Physics prize takes another tour de force.

When a trio of scientists in the 1960s achieved one of the great quests of modern physics, none of their colleagues believed they were right. Calculations based on their theory--which united two fundamental forces of nature, the electromagnetic and weak forces--generated absurd answers.

Now a pair of Dutch researchers has won the 1999 Nobel Prize in Physics for finding a way to sidestep the absurdities, which led to tests and acceptance of the so-called electroweak theory.

Gerardus `t Hooft of the University of Utrecht in the Netherlands and Martinus J.G. Veltman, now retired from the University of Michigan in Ann Arbor, invented a calculation technique that made possible ultraprecise predictions of real-world quantities based on the electroweak theory. Their tool, known as dimensional regularization and first described in 1971, also applies to similar theories that describe other forces.

Armed with this new mathematical capability, physicists went on to construct the so-called standard model of particle physics, a sweeping theory that explains all known particles and their interactions with unprecedented success.

"This work [`t Hooft and Veltman] did together was the key that unlocked the standard model," says Helen R. Quinn of Stanford (Calif.) Linear Accelerator Center.

"It was a watershed. It was a very important development," says Sheldon L. Glashow of Harvard University, a co-developer of the electroweak theory. He, the late Abdus Salam, and Steven Weinberg of the University of Texas at Austin won the 1979 physics Nobel for their work, which explains the behavior of the force responsible for nuclear decay.

Absurdities had also cropped up in the 1940s, when efforts to reconcile the theories of electromagnetism and quantum mechanics generated unacceptable, infinite values for properties such as charge and mass of the electron.

Richard P. Feynman, Julian Schwinger, and Sin-Itiro Tomonaga figured out a way to make the infinite values cancel out by means of a process called renormalization. In essence, the trio proposed that clouds of evanescent virtual particles obscure the properties of every real particle. They received the 1965 Nobel Prize in Physics for that achievement.

`t Hooft and Veltman did much more than retrace those steps. The electroweak theory is a different, more complex beast. The fields it describes involve more elaborate symmetry than is present in electromagnetic fields. As a result, physicists have to worry about the order in which certain transformations of the fields take place.

The Dutch method annihilated infinities there, too. It made meaningful calculations possible as it extended the notion of particle clouds to the Z and W particles of electroweak theory.

Using this method, physicists have accurately estimated properties of elusive particles, such as the top quark, prior to discovery (SN: 7/1/95, p. 10). Such estimates enable scientists to predict the correct energy ranges for accelerator experiments.

Researchers still use the 18-year-old method to hone estimates for the final unfound particle of the standard model, the Higgs boson (SN: 6/19/99, p. 399). Physicists believe that it confers mass on other fundamental particles.

The method also helps physicists construct so-called grand unified theories, which attempt to unify the electroweak force with the strong force that binds particles within the nucleus. Attempts to unify gravity and quantum mechanics also generate infinite values, but taming them requires a leap beyond what `t Hooft and Veltman have done, physicists say.

That they should win the prize comes as no surprise to particle physicists. In discussions before the announcement, "those were the names we were all saying," says Quinn. Weinberg adds, "I've hoped for [`t Hooft and Veltman to win] this prize for some time."