Scientists Examine ‘Dark Energy’ of Antigravity

[Celebration]

http://www.nytimes.com/2006/11/16/science/16cnd-dark.html?pagewanted=1

A strange thing happened to the universe five billion years ago. As if God had turned on an antigravity machine, the expansion of the cosmos speeded up, and galaxies began moving away from one another at an ever faster pace.

Now a group of astronomers using the Hubble Space Telescope have discovered that billions of years before this mysterious antigravity overcame cosmic gravity and sent the galaxies scooting apart like muscle cars departing a tollbooth, it was already present in space, affecting the evolution of the cosmos.

“We see it doing its thing, starting to fight against ordinary gravity,” said Adam Riess of the Space Telescope Science Institute about the antigravity force, known as dark energy. He is the leader of a team of “dark energy prospectors,” as he calls them, who peered back nine billion years with the Hubble and were able to discern the nascent effects of antigravity. The group reported their observations at a news conference today and in a paper to be published in The Astrophysical Journal.

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The data suggest that in fact dark energy has changed little, if at all, over the course of cosmic history. Though hardly conclusive, that finding lends more support to what has become the conventional theory: that the source of cosmic antigravity is the cosmological constant, a sort of fudge factor that Einstein inserted it into his cosmological equations in 1917 to represent a cosmic repulsion embedded in space.