The Nobel Foundations judging committees have made their annual selections. Four leading scientists will get their laurels--and a bonus of 7,900,000 Swedish crowns-- at the prize awarding ceremony on December 11, 1999. Three of the winners have published accounts of their work in the pages of Scientific American.
Here are sketches of the 1999 Nobelists and their work in physics,chemistry and medicine.
Since the 19th century, mathematicians have been laying a groundwork of theories that attempt to unify the symmetry of all physical forces. The saga began with James Clerk Maxwell's demonstration in the 1860s that electricity and magnetism are two aspects of a single electromagnetic force. And a string of Nobels have marked new developments in the story over the years.
The most recent benchmark is the award of the 1999 Nobel Prize for Physics to Gerardus 't Hooft of the University of Utrecht and Martinus Veltman, formerly of the University of Michigan and now retired, for having placed particle physics theory on a firmer mathematical foundation. According to the Nobel citation, the physicists' particular contribution was showing how particle theory may be used for precise calculations of physical quantities. Experiments at accelerator laboratories in Europe and the United States have recently confirmed many of their calculated results.
The work of 't Hooft and Veltman is the latest mathematical triumph in the search for a unified theory. Earlier in this century, quantum mechanics was combined with special relativity, resulting in quantum field theory. But while this theory successfully explained many phenomena, such as how particles could be created or annihilated or how unstable particles decay, it seemed to predict, nonsensically, that the likelihood for certain interactions could be infinitely large.
The problem was solved in the 1940s by Richard Feynman, Julian Schwinger and Sin-Itiro Tomonaga when they redefined the mass and charge of the electron. Their new theory, quantum electrodynamics (QED), won them the Nobel in 1965. The theory proved to be extremely precise and became the prototype for the electroweak theory, which draws the electromagnetic and weak nuclear forces into a single model, and won the 1979 Nobel for Sheldon L. Glashow, Abdus Salam and Steven Weinberg. This theory predicted the new particles W and Z, which were later detected in 1983 at the European CERN accelerator laboratory in Geneva--earning the 1984 Nobel Prize for Carlo Rubbia and Simon van der Meer.
Unfortunately, the electroweak model suffered from the same problems in prediction as the quantum field theory. This time, 't Hooft and Veltman overcame the difficulty through a "renormalization" comparable to Feynman's. Veltman was determined to crack the problem. And, unlike Feynman, he could use computers. In spring 1969 Veltman was joined in his efforts by a 22-year-old pupil, 't Hooft. In 1971, 't Hooft published two articles that represented an important breakthrough. With the help of a computer program developed by Veltman, the results were verified, and together the two investigators worked out a calculation method.
An essential ingredient in their scheme was the existence of another particle, called the Higgs boson. Its role is to confer mass upon many of the known particles. It is interactions between the Higgs boson and the various force-carrying particles that make the W and Z bosons (carriers of the weak force) so massive (with masses of 80 and 91 GeV, respectively), but the photon (carrier of the electromagnetic force) massless.With Veltmans and 't Hooft's theoretical machinery in hand, physicists could more reliably estimate the masses of the W and Z, as well as produce at least a crude guide to the likely mass of the top quark. The W, Z and top quark were subsequently created and detected in high-energy collision experiments. The elusive Higgs boson is now itself an important quarry. Whether it turns up as predicted waits to be seen. The only accelerator powerful enough to detect it will be CERN's Large Hadron Collider, which is being constructed in Geneva and is due for completion in 2005.