The Quark Hunters
Beneath the rolling hills just west of Stanford University is one of the longest, straightest structures in the world: a 3.2-kilometer (2-mile) linear accelerator. Founded in 1962, the SLAC National Accelerator Laboratory was built for a singular purpose: to accelerate electrons to 99.9999999% of the speed of light and smash them into targets to see what is inside.
In a series of experiments starting in 1968, a team from SLAC and MIT fired these high-energy electrons at protons and neutrons. The way the electrons scattered was unexpected. Instead of passing through or glancing off a uniform target, some ricocheted at sharp angles, revealing that the protons and neutrons were composed of hard, point-like objects. These objects were the quarks that physicists had theorized but never detected. For this direct proof of the quark model, Richard Taylor of SLAC and Jerome Friedman and Henry Kendall of MIT received the 1990 Nobel Prize in Physics. Research at SLAC has contributed to three other Nobel Prizes, including one for the 1974 discovery of a new type of quark called the "charm" quark.