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Lv 5
? asked in Science & MathematicsAstronomy & Space · 5 months ago

If one "fires" a photon (or electron etc), through a vacuum , will it have a known and definite position and momentum at all times  .?

That is ,it's trajectory is fully known from moment to moment -- it will not  be found randomly "anywhere" .   

Update:

Update : I don't think knowing the accuracy of its position /momentum, from moment to moment -- only to a factor of the Heisenberg constant -- is really "indefinite" .

I'm asking if there is a probability that it can be found "anywhere" within the spatial volume ,irrespective of what we "define as its trajectory"  

5 Answers

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  • ?
    Lv 7
    5 months ago
    Favorite Answer

    Feynman’s path integral formulation is a way of explaining the trajectories of quantum particles. It’s very complicated, but the basic idea is that you determine the probability that a particle takes a particular trajectory from A to B by summing the probabilities of ALL possible trajectories - even classically ridiculous trajectories. Each path has a kind of phase associated with it, and the phases interfere in such a way that the classical path becomes the most probable.

    Alternately, you can pick one of the many reality interpretations, wave a dead chicken in the air while chanting.... ah believe! ah believe! .. and you will know as much as anybody else does.

  • Anonymous
    5 months ago

    a photon was going through airport security . the TSA agent asks him if he has any luggage . the photon says " no , i'm traveling light " . 

  • 5 months ago

    No. A quantum particle does not have a position or momentum until measured. It could be found anywhere and have any velocity. But some positions and speeds are more probable than others. 

    If you measure it's position, then it's momentum can be anything. If you measure it's momentum, then it's position can be anywhere. 

  • ?
    Lv 7
    5 months ago

    No. This is?where you run into the Heisenberg uncertainty principle. When you try to measure the position of the electron you introduce additional forces into the frame of reference changing the system. Schroedinger's cat is either dead or alive, but not both aft the same time. This?also assumes the frame of reference is?stationary, not moving relative to something else. 

  • 5 months ago

    No.  At this scale level of a single particle, quantum mechanics dictates the physics and the Heisenberg Uncertainty Principle kicks in.  This principle says that you cannot simultaneous know the exact momentum and position of a particle, and you cannot simultaneously know the exact energy of a particle at any give time.  Mathematically the principle readas:

      dp*dx >= h_bar/2     dE*dt >= H_bar/2  where h_bar is Planck's constant over 2*pi and dx, dp, dE, and dt are uncertainties in position, momentum, energy and tie respectively

    Thus, you can't know the exact trajectory taken by a particle.

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