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Static light

  1. Dec 28, 2012 #1
    If light is both a partial and a wave; and the speed of light is an absolute; and a partial travelling at the speed of light experiences zero passage of time (I think that’s what Einstein was on about)how can light move at all through space time? Or is that what we experience as matter?
  2. jcsd
  3. Dec 28, 2012 #2

    Simon Bridge

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    Welcome to PF;
    "if light is a particle and a wave"
    ... it isn't. Or rather, that is an unhelpful way of thinking about it.
    I don't think it is fatal to your question though.

    "a particle travelling at the speed of light experiences zero passage of time"
    ... in the limit. You are finding out that it is not helpful too try to see what happens from the reference frame of a photon.

    "how can light move trough space and time?"
    ... you said it yourself: it has a speed. Motion in space with respect to time.
    Light moves from place to place in the reference frame of us poor slow massive objects.
    In the speed-of-light limit, all distances are zero - so, in this sense, light does not need to go anywhere in it's own reference frame... see why it's not helpful?
  4. Dec 28, 2012 #3
    Thanks. I think. It was more of a philosophical question. I was trying to imagine if I was light (or more precise a photon) would I experience time and therefore be aware of myself?

    Perhaps not the right place to ask these questions.
  5. Dec 28, 2012 #4
    Thanks QP. Just trying to understand relativity a bit better, so if "the thing we see" takes say one light year to reach us from its source, would it know it took one year to get here or think it instantly was created then hit my eye?
  6. Dec 28, 2012 #5
    It's not really a meaningful question. As Simon said, if you look at the equations of Relativity and look at what happens as you take a particle whose speed approaches light speed, you'll say that the time the particle experiences approaches 0. But the second you actually make that speed of the particle light speed, instead of just close to light speed, the equations stop working.
  7. Dec 29, 2012 #6
    Interesting. I guess that means as far as light is concerned there is no universe. Just 'I was" not "I am". Kind of throws the whole 'time exists' arguement out the window.
  8. Dec 29, 2012 #7
    Not at all, in any way.

    First of all, and obviously, light does not think, so nothing concerns it.
    Second of all, obviously time exists, or how else can you explain that and this moment I am here and at the next moment I am there?
  9. Dec 29, 2012 #8

    Simon Bridge

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    Recall that, in relativity, time is another dimension of space ... saying time does not exist just because something does not experience it is like saying that sideways does not exist just because something only goes forwards.
  10. Dec 29, 2012 #9
    That was a damn good analogy, what he said :smile:
  11. Dec 29, 2012 #10
    Something moving does not create time. It just moves. Just because things move at different rates based their physical surroundings doesn't make it time. Has anyone actually proved time exists rather than things occur at different rates in different circumstances?
  12. Dec 29, 2012 #11
    How do you propose we define what 'occuring at a different rate' means without time?
  13. Dec 29, 2012 #12
    Got me there. No idea. Not a professional. I think the best answer would be ‘perspective’. I just watch a lot of doco’s and they all seem to contradict each other. Makes it hard for those of us that are smart enough to ask the questions but don’t have the time to learn the answers.

    But thanks guys, you have given me something more to think about.
  14. Dec 29, 2012 #13
    I'm weary to leave you here because I think you're going down the wrong path.

    Time does exist, in relativity theory it's treated as a fourth dimension (after the three spatial ones).

    This is a pretty good introduction to this idea, called spacetime, though it gets a bit mathy at the bottom:
  15. Dec 29, 2012 #14
    Thanks Vorde. Looked at space-time a lot, came to the conclusion that they got the name wrong. It should have been called “strange gooey stuff that does strange gooey things that isn’t really gooey”. :-)
  16. Dec 29, 2012 #15

    Simon Bridge

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    The thing to remember about pop-science docos is that they are not, primarily, science shows - they are entertainment shows. Of course they are contradictory and incomplete... they sell advertising better that way.

    "Time" is a valid concept - however, your understanding of what it is and how it behaves should deepen as you explore it - but it doesn't go away. The "perspective" idea is pretty much what relativity describes ... but it remains that we have a special relationship to one of our space dimensions which is tied up with entropy and so on... it's a big topic.

    The trick it to try to be exact with your terminology -i.e. you cannot have a "rate" without having time: it's what the word means.
  17. Dec 29, 2012 #16

    Vanadium 50

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    This thread is, as the OP admits, going down the road of philosophy (and not very good philosophy at that). We don't do that here, so the thread is closed.
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