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Stars say relativity still works

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The Special Theory of Relativity may be under re-evaluation following CERN’s astonishing neutrino observations, but over in the world of astronomy, general relativity has had another reconfirmation from the Neils Bohr Institute at the University of Copenhagen.

Radek Wojtak, Steen Hansen and Jens Hjorth have published in Nature the results of observations of distant galactic clusters. The 8,000 distant clusters sampled in the experiment have such immense gravity that general relativity predicts it will affect light emerging from them.

In particular, the gravity red-shifts the light emerging from the cluster. Since the speed of light is fixed (at least for light; neutrinos might be another matter), gravity can’t slow it down, so the impact of very high gravity on light is to soak up some of its energy, moving it towards the red end of the visible light spectrum.

In their observations, the three researchers compared the amount of red shift experienced by light emerging from the centre of the galactic clusters to that observed for light emitted from near the edge of the cluster.

"We could measure small differences in the redshift of the galaxies and see that the light from galaxies in the middle of a cluster had to 'crawl' out through the gravitational field, while it was easier for the light from the outlying galaxies to emerge", said Radek Wojtak.

While this is “only” a reconfirmation of what we already knew about light, the new research is believed to be the first time the theory has been applied on such a large scale. With a measurement of the cluster’s total mass (El Reg would like to know how that’s accomplished, commenters), the researchers were able to predict the difference in red shift between the centre and the periphery, and say that their observations were “in complete agreement” with the prediction.

In addition, they say such research can help increase our knowledge of the “dark universe”, since Wojtak said the result is “a strong indication for the presence of dark energy”.

Meanwhile, here’s an interesting discussion of the CERN results: could they have been affected by the behavior of the field-programmable gate arrays (FPGAs) used in CERN’s equipment?

High-performance computing enthusiast Marc Bevand speculates that the neutrino observations may have affected by FPGAs in the data acquisition system.

The Register isn’t prepared to make a call one way or the other. It is, however, an interesting discussion and underlines the importance of CERN’s decision to release its data for all and sundry to analyse. ®

Mea Culpa Thanks to the readers that pointed out my error. I gave a distance when I should have referred to the number of galaxies sampled. This is now corrected.

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