I’m assuming many of you will know what a sonic boom is, if you travel fast enough through a medium sound waves will compress in front of you and produce a sonic boom. Of course, this only happens if you are traveling at greater than the speed of sound in a given medium. Cherenkov Radiation can be described as the light equivalent of the sonic boom. So here’s (a simplified version of) what happens. Nothing can travel at speeds greater than c, the speed of light in a vacuum, but light in a medium will travel slower than c and in that sense a particle could travel faster than light through that medium, and when a charged particle travels through a medium at a speed greater than light travels through that medium it excites nearby molecules, which in turn emit light. Doing this requires lots of energy, which is why it’s commonly seen in the cooling tanks of nuclear reactors.