I saw a show on PBS where a scientist transmitted music faster than c. He recorded it and played it back on a tape recorder. It was staticy, but recognizable.
--Alan D
See plea for help in article....
- As far as I understand it, the evanescent wave coupling stuff is the same as the other group velocity > c stuff in the case of extreme absorption.
- There seems to be a lot of interest and half-explainations of this topic scattered around the wikipedia, I may try to write a superluminal communication article, In My Copious Free Time.
- What's really interesting is the effect that occurs between the plates of a Casimir Force experiment, that's the only legitimate v>c stuff I know about. -- DrBob
How is "velocity" incorrect? It was good enough for Einstein:
- In short, let us assume that the simple law of the constancy of the velocity of light c (in vacuum) is justifiably believed by the child at school. [1]
I suppose we should make it clear that we are referring to the velocity of the propagation of light. --
TheCunctator
- Well, if the velocity of light was a constant, then it would always move in the same direction. (Velocity being a vector quantity.) This is not true for all observers (the direction of light propogation being different in different reference frames, e.g. the light-clock thought experiments), and not even true for a single observer (light being able to go in any direction). However, the speed of light, being the magnitute of the velocity, is the same for all observers.
- Maybe I'm being nit-picky but it seems that Einstein was being loose with the terminology in the article you reference. I still think 'speed' is the most technically correct. -- DrBob
I agree, velocity is generally taken to be a vector quantity and speed is a scalar. The speed of light in vacuum is constanct and equal to c; the velocity vector of light in vacuum is not constant, because light can travel in different directions; the magnitude of the velocity vector is c. --AxelBoldt
- Fine with me. I think it would be fair to note that Einstein used "velocity", and define speed. --TheCunctator
Are light-years really the prefered unit in Astronomy? I have heard that they are mostly used in popular science articles, but real astronomers use Parsecs instead. I'm not a real astronomer, so i can't vouch for this. -- Geronimo Jones.
The star and galaxy catalogs tend to use parsecs rather than light-years, so I'd guess it's a safe bet.