| A map of concentric rings on the actual sky,|
as measured by WMAP.
“We found there was nothing strange in the [cosmic microwave background] data at all,” said astrophysicist Ingunn Wehus of the University of Oslo, coauthor of a paper published online in the Astrophysical Journal Letters May 9. The difference in their analyses, she says, is “We do it correctly, and they do not.”
The original claim, made in research published on arXiv.org by theoretical physicist Roger Penrose of the University of Oxford in England and Vahe Gurzadyan of the Yerevan Physics Institute and Yerevan State University in Armenia, made a small media splash (and was one of Wired Science’s Top Scientific Breakthroughs of 2010).
Penrose had previously championed the idea that the universe got its start well before the Big Bang, and has been cycling through an endless series of bangs for eons. As evidence for this strange claim, he and Gurzadyan pointed out funny concentric circles in the universe’s baby photos, the cosmic microwave background. The CMB shows a universe that looks more or less the same in every direction, with a nearly uniform temperature of about 3 degrees Kelvin.
But some spots are hotter or colder than others. These fluctuations, which ultimately led to the clumps of matter that make up galaxies and other cosmic structures today, are not as random as they look, Penrose and Gurzadyan claimed. Making a statistical search of the CMB revealed concentric circles where the tiny temperature variations between one spot and its neighbors are smaller than average.
Those circles are sure signs of pre-Big Bang activity, Penrose says. He suggests they were generated by collisions between supermassive black holes in an earlier eon, which gave off an intense burst of energy. The burst would radiate outward in a uniform sphere of gravitational waves, which would leave circles on the CMB when they entered the epoch we live in.
“Because they claimed this, they got a lot of media attention. Everybody was talking about this,” Wehus said. “It just seemed strange that nobody else had noticed this before. It’s a very simple thing to check. Since nobody else had checked it, we just decided to do it.”
Wehus and University of Oslo physicist Hans Eriksen redid Penrose’s analysis of data from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP), which spent nine years mapping the glow of the first atoms to release their radiation 380,000 years after the Big Bang. Another independent group led by Adam Moss of the University of British Columbia made a similar analysis, and published their results in the Journal of Cosmology and Astroparticle Physics April 26.
To their surprise, both groups actually saw the same circles that Penrose did. The circles are really there.
But then the skeptical researchers built thousands of random simulations of the CMB, built up from the principles of the commonly accepted standard model of cosmology. The circles showed up there too, in the same numbers.
“In our case we found that the rings are in all the simulations, so they’re just a feature of the standard model,” Wehus said. “It’s not a signature of new physics.”
Moss and colleagues even found concentric equilateral triangles in the CMB, a feature for which Penrose’s cyclic cosmology has no explanation.
“There is nothing special about the presence of low-variance circles on the sky,” Moss concludes. “If there are signals of extraordinarily early times buried in the CMB, they have not yet been found, and we will have to keep looking.”
Penrose and Gurzadyan compared their results to simulations, too, but Wehus and Moss claim they set their simulations to the wrong baseline. Wehus and Moss assumed that the average variations in the CMB were set by the laws of the standard model of cosmology; Penrose’s original paper apparently used white noise. Even an updated version of the paper, posted to arXiv on April 29, failed to hit the mark, Wehus says.
“Some way or another they screwed up their simulations,” Wehus said. “They used wrong simulations.”
This doesn’t necessarily mean the cyclic universe theory is wrong, she adds.
“We are not knocking down the idea of Penrose, of there being a cyclic universe,” she said. “We’re just saying there’s no evidence for it.”
Penrose is sticking to his story. In the most recent paper, he looks for concentric sets of three or more circles in both the WMAP data and a simulated sky. The patterns and colors for the simulated sky look random, he says, but the patterns on the actual sky do not.
“Such a pattern is consistent with [a cyclic cosmology], but hard to square with the standard inflationary view of the origin of the temperature variations,” Penrose wrote to Wired.com in an e-mail. “I think that Eriksen and Werhus may have read that part of our paper rather hastily … evidently not having understood what we were doing.”
“I suppose there may well be further argument about all this — which is to be expected, of course — and maybe we have missed something important,” he added. “But it seems to me that here is something to be taken very seriously.”
|A map of concentric rings on a simulated sky. arXiv/V.G. Gurzadyan and R. Penrose|