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#11
June 12th 07, 03:42 AM
posted to rec.radio.amateur.antenna
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Water burns!
Mike Kaliski wrote:
snip In 1993, the most solid experimental evidence came from Chiao and his colleagues Aephraim Steinberg and Paul Kwiat at the University of California at Berkeley. Using the Hong-Ou-Mandel interferometer ... they were able to measure the tunneling times of visible light. According to Brown, "the researchers found that the photons that tunneled their way through the optical filter arrived 1.5 femtoseconds sooner than the ones that traveled through air. The tunneling photons seemed to have traveled at 1.7 times the speed of light" ... Similar experiments by Ferenc Krauss et al at the Technical University in Vienna in October of 1994 "strongly suggest that as they progressively increased the thickness of the barrier the tunneling time saturated toward a maximum value" ... snip This was in "evanescent mode", in other words, waveguide or something similar. Not "free space". So very very very unlikely exceeding the speed of light in a vacuum. As in it didn't. No laws were broken. tom K0TAR Tom, The speed of light in air is not vastly different from the speed of light in a vacuum. If photons were apparently travelling at 1.7 times the speed of light in air, they clearly must have been exceeding the speed of light in a vacuum. This result was observed using visible light. Current theory is usually quoted as nothing can travel faster than the speed of light in a vaccum. It is probably more correct to state that objects with mass cannot exceed the speed of light in a vacuum. Photons, having no mass, are not necessarily subject to this rule and seem to be observed travelling at superluminal velocity under certain very specific conditions. If the photons are tunnelling and travelling faster than light in a vacuum, it does not necessarily mean that any laws have been broken. One way of imagining a way in which this could happen is if a block of material is energised to a high energy state. Photons are continually fired into the material and are absorbed one by one with atoms within the structure absorbing each new photon. At some point, the material becomes completely saturated and cannot absorb any more photons. When the next photon hits and is absorbed, a shockwave propogates through the material and a photon is emitted from the opposite side travelling at the same speed and in the same direction as the original absorbed photon. Stability is restored and energy is conserved. But, it is the shockwave that has propogated faster than the speed of light and it is not the original photon that entered the material that is emitted. The emitted photon will contain exactly the same properties as the absorbed photon and the two would be indistinguishable. So the photon appears to have been transmitted through the material at faster than light speed, but no laws have been broken. A Newtons cradle can help with visualising how this can happen. Mike G0ULI Keep smoking, it must be good stuff. tom K0TAR |
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