Neutrinos are the phantoms of the subatomic world. They seem to have no mass, may travel at the speed of light and are virtually impossible to detect. According to the standard theories of physics, these exotic particles are produced by various nuclear reactions. Quadrillions of neutrinos from the sun bombard the earth every second, yet most of them pass right through the planet without causing so much as a ripple.
Since 1968 scientists have been monitoring huge detectors for signs of these fleeting visitors from the sun. But so far, the results have been both disappointing and intriguing: the experiments have...