The 4% Universe: Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality

by Richard Panek

The combination of Ford’s spectrograph and a significantly larger telescope would allow them to take their study of galaxies both deeper into the universe and farther along the arms of the spirals. In 1978 Ford and Rubin published the rotation curves for eight more galaxies: all flat. Once again radio astronomers were getting the same results. Mort Roberts kept pushing along a ring of hydrogen gas clouds that lay beyond the visible swirl of stars and gas. In 1975 Roberts and a collaborator found that even there, half the length of Andromeda beyond what previous generations had unthinkingly assumed was the galaxy in its entirety, the rotation wasn’t tapering off. It was essentially flat, as if even at this great distance the galaxy was still spinning at a seemingly suicidal rate. A 1978 survey using the same method found the same shape for the curves in twenty-two of twenty-five other galaxies: flat. Rubin had gotten her wish. The data spoke with one voice, and it spoke clearly: Galaxies were living fast but not dying young.