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Thread: The Uncertainty Principle

  1. #1 The Uncertainty Principle 
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    My understanding of the uncertainty principle is probably wrong. I picture it as each particle has a a range of possible values, and at all time it is equalling all of those values. And what we normally observe is just the average. I was thinking about this and I recalled that teleportation is impossible because the uncertainty principle means you could never put people back together right.

    Then that gave me a thought. If you could somehow observe all the particles a person or an object or just mimic the effects of observing every single particle in a person or an object would they just fall apart?

    And if so how hard would it be to weaponize the effect of observation?


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  3. #2  
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    Every particle in a person is already observing every other particle (or at least all of its neighbors).


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    Oh.
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  5. #4  
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    Quote Originally Posted by Humility View Post
    My understanding of the uncertainty principle is probably wrong.
    Complementary variables -- like position and momentum -- are related by Fourier transforms. Thus, more precision in one quantity mathematically implies less in its complement. The spectrum of a true sinusoid is infinitesimally narrow, while the sinusoid is everywhere. If you extract one cycle of a sinusoid, its spectrum broadens. You cannot simultaneously know both to arbitrary precision. If you aren't familiar with FTs, it would probably help you immensely to study them. Then the HUP becomes less confusing.

    Then that gave me a thought. If you could somehow observe all the particles a person or an object or just mimic the effects of observing every single particle in a person or an object would they just fall apart?

    And if so how hard would it be to weaponize the effect of observation?
    I think you have been misled by many pop-sci articles that talk about the role of the observer in a mystical way. Ignore such Deepak Chopra-esque bollocks.
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    Quote Originally Posted by tk421 View Post

    Complementary variables -- like position and momentum -- are related by Fourier transforms. Thus, more precision in one quantity mathematically implies less in its complement. The spectrum of a true sinusoid is infinitesimally narrow, while the sinusoid is everywhere. If you extract one cycle of a sinusoid, its spectrum broadens. You cannot simultaneously know both to arbitrary precision. If you aren't familiar with FTs, it would probably help you immensely to study them. Then the HUP becomes less confusing.
    Nice tk421 :-))

    If you look deeply at HUP which is embedded in Quantum Theory, the significance of this principle yields insights into why we currently cannot simply merge QM and GR into a single unifying theory. This relates to the notion that classical experiment and more importantly observations from the perspective of GR takes place from the position of an observer embedded within the system. This positioning requires that the observer must use the spacetime coordinates of their reference frame as yard sticks in the measurements. Yes you can apply Lorentz or diffeomorphic transforms to translate between different reference frames but this perspective differs from QM where we take classical measurements from the vantage outside a quantum system.

    In probing the quantum world, we use a classical measuring device which is embedded outside the quantum system in a classical reality. The classical measuring instrument probes the superposition by projecting the system onto an eigenstate of the measuring apparatus. What this means is that it is mapping the quantum system to a classical frame of reference. If measurements commute then the consequence of spacetime mapping is unimportant. Conversely if the observables do not commute then the measurements interfere with each other. The nature of the quantum world suggests however that the reality is that both the measuring device and the system under investigation are in a superposition of states where all possible reference points have an equally valid vantage. Taking a classical measurement of a quantum system requires that the measuring device is embedded within a unique frame of reference and hence a single 'time ordered' reference frame will result in classical results where those physical variables that do not have a role to play in the mapping process will therefore be found to all commute.

    Whenever we attempt to map a superposition of states to a classical spacetime reference frame to measure the properties of a particle we see uncertainty arise with those observable's that have a dependency on spacetime mapping such as position and momentum, angle and angular momentum, phase and particle number etc. Either observables commute or they do not. If they commute there are no restrictions classically on how we measure them. If they don't commute the uncertainty principle holds. Whether or not they commute seems to relate to whether time ordering is important or not. If time ordering is not important then the commutor is zero. If it is, then the commutor is non-zero and uncertainty limits apply.

    We are familiar with the notion that in QM a particle does not have any 'real' classical attributes until someone measures them. Certain attributes can't exist at the same time. No matter how you set the experiment up, the classical result will reflect that the two measurements are mutually exclusive. A Fourier Transform is a representation of two equally true but mutually exclusive ways of looking at the same thing. If you choose to select one attribute, you obliterate the other. You cannot look at both attributes at the same time. This is because the probability distributions encoded in the wavefunction reflects this mutual exclusivity. The true reality is therefore the wavefunction itself and not the classical result which is a mapping result (a perspective) from the frame of reference of an observer.

    Relativity insists that before we can talk about space or time we first must specify a frame of reference otherwise the measuring loses all meaning. For example one observers time is another observers space. QM on the other hand teaches us that we cannot talk about the properties of matter without first specifying what we are classically measuring.......in a nutshell, frame of reference matters.
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    [QUOTE=Humility;581711]My understanding of the uncertainty principle is probably wrong. I picture it as each particle has a a range of possible values, and at all time it is equalling all of those values. And what we normally observe is just the average. I was thinking about this and I recalled that teleportation is impossible because the uncertainty principle means you could never put people back together right.

    Then that gave me a thought. If you could somehow observe all the particles a person or an object or just mimic the effects of observing every single particle in a person or an object would they just fall apart?

    I think you are confusing the uncertainty principal with phenomenon of state vector reduction whereby an observation or measurement causes a quantum system to collapse - read up on the 2 slit experiment

    The uncertancy principle is that within a quantum frame of reference, you can get an accurate reading of a particles velocity or location but never both. - read up on Max Planck.
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    After getting the first reply I didn't think to come back to see the rest of the replies.

    Umm... so to see if I have a simple understanding of it. The properties of the quantum particles don't actually have a single value, they have a bunch of values simultaneously (from our point of view) and when an observer tries to measure this value in any way that would limit it to a single value. That single number will be just an arbitrary pick of one of the values in the set, not technically incorrect but not absolutely right either. So if you try to measure the other properties related to the property you just measured you will end up with a bunch of arbitrary numbers that can't be added together in a decent way. Hence the HUP stating that you can only measure one of these properties at a time.

    Thats probably wrong but I'm hoping I understood the most relevant part which is the HUP is not describing an observer effect like with the double slit experiment. (The one about the light particles taking two paths at once normally, but if watched take only one.) But more of an Observer affect, with the nature of the particles affecting the observer's measurements rather then the observer's measurements effecting the particle, which is what I thought happened.
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    Quote Originally Posted by Humility View Post
    After getting the first reply I didn't think to come back to see the rest of the replies.

    Umm... so to see if I have a simple understanding of it. The properties of the quantum particles don't actually have a single value, they have a bunch of values simultaneously (from our point of view) and when an observer tries to measure this value in any way that would limit it to a single value. That single number will be just an arbitrary pick of one of the values in the set, not technically incorrect but not absolutely right either. So if you try to measure the other properties related to the property you just measured you will end up with a bunch of arbitrary numbers that can't be added together in a decent way. Hence the HUP stating that you can only measure one of these properties at a time.

    Thats probably wrong but I'm hoping I understood the most relevant part which is the HUP is not describing an observer effect like with the double slit experiment. (The one about the light particles taking two paths at once normally, but if watched take only one.) But more of an Observer affect, with the nature of the particles affecting the observer's measurements rather then the observer's measurements effecting the particle, which is what I thought happened.
    Yes I think you are getting close. It's a hard concept to visualise and most real physicists will explain it mathematically, via reference to Fourier transforms or non-commuting operators, which is not a lot of help to the layman. It's not far wrong to think of the "particle" (or wave-particle) as having a clump of values, only one of which can be seen in an individual measurement. But in my opinion it is important to think of these entities as wave-particles, not just as particles, because it is wavelike behaviour that causes all these effects (this is where Fourier superposition and so on comes into things).

    The Wiki article has an animation that shows what happens with moneumtum and position quite nicely: Uncertainty principle - Wikipedia, the free encyclopedia
    (See second box down on the right, before all the hairy maths begins.)
    Last edited by exchemist; September 21st, 2014 at 12:10 PM.
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  10. #9  
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    Quote Originally Posted by Humility
    I picture it as each particle has a a range of possible values, and at all time it is equalling all of those values. And what we normally observe is just the average. I was thinking about this and I recalled that teleportation is impossible because the uncertainty principle means you could never put people back together right.
    The excepted orthodox and experimentally consisted interpretation of the wave function is that the magnitude squared is the probability density is the probability density of finding the particle in the state.

    Quote Originally Posted by Humility
    Then that gave me a thought. If you could somehow observe all the particles a person or an object or just mimic the effects of observing every single particle in a person or an object would they just fall apart? And if so how hard would it be to weaponize the effect of observation?
    No. Why would observing a particles of an object make it fall apart?
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  11. #10  
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    Quote Originally Posted by physicist View Post
    Quote Originally Posted by Humility
    I picture it as each particle has a a range of possible values, and at all time it is equalling all of those values. And what we normally observe is just the average. I was thinking about this and I recalled that teleportation is impossible because the uncertainty principle means you could never put people back together right.
    The excepted orthodox and experimentally consisted interpretation of the wave function is that the magnitude squared is the probability density is the probability density of finding the particle in the state.

    Quote Originally Posted by Humility
    Then that gave me a thought. If you could somehow observe all the particles a person or an object or just mimic the effects of observing every single particle in a person or an object would they just fall apart? And if so how hard would it be to weaponize the effect of observation?
    No. Why would observing a particles of an object make it fall apart?
    I think Humility's understanding has moved on since the original post you are replying to.
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    Quote Originally Posted by exchemist
    I think Humility's understanding has moved on since the original post you are replying to.
    Whooops! My sincere apologies Humility!
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    While many here dismiss YouTube entirely, there are a few good videos on there. Here's a Ted-ED video on the HUP that I think gives a good overview of the situation, although it sounds like you may have already grasped most of what they cover: https://www.youtube.com/watch?v=TQKELOE9eY4
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    Thank you all, you've been a big help.

    But in my opinion it is important to think of these entities as wave-particles, not just as particles, because it is wavelike behaviour that causes all these effects (this is where Fourier superposition and so on comes into things
    When you say wave particles and I looked it up in Wikipedia. From I picture then, the values are actually a back and forth back and forth. Just it goes back and forth at an infinitely fast rate. Which gives it the appearance of being all those values at once, or more specifically, any of those values at a given time that cannot be predicted within a human frame of reference.
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  15. #14  
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    Quote Originally Posted by Humility View Post
    Thank you all, you've been a big help.

    But in my opinion it is important to think of these entities as wave-particles, not just as particles, because it is wavelike behaviour that causes all these effects (this is where Fourier superposition and so on comes into things
    When you say wave particles and I looked it up in Wikipedia. From I picture then, the values are actually a back and forth back and forth. Just it goes back and forth at an infinitely fast rate. Which gives it the appearance of being all those values at once, or more specifically, any of those values at a given time that cannot be predicted within a human frame of reference.
    Not at an infinitely fast rate, no. The frequency of a wave-particle is related to its momentum (or its energy in the case of the photon), so it has a finite value - or group of values. The more closely its position is defined the less certain its momentum (because a defined position requires the superposition of a lot of different frequencies) and the less well defined the position the closer it can be to a single, monochromatic, frequency and hence the better defined the value of the momentum.

    None of this would arise if it were not for de Broglie's relation between momentum and wavelength - this is one of the key "wave-particle" insights.
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    Quote Originally Posted by Humility View Post
    Thank you all, you've been a big help.

    But in my opinion it is important to think of these entities as wave-particles, not just as particles, because it is wavelike behaviour that causes all these effects (this is where Fourier superposition and so on comes into things
    When you say wave particles and I looked it up in Wikipedia. From I picture then, the values are actually a back and forth back and forth. Just it goes back and forth at an infinitely fast rate. Which gives it the appearance of being all those values at once, or more specifically, any of those values at a given time that cannot be predicted within a human frame of reference.
    Perhaps you have answered your own question.

    As layman, when I imagine light as a wave, it is not so difficult to visualize these waves to be affected every instant (quantum event) by the interaction with other waves.

    I can imagine a wide river meandering as a grand stream, but within this stream are obstacles which create untold eddies and wave interferences. IOW the interaction of waves (even quantum waves), locally cause an uncertainty within the larger stream which relentlessly keeps everything moving along the lifeline within the boundaries of the river's edges.
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    Quote Originally Posted by Write4U View Post
    Quote Originally Posted by Humility View Post
    Thank you all, you've been a big help.

    But in my opinion it is important to think of these entities as wave-particles, not just as particles, because it is wavelike behaviour that causes all these effects (this is where Fourier superposition and so on comes into things
    When you say wave particles and I looked it up in Wikipedia. From I picture then, the values are actually a back and forth back and forth. Just it goes back and forth at an infinitely fast rate. Which gives it the appearance of being all those values at once, or more specifically, any of those values at a given time that cannot be predicted within a human frame of reference.
    Perhaps you have answered your own question.

    As layman, when I imagine light as a wave, it is not so difficult to visualize these waves to be affected every instant (quantum event) by the interaction with other waves.

    I can imagine a wide river meandering as a grand stream, but within this stream are obstacles which create untold eddies and wave interferences. IOW the interaction of waves (even quantum waves), locally cause an uncertainty within the larger stream which relentlessly keeps everything moving along the lifeline within the boundaries of the river's edges.
    Very poetic, certainly. However this is not a scientific way of looking at it. Better in my view to picture everything having slightly fuzzy edges, due their wavelike nature at the atomic scale, and then expanding this fuzziness to apply to other properties as well as location in space.
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    I think there should be a way of observing all the value's of an atom, without destroying it, or changing its properties.

    We use XRD, x-ray diffraction to observe an atom in a non destructive way. By beaming it with x-rays under a specific angle, we can know which element it is. I do understand that the electrons this way do get exited and change their energy value, or shell. XRF is slightly more destructive because it uses the EM fluorescence of this element.

    But what if we could fit an unknown atom, or group of atoms, in a box, or a slide. We know this slide, and its properties, and we see how much the properties of this slide will change because of the other atoms which we do not know are interacting with it. By indirect observation, combined with a computer model, we could study these elements, and depending on the computing power, we could analyse larger groups or atoms this way. I believe up to a human.

    XRD or XRF are not the ways i am suggesting for this indirect obvervation of these elements. I was more thinking about NMR, or a particle accelerator aiming on a detector (an MS basically).
    Growing up, i marveled at star-trek's science, and ignored the perfect society. Now, i try to ignore their science, and marvel at the society.

    Imagine, being able to create matter out of thin air, and not coming up with using drones for boarding hostile ships. Or using drones to defend your own ship. Heck, using drones to block energy attacks, counterattack or for surveillance. Unless, of course, they are nano-machines in your blood, which is a billion times more complex..
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    Quote Originally Posted by Zwolver View Post
    I think there should be a way of observing all the value's of an atom, without destroying it, or changing its properties.

    We use XRD, x-ray diffraction to observe an atom in a non destructive way. By beaming it with x-rays under a specific angle, we can know which element it is. I do understand that the electrons this way do get exited and change their energy value, or shell. XRF is slightly more destructive because it uses the EM fluorescence of this element.

    But what if we could fit an unknown atom, or group of atoms, in a box, or a slide. We know this slide, and its properties, and we see how much the properties of this slide will change because of the other atoms which we do not know are interacting with it. By indirect observation, combined with a computer model, we could study these elements, and depending on the computing power, we could analyse larger groups or atoms this way. I believe up to a human.

    XRD or XRF are not the ways i am suggesting for this indirect obvervation of these elements. I was more thinking about NMR, or a particle accelerator aiming on a detector (an MS basically).
    This may be what you are thinking of: Weak measurement - Wikipedia, the free encyclopedia
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