What is the mysterious dark energy thats causing the expansion of the universe to accelerate? Is it some form of Einsteins famous cosmological constant, or is it an exotic repulsive force, dubbed "quintessence," that could make up as much as three-quarters of the cosmos? Scientists from Lawrence Berkeley National Laboratory (Berkeley Lab) and Dartmouth College believe there is a way to find out.
The SuperNova/Acceleration Probe, SNAP, is a satellite designed to study dark energy through the discovery and precision measurement of thousands of distant supernovae.
Todays universe is expanding at an accelerating rate because dark energy counteracts the force of gravity. In the early universe matter was closer together, and gravity still slowed its expansion.
In a paper to be published in Physical Review Letters, physicists Eric Linder of Berkeley Lab and Robert Caldwell of Dartmouth show that physics models of dark energy can be separated into distinct scenarios, which could be used to rule out Einsteins cosmological constant and explain the nature of dark energy. Whats more, scientists should be able to determine which of these scenarios is correct with the experiments being planned for the Joint Dark Energy Mission (JDEM) that has been proposed by NASA and the U.S. Department of Energy.
"Scientists have been arguing the question how precisely do we need to measure dark energy in order to know what it is?" says Linder. "What we have done in our paper is suggest precision limits for the measurements. Fortunately, these limits should be within the range of the JDEM experiments."
Lynn Yarris | EurekAlert!
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