The first use of a hydrogen bubble chamber to detect neutrinos, on November 13, 1970. A neutrino hit a proton in a hydrogen atom. The collision occurred at the point where three tracks emanate on the right of the photograph.
Neutrinos are a type of elementary particle that exist all across the universe. The word neutrino means a small neutral particle. Physicists study these particles, but they are hard to find because they have a very small chance of interacting with regular matter. (For example, they usually pass through the whole earth without touching any other particles). Neutrinos travel near the speed of light.