European researchers said Friday they have measured the speed of neutrinos and found that the subatomic particles don't travel faster than light after all, refuting another team's measurements that prompted widespread disbelief among scientists last year.
Scientists with the rival OPERA experiment said in September that their tests appeared to show neutrinos speeding faster than light, a feat that goes against Albert Einstein's special theory of relativity which underlies much of modern physics.
Nobel Prize winning physicist Carlo Rubbia said his team, called ICARUS, used a similar experiment to trap neutrinos fired from the European Organization for Nuclear Research, or CERN, in Switzerland to a detector hundreds of miles (kilometers) away in Italy.
"It's a perfectly straightforward experiment, very clean," Rubbia told The Associated Press in a telephone interview. "The results are very convincing, and they tell us essentially that there was something not quite right with the results of OPERA."
Doubts about original experiment
Einstein's famous theory of relativity — a pillar of modern physics — says the speed of light in a vacuum, approximately 186,282 miles per second (299,792 kilometers per second), is the ultimate speed limit and that nothing in the universe can travel faster.
That speed factors into everything from estimates about the size and age of the universe to the radius of black holes to the power generated by nuclear reactors.
Doubts about the OPERA results were heightened last month when it was announced that researchers had found a flaw in the technical setup that could have distorted the experiment's figures.
Antonio Ereditato, a member of the OPERA team and the head of the Albert Einstein Center for Fundamental Physics in Bern, Switzerland, said he welcomed the latest results.
"These results are in line with our recent findings about the possible misfunctioning of some of the components of our experimental setup," he told the AP in an email.
Asked whether he was disappointed that the prospect of breaking light speed likely remains in the realm of science fiction, he said: "This is the way science goes. What matters is the global progress of scientific knowledge."
Results from trial run
The ICARUS team's results came from a trial run for a longer experiment planned to take place in April or May. OPERA, too, will repeat their experiment, this time with the technical glitches ironed out.
"The evidence is beginning to point toward the OPERA result being an artifact of the measurement," CERN Research Director Sergio Bertolucci said in a statement.
"Whatever the result, the OPERA experiment has behaved with perfect scientific integrity in opening their measurement to broad scrutiny, and inviting independent measurements."
The ICARUS team confirmed that, as Einstein predicted, neutrinos travel at the speed of light.
"I'm not displeased that Einstein was right again," said Rubbia.