universes would match his data. And one did. It was a universe that not only didn’t have enough matter to slow the expansion but had a mass density of negative 36 percent. It was a universe without matter. It was a universe that didn’t exist. “Lo and behold,” Riess told himself. Both teams had been operating under the assumption that the universe was full of matter and only matter. They knew some of it was dark, of course, but what was missing was still fundamentally matter. They had therefore assumed that only matter would be influencing the expansion of the universe.
