How can a neutrino be detected if it has not mass and does not interact with normal matter?

The existence of neutrinos was first suggested in the 1930's because some reactions didn't produce as many particles as they should have. Neutrino means "little neutral one". They haven't been detected directly because they only interact with the weak nuclear force. But scientists have detected neutrinos through a roundabout way.

A neutrino can only be detected when it interacts with matter we can can observe. Because it interacts so little, a neutrino would have to travel through a block of lead a light-year long before it would strike an atom and be detected. A light-year of lead is kind of hard to come up with so scientists used a different plan: instead of making sure they found one neutrino, they studied a source that made a lot of neutrinos and didn't use as much lead. Using this theory, scientists detected the neutrino through its collisions with the lead.


Submitted by Marc (Canada)
(October 24, 1997)


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