Others are skeptical about the incredible assertion, which would invalidate Einstein’s theory of special relativity.
If true, it will be the most important physics discovery in the last half-century: Neutrinos are elusive, practically massless subatomic particles that appear to travel at the speed of light, according to a team of European physicists. If this is the case, Einstein’s theory of special relativity, which states that nothing can move faster than light, would be shattered.
Indeed, the outcome would be so revolutionary that it would almost certainly be viewed with suspicion across the world. “I anticipate that the majority of the scientific community will not accept this as a final conclusion unless it can be replicated by at least one, preferably several experiments,” says V. Alan Kostelecky, an Indiana University Bloomington theorist. “If that were true,” he says, “I’d be happy.”
The information comes from the Oscillation Project with Emulsion-tRacking Apparatus, a 1300-metric-ton particle detector (OPERA). OPERA, an underground detector at Italy’s Gran Sasso National Laboratory, detects neutrinos shot through the soil from CERN, the European particle physics laboratory in Geneva, Switzerland. Because the particles barely interact with other matter, they flow right through the ground, with only a few contacting the detector’s substance and causing a visible shower of particles.
The nearly 16,000 neutrinos that originated at CERN and reported a hit in the detector were timed by OPERA researchers over the course of three years. They discovered that the neutrinos traveled 730 kilometers in 2.43 milliseconds on average, 60 nanoseconds quicker than predicted if moving at light speed. Antonio Ereditato, a physicist at the University of Bern and spokesperson for the 160-member OPERA project, adds, “It’s a basic time-of-flight measurement.” “We use the ratio of the distance and time to determine the velocity, exactly as you learnt in high school,” says the scientist. The measurement’s uncertainty, according to Ereditato, is 10 nanoseconds.
Even Ereditato, however, believes it is far too early to call relativity incorrect. He responds, “I would never say that.” Rather, the OPERA researchers are just providing a puzzling result that they are unable to explain and asking the public to examine it. “We’re compelled to speak up,” he continues. “We couldn’t just brush it under the rug; it would be dishonest.” The findings will be presented at a CERN session tomorrow.
The key question is whether the OPERA researchers discovered particles that travel faster than light, or if they were duped by an undisclosed “systematic mistake” in their experiment that made the time appear to be shorter than it actually is. Neutrino physicist Chang Kee Jung of Stony Brook University in New York believes the conclusion is the consequence of a systematic mistake. He replies, “I wouldn’t bet my wife and kids because they’d be upset.” “However, I’d put my home on it.”
The tough element, according to Jung, is correctly calculating the time between when the neutrinos are produced by slamming a jet of protons against a solid target and when they reach the detector. That time is based on the global positioning system, and GPS readings can have tens of nanoseconds of uncertainty. “I’m curious how they reached a 10-nanosecond uncertainty since, based on the systematics of GPS and electronics, I believe that’s a really difficult figure to achieve.”
According to Kostelecky, who has spent 25 years building a theory called the standard model extension that accounts for all potential sorts of violations of special relativity in the setting of particle physics, no previous data clearly rule out the finding. “I would be a lot more cautious if you told me there was a claim of faster-than-light electrons,” he adds. He claims that prior measurements have limited the possibilities for neutrinos.
Nonetheless, Kostelecky reiterates the old adage: Exceptional claims need extraordinary proof. Even Ereditato admits that a single measurement is insufficient proof.