Ghosts through the earth
On a 6,800-acre campus 40 miles west of Chicago, a herd of American bison (Bison bison) lives on a restored prairie. Beneath their hooves, a particle accelerator complex prepares to send trillions of neutrinos on an 800-mile (1,300-kilometer) trip through the Earth's crust. This is Fermilab, and its primary project is the Deep Underground Neutrino Experiment, or DUNE. The path for these "ghost particles" begins in the Main Injector, a particle accelerator with a circumference of 3.3 kilometers. Protons are accelerated to 120 billion-electron-volts (GeV) before smashing into a graphite target. The collision produces a shower of other particles which then decay into the world's most intense beam of neutrinos.
The neutrinos travel in a straight line, no tunnel required, from Batavia, Illinois, to massive detectors located 1.5 kilometers underground at the Sanford Underground Research Facility in South Dakota. By studying how the neutrinos change their type—or "oscillate"—during their flight, scientists answer questions about the universe, such as why matter exists at all. The experiment requires incredible precision, tracking particles that interact so weakly they can pass through a light-year of lead without stopping. The detectors waiting in South Dakota are huge, containing 70,000 tons of liquid argon kept at a temperature of -300 degrees Fahrenheit.
Quarks and cathedrals
The bison herd has been a feature of Fermilab since 1969, when the lab's first director, Robert Wilson, brought them to the site. Wilson wanted the animals to show the American prairie frontier, connecting it to the scientific frontier being explored at the lab. The herd began with one bull and four cows and has been a permanent fixture ever since. Genetic testing confirmed the herd is composed of pure-bred bison, without any DNA introgression from domestic cattle.
Before focusing on neutrinos, Fermilab's Tevatron was the world's most powerful particle collider. It was a four-mile circumference ring that accelerated protons and antiprotons to energies of nearly 1 trillion-electron-volts (TeV). Using the Tevatron, physicists at Fermilab made two landmark discoveries that completed a major part of the Standard Model of particle physics. In 1977, a team led by Leon Lederman discovered the bottom quark. This discovery was followed on March 2, 1995, with the announcement of the top quark, the bottom quark's predicted partner and the final undiscovered quark.
Robert Wilson was also a sculptor and was determined that the laboratory should be an inspiring place. He heavily influenced the site's architecture, most notably the central 16-story administrative building, now named Wilson Hall. Its twin-towered, upward-sweeping design was inspired by the Beauvais Cathedral in France, conceived as a modern "cathedral of science".