Physicists Win Nobel Prize for Quark Theory

Three American physicists shared the £760,000 Nobel prize for physics for calculating the bizarre properties of the ultimate fragments of matter. They provided the mathematics for a completely new theory, which in the last three decades, has helped scientists peer deeper into the atom and get closer to the mysteries of creation.

The arcane language of yesterday's citation - it talked of "the discovery of asymptotic freedom in the theory of strong interaction" - concealed the profound nature of the work that earned David Gross of the University of California, Santa Barbara, David Politzer of Caltech, Pasadena, and Frank Wilczek of Massachusetts Institute of Technology, the prize.

"They played a crucial role in explaining how atoms are built ... we now understand why the tiniest particles in the tiny nucleus of every atom stay permanently confined, apparently unable to escape their nuclear incarceration," said Graham Farmelo, an associate professor of physics at Northeastern University, Boston.

"They did this brilliantly by setting out the theory of the tiny particles' peculiar interactions: when they are squashed close together, they behave as if they are as free as they like, yet they are cruelly restrained by a confining force if they should try to escape."

The puzzle the three scientists set themselves involved the ultimate building blocks of matter. Although the Greeks coined the word, the reality of the atom was confirmed only in the last century or so. Then physicists showed the atom could be splintered into elementary particles and Einstein convinced the world that energy and matter were, in effect, the same thing.

By 1970, physicists were searching for theoretical particles called quarks. These strange beasts had mass, but no radius: a quark is just a one-dimensional point, but a bundle of quarks somehow added up to a proton, the nucleus of the hydrogen atom. The question was: what forces held them together, inside a proton that was itself one 10,0000th the radius of an atom?

The scientists came up with a theory called quantum chromodynamics which explains why quarks can only be found in strange conditions, such as atom-smashing machines which simulate the first instants of creation.

Quarks behave as if they are free of each other only at very short distances and very high energies. But within the proton they are held by something called the strong interaction.

"The quarks are running around independently of each other at very short distances," said Frank Close, a theoretical physicist at Oxford.

"As they start moving apart and try to escape, the force gets stronger and stronger and grabs them.

"It is as if they are in an ideal prison, where the prisoners are completely free but can never escape."