The universe, astronomers tell us, is expanding. But will it continue to do so forever, or does the universe have enough mass so that its own gravity will eventually slow it down and perhaps even make it collapse into a dense fireball? Because the mass of the universe can’t be measured directly, astronomers have been unable to choose among competing theoretical models. By 2001, though, astronomers may finally have an answer to what may be the ultimate question, thanks to a $70 million mission-- approved by nasa in April--that will map the background radiation left over from the Big Bang in unprecedented detail.
Astronomers got their first close look at the cosmic microwave background in 1992 from data collected by cobe, the Cosmic Background Explorer satellite. cobe revealed small temperature fluctuations in the microwave background. These arose, astronomers believe, as energy unleashed by the Big Bang dissipated, allowing freewheeling, high-energy ...
