system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:why do radio active nuclear facilities cores glow blue?
gpt
The blue glow is something known as *Cherenkov radiation,* first detected by Soviet physicist Pavel Cherenkov in the early 20th century.

This radiation occurs when a charged particle passes through a medium like water or air at a velocity greater than that at which light passes through said medium.

This velocity is slower than the "speed of light" that is the ultimate speed limit of the universe, so the presence of Cherenkov radiation is consistent with, and predicted by, physical law.