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Why does light travel

  1. Jun 1, 2003 #1
    Why does light travel as a wave through a complete vacuum? What is the force behind this?

    Michio Kaku said in his book Hyperspace this ...

    In my studies, I learned that one of the great debates of the nineteenth century had been about how light travels through a vacuum. (Light frow the stars, in fact, can effortlessly can travel trillions upon trillions of miles through the vacuum of out space.) Experiments also showed beyond question that light is a wave. But if light were a wave, then it would require something to be "waving." Sound waves require air, water waves require water, but since there is nothing to wave in a vacuum, we have a paradox. How can light be a wave if there is nothing to wave? So physicists conjurned up a substance called the aether, which filled the vacuum and acted as the medium for light. However, experiments conclusively showed that the "aether" does not exist.*


    *Surprisingly, even today physicists still do not have a real answer to this puzzle, but over the decades we have simply gotten used to the idea that light can travel through a vacuum even if there is nothing to wave.
     
    Last edited: Jun 1, 2003
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  3. Jun 1, 2003 #2

    mathman

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    Photons have wave properties and particle properties. There is a nice little book by Richard Feynman, entitled QED, which gives as good an explanation as possible to this whole question.

    Things we think of as particles, such as electrons, also exhibit wave properties (double slit pattern).
     
  4. Jun 1, 2003 #3

    light is made up of a magnetic wave traveling at a right angle to an electric wave (or another magnetic wave or something)thus allowing itself to go through a vacuum. (it's something like that,i'm a little rusty on my electromagnetics)
    somebody elaborate,please.
     
  5. Jun 1, 2003 #4
    This is not any easy question to answer.

    We don't really know what kind of "machinery" underlies the way the World works. We devise descriptions based on observation and reason. One description that works well is that light and other states can be described as "waves". We don't need to say what the waves are "of" or "in". When we try to use a description that involves something like "ether" it always makes predictions that are wrong, so the pros just use the equations and forget about any kind of mechanism. For some reason Nature needs to be described in a very abstract mathematical way, that is just the way it works.
     
  6. Jun 1, 2003 #5

    Claude Bile

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    In a vacuum, Maxwell's 4 equations of electromagnetsim can be reduced to a wave equation (Thus giving a wave solution) for both E and B fields. Can be thought of as an oscillating electric field generating an oscillating magnetic field, which generates an oscillating electric field so on and so forth.

    That argument is a bit obtuse and not 100% accurate, since e/m waves are quantum mechanical in nature, however for some applications it is sufficient.
     
  7. Jun 3, 2003 #6
    The way I understand it is that what we consider the wave nature of light is actually the probability that the particles will form wave like patterns. As mathman said even electrons exhibit wave properties.
     
  8. Jun 3, 2003 #7
    Look in the Feynman Lectures

    under the title "Bullets and Waves" for a good descriptiion of how light and other quanta work.

     
  9. Jun 7, 2003 #8
    Ok, so the wave on vacuum becomes from an oscillating magnetic field, and an oscillating electric field...

    An electric or magnetic field is how a particle will feel due to another surrounding particles if it were there.

    So in vacuum, what are the causes that creates the fields needed to create the travelling wave?. Where the fields came from or what keeps them oscillating? What are the causes of the oscillating fields on vacuum?.
     
  10. Jun 9, 2003 #9
    The changing electic field produces a changing magnetic field, which in turn produces a new changing electric field, all of which is moving forward as a wave from the source. The source contains moving charges which produced the initial wave, but the source isn't required to sustain the wave. That is a classical description.
     
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