Variations of the speed of light

[The Grim Squeaker]

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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.

[Winston Blake]

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?
[...]
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.

If they're going to use such a bold attention-grabbing opener, it'd be smart not to utterly invalidate it later and make themselves look like idiots.

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.

What misconception? The group velocity doesn't involve anything actually moving faster than light, not even information. Nice applet.

[NecronLord]

C is the speed of light in a vacuum. Light in optical fibers always moves slower than C. Of course, in this case, what they're actually doing is not at all what is suggested by the title.

[LauraG]

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.

Will this create the illusion of traveling in time?

[WyrdNyrd]

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.

Will this create the illusion of traveling in time?

No, it will create the illusion of sagacity in otherwise ignorant and moronic technology reporters.

[Magnetic]

One of the guys on my other forum gave this idea as evidence to show that the speed of light is not absolute, which is why it is possible that the entire universe can only be 6,000 - 10,000 years old.

As he says, (and I paraphrase)"You have no way to know how light is affected between galaxies......", hence was his stance on light traveling faster outside of the gravatational influences within galaxies.

[SirNitram]

One of the guys on my other forum gave this idea as evidence to show that the speed of light is not absolute, which is why it is possible that the entire universe can only be 6,000 - 10,000 years old.

As he says, (and I paraphrase)"You have no way to know how light is affected between galaxies......", hence was his stance on light traveling faster outside of the gravatational influences within galaxies.

He doesn't know what E=MC^2 means, I see.

[Xisiqomelir]

Frame of reference tricks don't work on us.

[SoX]

My physics teacher explained it by saying "its nothing actually moving just like a dot highlighted on the moon with a laser from earth can appear to travel faster then light due to the angles involved when the laser is moved or the point at which scissors blades intersect". I like that applet.