Skip to content Skip to navigation


The distinctive blue hue from Cherenkov radiation produced by a nuclear reactor's core.

An Optical Sonic Boom -- the Cherenkov Radiation

While nothing can outrun light in the vacuum of space, certain particles can edge out light in a short race inside water. Because light only travels at roughly 75% of its "top speed" inside water, it is possible for highly energetic particles to outrun light waves. In the case of a charged particle such as an electron, this results in a distinctive blue flash analogous to the sonic boom generated by a fighter jet when it exceeds the speed of sound. This distinctive blue flash is known as Cherenkov radiation.

Image credits:

Argonne National Laboratory

Rights information:

CC BY-SA 2.0