Albert Einstein called it the biggest blunder of his life, but scientists said Thursday that an idea he presented in 1917 about the universe may have been right after all.

Einstein came up with the "cosmological constant" to fix a problem: His general relativity theory clashed with his belief that the size of the universe was unchanging.The constant was a mathematical term that implied that the universe contains a repulsive force that acts against gravity. When Einstein added it to an equation describing his relativity theory, the equation predicted a constant-size universe.

But scientists later showed that the universe was actually expanding. The constant fell out of favor.

The late physicist George Gamow, in his autobiography "My World Line," wrote that Einstein told him that introducing the cosmological constant was "the biggest blunder he ever made in his life."

But there might be something to it after all, British scientists suggest in the British journal Nature.

George Efstathiou, William Sutherland and Steve Maddox of the physics department at the University of Oxford argue that the existence of the force represented by the cosmological constant would solve several problems with a standard theory about the universe. It "should be taken seriously," they say.

The standard theory includes the Big Bang that gave birth to the universe and says that by far most of the mass in existence now is unobserved stuff called "cold dark matter" that would have a gravitational effect on the rest of the universe.

Recent observations show more clustering of galaxies on very large scales than basic versions of the standard theory predict, the new report says. But the clustering could be accounted for by incorporating the force described by the cosmological constant into the standard theory, the scientists propose.

Their hypothesis suggests that the expansion of the universe was dominated by cold dark matter through perhaps the first one-third to one-half of the history of the universe but that the cosmological constant force governs it now, Sutherland said in a telephone interview.