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How we interpret quantum physics

  1. Dec 4, 2007 #1
    I find quantum theory fascinating, because it fundamentally changed the perception of science. Before quantum theory everything was definate, things had a definate position, things interact in a definitve way, but quantum theory does away with all of that by saying that the most accurate model we have is not a definitive, but instead assignes probabilities to them. So here we have a theory that is extremely concepually puzzling, but it is one of the most powerful tools to predict things science has ever had in its hands, so it can not be ignored, no matter how puzzling it is.

    I dont understand what chooses these probablilities to make them definate. For example, time reversal symetry should mean that milk jumps out of coffee just as often as it dissolves into it, that people get younger looking as often as they get older looking, we can influence the past just as much as we can effect the future. All of that is wrong, and comes into violent conflict with how we psychologically view the universe.

    What process chooses the potential probabilities of quatum mechanics, and makes them the definitive world we observe? thats what i dont get, it seems as if quantum theory leaves this area open to intuition and interpretation rather than actually explaining what chooses these possibilities to form what we observe.
     
    Last edited: Dec 4, 2007
  2. jcsd
  3. Dec 4, 2007 #2
    You are talking about the measurement problem and the wavefunction collapse. There has been many threads on this subject. The answer is still to be found.
     
  4. Dec 4, 2007 #3
    Are there any good theories out there that attempt to explain this then? what are your own opinions on why the universe seems definitive, but QT says something completely different?

    It just seems weird to me that the smaller science goes to try to undertsand the universe the universe seems to slip through your fingers, and you end up with something increasingly abstract, until you reach the realm of pure abstarction, pure potential, pure possibilities at the quatum level. What chooses these possibilities? could it be that it is our consciousness experience that chooses these possibilites and makes them seem definitive to us, when in reality everything is an illusion in superposition with multiple possibilities? thats my personal take on it, mybe its consiousness that chooses these possibilities and makes them real for us.
     
  5. Dec 4, 2007 #4
    If you think about it you can apply statistics to dice. The dice have any number of possible paths, but they always end up with on of six numbers facing up. What does that say about the dice? It says that even though you are uncertain about how the dice will roll, there is a degree of certainty about how they will end up.

    The same thing applies to QT, there is a certainty involved. If there was no solution there could be no science. I hate the fact, and this is my personal feeling, that just because QT deals with particles in a statistical manner that this means that the realm is bound to obscurity.

    I sympathize with Einstein, who argued against QT philosophically, and agree that there has to be a 'better model'. Until that model is found, we will be forced to accept the bizarre ontology that QT has created. Sadly.
     
  6. Dec 4, 2007 #5
    About such theories, I only know there exist one called "decoherence"; I don't know how good it is and I don't know about other theories.
    According to decoherence, when a quantum system interacts with the "environment", non linear effects arose and this generates a classical behaviour and the "choice" among the various possibilities.
    If you can explain me what is consciousness and how it works, then we could discuss about it; until then, science have to base itself on more objective things.
     
  7. Dec 4, 2007 #6
    I look at it this way. The atomic theory -- the idea of atoms -- is based on the idea that the visible world, and all its variety (all the different chemicals, the existence of life,etc.) is actually made up of a few simpler things. We look for simpler things and find them, the subatomic particles. This, to me, has always seemed to good to be true-- that the world is actually made up of simpler objects (why not the reverse?). But in fact, while they are simpler in some ways, they are more "complex" in others, i.e. they exibit what we call quantum behavior. So is like there is a conservation principle operating: the macroscopic world is very diverse but classical, and the microscopic world is in some ways simpler, but also random.
     
  8. Dec 4, 2007 #7
    As fascinating as consciousness is, I don't think consciousness chooses quantum probabilities and makes them real. As an example, we send robotic space vehicles far out into the solar system to take measurements and collect data, far far away from conscious beings (light-hours away!) and we get real data. So consciousness plays no role there. Quantum selections can be completely unconscious.
     
  9. Dec 5, 2007 #8
    I don't think consciousness perse is involved in the "choosing" of probabilities. Before "measurement" is taken, the definite position of the particle is unknown-the wavefunction (probability wave) of the particle indicates the probability the particle, if analyzed for it's position can be found at a certain location.

    Once "measurement" is taken and the particle is observed at a certain place, the wavefunction of the particle collapses to the location at which it is being detected. (In otherwords, there is 100% probability that the particle is in that area).

    The idea of consciousness has little to do with where the particle ends up. More importantly is the idea of "information". Once information -through measurement- is known about the particle, its wavefunction collapses. In the double slit experiment, finding out "which path" information, disrupts the wave nature of the photon.

    The existence of a particle in space, in "superposition, as you so term, is not an "illusion". Many books have argued that the notion of the particle's location, before and after measurement, is futile, for the best we can deduce, is the Probability of finding the particle at a certain location.

    Hope that helped.
     
  10. Dec 6, 2007 #9
    With the dice, there's really no reason we couldn't set up and solve equations for how they'd end up since we could find the forces for everything involved in the roll. Well, there is a reason actually -- it's just way too complex to actually do. So we assign probabilities to each outcome instead. But note that we work with probabilities here as a matter of convenience, not that the dice are really exhibiting any sort of randomness.

    With QM, we work with probabilites out of a seeming matter of reality. It's not just too complex, it really is random.
     
  11. Dec 6, 2007 #10
    You forgot one part of the equation. The observer has to look at the result of the experiment, and until they look at it, it isn't recorded at all.

    You can say, no, it is definately there, the equiptment records it, it is on the paper, its definately there, but the system always has to have conscious input on it, or no-one would know what happened. That why i think that consciousness could have some sort of link to Quantum physics.

    So no matter how you look at it consciousness is an intrecate part of everything we do. Whether it plays a major role, or a minor role, i dont have a clue.
     
  12. Dec 6, 2007 #11
    PlasmaSphere, what if a robot records it, and stores the information for 10 years, and then finally a conscious being looks at the data later. I am just trying to separate the two components: the act of recording, and the presence of consciousness.
     
  13. Dec 6, 2007 #12

    Doc Al

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    What if I refuse to look, but someone else does. Does that count? :wink:

    Why pick on quantum physics? Couldn't you make the same (dubious) claim about classical physics? In fact you are, since the equipment that records the results of the experiments--the moving pointers and counters and computer disks and such--are "classical" systems.

    Does a consciousness have to "know what happened" in order for something to have happened?
     
  14. Dec 6, 2007 #13
    Being conscious of an experimental result is just another type of interaction. Our being aware of the probabilities is a reaction to the averages involved in quantum mechanics, or an other type of mechanics. I would think that this is no different that other types of reactions to average behaviour like temperature.
     
  15. Dec 6, 2007 #14
    I'm going to put out a contentious viewpoint here:

    Who cares?

    I - personally - find discussions of philosophy in quantum mechanics exceedingly tiresome, and consider it a nuisance that gets in the way of solving problems. As far as I understand, you don't need to philosophise in order to use the mathematical framework of quantum mechanics to solve problems, so why pay it more attention than any other area of physics or indeed of science?
     
  16. Dec 6, 2007 #15
    All other areas of science are definite and deterministic, but QT is subject to possibilities and potential scenarios with no definitive outcome. That’s where I think that our free will comes in.

    I know how dubious it sounds, but I cant see any other valid interpretations of this, so i'm just having a go.

    I’ll try to be more specific.

    The problem that i see with the traditional brain = mind = computer is that it should mean that when a computer gets up to the processing ability of a human it should become conscious. I very much doubt that it would, AI proponents frequently make that claim, but there is absolutely no evidence that machines can be conscious in any way, or could be in the future.

    The problem with this is that the people who make these claims (that the brain is nothing more than a computer) assume that the neurons in the brain, and their connections, the synapses, work as fundamental units. So for example we have roughly ten billion neurons, with about a thousand or ten thousand connections to other neurons, which gives us about 1015 operations per second, with each neuron acting as a fundamental unit. The problem that i see with that is that neurons are much, much more complex than a simple switch. For example, consider a single cell, like a paramecium, it swims around, it finds food, if you suck it into a capillary tube it escapes, and if you do it again it will do it quicker and quicker each time, so it can learn, it can find mates, it has a sex life, it does all kinds of things. It does not have any neurons whatsoever, it is just one cell.

    So If a paramecium can do all these things why should we think that a neuron, or a synapse, is just a simple on off switch? The capacity of a neuron seems much greater than that.

    Then if you go down to the next level of the cell and ask how it does that, it uses its internal structure, the cytoskeleton, which seems like a structural support but it is also the nervous system within each cell, mainly comprised of microtubules, which are hollow cylindrical polymers that seemingly are perfectly designed to be information processing devices at the molecular level. They are the nervous systems within each cell, and the nervous system within each neuron too. So these proteins (that’s what they are made of) switch much faster than neurons and there is many, many more of them, ten million within each cell for example, switching within nano seconds. So if we think of processing going down to that level there is as much processing going on at that level as there is in the whole brain (according to the AI type estimates). So if we think that information processing in the brain goes down to the level of microtubules we roughly increase the information capacity from 1015 to 1027, so that pushes the goal way further for the AI people.

    The problem with that is that even if we go down to that level and accept that microtubules are the fundamental units of consciousness, that still does not explain why we have experience, why we have emotions, feeling, what philosophers call qualia. That’s just more reductionism, but it does not solve the problem. Like the problem of free will, or binding of preconsciousness to consciousness, or any of the other anomalies relevant to consciousness. However when you get down to the smallest level, the quantum level, everything changes and it is not deterministic with definate outcomes. There are possibilities, and the question arrises what chooses these possibilities to make the definitive world we see? i think it is probably us.

    If the brain is a computer then our lives are deterministic, we are just reacting to things in our environment, meaning we should be completely predictable, just like a computer is. We would be merely helpless spectators watching our lives unfold in front of us.

    I take a similar view to Roger Penrose, that the there is something about our minds that is non computable, something that is beyond the realm of computation. So we know things other than through algorithms, sort of related to Godel's famous theorem (which to be honest, I dont fully understand). The only thing that can give us this non computable element in nature is a process that is not deterministic like other areas of science, and the only area of science that is not thought of to be definitive and deterministic is Quantum physics. That’s my take on it anyway.

    I cant see how we would ever know the answer to that. That’s where the mystery of consciousness comes in. We cant ask a machine what is 'really' there, we can only consciously interpret what we see the machine is telling us. We can’t really ask another person, as they too are conscious.
     
    Last edited: Dec 6, 2007
  17. Dec 7, 2007 #16

    Doc Al

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    This is better suited for the philosophy forum, but I fail to see how introducing inherently random events (which quantum mechanics supposedly does) provides us with "free will".
     
  18. Dec 7, 2007 #17
    No, all other areas of science are neither definitive or deterministic. If you want a sensible notion on "Free Will" look up compatibilism (Freedom Evolves by Daniel Dennet for instance).
     
  19. Dec 7, 2007 #18
    What philosophy forum? There used to be one, but I'm not seeing it anymore.
     
  20. Dec 7, 2007 #19

    Doc Al

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    It was moved. The philosophy forum is now a subforum under General Discussion.
     
  21. Dec 7, 2007 #20
    good idea, can someone move this? it is not really about QT anymore, more biology and philosophy.

    Its in a subsection under the general discussion forum. https://www.physicsforums.com/forumdisplay.php?f=112
     
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