How to Measure the Absolute Value of Neutrinos

A neutrino is a mixture of different masses, and each of those masses flies through space differently. And it's that difference that causes them to change flavor to oscillate. We can only measure one neutrino at a time; we don't know what it was before. What we do is measure them statistically by making a huge number of neutrinos in the sun and then seeing how many disappear from their original identity.