Particles travelling faster than the speed of light?

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hi, I just heard about particles traveling faster than speed of light and somthing about cerenkov radiation. Is it possible for some subatomical particles to overcome speed of light? if yes, doesn't it contradicts einsteins relativity? I'm pretty confused please help.
 
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Particles going faster than light in vacuum do not exist. Overcoming speed of light means a violation of causality (even if possible formulations of relativity in this case exist and the corresponding field theories describe the so called tachyonic excitations, but these imply a vacuum instability and then they are never observed in nature).

Cerenkov radiation appears when a particle moves faster than the speed of light in the given medium (not vacuum). In a medium the speed of light is given by v=c/n being n the refraction index of the medium itself and so v is smaller than c. A particle can travel faster than v in the medium producing electromagnetic radiation much in the same way of the sonic bang of an aircraft moving faster than the sound speed in air.

Jon
 
Lester said:
Particles going faster than light in vacuum do not exist. Overcoming speed of light means a violation of causality (even if possible formulations of relativity in this case exist and the corresponding field theories describe the so called tachyonic excitations, but these imply a vacuum instability and then they are never observed in nature).

Cerenkov radiation appears when a particle moves faster than the speed of light in the given medium (not vacuum). In a medium the speed of light is given by v=c/n being n the refraction index of the medium itself and so v is smaller than c. A particle can travel faster than v in the medium producing electromagnetic radiation much in the same way of the sonic bang of an aircraft moving faster than the sound speed in air.

Jon

Thanks a lot! Now I am happy again!
 
And what about tachyons? Do they "exist"?
 
Only in the minds of some theorists.
 

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