John Mather & COBE

In the early 1970s a young NASA scientist had a crazy idea to build a strange-looking microwave satellite to test the Big Bang theory. After much stress and many false starts, his satellite finally launched in 1989 and by 1990 found nearly irrefutable evidence to support the big bang theory.

Until fairly recently very little was known about the origin of the universe. One theory, called the big bang, stated in the simplest of terms that, long ago, something happened and about a billion years later stars and galaxies appeared. John Mather helped fill in the pieces. The satellite mission he led was COBE, the Cosmic Background Explorer.

As early as 1974, Mather was determined to build a satellite that could find evidence for the big bang and how stars and galaxies formed. The big bang theory grew out of Einstein's theory of general relativity and was developed by a Jesuit priest named Georges Lemaitre and others in the 1920s.

The first striking evidence for the big bang came in 1963-1965 when Arno Penzias and Robert Wilson of Bell Laboratories stumbled upon some annoying microwave static interfering with their radio experiment. That interference, responsible for a sizable amount of static seen on your television set, turned out to be remnant radiation from the birth of the universe 13.8 billion years ago. Penzias and Wilson won the Nobel Prize in 1978 for this discovery.

Mather and Smoot greatly advanced the field by precisely measuring the temperature and spectrum of this cosmic microwave background, the afterglow of the big bang that has cooled considerably but still lingers with us today. If our eyes could detect microwaves, we'd see the entire sky bathed in this light.

The temperature they measured was 2.725 +/- 0.001 Kelvin, or about a minus 455 degrees Fahrenheit. More important, Mather and Smoot found slight temperature fluctuations within this near uniform light, which Stephen Hawking, independent of the COBE team, called "the most important discovery of the century, if not of all time."

Why the hyperbole? The temperature variations (about 10 parts per million) make life possible. Without them, no stars or galaxies or planets would have formed. These variations---a little more heat here, a little less there---pointed to density differences, regions with a little more matter and a little less matter. Through gravity over the course of billions of years, in a cosmic take on the rich get richer, those denser and warmer pockets attracted more matter and heat, which ultimately gave rise to the stars, galaxies and hierarchal structure we see today.

The simplest model of the big bang cannot explain why stars formed; but the tweaked model that Mather and Smoot found evidence for, can explain it.

When Mather presented a chart of the first nine minutes of COBE data at the 1990 meeting of the American Astronomical Society in Washington, he received a standing ovation. Scientists saw instantly how well the COBE data matched the temperature map predicted by theory. Rarely in science is a match between observation and theory so precise. The moment still gives Mather goose bumps today, he said.