A QUIRK, A QUARK AND A KEY DISCOVERY
Author: By David L. Chandler, Globe Staff
Date: Thursday, October 18, 1990
Page: 78
Section: METRO
"Three quarks for Muster Mark," says a character in James Joyce's enigmatic
novel "Finnegan's Wake." The obscure passage would be remembered only by the
most devoted Joyce scholars were it not for the Puckish wit of physicist
Murray Gell-Mann, who in the 1960s formulated a theory about the basic nature
of matter and borrowed the Joycean name for his invention.
When he came up with the idea of a building block of matter smaller than
the particles that make up atoms, he said later in an interview in Omni
magazine, "I thought it would be refreshing to use names based mostly on
jokes, because I wasn't sure any name I could give them would be applicable
permanently. If I had given them a pompous Greek name based on some property
we believe in today, they might in the future look antiquated."
"The real joke, of course, is that the name never meant anything in the
first place and so would never be obsolete," he said.
And so the most basic particle of matter known today, believed in by most
physicists and confirmed by a host of high-energy particle-beam experiments,
is known as the quark.
Although scientists did not recognize it for years, it is now clear that
the decisive moment when theory became fact -- when Gell-Mann's brainchild was
found to be a real, observable thing -- was in the series of experiments in
the late 1960s and early '70s for which three scientists, two of them from
MIT, were honored with Nobel Prizes yesterday.
Steven Weinberg of the University of Texas, a 1979 Nobel laureate in
physics, yesterday called the work of Henry Kendall, Jerome Friedman and
Richard Taylor a "landmark experiment" comparable to Lord Rutherford's work in
1911 proving the existence of the nucleus of the atom.
"This experiment served as a signpost toward the modern theory" of the
interactions among the basic building blocks of nature, Weinberg said.
In Rutherford's experiment, electrons were accelerated toward a thin film
of gold, and their motions after the collision were measured. The experiment
showed that matter was concentrated in tiny "targets" surrounded by vast empty
space. These targets were the first clear evidence of the atomic nucleus.
The work of Kendall, Friedman and Taylor extended this probing of the
nature of matter two levels deeper. Scientists in the intervening years had
determined that the nucleus was made up of smaller particles, called protons
and neutrons.
Some physicists unsuccessfully sought evidence of quarks, the components of
subatomic particles that Gell-Mann had postulated. Kendall, Friedman and
Taylor were not looking for quarks, but it was they who made the discovery.
Their work, like Rutherford's, involved smashing beams of subatomic
particles together and observing the resulting debris.
They found, much to their surprise, that the particles behaved as if there
were hard nuggets of matter within the space supposedly occupied by the
protons and neutrons. They concluded that these nuggets were the three quarks
that Gell-Mann had theorized would make up each of the subatomic particles.
The problem with the earlier experiments, it turned out, was that the
researchers had been looking for free-floating, separate quarks -- something
that is now believed to be impossible. Quarks, according to current theory,
are permanently bound in groups of three that form basic particles.
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