Nov. 17, 2006 — The mysterious anti-gravity force known as dark energy has been pushing apart the universe a lot longer than expected — for at least nine billion years — say astronomers who drew that conclusion by studying light from distant stellar explosions.
The idea that this repellant force is so persistent comes as a surprise to some cosmologists. Previous evidence supported the idea that dark energy was pushing galaxies apart as long as five billion years ago, but the new observations suggest that it has been around — in much the same form — much longer.
The discovery also supports the cosmological constant, the mathematical expression of dark energy required to make Einstein's theory of General Relativity work.
Ironically, Einstein didn't much like the cosmological constant and later expressed regret at ever coming up with something as weird as a repulsive force that perpetually carves cosmic real estate out of utterly nothing.
Dark energy is "a rather mysterious energy that appears to make up 70 percent of the energy in the universe," said astrophysicist Adam Riess of the Space Telescope Science Institute and Johns Hopkins University.
To find out how long dark energy has been at work, Riess and his colleagues used the Hubble Space Telescope to look at 24 very distant supernovae, large stars that explode at the ends of their lives.
