The axis of the universe debate sparked into life again last month with three papers in the 8 September issue of Physical Review Letters. The story began in April when Borge Nodland from the University of Rochester and John Ralston from the University of Kansas in the US claimed that there is a preferred direction in space, pointing from the constellation Sextans in one direction to Aquila in another. They based their claim on evidence that the plane of polarization of radiation travelling through the cosmos appeared to undergo a systematic rotation.

But Daniel Eisentstein from Princeton University and Emory Bunn from Bates College in the US now say that Nodland and Ralston's claim is based on a flawed statistical analysis - and that even if the effect existed, it would be impossible to measure. Nodland and Ralston, meanwhile, are standing their ground. "[Their comment] inaccurately reported what we did, is incorrect in several assertions and does not alter our conclusions, " they insist.

However, three other US scientists, led by John Wardle at Brandeis University, used Nodland and Ralston's method to analyse recent high-resolution radio and optical signals from various galaxies and quasars. They say that the effect claimed by Nodland and Ralston is "statistically indistinguishable from zero".