The water that surrounds the core of a nuclear reactor often emits a blue glow. That glow is produced by the Cherenkov (also, Cerenkov ) effect. This phenomenon was discovered in the 1930s by the Russian physicist Pavel Alexeyevich Cherenkov.

Cherenkov was born in the Voronezh region of Russia on July 15, 1904. He graduated from the Voronezh State University in 1928 and, in 1930, was appointed a senior scientific officer at the Lebedev Physical Institute in Moscow. It was at this institute that Cherenkov carried out the elaborate experiments that revealed the cause of the radiation that was eventually given his name.

The Cherenkov phenomenon can be observed when high-energy radiation passes through a transparent material, such as water. It had long been considered a form of luminescence, somewhat similar to the light emitted by certain dyes when they are exposed to light. By means of an ingenious series of...