Mysterious Dark Energy Has Existed For Most of Time, Scientists Say

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The find indicates, for example, that dark energy isn't being diluted by the expansion of the universe. This supports theories that the force might be "vacuum energy," an underlying background energy present throughout the universe even in the absence of matter.

"Understanding the nature of dark energy is arguably the biggest problem physics is facing today," Mario Livio, a colleague of Reiss, said. (Related: "Journal Ranks Top 25 Unanswered Science Questions" [June 30, 2005].)

Sean Carroll, a theoretician at California Institute of Technology in Pasadena, agrees. "Every clue helps," he said at the press conference.

Reiss looks forward to additional data when the Hubble telescope undergoes servicing in 2008. (Related: "Hubble Repair Mission Approved by NASA" [October 31, 2006].)

"With luck," he said, "the astronauts will plug another new camera into Hubble that would let us work even farther back in time and see what dark energy was doing not 9 billion years ago, but 11 or 12 billion years ago."

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