One neutrino, two neutrinos...

摘要

Physicists are willing to tolerate a certain amount of weirdness from elementary particles, but solar neutrinos have really been pushing their luck. For a start, there are far too few of them. They are produced by the nuclear reactions that power the sun, but only a third as many of the particles seem to reach earth as theory demands. On top of that, the number of those that eventually appear seems to ebb and flow as sunspot activity waxes and wanes. This is odd, as neutrinos are produced in the sun's core, while sunspots (patches of gas that are slightly cooler than their surroundings) appear some 750,000km (470,000 miles) away at its surface.