TO PERPLEXED LAYMEN, THE CELEbrated Nobel Prizes often seem to point down obscure pathways of science, focusing on narrow, highly specialized research that few nonscientists can understand or appreciate. Not this year. The $1 million 1995 prizes in physics, chemistry, economics, and medicine or physiology, announced in Stockholm last week, went to scientists who have wrestled with questions at once basic and easily grasped: What is the universe made of? How does DNA create complex life-forms? What made the hole in the ozone layer? And how do people decide how they spend and invest their money?
PARTICLE SLEUTHS When Wolfgang Pauli first proposed the existence of the neutrino in 1930, he labeled his hypothetical particle "a frightful thing." The neutrino would neatly explain a tiny energy imbalance in certain nuclear reactions, but it would also be so ethereal that the average neutrino could zip through a trillion-mile-thick chunk of lead without hitting a single atom. Since the particles would presumably sail undetected through any measuring device, Pauli lamented, his clever idea could never be proved correct.
"Never" turned out to be in around 25 years. It was in the mid-1950s that Frederick Reines and the late Clyde Cowan, then at Los Alamos, set out to find Pauli's impossible particle--the research that earned Reines, now at the University of California at Irvine, half of this year's prize. (Cowan was ineligible because Nobels are not awarded posthumously.)
Rather than try to detect one neutrino at a time, Reines and Cowan used a nuclear reactor that spewed out trillions of neutrinos every second. With so many particles, they reasoned, observed over a long enough period of time (it ended up being years), they should be able to measure at least a few neutrino impacts in their detector, a tank of chemical-tinged water.
The discovery of what the Nobel citation called one of "nature's most remarkable subatomic particles" tied up an important theoretical loose end and spawned a new field of neutrino physics. But by the early 1970s, it was also clear that the neutrino was only one element in an elegant organizational scheme, now known as the Standard Model, by which nature groups the subatomic particles.
All ordinary matter, physicists had learned, was made of four basic particles: electrons, neutrinos and two kinds of quarks. But there was another family of particles, plentiful in the early universe but now found almost exclusively in nuclear accelerators, that seemed to be divided into the same four types: the muon (a sort of heavy electron), the muon neutrino and two more quarks. And in 1976, Stanford University physicist Martin Perl announced he had found a third, even heavier electron, which he dubbed the tau--a discovery that earned him the other half of this year's physics Nobel. Perl's finding suggested that there might be a third family of particles, most of the other members of which were also found in the 1970s. Last spring, with the discovery of the top quark, the third family was finally, satisfyingly complete.