Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B "travel time" of appearing and disappearing?

  1. Aug 5, 2017 #1

    Suppaman

    User Avatar
    Gold Member

    I was reading a book on how to teach your dog physics. In it I remember a section on probability where something could show up anywhere, even on the moon. I understand that is not really going to happen but it is in theory, possible. My question is when something can be somewhere is there a travel time? In theory, that thing that could show up on the moon, would it have to travel there at light speed or less?
     
  2. jcsd
  3. Aug 6, 2017 #2

    vanhees71

    User Avatar
    Science Advisor
    2016 Award

    The speed of light is indeed the ultimate speed limit in the universe according to the theory of relativity. Also tunneling takes time, although the "tunnel time" is hard to define thttps://arxiv.org/ct?url=http%3A%2F%2Fdx.doi.org%2F10%252E1103%2FPhysRevLett%252E119%252E023201&v=e8123023o begin with let alone to measure it accurately. Very recently there was a breakthrough in this direction:

    https://arxiv.org/abs/1611.03701
    https://doi.org/10.1103/PhysRevLett.119.023201
     
  4. Aug 7, 2017 #3

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    The content of your post is not represented by the topic of this this thread. "When something can be somewhere" isn't due to tunneling.

    You need to go back to Chad Orzel's book and quote exactly where this is mentioned, and under what phenomenon he is describing.

    Zz.
     
  5. Aug 7, 2017 #4

    fresh_42

    Staff: Mentor

    That has been my fault. I changed the title from "speed of probability" to the current one in order to make it more descriptive. I thought the quantum tunnel effect has been the closest observation that fits to the question. So you have to blame me.
     
  6. Aug 7, 2017 #5

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    Then it should be changed. I think the original title, even if it isn't as descriptive, would have been less problematic than this one. The OP is probably invoking something like vacuum fluctuation, and somehow confusing that with having something traveling from one place to another.

    It is certainly isn't tunneling, and vanhees reply may add to the confusion.

    Zz.
     
  7. Aug 7, 2017 #6

    fresh_42

    Staff: Mentor

    I'll change it as soon as it is more transparent what the OP actually means. Quantum fluctuations earth-moon are as problematic as the speed of a mathematical quantity is. Thank you for the hint.
     
  8. Aug 7, 2017 #7
    Roland Omnes uses the same terminology, 'tunneling', to describe, for example, the very very very small probability of a car parked in one car space to then be seen parked in a carpark across the street. I think this is what the OP is talking about, except about a different system.
     
  9. Aug 7, 2017 #8

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor
    2016 Award

    And I wish these people would simply get out of their offices and actually go DO a tunneling measurement.

    This is perpetuating the idea that a particle doesn't pass through the "classically-forbidden" region during the tunneling process, and simply appear at its "destination". This is false. I've debunked this several times on here. Read this:

    https://www.physicsforums.com/threa...like-to-get-an-answer-on.460343/#post-3063909

    This is not a "Star Trek teleportation", which appears to be what is being described here.

    Zz.
     
  10. Aug 8, 2017 #9
    I think the authors (post #2 & Roland Omnes) have confused the phenomenon in question as tunneling, when it is something entirely different.
     
  11. Aug 9, 2017 #10

    vanhees71

    User Avatar
    Science Advisor
    2016 Award

    In post #2 I quoted a very recent PRL adding one more attempt to measure tunneling time in atomic physics. The problem is quite old, and the main problem is to define "tunneling time" to begin with. It's defined by the experimental setup, what's measured, and here we have some kind of breakthrough that the measured "tunnel times" are in (rough) accordance with the underlying theoretical description of what's measured in this experiment.
     
  12. Aug 12, 2017 #11

    Suppaman

    User Avatar
    Gold Member

    I am sorry if my post caused confusion. It was based on the fact that if something can be someplace because of probability does it take a measurable time to get there. That was all. I understand tunneling, I used an electrical component that did that back in the 70s long before I thought about what that meant.
     
  13. Aug 12, 2017 #12

    Mentz114

    User Avatar
    Gold Member

    Nothing ever happens 'because of probability' because it is not stuff and it cannot cause anything. Quantum mechanics only allows us to calculate the probability of certain outcomes chosen from a complete set of possibilities. For instance One might say that an atom entering a cavity might or might not absorb a photon with certain probability.
     
    Last edited: Aug 12, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: "travel time" of appearing and disappearing?
  1. Objects disappearing (Replies: 3)

Loading...