Speedy Neutrinos Could Turn Physics Universe Upside-Down
Sep 23, 2011 12:20 PM PT
A multinational research team says it's found neutrinos that travel faster than the speed of light.
For the Opera neutrino experiment (results of which can be read here), scientists basically shot a high-intensity, high-energy beam of muon neutrinos from the CERN SPS accelerator in Geneva toward the LNGS underground laboratory at Gran Sasso, Italy, 730 km (454 miles) away. They measured the speed at which the neutrinos traveled.
Their findings, which CERN has described as being at odds with the established laws of nature, were so startling that the Opera team has decided to invite further scrutiny.
CERN held a seminar on Friday to present the results of the Opera experiment. A webcast of the seminar can be viewed here.
The report has sent scientists into a tizzy because "a particle traveling faster than the speed of light would violate causality," Michael Witherell, vice chancellor for research at the University of California, Santa Barbara, physics department, told TechNewsWorld. "In other words, an event can have an effect on an earlier event."
That "would completely overturn our understanding of physical reality," and the results would have to be reproduced in several experiments using different techniques before they're accepted, Witherell said.
The Opera team did not respond to requests for comment by press time.
What the Opera Team Discovered and How
Scientists from the Opera team cooperated with experts in metrology, or the science of measurement, from CERN and other institutions to perform a series of high-precision measurements of the distance between CERN SPS and LNGS.
The distance between the two was measured with an uncertainty of 20 cm over 730 km, meaning there was a deviation of no more than 20 cm over that distance.
Advanced GPS systems, atomic clocks and other sophisticated instruments were used to ensure the scientists could measure the neutrinos' time of flight to within less than 10 nanoseconds of accuracy.
A neutrino, by the way, is an electrically neutral elementary subatomic particle with a small mass that usually travels close to the speed of light.
The neutrinos' velocity was determined using high-statistics data collated by the Opera neutrino detector at LNGS from 2009. This detector consists of two identical Super Modules, each being an instrumented target section with a mass of about 625 tons followed by a magnetic muon spectrometer.
Each of the modules consists of a number of walls filled with emulsion film and lead units interleaved with scintillating strips composing the target tracker.
Scintillating strips are used in tracking muons.
The emulsion film and lead units are essentially basic cameras, and there about 150,000 of them in the two Super Modules.
It took the neutrinos about three milliseconds to travel the 730 km. This is a measure of the time distribution of protons each time the beam was fired, aggregated and normalized. It's not possible to precisely measure the time of flight of any single neutrino because any proton might produce the neutrino detected by the Opera detector.
Blinded by the Light?
Scientists are questioning the results of the Opera experiment.
The problem is that Opera's findings might overturn Albert Einstein's theory of special relativity, which states that there's an ultimate speed limit, equal to about 300,000 km per second (186,000 mph).
Light particles travel at this speed in a vacuum because they have no mass, but neutrinos have mass, and those produced in high-energy collisions at CERN should travel "at about 99.9998 percent of the speed of light," stated Joseph Lykken, a scientist at the Fermi National Accelerator Laboratory.
Special relativity is only meant to hold when space-time is flat. Realizing this, Einstein developed his general theory of relativity to explain the physics of curved space, Lykken told TechNewsWorld.
"We have good evidence that space-time is quite flat near the Earth, so a violation of special relativity could mean that the curvature of space is somehow hidden -- perhaps it occurs in extra dimensions of space," Lykken remarked.
Another possibility is that special relativity doesn't exactly apply to neutrinos, Lykken suggested.
This "would cause a crisis in quantum theory since our understanding of elementary particles relies on a very delicate dance between quantum behavior and special relativity," Lykken elaborated.
So, time travel might be a possibility, or there might be pocket dimensions in space, and the pas de deux between quantum science and special relativity might turn into a tango. No wonder scientists are excited.