> But 16 years ago, Japanese researchers discovered that these ephemeral flecks did indeed have mass, and not only that - they changed from one form, or flavour

> But 16 years ago, Japanese researchers discovered that these ephemeral flecks did indeed have mass, and not only that - they changed from one form, or flavour, to another as they travelled. If the author changed "did indeed have mass, and not only that, they changed ..." to "did indeed have mass, and therefore they changed", it would more accurately represent the physics. A massless particle cannot change in flight, because it's traveling at the speed of light and therefore doesn't experience time. No time, no possibility of change. The real discovery sequence went like this: solar neutrinos were observed morphing from one neutrino type to another. On this basis it was realized that they experience time, and therefore were not traveling at the speed of light -- therefore they have mass. The linked article tries to describe a neutrino's mass, its velocity and its ability to change types as unrelated, independent things. But they're interdependent.