When Vera Rubin was 14, she fashioned a home-made telescope out of a cardboard tube and began scanning the night sky. Her early enthusiasm paid off in 1950 when, as a 22-year-old mother of a month-old baby, she hit the headlines of the Washington Post with a provocative theory that the universe is rotating. Her later observations of orbiting stars on the outskirts of galaxies helped spark a remarkable realization: the vast majority of matter in the universe is invisible, or 'dark'. Now 73, she continues her cosmic exploration at the Carnegie Institution of Washington, D.C. She shared some recent insights with associate editor Josie Glausiusz.
How did you first realize the universe is filled with invisible matter? In a spiral galaxy like our own, a couple hundred billion stars orbit around the center. Spirals appear to thin out toward the edges, so the gravitational pull on the outer stars ...
