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Thread: would this thought experiment prove or disprove randomness in quantum mechanics

  1. #1 would this thought experiment prove or disprove randomness in quantum mechanics 
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    I was told of a thought experiment by a friend of mine who says that his thought experiment will either prove or disprove randomness in quantum mechanics, and this was in fact verified by several other physicists, who said that if this experiment was ever successfully carried out it would either prove or disprove quantum randomness. His thought experiment imagines(in laymans terms), two teams of scientists who want to measure the position of 10 000 neutrons which will be fired, so that they travel 1 at a time. The scientists will measure the position of these neutrons by bouncing gamma rays off of the neutron to find its location, and they will measure it at exactly the same time. You would naturally expect both parties to measure the exact same position each time for each particle. However because the probability of the wave function is relative to each observer, the wave function collapse would have to collapse randomly relative to each of the two observers. Therefore if they observe the same location for each neutron 100% of the time it would prove determinism because if the wave function is randonmy collapsing 100%(all of the time) of the time to produce the same result for its location for both observers it is by definition not a random process(because you cannot consistently get the same result from two random process all of the time, that would suggest if this took place that it was not random but that it was fixed and that there was a defined process taking place underneath), however the only way for randmness to then be proven would be for the scientists to observe to conflicting results for the same particle at exactly the same time, for it's position, because it was shown earlier that it would not be random for two random relative processes(the collapse of the wave function), to yield the same result for the position of a large sample of particles, so the only way to disprove this would be to observe an instance in which tow conflicting results for the position of a particle is measured at exactly the same time. would this experiment be a proof if it could be done? (my friend added that it is a thought experiment because it is impossible to measure something at exactly the same time, furthermore he said that invoking heisenbergs uncertainty principle as an objection is not valid, because it is not about obtaining results for its original position but its position)


    Last edited by 2012taylorj; March 13th, 2018 at 06:03 PM.
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  3. #2  
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    Quote Originally Posted by 2012taylorj View Post
    I was told of a thought experiment by a friend of mine who says that his thought experiment will either prove or disprove randomness in quantum mechanics, and this was in fact verified by several other physicists, who said that if this experiment was ever successfully carried out it would either prove or disprove quantum randomness. His thought experiment imagines(in laymans terms), two teams of scientists who want to measure the position of 10 000 neutrons which will be fired, so that they travel 1 at a time. The scientists will measure the position of these neutrons by bouncing gamma rays off of the neutron to find its location, and they will measure it at exactly the same time. You would naturally expect both parties to measure the exact same position each time for each particle. However because the probability of the wave function is relative to each observer, the wave function collapse would have to collapse randomly relative to each of the two observers. Therefore if they observe the same location for each neutron 100% of the time it would prove determinism because if the wave function is randonmy collapsing 100%(all of the time) of the time to produce the same result for its location for both observers it is by definition not a random process(because you cannot consistently get the same result from two random process all of the time, that would suggest if this took place that it was not random but that it was fixed and that there was a defined process taking place underneath), however the only way for randmness to then be proven would be for the scientists to observe to conflicting results for the same particle at exactly the same time, for it's position, because it was shown earlier that it would not be random for two random relative processes(the collapse of the wave function), to yield the same result for the position of a large sample of particles, so the only way to disprove this would be to observe an instance in which tow conflicting results for the position of a particle is measured at exactly the same time. would this experiment be a proof if it could be done? (my friend added that it is a thought experiment because it is impossible to measure something at exactly the same time, furthermore he said that invoking heisenbergs uncertainty principle as an objection is not valid, because it is not about obtaining results for its original position but its position)
    Ingenious! I'm not sure I understand the last sentence however. Presume your friend was saying you not trying to measure momentum and position simultaneously.


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    Do you think this is a potential proof, if it could be carried out
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    I think you're going to run into problems when you start using the word "exact" - as in: "measure it at exactly the same time".

    Since the neutron is subject to HUP, its position and momentum will have some error. Therefore both teams won't be able measure it at "exactly" the same time.
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    It's not about measuring its original position but about measuring a position, and this is why this is not a valid objection(according to my friend).
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    Furthermore my friend talked of a method in which you could discard measurements which did not successfully measure the neutrons at the exact same time, and that this could be done by carrying out lots of measurements and somehow discarding the measurements which were not successful.
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    By exact, he means what? And ow does that not equate to cherry picking the data?
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    Quote Originally Posted by 2012taylorj View Post
    Do you think this is a potential proof, if it could be carried out
    No. A neutron is a system of three interacting quarks, and hence a spatially extended object; it does not have anything resembling an “exact position”, all you can meaningfully define is the region of space within which those aforementioned quarks may or may not be found.

    The other problem of course is that the process of measurement itself - regardless of whether it is done with gamma rays or anything else - is an interaction that does not happen instantaneously. This is also a manifestation of the HUP - the shorter the time frame of the interaction which constitutes the measurement, the more energy is needed to perform it. For an instantaneous measurement - i.e. a measurement at an exact moment in time - an infinite amount of energy would be needed, which is of course not meaningful or possible. Even if you allow for a “short interaction” (as opposed to instantaneous), then the energy you invest will change the system, and the actual duration of the measurement remains a probabilistic variable.

    There are many other problems too, such as the issue of clock synchronisation, and the fact that you won’t know where within the volume of the neutron the three quarks are when you set off your gammma ray, so you are literally shooting into the dark, and any inelastic scattering you get is an inherently random “hit” anyway. And since two of the quarks are of the same kind, you won’t even be able to tell who has hit which quark, so there is no way to meaningfully correlate the data.

    So no matter how you look at this, the experiment cannot be meaningfully performed in reality. And it does not need to either, since we already know from other experiments that Bell’s inequalities are violated, so realism does not hold in our universe, hence there cannot be determinism on the quantum level.
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    Quote Originally Posted by 2012taylorj View Post
    However because the probability of the wave function is relative to each observer, the wave function collapse would have to collapse randomly relative to each of the two observers. Therefore if they observe the same location for each neutron 100% of the time it would prove determinism because if the wave function is randonmy collapsing 100%(all of the time) of the time to produce the same result for its location for both observers it is by definition not a random process
    This statement is based on a flawed understanding of quantum mechanics. If two observers were to somehow measure the position of the same particle at the same time, then they would obtain the same value. Depending on the initial state of the particle, the value obtained by each observer would be random, but the two values obtained would not be independently random.
    There are no paradoxes in relativity, just people's misunderstandings of it.
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    i also read about a new interpretation of quantum mechanics, which was able to successfully demonstrate that it is possible to have a physical interpretation of the wave function and when observed this wave function starts to behave as a particle. In summary it says that all outcomes, of a particle’s wave function manifest but manifest in more than three dimensions, and when the wave function collapses, we see the outcome of the wave function, which only exist in three dimensions. Furthermore, a particle is a much larger object, and exists physically as a wave across more than three dimensions and our best description of this is the Schrodinger wave, because it only describes it in three dimensions. We cannot observe the particle as a wave because it is spread out as an object in which most of it exists in more than three dimensions, but when we observe the part or outcome of a wave function that does exist in three dimensions, which is when collapse occurs it leads to particle like properties, due to not being able to interact with the rest of the wave because it is confined to just interacting on a three dimensional scale because we are observing it in three dimensions. Furthermore we cannot observe the part of the wave function that exists in more than three dimensions, in three dimensions because of the principle that in order to observe an object in it's entirety it needs to be observed in all of it's dimensions. Strange phenomenon in quantum mechanics such as tunneling, can be explained by saying that there is a probability of finding the part of wave function that exists in three dimensions on the other side of the barrier, which has travelled over that barrier classically and the probability of it travelling over the barrier decreases expontentially to the width of the barrier increasing
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    what do you think of this interpretation
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    i also read about a new interpretation of quantum mechanics, which was able to successfully demonstrate that it is possible to have a physical interpretation of the wave function and when observed this wave function starts to behave as a particle.
    But it's not an interpretation - those are observed and well known facts.

    Furthermore we cannot observe the part of the wave function that exists in more than three dimensions, in three dimensions because of the principle that in order to observe an object in it's entirety it needs to be observed in all of it's dimensions.
    Besides any attempts of measuring some specific property of a wave function, on a 3D "level", will collapse it into a determined state in 3D space.

    Strange phenomenon in quantum mechanics such as tunneling, can be explained by saying that there is a probability of finding the part of wave function that exists in three dimensions on the other side of the barrier, which has travelled over that barrier classically and the probability of it travelling over the barrier decreases expontentially to the width of the barrier increasing
    Strange phenomenons can be explained in many strange ways. I think, that the key is to look for the most possible solution.
    There's nothing, what would support the idea of alternative 3D realities and "barriers" between them.

    From the perspective of a wave function, our 3D reality is just a possibility. Your alternative 3D realities remain in a constant superposition, until they won't happen in a specific period of time. Observation determines the timeframe and collapses the wave function into a determined state. It can't be more logical.
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    Quote Originally Posted by KJW View Post
    Quote Originally Posted by 2012taylorj View Post
    However because the probability of the wave function is relative to each observer, the wave function collapse would have to collapse randomly relative to each of the two observers. Therefore if they observe the same location for each neutron 100% of the time it would prove determinism because if the wave function is randonmy collapsing 100%(all of the time) of the time to produce the same result for its location for both observers it is by definition not a random process
    This statement is based on a flawed understanding of quantum mechanics. If two observers were to somehow measure the position of the same particle at the same time, then they would obtain the same value. Depending on the initial state of the particle, the value obtained by each observer would be random, but the two values obtained would not be independently random.
    Exactly! Two independent observers will get the same result for each measured property. Single particle can't be determined in different locations by different observers - it has to be in the same place for both of them (more or less) If it wouldn't be true, everyone would experience completely different 3D reality.

    Measurement affects the shape of wave function. After the observation, distribution of probability will be different, than before - but it has to be consistent with cause/effect relation for every other observer.

    However because the probability of the wave function is relative to each observer, the wave function collapse would have to collapse randomly relative to each of the two observers.
    This is the problem - it's the observer, which is relative to wave function and not the other way oround. Our perception of reality is limited to 3D space - but wave function doesn't have to...
    Last edited by AstralTraveler; March 16th, 2018 at 05:30 PM.
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    Quote Originally Posted by Markus Hanke View Post
    So no matter how you look at this, the experiment cannot be meaningfully performed in reality. And it does not need to either, since we already know from other experiments that Bell’s inequalities are violated, so realism does not hold in our universe, hence there cannot be determinism on the quantum level.
    I would say, that reality is determined only by it's own possibility. It is however somekind of limitation - impossible things don't happen...
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    Quote Originally Posted by AstralTraveler View Post
    Quote Originally Posted by Markus Hanke View Post
    So no matter how you look at this, the experiment cannot be meaningfully performed in reality. And it does not need to either, since we already know from other experiments that Bell’s inequalities are violated, so realism does not hold in our universe, hence there cannot be determinism on the quantum level.
    I would say, that reality is determined only by it's own possibility. It is however somekind of limitation - impossible things don't happen...
    what do you think of the thought experiment proposed though?
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    what do you think of the thought experiment proposed though?
    he scientists will measure the position of these neutrons by bouncing gamma rays off of the neutron to find its location, and they will measure it at exactly the same time. You would naturally expect both parties to measure the exact same position each time for each particle. However because the probability of the wave function is relative to each observer, the wave function collapse would have to collapse randomly relative to each of the two observers. Therefore if they observe the same location for each neutron 100% of the time it would prove determinism because if the wave function is randonmy collapsing 100%(all of the time) of the time to produce the same result for its location for both observers it is by definition not a random process(because you cannot consistently get the same result from two random process all of the time, that would suggest if this took place that it was not random but that it was fixed and that there was a defined process taking place underneath)
    It's simple - all scientists will get the same result for each single particle. If a wave function is collapsed into a determined state, it is collapsed for all possible observers (in 3D perspective). Neutron can't be physically present in 2 locations at the same time - but it's exact location is only possible, until it is observed. 2 independent observers always will observe the most possible result.

    Distribution of probability in space means, that something is more possible in one place and less possible somewhere else. Neutron is placed in the area, where it's possibility reaches it's peak. Nothing complicated

    But does it prove determinism? Yes and no. It depends, if you consider possibility, as a way to determine the physical reality. I do - until I won't start seeing things, which only I can see (without taking some drugs)... Even miracles need to be witnessed by more observers, to be miracleas, instead of hallucinations...

    Professional scientists seem to assume, that possibility exists as infinite number of alternative and parallel 3D realities. I say, that possibility exists only as possibility. However, I'm not a professional scientist, so I can be wrong...
    Last edited by AstralTraveler; March 16th, 2018 at 06:41 PM.
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    Quote Originally Posted by AstralTraveler View Post
    what do you think of the thought experiment proposed though?
    he scientists will measure the position of these neutrons by bouncing gamma rays off of the neutron to find its location, and they will measure it at exactly the same time. You would naturally expect both parties to measure the exact same position each time for each particle. However because the probability of the wave function is relative to each observer, the wave function collapse would have to collapse randomly relative to each of the two observers. Therefore if they observe the same location for each neutron 100% of the time it would prove determinism because if the wave function is randonmy collapsing 100%(all of the time) of the time to produce the same result for its location for both observers it is by definition not a random process(because you cannot consistently get the same result from two random process all of the time, that would suggest if this took place that it was not random but that it was fixed and that there was a defined process taking place underneath)
    It's simple - all scientists will get the same result for each single particle. If a wave function is collapsed into a determined state, it is collapsed for all possible observers (in 3D perspective). Neutron can't be physically present in 2 locations at the same time - but it's exact location is only possible, until it is observed. 2 independent observers always will observe the most possible result.

    Distribution of probability in space means, that something is more possible in one place and less possible somewhere else. Neutron is placed in the area, where it's possibility reaches it's peak. Nothing complicated

    But does it prove determinism? Yes and no. It depends, if you consider possibility, as a way to determine the physical reality. I do - until I won't start seeing things, which only I can see (without taking some drugs)...

    Professional scientists seem to assume, that possibility exists as infinite number of alternative and parallel 3D realities. I say, that possibility exists only as possibility. However, I'm not a professional scientist, so I can be wrong...
    It's quite impressive considering this experiment was created by a 16 year old.
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    Note to Taylor: feel free to ignore any and all comments from AstralTraveler - he doesn't have much of a clue about anything he comments on.
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    It's quite impressive considering this experiment was created by a 16 year old.
    Interesting - considering the fact, that scientists prefer to rather avoid the problem of determinism in QM. Is it determined - or no?
    And I say: yes and no Observers determine, what is real, according to possibility of things to happen. But it's not a scientific answer - I don't even know, if there is any... Anyway it's not that hard to understand.

    It's great, that 16 year old kids like to spend time, trying to learn physics. Problem is, that in many cases you will be called, as an idiot by people, who think, that they know everything.
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    Quote Originally Posted by Dywyddyr View Post
    Note to Taylor: feel free to ignore any and all comments from AstralTraveler - he doesn't have much of a clue about anything he comments on.
    Ok, so what is your opinion on this thought experiment?
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    Before we move on, 2012taylorj what is YOUR opinion of the information provided already provided regarding why the excitement won't work?
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