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Special relativity says that anything moving (almost) at the speed of light will look like its internal clock has (almost) stopped from the perspective of a stationary observer. How do we see light as alternating electric and magnetic fields? Also does light never age?


marked as duplicate by Waffle's Crazy Peanut, Brandon Enright, Qmechanic Jun 1 '13 at 12:35

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The time stands still for light indeed, so it will never age.

You can think of the photon as a sine wave shaped electric field fragment traveling at $c$, and you can measure it's amplitude and frequency as it flys past your instrument. The photon itself does not oscillate.

(Bit oversimplified but probably you get the point.)

  • $\begingroup$ +1 this is right but you might want to add how it's the source whose electric and magnetic fields are actually alternating as the photon is produced. Or something like that; just to increase clarity $\endgroup$ – Jim May 31 '13 at 16:37
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    $\begingroup$ @Jim: I think that would cause more confusion, as there is no sine wave shaped things that moving at $c$. Electromagnetic field oscillates locally and this disturbance propagates with $c$. Actually no movement here at all. Waves are tricky... If you can word your suggestion in a non-confusing manner, feel free to edit my answer. $\endgroup$ – Calmarius May 31 '13 at 17:31
  • $\begingroup$ Actually, what you just said to me was exactly what I was trying to suggest to you. Kudos for wording it much better $\endgroup$ – Jim May 31 '13 at 17:34

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