Data Back Einstein Theory of a Repelling Cosmic Force

In what may be a major insight into the nature of space itself, astronomers have discovered evidence that the universe is expanding rapidly under pressure of an anti-gravity-like force first proposed by Albert Einstein.

Although he later called his proposal the worst blunder of his life, the great scientist’s idea has resurfaced over the past decade as a way to solve a host of cosmological conundrums, including suggestions that the universe is younger than some of its stars.

“This is the first believable direct evidence that there might be” such a repulsive force, said astrophysicist Rocky Kolb of Fermi National Accelerator Laboratory. “It may have been a blunder for [Einstein] to think it was a blunder.”

The discovery was made by an international group of astronomers, including several at UC Berkeley, who looked at exploding stars, or supernovas, that appear to be hurtling away from each other at surprisingly rapid rates.

Astronomers have long known that the universe has continued to expand ever since its explosive birth in the big bang. However, it was thought that the mutual gravitational attraction of all the matter and energy in the universe would slow the expansion down. The inward pull of gravity, in other words, would put a brake on the explosive outward expansion.

The supernovas examined by the researchers appeared to be so far away, however, that they indicate that the expansion of the universe is actually speeding up, rather than slowing down. It’s as if the supernovas were actually picking up speed from some outward-pushing force, like an airplane gunning its engines.

“Our observations show that the universe is expanding faster today than yesterday,” said UC Berkeley astronomer Adam Riess, one of the scientists who presented the findings during a meeting at UCLA last week. After trying to rule out every other possible explanation, he said, his team proposed that the reason might be Einstein’s long-abandoned repulsive force.

Anti-gravity it’s not, however. Gravity is the mutual attraction of matter and energy. Anti-gravity would imply that matter and energy would somehow mutually repel. If gravity causes two planets to attract each other, anti-gravity would cause them to repel each other.

The repulsive force, however, is the property of empty space itself.

“There’s energy in the vacuum of space, and that energy wants to stretch that vacuum,” Riess said. In other words, the repulsive force doesn’t cause the planets to push away from each other; it causes the space between them to expand. “If it’s true, it’s the craziest thing you could think of,” said physicist Lawrence Krauss of Case Western Reserve University in Cleveland.

The question of whether there really is such a force in the universe is so central, Kolb said, that “no one’s going to completely believe it until they find another way to measure it.”

However, said Krauss, “if the expansion rate is really increasing with distance, then you have some evidence that the universe is dominated by this repulsive stuff.”

Krauss is especially pleased because he has proposed for years that Einstein’s so-called cosmological constant--the repulsive force--would solve a host of vexing problems.

“I’m biased, because I’ve been arguing in favor of a cosmological constant for a long time,” he said.

The theory would resolve, for example, the possible contradiction between the age of the universe and the oldest stars.

The problem would be solved by a universe that is expanding more rapidly today than yesterday, because such a universe would be older than a steadily expanding one. Imagine a car cruising from Los Angeles to New York at 50 mph, said Krauss. If it’s been traveling at a steady pace, and you know what time it gets to New York, you can easily calculate the time it left L.A.

But if the car is traveling faster now, at 50 mph, than it was at the outset of its journey, then a longer time would have elapsed. In the same way, a universe that was once expanding more slowly would be older than one that expanded steadily.

“It would be taking a leisurely time to reach the size it is today,” said Riess.

Einstein originally proposed the cosmological constant as a way to “prevent” the universe from falling in on itself. At the time, scientists were not aware that the universe was expanding with energy left over from the big bang. Once the expansion was discovered, the extra repulsive force, theoretically, was no longer needed, which prompted Einstein to call it a blunder.

But over the last decade, the idea of a repulsive force has regained some support among scientists who see it as the key to solving major cosmic mysteries.

The seemingly nonsensical idea that empty space has energy is tried, true and well-measured by physicists. However, the energy of empty space behaves very differently from regular energy. Regular energy and matter (which are different states of the same thing, according to Einstein’s E=mc2 )always attract other energy and matter. However, the energy of empty space is repulsive.

“I don’t know a good [rule of thumb] argument about why the energy that comes out of nothing is so different from the energy that comes out of something,” Krauss said. However, many solid mathematical and physical arguments devised by physicists since Einstein suggest that the energy of nothing has to be repulsive.

Indeed, the big question has been: Why isn’t the repulsive force even stronger than it is? The late Caltech physicist Richard Feynman once calculated that the energy of empty space should be enormous--and produce such a repulsive force, Krauss said, that you wouldn’t be able to see the hand in front of your nose. Even at the speed of light, the light from your hand wouldn’t have time to reach your eyes before the expanding universe pulled it away.

The small repulsive force suggested by the new observations wouldn’t have such a dramatic effect, Kolb said, although it would certainly make our galaxy a lonelier place billions of years from now, when the expanding universe would have pulled all our cosmic neighbors out of our line of sight.

The repulsive force hasn’t been seen before because it is so weak at comparatively short distances, said Riess. In the solar system, for example, it has no effect at all. “It adds up over space,” he said. “It can push the universe, but it can’t push the solar system.”

Still, scientists will need a lot more evidence before they “jump on the bandwagon,” said Krauss. “It’s intriguing, but not definitive,” he said.

Kolb agreed. “Because it’s such an important issue, it has to be beyond a reasonable doubt.”