The universe is seriously underweight, and most of the stuff in it is so-called vacuum energy—not properly stuff at all. That's the conclusion emerging from the largest survey of galaxies to date.
At a meeting of the American Astronomical Society in Rochester, N.Y., this week, a team of British, Australian, and U.S. astronomers announced that it has now surveyed 100,000 galaxies. The researchers' analysis shows that the density of all visible and dark matter in the cosmos is only a third of what would be required to account for a so-called flat universe. Yet earlier studies indicated that we do in fact live in a flat universe, one with just enough density to expand forever (SN: 12/19/98, p. 392: http://www.sciencenews.org/sn_arc98/12_19_98/Bob1.ht