Sit quietly, and count off 10 seconds to yourself. Roughly 200 trillion neutrinos from the sun, from cosmic rays, and from distant supernovas have just passed through you, but you'd never know it. Neutrinos are the ghostliest of subatomic particles. They have no electrical charge, so they're not subject to electromagnetic forces. They're immune to the strong nuclear force, which binds atomic nuclei together. In fact, you could shoot your average neutrino through a light-year's worth of lead bricks before anything would happen to it. These few interactions are a result of the weak nuclear forceÜa wimpy excuse for a fundamental force that causes neutrons to turn into protons via a process called beta decay, and whose effective range is less than the diameter of the decaying neutron. And until recently, everybody thought neutrinos were massless, like photons of light. For the entire story, click here. For Text Only version click here.