Monday, November 21, 2011

Is Einstein Wrong about the Speed of Light

             Travel faster than the speed of light? Really?

Back in September, scientists found that tiny particles called neutrinos appeared to do just that, defying Einstein's special theory of relativity.

   It could be a fluke, but now the same experiment has replicated the result. It's not hard proof yet, though; other groups still need to confirm these findings.

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Physicists with the OPERA (Oscillation Project with Emulsion-tRacking Apparatus) experiment said in September that neutrinos sent about 454 miles (730 kilometers) from CERN in Switzerland arrived at Italy's Gran Sasso National Laboratory a fraction of a second sooner than they should have according to Einstein's theory.

Other scientists were skeptical, raising questions about possible flaws in the study.

So OPERA scientists rechecked parts of the experiment to take intoaccount suggestions from their critics. They announced Friday that the new test confirms the initial findings.

"This result confirms that neutrinos arrived at Gran Sasso lab 62.1 nanoseconds in advance with respect to the time computed assuming the speed of light in vacuum," according to Lucia Votano, director of INFN-Gran Sasso Laboratory.

The OPERA team's initial result was based on observing more than 15,000 bunches of neutrinos, or electrically neutral subatomic particles. But the scientists did not track any one specific neutrino. Instead, the neutrinos were produced in long pulses that lasted about 10 millionths of a second.

"Although this sounds short, it is hundreds of times longer than the 60 nanoseconds early arrival time of the neutrinos at the Gran Sasso in Italy," said Andy Cohen, a professor of physics at Boston University, who is not involved in OPERA.

This means that when a neutrino arrived at Gran Sasso there was no way to know exactly when it was produced during the pulse, preventing an accurate measurement of its speed.

The new study used shorter pulses making it easier to know more precisely when an individual neutrino was generated.

"They did this for only 20 neutrinos," Cohen said, "but since the speed of each one is known, this leads to a very precise result, confirming that the neutrinos appear to be arriving 60 nanoseconds earlier than expected."

But don't throw your physics book just yet. Cohen said there are other potential issues with the experiment that haven't been addressed yet. "While this result is a very significant improvement over the previous measurement, many of the concerns that have been raised about possible sources of uncertainty remain.

"We should probably remain skeptical until we have confirmation from other experiments," he said.

Votana agrees and said the OPERA measurement needs to be confirmed by independent scientists. Even if the results are confirmed, we won't toss out all of Einstein's theory. A broader theory would be generated that would include Einstein's theory, Votana said.

Scientists at Fermilab in Illinois and in Japan are expected to try to replicate the findings.

"If the neutrinos are truly traveling faster than light this would require profound changes in the way we understand space and time," Cohen said.

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