> "Nothing can exceed the speed of light".......
> I've heard that many times. Well apparently that is not true. Since soon a
> turtle will be able to do it.
> Only kidding here...since I've neglected the "in a vacumn" part of that
> However...that leads to a question. If light is "slowest" in a Bose-Einestein
> Condesate...and "fastest" in a vacumn......is there anything "less" than a
> vacumn? It is possible to slow light down...is it even theoretically
> possible to speed light up?
> No clue here...a vacumn is a vacumn right?
Yes. It is. c in a vacuum is as high as anything can go. If you put more energy into the photon, it simply increases in frequency. This is why the researchers knew they had measured an extremely slow speed in the condensate, because if they had just drained energy from the light, it would have changed frequency. What it did do was retain its energy at the same frequency, which told them they were getting a refractive phenomenon.
This is not exclusive to BE condensates. The speed of light is different in any material, and different in each state, for example, different for steam, water, and ice. The absolute we refer to as c, though, in most physics equations is usually refered to as being in vacuum conditions, unless there is actually work being done within materials.
As the article that was referred to states, the phenomemon of refraction in optics is entire dependent on the fact that light travels slower in glass than in air or in a vacuum. Rather than traveling a straight line, when light strikes glass at an angle, the photons will run through their path integral of possible paths (all possible paths), and take the one which takes the least amount of time between its emission point and is receiving point.
Remember that it knows what its receiving point is because the photon exits as a result of the handshake of the particles on the emission and reception ends with virtual particles that are in phase but moving in opposite directions in time. (As per Feynman's Transactional Interpretation of Quantum Electro-Dynamics).
Thus, the light will strike the glass at a shallow angle and travel through the glass at a steeper angle to reach the reception point, because that path takes the least amount of time, as it wants to travel through as little of the slow medium (the glass) as is possible in the trip, and as much of the fast medium (the vacuum).
I never completely understood why refraction worked until I learned how the transactional interpretation worked....