US scientists measure dark energy, show Einstein was right

December 17th, 2008 - 5:29 am ICT by IANS  

Washington, Dec 17 (DPA) A group of US scientists said Tuesday that they have used a new technique to confirm the existence of dark energy, a mysterious force believed to be responsible for the accelerating expansion of the universe.Their findings appear to verify that Albert Einstein’s Theory of General Relativity works on a huge scale and that dark energy is the so-called cosmological constant, a part of his theory in which empty space has energy.

Einstein’s theory says that gravity is caused by the interaction of space and time on an object and is the foundation of modern astrophysics.

Einstein later abandoned the cosmological constant, which he had added to the theory to account for a stable universe, as nonsensical. But as scientists discovered the universe was actually expanding at an accelerating rate, the idea has attracted renewed interest.

The astronomers used NASA’s Chandra X-ray Observatory to measure dark energy by looking at how galaxy clusters grow over time. They found that as dark energy has pushed out the boundaries of the universe, the formation of the clusters has slowed and they have become less dense.

Scientists first said a decade ago that not only was the universe expanding, but that it was expanding at an accelerating rate.

David Spergel, an astrophysicist at Princeton University, said that the results from the Chandra observatory agree with earlier findings and “suggest that Einstein is right”.

Earlier efforts to examine dark energy have involved observing supernovas, and Spergel said the new technique was similar to football referees looking at a play from different angles to make a call.

The corroboration of earlier results is key as scientists continue to test Einstein’s theory and determine the properties of dark matter with more advanced instruments.

“Putting all this data together gives us the strongest evidence yet that dark energy is the cosmological constant, or in other words, that ‘nothing weighs something’. A lot more testing is needed, but so far Einstein’s theory is looking as good as ever,” said Alexey Vikhlinin of the Smithsonian Astrophysical Observatory.

The data show the universe will likely continue to expand, but not rip apart as some have predicted, eventually pushing some nearby galaxies out of sight of Earth in tens of billions of years, Vikhlinin said.

But researchers cautioned that very little is known about dark energy beyond its existence and its results. They note that Einstein’s theory could still require modifications as more becomes known about the properties of the universe, much as Isaac Newton’s law of gravity proved not to explain phenomena in space.

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