It's known that a neutrino can spontaneously change into another type (between tau, muon, and electron varities)... and it's been demonstrated that a neutrino has mass, however the last time I look at a table of their masses... I noticed they have different masses. How is gaining and losing mass not a violation of mass conservation if mass is gained-obviously if mass is lost it was converted to energy; but what mechanism would allow for a gain of mass while changing types?

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Fafalone
http://www.scienceforums.net

neutrino oscillation exists because the mass eigenstates are not the same as the flavour eigenstates. if you prepared a neutrino in a pure mass eigenstate, it would stay with that mass. but since neutrinos interact through the weak force, it is much easier to find neutrinos in a flavour eigenstate. these neutrinos don t have a definite mass, they actually have a superposition of masses.

so you can measure several different mass eigenstates. conservation of mass/energy is not violated, any more so than it would be if you measured the energy of an electron in a superposition of 1s and 2s states.