Faster than light

The team of European physicists that claimed to have measured a faster-than-light particle in September says new tests have confirmed the results of its first experiment.

In a result that could have a profound impact on the physics world, scientists from the Oscillation Project with Emulsion-tracking Apparatus (OPERA) claimed to have detected neutrinos moving faster than the normally accepted speed of light.

Neutrinos, fundamental sub-atomic particles that remain a mystery for particle physicists, were created and fired from a particle accelerator at CERN, outside Geneva, to a detector at the Gran Sasso laboratory in Italy, 723 kilometers (450 miles) away.

The OPERA team found that their neutrinos travelled 300,006 kilometers per second, which is just above the established speed of light, which is usually measured at 299,792 kilometers per second. Einstein's special theory of relativity says nothing can travel faster than light.

Reducing pulse time

One issue that many skeptics centered on was the relatively long length of the proton pulses that create the neutrinos that the Italian detector receives. In new experiments run last month, CERN reduced the time of the proton pulses from 10.5 microseconds to three microseconds. In the new experiment, the neutrinos still traveled faster than the speed of light.

But even with this new confirmation, the physicists themselves are not quite ready to fully accept these results.

"Despite the large significance of the measurement reported here and the stability of the analysis, the potentially great impact of the result motivates the continuation of our studies in order to investigate possible still unknown systematic effects that could explain the observed anomaly," they wrote in the conclusion of the paper, which was published on the website ArXiv.org shortly before midnight, Thursday evening, Greenwich Mean Time. "We deliberately do not attempt any theoretical or phenomenological interpretation of the results."

Caution prevails

According to Nature, a highly-respected scientific journal, many OPERA team members who initially declined to sign their names to the paper have now come on board. That includes Caren Hagner, a professor of physics at the University of Hamburg, who had been one of the most skeptical members of the group.

"There can be an error in the measure of distance, or the measurement of time, or - because we use statistical methods to disentangle, to measure the time of flight of the neutrinos - it could also result in some nasty statistical effects," she told Deutsche Welle in September.

After the new experiment improved precision and augmented the statistical analysis, Hagner told Nature that she has "much more confidence" in the new results.

But many cautious scientists often cite Carl Sagan, a giant among 20th century astrophysicists, who once said: "Extraordinary claims require extraordinary evidence."

"A measurement so delicate and carrying a profound implication on physics requires an extraordinary level of scrutiny,” Fernando Ferroni, president of Italian Institute for Nuclear Physics, said in statement published on Friday.

Results from American comparative study to come in 2012

Still, physicists worldwide generally agree that the real test will come once CERN's counterpart in the United States, Fermilab, conducts a similar experiment on its apparatus outside Chicago, known as MINOS.

"OPERA's observation of a similar time delay with a different beam structure only indicates no problem with the batch structure of the beam; it doesn't help to understand whether there is a systematic delay which has been overlooked," MINOS co-spokesperson Jenny Thomas said in an interview with Agence France Presse.

MINOS representatives added that they may have preliminary results to compare to the OPERA experiment by early next year.

Author: Cyrus Farivar (AFP, Nature, Reuters)
Editor: Sam Edmonds