Hark, Hark, a Quark--Maybe

They have been sought in the showers of particles from space, in the depths of the sea and even in the stained glass windows of ancient cathedrals. Yet in more than a decade of searching, physicists have been unable to find quarks, the elusive particles that many believe to be the basic building blocks of matter (TIME, May 19, 1967). Indeed, even Nobel Laureate Murray Gell-Mann, of Caltech, who hypothesized quarks in 1962, had doubts that their existence could ever really be confirmed.

Now, suddenly, the hunt for these tiny particles has taken a dramatic turn. At the American Physical Society's annual meeting in Washington, D.C., this week, Physicist William Fairbank and his colleagues at Stanford University are expected to reveal the results of an experiment that could demonstrate the existence of quarks. Said Columbia University's Gerald Feinberg: "If it's true --and I'm skeptical--it would force us to alter our ideas quite radically."

Heeding traditional scientific protocol, Fairbank last week was not talking publicly in advance of the scheduled publication of his results in Physical Review Letters. But the basic operation of his quark-hunting experiment is known. As their tool, Fairbank and two young colleagues--Arthur Hebard, now at Bell Laboratories, and George LaRue--devised an updated version of the classical "oil drop" experiment, first used by Robert Millikan in 1910 to measure the charge on a single electron. Instead of oil drops, the Fairbank team relied on tiny spheres of niobium, a metal that becomes a superconductor when it is chilled to near absolute zero. When the sphere is levitated in a strong magnetic field, and virtually stripped of electrical charge, any charge that remains--even the minuscule charge of a single electron or, more significantly, a fraction of that charge--can be detected.

Tiny Spheres. Physicists say the Stanford team measured on their tiny spheres positive and negative charges equal to a third of an electron's normal charge. Such a result fits in neatly with the original predicted charges for quarks, which theoreticians said should be either one-third or two-thirds of those of electrons. Whether the fractional charges measured by the Stanford scientists actually indicate the presence of quarks remains to be seen. But if quarks have indeed been found, their discovery will provide stunning verification of Gell-Mann's brilliant theory about the ultimate structure of matter.

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