moth Posted February 20, 2009 Share Posted February 20, 2009 check these out http://www.vega.org.uk/video/subseries/8 all about light from a master of exposition. Link to comment Share on other sites More sharing options...
NowThatWeKnow Posted February 20, 2009 Share Posted February 20, 2009 I am not disputing what is being said here but the speed of light, relative to different observers, is not observed as constant. Warped space or water, the time to travel a given distance is variable. Hence, the speed of light being constant may confuse many. Link to comment Share on other sites More sharing options...
ydoaPs Posted February 20, 2009 Share Posted February 20, 2009 I am not disputing what is being said here but the speed of light, relative to different observers, is not observed as constant. Warped space or water, the time to travel a given distance is variable. Hence, the speed of light being constant may confuse many. Read my post above. You're confusing average and instantaneous. Link to comment Share on other sites More sharing options...
NowThatWeKnow Posted February 20, 2009 Share Posted February 20, 2009 Read my post above. You're confusing average and instantaneous. I did read your post above. The average speed and instantaneous speed being different is what may be confusing to some. Then you have the observed speed from different frames to complicate it more. Link to comment Share on other sites More sharing options...
swansont Posted February 20, 2009 Share Posted February 20, 2009 I am not disputing what is being said here but the speed of light, relative to different observers, is not observed as constant. Warped space or water, the time to travel a given distance is variable. Hence, the speed of light being constant may confuse many. "Speed of light is a constant" is for a vacuum, i.e no absorptions, and applies to locally flat space, i.e. no curvature. As for it being confusing, nature is under no obligation to be easy to understand. Link to comment Share on other sites More sharing options...
Klaynos Posted February 20, 2009 Share Posted February 20, 2009 Whilst the photon is absorbed it does not exist. Link to comment Share on other sites More sharing options...
NowThatWeKnow Posted February 20, 2009 Share Posted February 20, 2009 Whilst the photon is absorbed it does not exist. With the first law of thermodynamics in mind, what is the photon converted into and out of when being absorbed? Link to comment Share on other sites More sharing options...
Klaynos Posted February 20, 2009 Share Posted February 20, 2009 With the first law of thermodynamics in mind, what is the photon converted into and out of when being absorbed? The energy of the absorber... so an electron jumps up to a different energy state. Link to comment Share on other sites More sharing options...
GDG Posted February 20, 2009 Share Posted February 20, 2009 With the first law of thermodynamics in mind, what is the photon converted into and out of when being absorbed? The excitation of the absorbing atom. Of course, this assumes that there is a pair of available energy levels separated by just the right amount so that the photon can be absorbed. One could alternately treat light as a wave, and simply accept the fact that the wave slows down as it encounters a material with permeability and permittivity that is different from vacuum. Link to comment Share on other sites More sharing options...
swansont Posted February 20, 2009 Share Posted February 20, 2009 The excitation of the absorbing atom. Of course, this assumes that there is a pair of available energy levels separated by just the right amount so that the photon can be absorbed. Under the circumstances of this discussion (reduction in the speed of light propagation) the absorptions are not into real states and are not constrained to match a real transition in the material. Link to comment Share on other sites More sharing options...
NowThatWeKnow Posted February 20, 2009 Share Posted February 20, 2009 (edited) One could alternately treat light as a wave, and simply accept the fact that the wave slows down as it encounters a material with permeability and permittivity that is different from vacuum. It does not seem that is going to be the case around here. Edited February 20, 2009 by NowThatWeKnow Link to comment Share on other sites More sharing options...
timetes Posted March 2, 2009 Share Posted March 2, 2009 Nope: the index of refraction is due to the fact that light travels at different speeds in air vs. water, glass, etc. Look at the electromagnetic wave equation, which depends on the electric and magnetic constants for the medium. It is in fact possible to slow light down to a stop. Enjoy, Grant are you guys saying that this woman in the article is lying, or making this up Link to comment Share on other sites More sharing options...
Klaynos Posted March 2, 2009 Share Posted March 2, 2009 are you guys saying that this woman in the article is lying, or making this up It is poor wording/writing. I dislike the term slow light when talking to people outside the field because they think we mean something that we do not. Link to comment Share on other sites More sharing options...
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