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cmancone
approved users
| Joined: | Thu Oct 12th, 2006 |
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| Posts: | 33 |
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Posted: Thu Oct 12th, 2006 05:54 pm |
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It seems to me that when an electron in the IGM absorbs a photon, it would "recoil" into the direction of motion of the orginal photon. Then, when re-emitting said photon, the electron would recoil away from the direction of motion of the original photon. Therefore, there would be no net loss of energy for the photon, and no mechanism for a tired light theory.
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lyndonashmore
Administrator
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Posted: Fri Oct 13th, 2006 08:09 pm |
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Hi cmancone, welcome!
Sign error? no way!
the only way that there is no net loss of energy is in a billiard ball collision where one ball stops and the other moves off with the same velocity as before.
If the photon is absorbed by the electron then momentum, not energy is conserved, and so redshift is explained - the universe is not expanding.
cheers,
lyndon
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cmancone
approved users
| Joined: | Thu Oct 12th, 2006 |
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| Posts: | 33 |
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Posted: Fri Oct 13th, 2006 08:42 pm |
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In the case of collisions between photons and electrons, energy has to be conserved. Inelastic collisions (where momentum, and not energy are conserved) can only occur in macroscopic processes. Energy can't be created or destroyed, but can change forms. So, in macroscopic collissions you can have energy that is transfered from kinetic energy of your colliding objects to kinetic energy of the constiuent particles (heat). However, when you have a photon colliding with an electron, there is nowhere else for energy to go. It either shows up in the electron, or it shows up in the photon. Energy has to be conservered.
The short of it is that collisions between electrons and photons are elastic - momentum and energy are conserved. So, when an electron absorbs a photon, it will recoil away from the photon (or towards the line of motion). When the electron then re-emits the photon, it will again recoil away from the photon, this time away from the line of motion. Since the two effects occur in opposite directions, and energy has to be conserved, the net result is no change in energy of the photon.
The only thing that could really change this result is if the electron collides with another electron before re-emiting the photon. However, densities in the IGM are very low, so that would most likely be a negligable effect.
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lyndonashmore
Administrator
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Posted: Sat Oct 14th, 2006 06:33 pm |
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Hi Cmancone,
Wrong!
It is well known that whenever an electron/atom emits or absorbs a photon, it loses energy due to recoil.
Mossbauer had something to say about this and became famous for stopping the recoil.
Try
http://www.britannica.com/nobel/micro/406_43.html
Cheers,
Lyndon
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