By GAUTAM NAIK
It's looking more like Einstein was right after all.
In September, scientists in Geneva made the startling announcement that they had recorded ghostly particles known as neutrinos apparently traveling faster than the speed of light—a finding that challenged Einstein and threatened to upend the entire field of modern particle physics.
It now turns out that a flawed cable could have been responsible for garbling the result.
"There is a screw and you have to turn it, but we're not sure if it was well-calibrated," said Arnaud Marsollier, a spokesman for the European Organization for Nuclear Research, or CERN, which ran the experiment. "It would be embarrassing if a nasty cable is the reason."
CERN garnered headlines around the world when it said that neutrinos zapped from a lab in Geneva to one 450 miles away in Italy had seemingly made the trip in about 60 nanoseconds less than it would have taken light to get there. The news induced much head-shaking among other scientists.
Now, CERN plans to take new measurements in May to check its work.
"You have to wonder why they didn't sit tight and check the connections to every cable before making such an incredible announcement," said Jim Al-Khalili, a professor of physics at the University of Surrey in England, who vowed to eat his boxer shorts live on television if the CERN neutrino result was upheld.
The main piece of the experiment, known as the Oscillation Project with Emulsion-Tracking Apparatus, is a house-sized tangle of computers, plugs and wires.
"It's a complicated machine," said Mr. Marsollier. "There are many places where an error could be hidden."
CERN now says it had identified two possible effects that could have affected the interpretation of the data. One relates to a device known as an oscillator that plays a role in synchronizing clocks at the Swiss and Italian ends. If the oscillator was wrongly calibrated, that would mean the neutrinos had actually traveled slower than light, and all would be right with the world.
A separate—and more troublesome—glitch may have occurred in a fiber-optic cable that brings a Global Positioning System, or GPS, signal to a master clock.
"If this is the case, it could have led to an underestimate of the time of flight of the neutrinos," CERN said in a one-paragraph "update" posted on its website.
Science tends to proceed cautiously, in fits and starts. Claims confidently made one day may be debunked the next, a process that is vital to the scientific method. Sometimes, complex or poorly understood effects can gnarl an experiment.
Less often—and this may have tripped up CERN—a high-profile finding can be undone by a small blunder that initially escaped notice.
Two decades ago, a design mistake in the main mirror of the Hubble space telescope had to be fixed by astronauts at a cost of hundreds of millions of dollars. In 1999, the National Aeronautics and Space Administration lost its $125 million Mars Climate Orbiter spacecraft because one group of scientists in the project failed to convert English Imperial units to metric.
The CERN claim was breathtaking because it promised to overthrow the fabric of modern particle physics. Confirmation that neutrinos could zoom around faster than light would force scientists to rethink everything from the evolution of the universe to the behavior of subatomic particles.
Einstein's theory of relativity maintains that the speed of light—about 186,000 miles a second—is a barrier that can't realistically be breached. In his famous E=mc2 equation equating mass with the energy contained within it, the "c" represents the speed of light.
But if particles outrun light, things get weird. For example, it would theoretically be possible for particles to travel backward in time—though no one is quite sure what that means.
The assertion that the speed of light is the highest possible speed is also partly the basis for Einstein's theory of gravity. That, in turn, is vital to existing theories about how the universe evolved.
The light-speed notion has been incorporated into billions of measurements done at particle accelerators to figure out how elementary particles behave. If the CERN result holds true, most of those calculations would have to be redone.
Neutrinos are among the odder denizens in the cosmic sea. They have almost no mass and no charge and can pass through ordinary matter unaffected. At any given moment, billions harmlessly stream through a person's body.
In the CERN experiment, neutrinos were measured as traveling slightly faster than light on a 450-mile trip from CERN near Geneva to the Gran Sasso underground lab in central Italy. That result was based on more than 15,000 neutrino events measured.
The faster-than-light finding was "a complete surprise," a spokesman for the experiment said at the time. He said researchers had spent months cross-checking the data and the unexpected finding couldn't be explained away. Soon after, other scientists got into the act, trying to replicate the results.
But many scientists questioned whether Einstein could get knocked off his perch so easily. They pointed out earlier measurements showing that neutrinos reaching the Earth from a supernova explosion traveled at light speed, which contradicted the CERN finding.
Others wondered whether the setup of the experiment or statistical errors could have affected the conclusion.
"There's a small part of me that's disappointed that I won't have to" consume underwear on TV, said Prof. Al-Khalili, a well-known broadcaster in the U.K. "The public humiliation would have been a small price to pay for a revolution in physics" if the CERN results were confirmed.
Write to Gautam Naik at firstname.lastname@example.org