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

by Richard Panek

In 1976, the same year that Rubin and colleagues published the paper on the Rubin-Ford effect, a team led by Richard Muller and George Smoot at LBNL had taken a suggestion by Peebles in Physical Cosmology and, planting a Dicke radiometer aboard a U-2 plane, tried to measure the motion of our galaxy against the cosmic microwave background to determine whether the universe as a whole rotates. What they discovered instead was that our galaxy seemed to be racing through space at nearly 400 miles per second. Smoot made the announcement in April 1977 at an American Physical Society meeting during time that Peebles had yielded to him from his own talk. The phenomenon “is a real dilemma for theorists,” Peebles said, and Smoot suspected that the two of them were the only physicists in the room who understood the implications: For the universe to contain such local volatility yet still appear homogeneous and isotropic on a large scale, that scale was going to have to be much larger than anyone had ever imagined.