The SLAC Accelerator: Two Miles of Physics Under a Suburb

Somewhere beneath the Menlo Park neighborhood you are near or passing through is a two-mile-long scientific instrument. It is the Stanford Linear Accelerator, completed in nineteen sixty-two, and it is buried under the Stanford hills in a tunnel that runs from Interstate Two Eighty to Sand Hill Road. By some measurements it is the longest building in the United States. From the road, it is invisible.

The facility was designed to accelerate electrons to near the speed of light and smash them into targets, producing particle showers that physicists could read for information about the structure of matter. The Stanford University Libraries and the California History journal document the facility's research program. Experiments conducted here in the late nineteen sixties contributed to the experimental evidence for quarks, the subatomic particles that comprise protons and neutrons, according to those sources.

The scale of the machine is hard to visualize from the surface. Two miles of precision-engineered accelerating cavities, aligned to tolerances measured in fractions of a millimeter, under a residential neighborhood with single-family houses and cul-de-sacs above. The facility is now called SLAC National Accelerator Laboratory and operates under the United States Department of Energy. It is still doing science.

The particle physics that came out of this tube changed what we know about what everything is made of. The neighborhood above it does not appear to know it is there.