COBE
 This map of the universe shows tiny variations in temperature a few hundred thousand years after the Big Bang. These variations allowed matter to begin clumping together to form the first stars and galaxies. The map was compiled from data from COBE, a satellite launched in 1989. It measured variations in the cosmic microwave background, the faint "afterglow" of the Big Bang, which fills the universe. The differences in temperature are only a few thousandths of a degree, but are exagerrated in this map, in which the warmest temperatures are in red. [NASA]
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
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