Galaxy Clusters Back Up Einstein’s Theory of Relativity

Yudhijit Bhattacharjee, ScienceNOW
September 28, 2011
http://www.wired.com/wiredscience/2011/09/galaxies-einstein-relativity

Testing gravity is simple: walk out of a second-floor window and see what happens. It’s a lot tougher to test Albert Einstein’s theory of gravity — the general theory of relativity — which says that the gravity of an object warps space and time around it. Although researchers have proved general relativity on the scale of the solar system, validating it on cosmic scales has been more challenging. That’s exactly what a group of astrophysicists in Denmark have now done.

The researchers, led by Radek Wojtak of the Niels Bohr Institute at the University of Copenhagen, set out to test a classic prediction of general relativity: that light will lose energy as it is escaping a gravitational field. The stronger the field, the greater the energy loss suffered by the light. As a result, photons emitted from the center of a galaxy cluster — a massive object containing thousands of galaxies — should lose more energy than photons coming from the edge of the cluster because gravity is strongest in the center. And so, light emerging from the center should become longer in wavelength than light coming from the edges, shifting toward the red end of the light spectrum. The effect is known as gravitational redshifting.

Wojtak and his colleagues knew that measuring gravitational redshifting within a single galaxy cluster would be difficult because the effect is very small and needs to be teased apart from the redshifting caused by the orbital velocity of individual galaxies within the cluster and the redshifting caused by the expansion of the universe. The researchers approached the problem by averaging data collected from 8000 galaxy clusters by the Sloan Digital Sky Survey. The hope was to detect gravitational redshift “by studying the properties of the redshift distribution of galaxies in clusters rather than by looking at redshifts of individual galaxies separately,” Wojtak explains.

Sure enough, the researchers found that the light from the clusters was redshifted in proportion to the distance from the center of the cluster, as predicted by general relativity. “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,” Wojtak says. The findings appear online today in Nature.

Besides confirming general relativity, the results strongly support the Lambda-Cold Dark Matter model of the universe, an already popular cosmological model according to which most of the cosmos is made up of invisible stuff that does not interact with matter constituting stars and planets. The test also lends support for dark energy, the mysterious force that appears to be pushing the universe apart.

David Spergel, an astrophysicist at Princeton University, compliments Wojtak and his colleagues on “cleverly combining” a large cluster data set to detect a “subtle effect.” Spergel says, “This is another victory for Einstein. … This cluster test suggests that we do live in a strange universe with dark matter and dark energy, but one in which Einstein’s theory of gravity is valid on large scales.”

Faster Than Light Particles Could Wreck Einstein’s Relativity Theory

Jesus Diaz September 22, 2011
http://gizmodo.com/5843006/faster-than-light-particles-could-wreck-einsteins-relativity-theory

This is extremely shocking: CERN scientists using a 1300-ton particle detector have measured particles travelling faster than the speed of light. If confirmed, this discovery could invalidate Albert Einstein's 1905 theory of special relativity and revolutionize physics.

Einstein's theory says that there's nothing in the universe that could travel faster than light. Now, CERN scientists believe this may be wrong according to their latest experiment.

The 3-year experiment timed about 16,000 neutrino packets launched from CERN facilities in Geneva, travelling through Earth and arriving 2.43 milliseconds later to the subterranean facilities of Italy's Gran Sasso National Laboratory. There, the Oscillation Project with Emulsion-tRacking Apparatus (the OPERA particle detector) recorded the hits.

When scientists discovered that the particles were arriving 60 nanoseconds faster than the speed of light—with only a 10 nanosecond error margin—they freaked out. I don't blame them. Imagine someone comes to you to tell you that a new observation shows that planet Earth is actually flat.

But University of Bern's Antonio Ereditato—spokesperson for the 160-member OPERA team—says that the experiment is "a straightforward time-of-flight measurement." It was repeatable, so they couldn't ignore it because that would be dishonest: "[T]he consequences can be very serious [...] We are forced to say something [...] We have high confidence in our results. But we need other colleagues to do their tests and confirm them."

The news are so extraordinary that other physicists are already saying this is impossible. Chang Kee Jung—a neutrino physicist at Stony Brook University in New York—believes it's a systematic error. Jung is the spokesperson for a similar project in Japan. Indiana University's physicist Alan Kostelecky believes that, while it may be possible that neutrinos can travel faster than light, the experiment needs to be repeated "by at least one and preferably several experiments." There are other facilities that could be used to run the same test, one of them is Fermilab in Chicago. The other one is the T2K experiment in Japan, the one in which Jung participates.

Still, Kostelecky confesses that he "would be delighted if it were true." I would be delighted too. I love when the world goes crazy.