Saturday, February 22, 2014

What is Dark Energy?

by Nola Taylor Redd, SPACE.com Contributor | May 01, 2013
The galaxy cluster Abell 1689 is famous for the way it bends light in a phenomenon called gravitational lensing. A new study of the cluster is revealing secrets about how dark energy shapes the universe. Full story.
A mysterious quantity known as dark energy makes up nearly three-fourths of the universe, yet scientists are unsure not only what it is but how it operates. How, then, can they know this strange source exists?

The expanding universe
In 1929, American astronomer Edwin Hubble studied exploding stars known as supernovae to determine that the universe is expanding. Since then, scientists have sought to determine just how fast. It seemed obvious that gravity, the force which draws everything together, would put the brakes on the spreading cosmos, so the question many asked was, just how much was the expansion slowing?........In the 1990s, two independent teams of astrophysicists again turned their eyes to distant supernovae to calculate the deceleration. To their surprise, they found that the expansion of the universe wasn't slowing down, it was speeding up! Something must be counteracting gravity, something which the scientists dubbed "dark energy."......To Read More....

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