- News Home
5 December 2013 11:26 am ,
Vol. 342 ,
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
- 5 December 2013 11:26 am , Vol. 342 , #6163
- About Us
"Dark Energy" Dispute Heats Up
19 April 2005 (All day)
Is dark energy an illusion? Perhaps, says Edward Kolb, a physicist at the Fermi National Accelerator Laboratory in Batavia, Illinois. In mid-March, Kolb and three Italian collaborators posted a provocative paper arguing that dark energy--the mysterious antigravity force that makes the universe expand ever faster--is actually a byproduct of enormous ripples in the fabric of spacetime. Kolb's paper created ripples of its own, and now two theorists from Princeton University argue that Kolb's team made an accounting error that invalidates the result.
Kolb's paper, which appeared on the arXiv preprint server [www.arxiv.org], suggested that dark energy--whose effects have been observed by supernova hunters and other astronomers--is not really an energy or a substance. Instead, Kolb says, enormous "perturbations" or ripples in spacetime much larger than the observable universe cause the accelerating expansion of the universe. These ripples, which were caused by the rapid period of inflation just after the big bang, would mimic the fluidlike substance scientists now call dark energy.
But not so fast, say Princeton physicists Uroš Seljak and Chris Hirata. In a paper also posted on the archive, the scientists launched a two-pronged attack on the Kolb hypothesis. First, using a powerful equation derived from those of general relativity, the two derive a "no-go" theorem that says that huge ripples can't make the universe expand faster and faster. "The equation shows they cannot lead to acceleration," says Seljak. "You cannot have acceleration with only ordinary matter" in the universe; there has to be dark energy.
Next, Seljak and Hirata attack Kolb's mathematics. They argue that in the intricate mathematical calculations leading to the result, Kolb and colleagues inadvertently left out some crucial terms that exactly cancel the effect that they are claiming. "They have been fooled into thinking that there's no cancellation," Seljak says. "These things happen. It's not an easy calculation."
Some physicists, such as Edmund Bertschinger of the Massachusetts Institute of Technology, say Seljak and Hirata have put the matter to rest. "This is definitive in my mind," he says. Kolb, however, holds firm. "I think the no-go theorems eventually will go," he says, adding that he believes Seljak and Hirata have themselves made subtle errors that invalidate their criticisms. "But their work is sharpening our thinking, and we are writing another paper."