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Name: Rich
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Your site states that an electron can, under certain circumstances, travel faster than the speed of light in certain media. How is it possible that this can be true when mass grows as it approaches the speed of light. The cosmic speed limit according to "Al".

You are correct to think that there might be a problem here.

It is true that we cannot accelerate massive objects up to the speed of light in vacuum. However, the speed of light as it passes through other things. While the difference of the speed of light in air is almost identical to vacuum, the speed of light through water is noticeably slower (about 3/4 of its speed in vacuum). Here it is possible to have charged particles that will actually move faster than the speed of light in water. In fact, it is not really that difficult to produce them or find a material that will produce them.

When this occurs, it gives rise to a beautiful phenomena called Cherenkov radiation. The as the charged particle zips along it interacts with the electrons and EM fields of the media through which it passes. These interactions propagate with a speed slower than the particle is moving. In effect they are unable to "get out of the way" quickly and a an electro-magnetic "shock wave" forms. This is very similar to a sonic boom from a supersonic aircraft or the wake generated from a very fast boat traveling across the water.

Michael S. Pierce
Materials Science Division
Argonne National Laboratory

Are you referring to this post?

I agree that "Al" probably will not like this answer very much, but there are several ways electrons (or other wave-particles) can travel faster than light. One has to do with their wave character. The 'front' of the particle's wave function moves faster than light, but the average (the whole wave) doesn't. So in a way it is traveling faster than light, but in a way it is not. Another way is with the Casimir effect, on which I am no expert. But read this for more info:

You can also change the speed of the light itself -- which can be done in several ways (theoretically and practically), such than an electron has an instantaneous velocity faster than the speed of light. I am getting way outside of my area of expertise here, but there are lots of possibilities. Google 'faster than light' and you will have enough reading to last you on a trip to another galaxy traveling at regular speed.

I hope this is a good start,

Burr Zimmerman

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