Satellite Answers Big Questions, Poses More
(From the May/June 2003 issue of StarDate magazine)
The age of the universe. Its evolution. What it’s made of. Astronomers have been puzzling over these questions, and getting closer to the answers, for decades. Now, they are calling new data from a NASA satellite “stunning” — and suggesting that these questions have been definitively answered. “This is a true turning point for cosmology,” said Anne Kinney, NASA’s director for astronomy and physics.
“This” is a flood of data from the Wilkinson Microwave Anisotropy Probe (WMAP), which spent a year making a detailed map of the sky. It specifically looked at radiation left over from the Big Bang, called the “cosmic microwave background” (CMB). Temperature differences (or “anisotropies”) make patterns in the CMB that mark the seeds of what later grew into clusters of galaxies.
Theories about the evolution of the universe make specific predictions of what these patterns would look like. The WMAP team compared their satellite’s “baby picture” of the universe to various predictions — and found a match.
Age of the universe? 13.7 billion years. Evolution? Well, here’s part of it: The first stars started shining only 200 million years after the Big Bang — earlier than thought. And what in the world is the universe made of? Ordinary atoms make up only about four percent. Dark matter, which probably is ordinary matter that we just can’t see, makes up about 23 percent. The rest — 73 percent — is an enigmatic “dark energy.”
The WMAP results support the Big Bang theory of the universe’s birth, as well as inflation theory (which states that the universe expanded exponentially for a brief period soon after its birth).
The work of astronomers is not over yet. Why did stars begin to shine so early on? And just where did this “dark energy” come from? As one astronomer used to say, “Time to make the doughnuts.” — Rebecca Johnson
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