QotD: The missing universe

Fritz Zwicky of Caltech noted in 1933 that large clusters of galaxies don't contain enough visible matter to keep themselves from flying apart. By the 1980s, it had become apparent that individual galaxies don't contain enough visible matter to hold their stars. This triggered the searches for "dark energy" and "dark matter," postulated cosmic forces. Many projects are seeking evidence of dark energy and dark matter, including the Korean Invisible Mass Search, a set of detectors buried inside Jeombong Mountain. The latest estimate from NASA's Microwave Anisotropy Probe suggests that space is 4 percent ordinary matter, 22 percent dark matter and 74 percent dark energy. What might dark energy and dark matter be? No one has the slightest idea. We can't locate 96 percent of the universe. But trust us, we're experts!

Gregg Easterbrook, "TMQ: State of the Nation", ESPN Page 2, 2007-11-12