STOCKHOLM, Sweden, Oct. 5 -- Three American scientists won the 2004 Nobel physics prize today for a "colorful" discovery in the world of quarks, the building blocks of the atomic nucleus. The work, which involves the dominant, or "color," force between quarks, is key to several major problems in particle physics and beyond. David Gross, a professor at the Kavli Institute for Theoretical Physics at the University of California at Santa Barbara; H. David Politzer, a professor at the Department of Physics of the California Institute of Technology; and Frank Wilczek, a physics professor at the Massachsuetts Institute of Technology; will share the prize of about $1.3 million. NOBEL TRIO: Winners of this year's Nobel Prize in Physics (Photos courtesy Royal Swedish Academy of Sciences) The three won "for the discovery of asymptotic freedom in the theory of the strong interaction," according to the Royal Swedish Academy of Sciences. Asymptotic freedom is a phenomenon whereby quarks behave as free particles when they are close together, but become more strongly attracted to each other as the distance between them increases. This theory forms the key to the interpretation of almost all experimental studies involving modern particle accelerators. "Thanks to their discovery, David Gross, David Politzer and Frank Wilczek have brought physics one step closer to fulfilling a grand dream, to formulate a unified theory comprising gravity as well -- a theory for everything," the Academy said in announcing the prize. MIT said Wilczek's earliest work, done with Gross at Princeton in the 1970s, concerned the change of fundamental couplings with energy. This work led to the discovery of asymptotic freedom, which makes it possible to understand the behavior of matter under extreme conditions, such as occurred in the earliest moments of the Big Bang. Also, it permits the construction of unified models of particle interactions, which have concrete predictive power. The Academy said, "What this year's laureates discovered was something that, at first sight, seemed completely contradictory. The interpretation of their mathematical result was that the closer the quarks are to each other, the weaker is the 'color charge.' "When the quarks are really close to each other, the force is so weak that they behave almost as free particles. The converse is true when the quarks move apart: The force becomes stronger when the distance increases. This property may be compared to a rubber band. The more the band is stretched, the stronger the force." The Academy said this discovery was expressed in 1973 in an "elegant mathematical framework" that led to a completely new theory, quantum chromodynamics (QCD). "This theory was an important contribution to the Standard Model, the theory that describes all physics connected with the electromagnetic force (which acts between charged particles), the weak force (which is important for the sun's energy production) and the strong force (which acts between quarks). With the aid of QCD, physicists can at last explain why quarks only behave as free particles at extremely high energies. In the proton and the neutron, they always occur in triplets," the Academy said. For more information, visit: nobelprize.org