Tuesday, March 06, 2007

Speed Of Light Exceeded?

The CBC is reporting that NEC researchers have designed an experiment that is the "first ever evidence of faster-than-light motion". I don't think so Bubba. I haven't seen their paper, but based on the CBC description it sounds as if they are describing the group velocity of the waveform. In certain media group velocity can exceed the speed of light although it doesn't carry information. This is nothing new, so I'm not sure what breakthrough is being claimed.
Light travels slower in any medium more dense than a vacuum, which has no density at all. For example, light travelling through glass slows to two-thirds its speed in a vacuum. If the glass is altered, the light can be slowed even further.

The NEC team produced the opposite effect. Inside a chamber, they changed the state of a vapour in a way that light travelling through it would travel faster than normal. When the pulse of light travelled through the vapour, the pulse reconfigured as some component waves stretched and others compressed. As the waves approached the end of the chamber, they recombined, forming the original pulse.

The key to the experiment was that the pulse reformed before it could have gotten there by simply travelling through empty space. This means that, when the waves of the light distorted, the pulse traveled forward in time.

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