Faster than the speed of light: Just how possible is it?
On Thursday, scientists in Europe reported an experimental result thought to be impossible: They had observed particles moving faster than the speed of light.
On Friday, more details emerged.
A press release from the OPERA collaboration at the European Organization for Nuclear Research, or CERN, reviewed the basics. It noted that the surprising result was based on more than 15,000 "neutrino events" that had been created when researchers sent a beam of subatomic particles called neutrinos from the organization's headquarters near Geneva to a detector at the Gran Sasso Laboratory in Italy, about 450 miles away.
But the release also further addressed the question of the claim's believability.
Physicists around the world have expressed skepticism that the CERN neutrinos traveled faster than the speed of light -- or, as the CERN release put it, "nature's cosmic speed limit." Einstein's 1905 theory of special relativity says that light travels at a constant speed, regardless of how fast an observer is traveling, and that nothing in the universe can go faster than it.
If these particles truly did outpace light, that would upend physics as we know it, as this L.A. Times story explains.
The release acknowledged as much, pointing readers to the paper detailing OPERA's discovery and asking outside scientists to chip in to confirm the result or figure out what else might be going on.
"When an experiment finds an apparently unbelievable result and [can't] account for it, it's normal procedure to invite broader scrutiny," CERN research director Sergio Bertolucci said in a statement. "If this measurement is confirmed, it might change our view of physics, but we need to be sure that there are no other, more mundane, explanations. That will require independent measurements."
Several physicists contacted by the Los Angeles Times on Thursday evening said the OPERA team had probably made errors in its measurements.
Clocking with precision how long it takes neutrinos to leave a collider and hit a target 450 miles away "is not a simple thing," said Stan Wojcicki, an emeritus professor of physics at Stanford University. "It's not like measuring the speed of someone doing the 100-meter dash."
Friday's news release from CERN began addressing questions about the team's methods. It noted that the scientists had teamed up with metrologists -- experts in making measurements -- from several institutions, and used state-of-the-art GPS systems and atomic clocks, to make their observations. The margin of error was within 10 nanoseconds, CERN reported.
"Our measurements have low systematic uncertainty and high statistical accuracy and we place great confidence in our results," Dario Autero, a researcher on the team, said in the release.
Wojcicki said Thursday that he was reserving judgment on the results until he had a chance to read the paper and view a seminar on the results that took place at CERN on Friday morning. "I tend to be skeptical," he told The Times. "Then again, when I was younger and the field was just starting, there were a lot of surprising developments early in the game."
For example, physicists discovered just in the last 15 years that neutrinos have mass and that they can change from one type to another. "People were very skeptical," Wojcicki said. "If you asked many respectable physicists early in the game at a comparable stage [then], they would have said it was wrong."
Lisa Randall, a professor of physics at Harvard University and author of "Knocking on Heaven's Door," said that the neutrino discovery -- and scientists' reactions to it -- offer a good view of the way the scientific process is supposed to progress.
"This is how science works," she told The Times. "It could turn out it's wrong. But if it's right, it forces us to extend our theories."
-- Eryn Brown
Photo: In this 2005 photo provided by CERN, technicians with the European Organization for Nuclear Research check the magnets that will direct protons towards the target for the CERN Neutrinos to Gran Sasso (CNGS) project in Geneva. The project team fired a neutrino beam 454 miles (730 kilometers) underground from Geneva to Italy. They found that it traveled 60 nanoseconds faster than light. Credit: CERN