Absolute Zero and Electromagnetic Waves
What effect does temperature have on the light
(Electromagnetic waves) at zero Kelvin?
This actually depends on the material through which the light is passing.
When passing through empty space, it has no effect. In fact, temperature is
not clearly defined in truly empty space.
When traveling though material, zero Kelvins usually means atoms are closer
together. This in turn increases the chances of an electromagnetic wave
making contact with an atom. Electrons are still orbiting the atoms. E-M
waves can still be absorbed. I do not expect a great change in this.
The greatest effect is be the loss of background radiation. Once an atom
absorbs the energy of a wave, it will be less likely to emit it. You will
have no extra energy shooting around within the material. The absorbed
energy will be more likely to stay within the material, thus making it a
little bit warmer.
This is a bit tricky to answer because it depends upon conditions. In a
vacuum and over large distances the answer is "no effect". However, light
traveling through condensed matter -- called Bose Einstein condensates --
can have a speed very close to zero velocity. Here where the quantum
rules, some very strange things happen.
Absolutely none. Temperature is related to the average energy of a group of
molecules. Light travels in the vacuum between molecules.
A photon, which is a quantum of light, can interact with a molecule, but it
is then absorbed. It may be re-emitted as another photon. The probability
of this scattering can be affected by the speed of the molecule, but the
photon must always travel at the speed of light (300,000,000 m/s) in order
In attempting to traverse a non-transparent material, the photons will be
absorbed. In traversing a transparent medium, the photons are absorbed and
then emitted as new photons travelling in the same direction (stimulated
emission), but all photons always travel at the speed of light.
Even in the vacuum of outer space, photons can scatter off molecules, but it
is extremely unlikely. The density of molecules in interstellar space is
roughly one per cubic centimeter.
Best, Dick Plano, Professor of Physics emeritus, Rutgers University
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Update: June 2012