A theory that Earth has a special place in the universe and the accelerating expansion of the universe is an illusion has been discounted, U.S. physicists say. The discovery that the expansion of the universe is accelerating, which sparked the awarding of a Nobel Prize in 2011, led to the theory of dark energy, a mysterious force thought to make up almost three-fourths of the energy in the universe and which has so far eluded detection. But some scientists had proposed a theory that Earth, our solar system and Milky Way galaxy are at the exact center of the universe, and although that violates the standard assumption that the universe has no center, if true it could explain cosmic acceleration without dark energy or any new laws of physics. However, that theory doesn't hold up to observational tests, scientists at Dartmouth College reported Thursday. They calculated how the light left over from the Big Bang, also known as the Cosmic Microwave Background, would be affected it the Earth occupied such a special position, and found their measurements proved that impossible. "Essentially, we held a mirror up to the universe and asked if the reflection was special," physics and astronomy Professor Robert Caldwell said. "The reflection shows that we do not appear to live in a special location, and decisively excludes this explanation for the universe's accelerating expansion. "It would be a great relief to be able to understand a basic problem of cosmology within the known laws of physics," he said, "but our research is an important step in explaining the physics responsible for the cosmic acceleration."