Scientists Mess with the Speed of Light
- From: "tony" <tony@xxxxxxxxxxxx>
- Date: Sat, 20 Aug 2005 22:26:43 +0800
Scientists Mess with the Speed of Light
By Ker Than
LiveScience Staff Writer
posted: 19 August, 2005
3:41 pm ET
Researchers in Switzerland have succeeded in breaking the cosmic speed
limit by getting light to go faster than, well, light.
Or is it all an illusion?
Scientists have recently succeeded in doing all sorts of fancy things
with light, including slowing it down and even stopping it all together. Now
a team at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland
is controlling the speed of light using simple off-the-shelf optical fibers,
without the aid of special media such as cold gases or crystalline solids
like in other experiments.
"This has the enormous advantage of being a simple, inexpensive
procedure that works at any wavelength," said Luc Thévenaz, lead author of
the study detailing the research.
Using a technique called Stimulated Brillouin Scattering, the
researchers were able to slow down or ratchet up the speed of light like the
gas pedal on a car. They succeeded in reducing the speed of light by almost
a factor of 4 (although that's still plenty fast at 46,500 miles per
second), but even more dramatically, the team was also able to speed up the
speed of light.
Light in a vacuum travels at approximately 186,000 miles per second,
but a popular misconception is that, according to Einstein's special theory
of relativity, nothing in the universe can travel faster than this speed.
This seeming paradox can be resolved because a pulse of light is
actually made up of many separate frequency components, each of which moves
at their own velocities. This is known as the pulse's phase velocity. If all
the frequency components have the same phase velocity, then the overall
pulse will also appear to move at that velocity.
However, if the components have different phase velocities, then the
pulse's overall velocity will depend on the relationships between the
velocities of the separate components. If the velocities differ, the pulse
is said to be moving at the group velocity.
By tweaking the relationship between phase velocities, it's possible
to adjust the group velocity and create the illusion that parts of the pulse
are traveling faster than the speed of light.
One area where such an advance could be enormously beneficial is in
the telecommunications industry.
Although information can be channeled through fiber optics at the
speed of light, it can't be processed at this speed because with current
technologies, light signals must be transformed into much slower electrical
signals before they are useful.
Thevenaz's technique would essentially allow light to be processed
with light without a costly electrical conversion.
The group's research will be published in an August 22nd issue of the
journal Applied Physics Letters.
http://www.livescience.com/technology/050819_fastlight.html
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