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Astrophysics/Stopping_light

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Expert: - 1/15/2007


Question
Can light be stopped? If yes, the how?

Answer
Hi Kevin,

No, light cannot be stopped.  It can only be absorbed and emitted.  Even reflection of light is not light "bouncing" off a surface, but is an absorption and re-emission process.  There is no such thing as a stationary photon.  According to Einstein, the speed of light is a constant, regardless of the observer.  Even in a black hole, light is not stopped; it just never can have sufficient energy to start (and try to escape from the black hole).  Of course, to be perfectly correct, Quantum Electrodynamics says that photons can have a range of speeds (some less than c, some more than c), but the average is always c.

Hope than helps answer your question.

Prof. James Gort  

Astrophysics

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James Gort

Expertise

Questions on observational astronomy, optics, and astrophysics. Specializing in the evolution of stars, variable stars, supernovae, neuton stars/pulsars, black holes, quasars, and cosmology.

Experience

I was a professional astronomer (University of Texas, McDonald Observatory), lecturer at the Adler Planetarium, professor of astrophysics, and amateur astronomer for 42 years. I have made numerous telescopes, and I am currently building one of the largest private observatories in Canada.

Publications
StarDate, University of Texas, numerous Journal Publications

Education/Credentials
B.A. Physics and Astronomy M.Sc. Physics Ph.D. Astrophysics

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