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Does Cerenkov radiation travel faster than light?

I have always heard that nothing travels faster then the speed of light, but I recently read an article on Cerenkov Radiation, which states that it does travel faster then light.

Nothing can travel faster than the speed at which light travels *in a vacuum*. But, as explained here, it's possible to slow light down in a medium other than vacuum. In such a medium, it's possible to have a source of light that travels faster than light does *in that medium*. When this happens, you get the equivalent of a sonic boom for light: Cerenkov Radiation. You can read more about it here.

June 2004, Christopher Springob (more by Christopher Springob) (Like this Answer)

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