Electrons Faster Than Light

Name: Rich
Status: educator
Grade: 9-12
Location: NJ

Question: 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".
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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.

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Michael S. Pierce
Materials Science Division
Argonne National Laboratory
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Are you referring to this post?

http://www.newton.dep.anl.gov/askasci/phy99/phy99372.htm

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:

http://math.ucr.edu/home/baez/physics/Quantum/casimir.html. 

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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