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

by Richard Panek

And the universe did seem to be homogeneous and isotropic. The discovery of the cosmic microwave background seventeen years earlier had satisfied most cosmologists that they now had the answer to the question of whether the universe was simple: Yes. On the largest scale it would look the same no matter where you were in it. And they had answered the question of how simple the universe was: Very. The cosmic microwave background was extremely smooth, just as theory had predicted. But assuming that something is the way it is—even if those assumptions turn out to be correct, as the Big Bang theory’s apparently were—is no substitute for understanding how it got that way. Why would a universe be, of all things a universe could be, simple—and not just simple, but so simple? On reflection, maybe the answer to the question of how simple the universe was shouldn’t have been the satisfying “Very” but a suspect “Too.” Now, however, cosmology had a possible answer to the question of how the universe became so simple.