Absolute Zero and Electromagnetic Waves ```Name: Venkat Status: other Grade: other Location: IL Country: N/A Date: 10/2/2005 ``` Question: What effect does temperature have on the light (Electromagnetic waves) at zero Kelvin? Replies: Venkat, 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. Ken Mellendorf 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. Vince Calder 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 to exist. 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 Click here to return to the Physics Archives

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