Scientists Mess with the Speed of Light

[tocqueville]

Ker Than
LiveScience Staff Writer
LiveScience.com
Fri Aug 19, 4:00 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 Fdrale 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.

http://news.yahoo.com/s/space/20050819/sc_space/scientistsmesswiththespeedoflight

[bananas]

1. "Stimulated Brillouin Scattering"

sounds like something a French chef would do.

[Tesha]

7. It's what happens when you trip while carrying in the fancy dessert. (NT)

[TalkingDog]

2. But we all knew this...right?

I mean, light as an absolute speed, was in question for years. And any rule that absolute was just begging to be broken....

Now finally we can get onto warp drive.

[Tace]

3. And Replicators!

[TlalocW]

4. And holodecks

So I can finally have sex with Counselor Troi!

Ooops... I normally just say that inside my head.

TlalocW

[Syncronaut Seven]

5. Nominated!

:evilgrin:

[Salviati]

6. To be fair...

this sort of thing has been known about for years, and it doesn't really violate the speed of light as an absolute limit on the speed at which information or influances can travel.

The key to this sort of thing is the differences between the 'phase velocity' of a wave and the 'group velocity'

This page has a good (though somewhat mathematical) discussion about the issue, here's a snip that applies to just this situation:

Unfortunately we frequently read in the newspapers about how someone has succeeded in transmitting a wave with a group velocity exceeding c, and we are asked to regard this as an astounding discovery, overturning the principles of relativity, etc. The problem with these stories is that the group velocity corresponds to the actual signal velocity only under conditions of normal dispersion, or, more generally, under conditions when the group velocity is less than the phase velocity. In other circumstances, the group velocity does not necessarily represent the actual propagation speed of any information or energy. For example, in a regime of anomalous dispersion, which means the refractive index decreases with increasing wave number, the preceding formula shows that what we called the group velocity exceeds what we called the phase velocity. In such circumstances the group velocity no longer represents the speed at which information or energy propagates.

[On the Road]

8. The Article States The Technology Could be Used for Optical Switching

How would it do that? Or is it just popular journalistic hyperbole?