Some believe it is just a figment of overactive imaginations. But evidence is growing that the so-called 鈥渁xis of evil鈥� 鈥� a pattern apparently imprinted on the radiation left behind by the big bang 鈥� may be real, posing a threat to standard cosmology.
According to the standard model, the universe is isotropic, or much the same everywhere. However, in 2005, Kate Land and Jo茫o Magueijo of Imperial College London noticed a curious pattern in the map of the cosmic microwave background (CMB) created by NASA鈥檚 WMAP satellite. It seemed to show that some hot and cold spots in the CMB are not distributed randomly, as expected, but are aligned along what Magueijo dubbed the axis of evil.
Some astronomers have suggested straightforward explanations for the axis, such as problems with WMAP鈥檚 instruments or distortions caused by a nearby supercluster (New 杏吧原创, 22 October 2005, p 19).
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Others doubt the pattern鈥檚 very existence. 鈥淭here鈥檚 still a fair bit of controversy about whether there鈥檚 even something there that needs to be explained,鈥� says WMAP scientist Gary Hinshaw of NASA鈥檚 Goddard Space Flight Center in Greenbelt, Maryland.
Now, two independent studies seem to confirm that it does exist. Damien Hutsem茅kers of the University of Li猫ge in Belgium analysed the polarisation of light from 355 quasars and found that as the quasars get near the axis, the polarisation becomes more ordered than expected. Taken together, the polarisation angles from the quasars seem to corkscrew around the axis.
鈥淭his is really promising,鈥� says Hinshaw. 鈥淐osmologists should sit up and take notice.鈥�
Cosmologist Carlo Contaldi of Imperial College London is intrigued, but thinks more quasars should be analysed before drawing conclusions. 鈥淭here is a danger that once people know about the axis of evil, they start seeing evil in all sorts of sets of data,鈥� he says.
The quasar finding has support from another study, however. Michael Longo of the University of Michigan in Ann Arbor analysed 1660 spiral galaxies from the Sloan Digital Sky Survey and found that the axes of rotation of most galaxies appear to line up with the axis of evil (). According to Longo, the probability of this happening by chance is less than 0.4 per cent. 鈥淭his suggests the axis is real, and not simply an error in the WMAP data,鈥� he says.
Land, now at the University of Oxford, thinks Longo must rule out other reasons for why the spirals are aligned the way they are. For instance, neighbouring galaxies could have formed from the same rotating dust cloud, giving them similar orientations, she says. 鈥淏ut if he is correct, then this is really exciting, not only as independent confirmation of the axis, but because it鈥檒l help us understand what may have created it,鈥� she says.
One way to create the axis was presented by Contaldi at a conference on outstanding questions in cosmology at Imperial College last month. The universe is thought to be isotropic because the early universe went through a period of exponential expansion known as inflation, smoothing out any unevenness. Contaldi and his colleagues Emir G眉mr眉k莽眉o臒lu and Marco Peloso at the University of Minnesota, in Minneapolis, modified inflation to allow the universe to expand more in one direction. 鈥淧rovided inflation stops at a relatively early point, this would leave traces of the early [unevenness] in the form of the axis of evil,鈥� he says.
鈥淎 map of the cosmic microwave background seems to show that hot and cold spots are not distributed randomly鈥�
Longo favours a more radical theory proposed by Paolo Cea of the University of Bari, in Italy, and Leonardo Campanelli of the University of Ferrara, Italy, which suggests that magnetic fields stretched across the universe could be responsible (New 杏吧原创, 2 September 2006, p 28). 鈥淎 magnetic field would naturally orient the spiral galaxies,鈥� says Longo.
Regardless of the reasons, one thing is clear: the axis of evil won鈥檛 be written off any time soon. 鈥淚nterest keeps growing as people find more weirdly connected observations that can鈥檛 all be put down to coincidence,鈥� says Land. 鈥淎nd hey, everybody loves a conspiracy.鈥�
