Re: Constant Speed of Light


"Axel Kline" <AxelK@xxxxxxxxx> wrote in message
news:ra0334t7l4r3f4clf70ooeb782iehmskpv@xxxxxxxxxx
| On Mon, 19 May 2008 09:37:35 +0100, Martin Hogbin
| <goatNOSPAM1@xxxxxxxxxx> wrote:
|
| >Axel Kline wrote:
| >> I just had an argument with a friend about the speed of light. He says
| >> that photons are slowed down as they pass through various materials or
| >> substances and that this varies depending on what the material is. But
| >> I think that the photons never actually slow down. They get captured
| >> by atoms and disappear for a certain length of time while their energy
| >> is used to kick electrons up to higher energy levels. When an electron
| >> drops down to a lower energy level it releases or generates a photon.
| >> It's the *rest-time* that actually varies with materials. So the
| >> photons are always traveling at 300,000 kilometers per second *when
| >> they exist*. We bet 20$ on this. Can anyone tell me which of us won?
| >
| >It is probably fairest to call the bet off although I
| >would say that you are you are a bit more right than he is.
| >
| >According to classical electromagnetism, the overall
| >action of electrons in a medium (that transmits light)
| >is to extinguish the incoming electromagnetic wave and
| >replace it with another one travelling at a slower
| >speed. There are no photons in classical EM theory.
| >
| >The best theory of light that we have is Quantum
| >Electrodynamics (QED). In this theory photons are
| >absorbed and emitted by atoms. However photons are
| >quantum entities, and cannot be considered as ordinary
| >objects having such things as trajectories or even
| >speeds. However, over long distances it can be said
| >that photons always travel at a speed of c, on average.
| >
| >If you want to know more about the subject then I
| >suggest that you look at this book:
| >
| >QED - The strange theory of light and matter
| >by Richard P Feynman
| >Penguin science paperback
| >ISBN 0-14-012505-1
| >
| >MArtin Hogbin
|
| Thanks. I was already going to call off the bet after people on this
| group gave me opposite answers to my question. Your own answer sounds
| most informed and lets us both be partly right, so the bet's off
| unless I decide to read the book. I've read something by Feynman
| before and it was interesting. I may just tell him going to do some
| research before I payup or demand payment. We should have stuck to
| arguing about sports. It's easier to find who's right.


Remind others never to bet with someone who reneges on a deal.
YOU LOST! HAVE THE DECENCY TO PAY UP!



.

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