While it’s relatively easy to locate galaxies in two dimensions—simply spread a picture of the night sky across a flat surface—finding their distance from Earth required an analysis of each individual galaxy’s light spectrum. At New Mexico’s Apache Point Observatory each night, scientists would focus the Sloan Foundation 2.5-meter telescope on a specific spot of sky. To prevent light from the Milky Way from interfering, they covered the view with an aluminum plate about 1 meter across. The plate contained about 1,000 holes, each drilled at the precise two-dimensional location of a galaxy. Optical fibers carried light from those holes to a spectrograph, a machine that analyzed the light to find out how fast each galaxy is moving away from us—and thus how far away it is. In a given night, the team went through about five plates and pinpointed thousands of galaxies.