Closing in on the Missing Matter T he ultimate destiny of our expanding universe depends on how much matter it contains and whether that will be enough to one day stop the expansion. When astronomers count up all the visible matter the stuff that gives off light the answer is clearly no.
Observations reveal that vast halos of invisible matter surround galaxies and galaxy clusters.
This dark matter adds up to about ten times more mass than the visible stars, gas, and dust seen in galaxies. And there may be more. The inflationary theory, if true, demands that this dark stuff makes up between 90 and 99 percent of the universe.