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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