PHYSICISTS WERE UNDERSTANDABLY overjoyed in 1994 when they discovered the top quark. At last, after 17 years of searching, they had found the sixth--and, according to the theorists, the last--of matter's tiniest, most fundamental building blocks. The most troublesome loose end in the so-called Standard Model of particle physics had been tidied up.
Or so they thought. According to a report in the current Science, the same people who discovered the top quark may have inadvertently made a much more revolutionary discovery. Contrary to what physicists have believed for the past 30 years, quarks may not be the most basic units...