Re: SCI: slow light

Ron Kean (ronkean@juno.com)
Fri, 19 Feb 1999 20:18:04 -0500

On Fri, 19 Feb 1999 00:36:45 -0500 "joe dees" <joedees@bellsouth.net> writes:
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>At Fri, 19 Feb 1999 00:05:31 EST, you wrote:
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>>"Nothing can exceed the speed of light"....
>>
>>I've heard that many times. Well apparently that is not true. Since
>soon a
>>turtle will be able to do it.
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>>Only kidding here..since I've neglected the "in a vacumn" part of
>that
>>quote".
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>>However..that leads to a question. If light is "slowest" in a
>Bose-Einestein
>>Condesate..and "fastest" in a vacumn...is there anything "less" than
>a
>>vacumn? It is possible to slow light down..is it even
>theoretically
>>possible to speed light up?
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>>No clue here..a vacumn is a vacumn right?
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>>Right?
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>>EvMick
>>Winslow Arizona
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>And does the frequency (wavelength) matter as to speed, either in a
>vacuum or in a Bose-Einstein condensate?
>Joe E. Dees
>Poet, Pagan, Philosopher
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>

The speed of light (electromagnetic waves) in a vacuum is completely independent of the frequency or wavelength of the photons or waves, according to Maxwell's theory, and such a phenomenon has never been observed as far as I am aware.

But there is a theoretical possibility that light in a vacuum could be slightly slowed over cosmic distances by the presence of electromagnetic energy in the space (e.g. the cosmic background radiation, starlight, quasar light, etc.)

On a cosmic scale, the frequency of light travelling through space becomes red-shifted as the space through which the light travels expands.

Light travelling out of a gravitational potential well (away from a star or the vicinity of a black hole) will be red-shifted as the photons lose energy as they climb.

Light falling into a gravitational well is blue-shifted, all else being equal.

For media with a refractive index greater than that of vacuum, the speed of light generally varies with frequency. Glass prisms, for example, break up white light into a rainbow spectrum.

I don't know if speed varies with frequency in a Bose-Einstein condensate, but it seems likely since it does with seemingly most material media.

Ron Kean

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