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I Photon and time

  1. Jun 6, 2017 #1
    I have read that photons do not experience time....
    If that's the case then if a particular photon is emitted by a body then that should exist in every time relative to us i.e that same photon should be there at exactly the same point forever.
     
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  3. Jun 6, 2017 #2

    phinds

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    You have not read that in a physics text, it is pop-sci nonsense.

    It is one of the most common misconceptions in pop-sci presentations and we even have a FAQ on it here somewhere on the forum but I don't have it bookmarked so can't point you to it. Try a forum search. The links at the bottom of this page are a good place to start.
     
  4. Jun 6, 2017 #3

    Dale

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    What is the specific source where you read this? It is wrong for several reasons. As @phinds mentioned, it is probably not a valid source

    This doesn't follow. We still experience time regardless.
     
  5. Jun 6, 2017 #4

    Ibix

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    It's not that photons don't experience time so much as photons don't experience full stop. It's impossible to describe a photon's point of view in relativity, so any attempt to work backwards from what you think that experience is fails even before it starts.
     
  6. Jun 6, 2017 #5

    PeterDonis

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  7. Jun 6, 2017 #6
    https://www.quora.com/Does-a-photon-experience-time
    see the post of a guy named Jerzy Michał Pawlak
     
  8. Jun 6, 2017 #7

    Nugatory

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  9. Jun 6, 2017 #8

    phinds

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  10. Jun 7, 2017 #9
    sorry to ask a stupid question.Can't rely on phd....
     
  11. Jun 7, 2017 #10

    PeroK

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    Here is Jerzy's post:

    The only way particles can "experience time" is by having their internal state evolve. The easiest case to observe is probably particle decay into other particles. Photons don't decay (nor do any other massless particles). They also don't spontaneously change any of their observable properties, like energy or polarisation - this would be violation of energy/momentum/angular momentum conservation. So, to the best of our knowledge, they don't "experience time".

    There is no mention of a photon's point of view that I can see.
     
  12. Jun 7, 2017 #11

    phinds

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    Here it is
    But to be fair, I now see that he is saying this would be absurd. I just scanned it prior to my previous post and was struck by the "photon's point of view".
     
  13. Jun 7, 2017 #12

    PeroK

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    To be even fairer that quotation is not attributable to Jerzy Michal Pawlak. It's not clear who is the originator of that particular entry.
     
  14. Jun 7, 2017 #13

    vanhees71

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    I don't understand what the authors of this popular-"science" book want to express with the phrase "a particle experiences time". It's an undefined empty phrase. Forget popular-science books and read real physics books. It's very difficult to write a good popular-science book, way more difficult than to write a good physics textbook, because in the former you are not allowed to use the adequate language to describe physics, which is mathematics. On the other hand, making a statement like "a particle experiences time" is, in fact, utter nonsense even in a popular-science-book context! I'm pretty sure they explain somewhere that photons are massless particles, implying a "billard-ball picture" of "particles". That's as misleading as you can be.
     
  15. Jun 7, 2017 #14

    Mister T

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    No, you absolutely cannot rely on something just because it was written by someone with a Ph.D. in the discipline. For example, suppose two of them disagree, as is often the case? Most if not all of the physicists who have replied to you here have Ph.D.'s in physics or closely related disciplines!

    In the early 1990's there was a problem known as the solar neutrino problem. The number of neutrinos from the sun hitting detectors on Earth was less than what theorists predicted based on the nuclear reactions that they calculated must be occurring to produce the amount of heat and light being output by the sun. In other words, there was no way to explain how the sun could be so bright and so hot without these nuclear reactions, and no way to explain the nuclear reactions without a sufficient number of neutrinos being produced. But when experimentalists used their detectors to look for these neutrinos, a significant fraction of them were missing!

    One possible explanation, that later turned out to be right, is that the missing neutrinos changed flavor on their way from the sun to Earth.

    I was in attendance at a seminar for physicists at the University of Houston when the Nobel prize-winning physicist Sheldon Glashow, who was the invited guest and speaker, stated that if neutrinos are massless then they travel at the speed of light and, loosely speaking, can't experience time so therefore can't oscillate (change) from one flavor to another.

    Of course we now know that neutrinos are not massless, that they therefore travel at speeds less than the speed of light, and that they do indeed oscillate.

    So why the caveat "loosely speaking"? The other posters are trying to get you to understand why. The moral of the story is information processing. You can't simply take something you hear or read at face value without trying to understand why it was said or written. If you do you run the risk of drawing a false conclusion from it, as you have done here in your original post.
     
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