Gell-Mann chose the whimsical name of "quarks" for these constituents. This word appears in the phrase "three quarks for Muster Mark" in James Joyce's novel, Finnegan's Wake .
The revolutionary part of their idea was that they had to assign the quarks electric charges of 2/3 and -1/3 in units of the proton charge: such charges had never been observed. At first the quarks were regarded as mathematical fiction, but experiments have convinced physicists that quarks do exist.
The two lightest are called UP and DOWN.
The third quark is called STRANGE. That name had already
been associated with the K mesons because their
long lifetimes seemed a "strange" or
unexpected property. (K mesons contain strange quarks.)
CHARM,
the fourth quark type, was named on a whimsy. It was
discovered in 1974 at the
Stanford Linear Accelerator Center
in the particle they called
(psi) and simultaneously at
Brookhaven National Laboratory
in what they called "J".
The 
is a charm-anticharm
combination
(
).
The fifth and sixth quarks were originally called truth and beauty, but even physicists thought that was too cute. Now they are called TOP and BOTTOM (still t and b.)
The
BOTTOM quark,
in a bottom-antibottom
(
)
combination called Upsilon
(
),
was first observed at Fermi
National Laboratory in 1977.
The sixth flavor of quark,
TOP, is the most massive quark.
It is about 35,000 times more
massive than the up and down quarks that make up most of
the matter we see around us. On March 2, 1995
Fermi National Accelerator Laboratory
announced the discovery of the
top quark.
Of the six quarks predicted to exist by current
scientific theory the top quark was the last to be discovered.
Use your browser's "back" button or
go back to the
Standard Model Path.