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The quantum wave.

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  • #31
    Originally posted by JimL View Post
    Okay, another question then comes to mind. If the quantum [properties] is both a particle and a wave, and the particle and the wave somehow goes through both slits, what happens to the wave, does it break in two, each half going through each slit.
    I do not like this wording. I prefer to say the the particle moving through the slits exhibits quantum properties as quantum waves, and behavior as a particle.
    Glendower: I can call spirits from the vasty deep.
    Hotspur: Why, so can I, or so can any man;
    But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

    go with the flow the river knows . . .

    Frank

    I do not know, therefore everything is in pencil.

    Comment


    • #32
      Originally posted by shunyadragon View Post
      I do not like this wording. I prefer to say the the particle moving through the slits exhibits quantum properties as quantum waves, and behavior as a particle.
      And how does a particle have the properties of a wave, go through both slits at once, and yet not be a wave? I'm not sure that any of us knows, or has an explanation, for whats going on here.

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      • #33
        Originally posted by JimL View Post
        And how does a particle have the properties of a wave, go through both slits at once, and yet not be a wave? I'm not sure that any of us knows, or has an explanation, for whats going on here.
        Since this the observed behavior of the particle, and it is known that particle are not discreet entities, but made up of other particles with quantum properties. Remember we observe properties of things at the quantum level and not things themselves.

        Actually our solutions as to the nature of the Quantum World is simply based on our observations of the behavior of the things of the Quantum World and not what they actually are. Like the particles moving through slits, we see only the effects of the particles in the experiment as images of particle and wave behavior.
        Glendower: I can call spirits from the vasty deep.
        Hotspur: Why, so can I, or so can any man;
        But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

        go with the flow the river knows . . .

        Frank

        I do not know, therefore everything is in pencil.

        Comment


        • #34
          Originally posted by JimL View Post
          And how does a particle have the properties of a wave, go through both slits at once, and yet not be a wave? I'm not sure that any of us knows, or has an explanation, for whats going on here.
          The electron (or whatever) has the properties of a wave function; that's why it's described by a wave function. Wave functions can pass through multiple slits and interfere, properties that are analogous to the behavior of a physical wave, but that doesn't mean the wave function is a kind of stuff that vibrates. The wave function describes the probability of the electron being found in a certain state when you make a measurement.

          As for what a wave function, or the particle it describes, really is, well, physics can't tell you what anything really is. All it can do is describe how something behaves, or decompose it into other things so it can describe how they behave and interact. You have some intuitive sense of what waves and particles are, because you're used to the behavior of wave-like and particle-like things. But what is a wave or a particle really?

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          • #35
            Originally posted by shunyadragon View Post
            ...it is known that particle are not discreet entities, but made up of other particles with quantum properties.
            This is incorrect. Particles like electrons and photons are entirely elementary, according to the standard model. They are not made up of other particles. They are the smallest possible unit, already.

            Originally posted by sfs1 View Post
            The electron (or whatever) has the properties of a wave function; that's why it's described by a wave function. Wave functions can pass through multiple slits and interfere...
            This isn't accurate. A wave function is not a physical entity. It is a description of a physical entity. Wave functions don't pass through anything-- they describe to us how quanta pass through things (in the case of the double-slit experiment).

            Originally posted by JimL View Post
            Okay, another question then comes to mind. If the quantum is both a particle and a wave, and the particle and the wave somehow goes through both slits, what happens to the wave, does it break in two, each half going through each slit.
            Nope, it doesn't break in two. It can't-- it's an elementary particle, not composed of any other things. There's nothing that it can break into. It is physically impossible for a quantum to break into pieces.

            The completely strange but apparently true answer to your question is that the single, whole quantum simultaneously passes through both slits at once. Not part of it through Slit A and the rest through Slit B, but all of it through Slit A and, at the same time, all of it through Slit B.
            "[Mathematics] is the revealer of every genuine truth, for it knows every hidden secret, and bears the key to every subtlety of letters; whoever, then, has the effrontery to pursue physics while neglecting mathematics should know from the start he will never make his entry through the portals of wisdom."
            --Thomas Bradwardine, De Continuo (c. 1325)

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            • #36
              Originally posted by Boxing Pythagoras View Post
              This isn't accurate. A wave function is not a physical entity. It is a description of a physical entity. Wave functions don't pass through anything-- they describe to us how quanta pass through things (in the case of the double-slit experiment).
              I didn't say the wave function was a physical entity; I said the physical entity was described by the wave function. But I think trying to completely separate the description from the entity, as you're doing here, is likely to lead to more confusion than clarity; you're likely to end up talking about what the particle is "really" doing, as opposed to its wave-mechanical description. In any case, it's pretty standard physics usage to talk about wave function behavior. (And not unique to QM. When we talk about the motion of the center of mass, say, we're talking about the behavior of a description. In the end, that's all we really can talk about.)

              The completely strange but apparently true answer to your question is that the single, whole quantum simultaneously passes through both slits at once. Not part of it through Slit A and the rest through Slit B, but all of it through Slit A and, at the same time, all of it through Slit B.
              That's the kind of danger I mean. What is this "whole quantum" you're talking about? The only description we have of the particle is the wave function; you're talking as if there were a more fundamental description available, something that really goes through both slits at the same time.

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              • #37
                Originally posted by Boxing Pythagoras View Post
                The completely strange but apparently true answer to your question is that the single, whole quantum simultaneously passes through both slits at once. Not part of it through Slit A and the rest through Slit B, but all of it through Slit A and, at the same time, all of it through Slit B.
                Your authority in the scientific literature for that? I understand that a complete solution of the wave function equation necessarily takes in the whole spacetime, including the past, present, and future. So it would be wrong to say that the solution all goes through some place at some time.
                The greater number of laws . . . , the more thieves . . . there will be. ---- Lao-Tzu

                [T]he truth I’m after and the truth never harmed anyone. What harms us is to persist in self-deceit and ignorance -— Marcus Aurelius, Meditations

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                • #38
                  Originally posted by Truthseeker View Post
                  Your authority in the scientific literature for that? I understand that a complete solution of the wave function equation necessarily takes in the whole spacetime, including the past, present, and future. So it would be wrong to say that the solution all goes through some place at some time.
                  I think you're confusing the wave function of a single quantum with the wave function of the whole universe. You certainly don't need to evaluate a wave function over the whole of space-time in order to make accurate predictions of quantum phenomena.

                  As for documentation on what the Double Slit Experiment implies about the position and path of the quantum, these lecture notes from MIT's Open Course on QM might help:
                  http://ocw.mit.edu/courses/physics/8...lecture-notes/
                  "[Mathematics] is the revealer of every genuine truth, for it knows every hidden secret, and bears the key to every subtlety of letters; whoever, then, has the effrontery to pursue physics while neglecting mathematics should know from the start he will never make his entry through the portals of wisdom."
                  --Thomas Bradwardine, De Continuo (c. 1325)

                  Comment


                  • #39
                    Originally posted by Boxing Pythagoras View Post
                    I think you're confusing the wave function of a single quantum with the wave function of the whole universe. You certainly don't need to evaluate a wave function over the whole of space-time in order to make accurate predictions of quantum phenomena.

                    As for documentation on what the Double Slit Experiment implies about the position and path of the quantum, these lecture notes from MIT's Open Course on QM might help:
                    http://ocw.mit.edu/courses/physics/8...lecture-notes/
                    So, is the wave function a discription of the state of an existing particle, or of the state of the whole of spacetime, prior to the ability of anyone to actually observe or experience it? Is it sort of like our consciousness/observation of reality, or of the events therein, lags behind the actual reality of those events? Are we just ignorant as to where the particle is prior to observation, or is it actually in a state of existing in many different locations at once prior to obsrvation?

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                    • #40
                      Originally posted by JimL View Post
                      So, is the wave function a discription of the state of an existing particle, or of the state of the whole of spacetime, prior to the ability of anyone to actually observe or experience it?
                      A wave function describes a particular quantum state, so there is a wave function for the state of a given electron, for example, while there would be another wave function which describes the quantum state of the whole universe (theoretically, anyway; that latter wave function would be far too complicated for any practical usage, even if we could write it down).

                      Is it sort of like our consciousness/observation of reality, or of the events therein, lags behind the actual reality of those events? Are we just ignorant as to where the particle is prior to observation, or is it actually in a state of existing in many different locations at once prior to obsrvation?
                      The answer to both of these questions depends upon the interpretation of Quantum Mechanics which one utilizes. For example, someone who supports the Copenhagen interpretation would answer the first question by saying that the observation literally informs reality, while a supporter of a Hidden Variables interpretation would say that the reality precedes our observation of it. Similarly, in the second question, a Hidden Variables interpretation would say that the quantum does have a discrete location, but we are ignorant of that datum; while Many Worlds or Feynman's Sum over Paths would state that the quantum really does exist in many different locations at the same time.
                      "[Mathematics] is the revealer of every genuine truth, for it knows every hidden secret, and bears the key to every subtlety of letters; whoever, then, has the effrontery to pursue physics while neglecting mathematics should know from the start he will never make his entry through the portals of wisdom."
                      --Thomas Bradwardine, De Continuo (c. 1325)

                      Comment


                      • #41
                        Originally posted by Boxing Pythagoras View Post
                        A wave function describes a particular quantum state, so there is a wave function for the state of a given electron, for example, while there would be another wave function which describes the quantum state of the whole universe (theoretically, anyway; that latter wave function would be far too complicated for any practical usage, even if we could write it down).
                        Yes, but "when" exactly does the wave function describe the quantum state of a particle? The wave function is the discription of the state of the particle before our consciousness/observation of it, no? Once it is observed, it is where it is observed to be, and only where it is observed to be, no? So, does a wave function of a particle have any meaning once the particle is observed, and if not, does it have any real meaning prior to its being observed other than our being ignorant as to where it actually is? But in either case it would seem to be telling us that reality of the particle exists prior to our consciousness/obsevation of it, no?
                        The answer to both of these questions depends upon the interpretation of Quantum Mechanics which one utilizes. For example, someone who supports the Copenhagen interpretation would answer the first question by saying that the observation literally informs reality, while a supporter of a Hidden Variables interpretation would say that the reality precedes our observation of it. Similarly, in the second question, a Hidden Variables interpretation would say that the quantum does have a discrete location, but we are ignorant of that datum; while Many Worlds or Feynman's Sum over Paths would state that the quantum really does exist in many different locations at the same time.
                        But even in Copenhagen, the wave function seems to be describing a pre-existing reality, a pre-existing world of sorts, prior to its collapsing to the familiar reality of our observation, no? So if Copenhagen is saying that observation literally informs reality, then doesn't that deny the reality of the wave function, or the pre-existing reality that that it bases that on?
                        Last edited by JimL; 03-01-2015, 06:23 AM.

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                        • #42
                          Originally posted by JimL View Post
                          Yes, but "when" exactly does the wave function describe the quantum state of a particle? The wave function is the discription of the state of the particle before our consciousness/observation of it, no? Once it is observed, it is where it is observed to be, and only where it is observed to be, no?
                          The wave function describes a probability distribution for the particle's behavior in a given state. If that state changes, the wave function also changes. When the particle is observed to be in a discrete location, the wave function collapses. Mathematically speaking, that just means that the wave function of the particle yields identical behavior as one would expect of a particle with a discrete location. The wave function never completely disappears; it just changes depending upon the quantum state of the particle.

                          Think of the speedometer on your car. When you're driving fast on the highway, the needle might hover around 80mph; when you're on a winding back road, the needle is around 20mph; and when the car is at a stop sign, the needle reads 0mph. Your speedometer always displays your vehicle's current speed, even though that speed is equivalent to no speed at all, when you happen to be stopped. Similarly, the wave function always describes the superposition of a quantum, even though that superposition is equivalent to a single discrete location given certain circumstances.

                          So, does a wave function of a particle have any meaning once the particle is observed, and if not, does it have any real meaning prior to its being observed other than our being ignorant as to where it actually is? But in either case it would seem to be telling us that reality of the particle exists prior to our consciousness/obsevation of it, no?
                          If by "real meaning," you're asking whether it describes precisely actual and extant properties of the particle, that largely depends upon the interpretation of QM under which you are operating.

                          But even in Copenhagen, the wave function seems to be describing a pre-existing reality, a pre-existing world of sorts, prior to its collapsing to the familiar reality of our observation, no?
                          Not really. On Copenhagen, the wave function describes the full gamut of probable states which the quantum can occupy, but none of those states become actualized until the quantum is observed. That's what I mean when I say that Copenhagen asserts that observation literally informs reality.

                          So if Copenhagen is saying that observation literally informs reality, then doesn't that deny the reality of the wave function, or the pre-existing reality that that it bases that on?
                          Yes, the wave function is analogous to a potentiality on Copenhagen, not an actual, physical property of the quantum.
                          "[Mathematics] is the revealer of every genuine truth, for it knows every hidden secret, and bears the key to every subtlety of letters; whoever, then, has the effrontery to pursue physics while neglecting mathematics should know from the start he will never make his entry through the portals of wisdom."
                          --Thomas Bradwardine, De Continuo (c. 1325)

                          Comment


                          • #43
                            Originally posted by Boxing Pythagoras View Post
                            The wave function describes a probability distribution for the particle's behavior in a given state. If that state changes, the wave function also changes. When the particle is observed to be in a discrete location, the wave function collapses. Mathematically speaking, that just means that the wave function of the particle yields identical behavior as one would expect of a particle with a discrete location. The wave function never completely disappears; it just changes depending upon the quantum state of the particle.

                            Think of the speedometer on your car. When you're driving fast on the highway, the needle might hover around 80mph; when you're on a winding back road, the needle is around 20mph; and when the car is at a stop sign, the needle reads 0mph. Your speedometer always displays your vehicle's current speed, even though that speed is equivalent to no speed at all, when you happen to be stopped. Similarly, the wave function always describes the superposition of a quantum, even though that superposition is equivalent to a single discrete location given certain circumstances.
                            Okay, so, the superposition, or so called superposition of the particle, is not a real superposition, but rather it is like the speedometer on your car which defines all of the possible discreet positions that the needle could possibly be located. In other words the particle itself is like unto the needle on the speedometer which could be located anywhere between 0 and 100 mph say, but we just don't know where it actually is until we observe it. So the particle itself, like the needle on the speedometer, is not really in a superposition?
                            If by "real meaning," you're asking whether it describes precisely actual and extant properties of the particle, that largely depends upon the interpretation of QM under which you are operating.
                            Hmm, I'm trying to figure out what I meant by that myself right now. Isn't the wave function, like the speedometer on your car, meaningless, if the particle, like the needle, is where it is even if we are not looking at it. I mean, what does it mean to say that the wave function collapses? There seems to be no actual superposition as you describe it, the probabilistic nature of the particle then seems only to be defining our ignorance of the particles discrete position.
                            Not really. On Copenhagen, the wave function describes the full gamut of probable states which the quantum can occupy, but none of those states become actualized until the quantum is observed. That's what I mean when I say that Copenhagen asserts that observation literally informs reality.
                            But isn't the state of the particle, like the needle on the speedometer, always actualized, whether we are looking at it or not. What is actually collapsing besides our ignorance of the particles/needles location?
                            Yes, the wave function is analogous to a potentiality on Copenhagen, not an actual, physical property of the quantum.
                            And in the many worlds interpretation the superposition of the particle is a reality, correct, and there is no collapse, true?

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