phenomena are "zoomed" at a level which makes them relevant to our daily experience. Or like Bohr's quantum devices, with exaggerated mechanical parts.
I am not sure that Wheeler really tried to design a workable experiment involving telescope and light from other galaxies. One big issue I think it is the lack of control of the source of light. By looking at Wheeler's drawing of the experimental setup, in Quantum Theory and Measurement, p. 139, we see that the device is more like Bohr's drawings of devices. But even so, I don't see in that picture how the telescope would block the path from a slit. Perhaps you analyzed a different picture than the one I found.
Thanks for the comment, and keep questioning everything! When we stop questioning, science stops.
Cristi
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Dear Eckard,
Thank you for the link to the paper, I don't remember knowing it. A short glance makes me add it on my to do list of readings. I hope I will come back soon with comments, but if you have a specific point which you have in mind, please let me know. Regarding delayed initial conditions, I think the idea is supported by quantum phenomena, but then, what interpretation of QM is not? Or, if by "did you get support", you refer to funds, I don't have.
Best regards,
Cristi
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Cristi,
I hope this link will work: Demystifying the Delayed Choice Experiments by B Gaasbeek (2010), arXiv:1007.3977v1 [quant-ph] 22 Jul 2010. I am curious.
Eckard
It works perfectly, thanks!
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Cristi
My comment about is has happened was in the context of observation. In general, mu comment about happened is that something definitive occurred, existence does not do vagueness. So the point is thatobservation can have no effect on the physical circumstance, and if we cannot discern what actually happened then that is our failure, not some inherent characteristic of physical existence.
Paul
Christi,
The statement "The experiment confirmed the theoretical prediction." is incorrect.
The experiment confirmed that the interference pattern vanishes. But it failed to confirm that the cause for the vanishing is due to the cause that was predicted. It was not.
The situation is analogous to preventing two cars from interfering (colliding) with each other at an intersection. Delaying one car will prevent the collision, but so will completely eliminating one car.
In effect, the experiment simply eliminates one travel path, via a spatial filter. The delayed choice is irrelevant - if there is no path, there can never be any interference, regardless of any delayed choice.
The telescope I was referring to is not an astronomical one. It is part of the laboratory interferometer, and used to "choose" the slit.
Rob McEachern
Robert,
Thank you for the clarifications. In fig. 2 and 3 in my essay I draw the two situations of the delayed choice experiment with the Mach-Zehnder interferometer. I don't see the detectors (are they the telescopes?) change, yet the result changes, depending on whether the second beam splitter is present or not. I don't understand your argument how it is the detector the one that makes the difference. Maybe, if you have some drawings, will help.
Best regards,
Cristi
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Dear Cristi,
While I consider myself unbiased, I enjoy common sense arguments like your delayed initial condition, Rob's car accident comparison, and Paul's independence of reality from observation. Of course, as an EE, I am familiar with the impossibility to measure something without disturbing it, for instance because there is no voltmeter with infinite resistance. The disturbed reality is not the reality one intends to observe.
When I asked you whether your idea has already been supported, I meant ideal support by other experts. I guess that it may be understood as undermining Wheeler's intention to justify his absorber theory, travel backward in time, and it from bit. Perhaps, many honest experts will be cautious, and I doubt that there will again be almost 300 contributions to the contest this time, although in particular the many experts of computer science are now addressed.
Best regards,
Eckard
Paul,
If by "happened" we understand what was observe, what has observable consequences, then we agree 100% that what "what happened has already happened". The only difference may be in the order of the events. In classical mechanics, time is linear, in quantum mechanics, in some cases, is not, as I will explain. Time is a parameter, very similar to how space coordinates are. In classical mechanics, the events happen as time goes. In other words, all the events labeled with time smaller than t already happened at time t. Time is linear. In quantum mechanics, the things are really different, in the sense that the order in which the events happen may be different for that of time labels. In the case of the Mach-Zehnder interferometer, the photon leaves the first beam splitter, and arrives at the place where the second beam splitter may or may not be. The interaction between the photon and the second beam splitter takes place or not (if the beam splitter is not there). This is the happening at the second beam splitter. Then, and only then, the happening at the first beam splitter takes place. The happening at the first beam splitter, so to speak, stays suspended, until the happening at the second beam splitter gives enough information to the system, so that the photon will know whether to go one way or both ways. So, I agree that "what happened has already happened", except that, for quantum phenomena like the one discussed, the order is not the linear order of events. If we want, we can say that the order is linear, and the happening at the first beam splitter took place before the happening at the second one, if we assume that the photon can guess the future. Even in this case, the causal order is reversed, because the photon's "choice" is decided by a future event which it guessed.
Best regards,
Cristi