COBE

StarDate: November 18, 2009

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Our universe is filled with the afterglow of its own creation. Special detectors see the afterglow, which corresponds to a temperature of only a few degrees above absolute zero, as a microwave "haze" that fills the universe.

A satellite that was launched 20 years ago today found tiny fluctuations in the glow. These fluctuations represent the "seeds" from which all the stars and galaxies in the universe grew. The discovery earned two of the project's scientists the 2006 Nobel Prize for physics.

The leading theory of how the universe was born is the Big Bang -- an instant of creation for all matter and energy, space and time.

Big Bang theory says the early universe was incredibly hot and dense. As it expanded, it cooled. We should still be able to see the energy produced by that early period, though, as a microwave glow filling the universe. Scientists discovered that glow in 1964.

But it was hard to explain how a smooth, evenly spread universe could give rise to the "lumpy" universe we see today -- a universe filled with galaxies.

The Cosmic Background Explorer found that the temperature of the afterglow varies by only about one ten-thousandth of a degree. But that tiny difference represents the structure of the early universe -- filaments of gas spanning millions of light-years. The gravity of these filaments caused them to split apart and collapse, forming stars and galaxies -- in other words, the universe we see today.

Script by Damond Benningfield, Copyright 2009

For more skywatching tips, astronomy news, and much more, read StarDate magazine.

The one constant in the Universe: StarDate magazine

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