Particles faster than light: Revolution or mistake?
By Brian Vastag,
In science, revolutions take time.
Eureka moments can stretch into noggin-scratching years.
So, the day after news broke of a possible revolution in physics — particles moving faster than light — a scientist leading the European experiment that made the discovery calmly explained it to a standing-room- only crowd at CERN, the giant particle accelerator straddling the Swiss-French border.
The physicist, Dario Auterio, made no sweeping claims.
He did not try to explain what the results might mean for the laws of physics, let alone the broader world.
After an hour of technical talk, he simply said, “Therefore, we present to you today this discrepancy, this anomaly.”
But what an anomaly it may be. From 2009 through 2011, the massive OPERA detector buried in a mountain in Gran Sasso, Italy, recorded subatomic particles called neutrinos generated at CERN arriving a smidgen early, faster than light can move in a vacuum. If confirmed, the finding would throw more than a century of physics into chaos.
“If it’s correct, it’s phenomenal,” said Rob Plunkett, a scientist at Fermilab, the Department of Energy physics laboratory in Illinois. “We’d be looking at a whole new set of rules” for how the universe works.
Those rules would bend, or possibly break, Albert Einstein’s special theory of relativity, published in 1905. Radical at the time, the theory tied together space and time, matter and energy, and set a hard limit for the speed of light, later measured to be about 186,000 miles per second.
No experiment in 106 years had broken that speed limit.
But some 16,000 wispy neutrinos zooming underground in Europe apparently have, out-racing light by 60 billionths of a second.
Physicists expect intense scrutiny to follow, which OPERA and CERN scientists welcomed.
Fermilab operates a similar experiment, called MINOS, that shoots neutrinos from Illinois to an underground detector in Minnesota. In 2007, MINOS sniffed a hint of faster-than-light neutrinos, but the margin of error was too big to “make a claim,” Plunkett said.
Fermilab scientists will reanalyze their data, which will take six to eight months. In 2013, the MINOS detector, now offline, will restart after an upgrade. It could then offer confirmation, or refutation, of the results.
Clocking the trip of a neutrino requires just two pieces of knowledge: the distance of the journey and how long it takes.
In Friday’s talk, Auterio detailed the extraordinary lengths his team took to ratchet up the accuracy of those measurements. “We spent six months in various cross-checks,” he said of the 160 physicists from 11 countries collaborating on the OPERA experiment, largely funded by the French, Japanese and Italian governments.
Starting with Global Positioning System measurements, then upgrading the readings by sophisticated means, they measured the distance traveled — some 454 miles — to within eight inches. They factored in the rotation of the Earth, which moves ever so slightly in the flash it takes neutrinos to zoom that far. They even stopped traffic in a tunnel running through Gran Sasso mountain to calibrate their instruments.
An audience member asked whether the team had accounted for the tugging of the moon on the Earth.
“We took data continuously over three years, so this movement should average out,” Auterio said.
His explanations satisfied prominent spectators.
“I want to congratulate you on a beautiful experiment,” said Samuel C.C. Ting, the Nobel Prize-winning particle physicist from the Massachusetts Institute of Technology, who was sitting in the second row of the auditorium. “The experiment is very carefully done, the systematic error very carefully checked.”
Some 15,000 viewers tuned into a webcast of the seminar, compared with the “low hundreds” that view a typical CERN talk, said lab spokesman James Gillies.
“My impression is they did all the reasonable cross-checks,” said one of those viewers, theoretical physicist Matthew Strassler of Rutgers University. “They did a very serious job, it’s clear.”
Still, a yet-unknown error could invalidate the results.
Physicists played down speculation about science-fiction scenarios, instant communication and starships zooming at warp speed.
Even if the finding holds, Einstein’s theory could still be true — up to a point, said some physicists. The faster-than-light neutrino might simply be pointing to an extension, not a rewrite of the rule, much as Einstein’s theories extended, not invalidated, Isaac Newton’s laws of motion.
Yet the finding could open up a new understanding of the universe. The neutrinos may have taken a shortcut along a fifth dimension (beyond the three dimensions of space and one of time), as proposed by exotic theories. Another option: There is no ultimate speed limit. Or perhaps there is, but light can’t reach it.
Whatever the case, the OPERA physicists know this: They were not trying to break the speed of light. Their enormous experiment was designed to detect something much more subtle, the predicted flip of one type of neutrino into another. So perhaps they, like many scientists before, have serendipitously glimpsed a frontier.
“There’s the chance that it’s a doorway into something fundamental and deep we don’t know about nature,” Strassler said. “All the great revolutions in science start with an unexpected discrepancy that wouldn’t go away.”