Faster Than The Speed Of Light

When I was growing up in Los Alamos, there was a nuclear reactor under this bridge.

In 1964, Los Alamos Scientific Laboratory (as it was called at the time) opened up for a week to families of employees. I had the opportunity to look through leaded glass down into the reactor core, and see the blue glow of Cherenkov Radiation. It is caused by particles travelling faster than the speed of light in water – the light equivalent of a sonic boom.

A sonic boom occurs when an object reaches the speed of sound in the atmosphere, and sound waves pile up in front of the object. Similarly, the speed of light in water is 25% less than the speed of light in a vacuum, and particles coming out of the fission reaction travel “faster than the speed of light” in water. The light waves pile up in front of the particle and create a blue glow.