In the dark - What is the universe made of?
Date: Sunday, April 10, 2011 @ 22:40:51 GMT
Topic: Science

By Alexandra Witze (Science News), April 23rd, 2011; Vol.179 #9 (p. 24)

In ancient times, listing the ingredients of the universe was simple: earth, air, fire and water. Today, scientists know that naming all of that, plus everything else familiar in everyday life, leaves out 95 percent of the cosmos’s contents.

From the atoms that make up an astronomer, to the glass and steel of a telescope, to the hot plasma of the stars above — all ordinary stuff accounts for less than 5 percent of the mass and energy in the universe. “All the visible world that we see around us is just the tip of the iceberg,” says Joshua Frieman, an astrophysicist at the University of Chicago and the Fermi National Accelerator Laboratory in Batavia, Ill.

The rest is, quite literally, dark. Nearly one-quarter of the universe’s composition is as-yet-unidentified material called dark matter. The remaining 70 percent or so is a mysterious entity — known as dark energy — that pervades all of space, pushing it apart at an ever-faster rate...

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