Science: Bring It Back Alive

In the three days that the cosmic-ray detector hung 130,000 ft. over Sioux City, Iowa, it marked the passage of 75 heavy atomic particles hurtling in from outer space. One of the particles was distinctly different from the others. Its telltale track through a sandwich of three dozen sheets of plastic, nuclear emulsion and photographic film looked unfamiliar to cosmic-ray researchers. Last week, nearly two years after their equipment was brought back to earth, scientists from the universities of California and Houston finally offered an explanation. The unexpected particle, they said, was almost...