Did You Ever Wonder: Saul PerlmutterDid You Ever Wonder Web SiteSaul Perlmutter
The Supernova Cosmology Project

In the 1920s astronomers learned that the universe is expanding, a picture that has come to be known as the "Big Bang." For most of the century, scientists thought that gravity was slowing this expansion, and that someday the universe might even recollapse in a Big Crunch.

The best way to measure the expansion of the universe is to compare the brightness and redshift of far-off exploding stars of the kind called type Ia supernovae -- to use them as "standard candles." Berkeley Lab researchers in the international Supernova Cosmology Project, based here, devised a method of finding very distant supernovae "by the batch" with only a few days of telescope time each year.

By the end of 1997, the Supernova Cosmology Project had found scores of these special supernovae and measured the expansion of the universe carefully enough to realize that the universe was not slowing fast enough to ever stop -- it would go on expanding forever.

At the beginning of 1998, the Supernova Cosmology Project, along with their colleagues in the High-Z Supernova Search Team based in Australia, announced that expansion is not slowing at all -- in fact, the universe is accelerating! (For more information visit www.lbl.gov/supernova, or for technical details, see panisse.lbl.gov.)

What property of empty space overcomes the attraction of gravity and causes galaxies to fly apart ever faster? No one knows. Cosmologists call it the "dark energy," and it fills the cosmos -- in fact, it seems that most of the stuff in the universe may be dark energy, whatever it is.

One of science's biggest challenges in the twenty-first century is to learn what dark energy accelerates the universe.

Did You Ever Wonder Web Site
Ernest Orlando Lawrence Berkeley National Laboratory