One of 2011's Biggest Science "Discoveries"?Big Bang Theory Episode 5.08: The Isolation Permutation
In September 2011, the OPERA neutrino experiment (located in the Gran Sasso tunnel in the Abruzzo region of central Italy) announced that a beam of neutrinos generated at the CERN accelerator in Geneva, Switzerland traveled 450 miles from Geneva to Italy faster than the speed of light. The experimenters claimed that the neutrinos beat a metaphorical beam by 60 nanoseconds. For reference, light travels about 60 feet in 60 nanoseconds.
In the Big Bang Theory TV show called The Isolation Permutation -- episode 5.08, theoretical physicist Sheldon Cooper tries to make fun dinner conversation by discussing this topic. He says, "Faster-than-light particles at CERN: paradigm-shifting discovery or another Swiss export as full of holes as their cheese?"
Are theoretical physicists the only ones who are skeptical of this experimental result because they can't imagine that Einstein’s theory of relativity could be wrong?
Despite all the headlines that one of the biggest science discoveries of 2011 centered around faster-than-light neutrino particles, it turns out that experimental physicists are equally skeptical, and not due to theoretical prejudice. In a nutshell, this experimental result contradicts what we learned from other observations in 1987.
In 1987, two experimental groups -- one in Japan and one in the USA -- detected a pulse of neutrinos originating from a supernova explosion. The SN1987A supernova was in the Large Magellanic Cloud about 168,000 light years from Earth, close enough to be visible to the naked eye. Traveling at the speed of light, the neutrinos reached Earth 3 hours before the light did. The neutrinos originated from the core of the supernova.
The light from the supernova was delayed because it had to get through the remnants of the stellar explosion, not because the neutrinos traveled faster than light. According to University of Rochester Physics Professor Arie Bodek, winner of the Panofsky Prize in Experimental Particle Physics, "If the neutrinos from SN1987A had the same speed as that reported by the OPERA experiment they would have arrived about 4 years before the light did."
Some would argue that neutrinos from a supernova are at substantially lower energy than the neutrinos from CERN, and that the CERN neutrinos travel at a speed faster than light because they are more energetic. According to Professor Bodek, this "explanation" is difficult to quantify because it implies that neutrinos at low energy, which travel a little slower than the speed of light (since we know that the neutrinos have small mass), can be accelerated to some energy that allows them to break the speed of light barrier. Tachyons, which are hypothetical particles that that can only travel at speeds faster than light, must have an imaginary mass. Although it is not clear what an imaginary mass means, the neutrinos either have a real mass, or an imaginary mass, but not both.
A devil’s advocate would say that we know that the SN1987A neutrinos are electron-type neutrinos, while the neutrinos from CERN are muon-type neutrinos, and therefore, there is no contradiction between the two results. However, the discovery of the phenomenon of neutrino oscillations, in which electron neutrinos oscillate and become muon neutrinos and then return to being electron neutrinos as they travel to earth from the sun, implies that electron-type and muon-type neutrinos are not really different from each other since one can turn into another.
So what should we believe?
A confused student at the University of Rochester asked a theoretical physics professor what he thought about the report that neutrinos travel faster than light. The professor paused for a moment and said, "I think it must have something to do with the European financial crisis."
For more information, please see:
Dennis Overbye, Scientists Report Second Sighting of Faster-Than-Light Neutrinos, The New York Times
OPERA experiment reports anomaly in flight time of neutrinos from CERN to INFN Gran Sasso, LNGS Gran Sasso Laboratory News
OPERA photo credit: Pasquale Migliozzi, INFN Napoli, OPERA Collaboration.
This is the first in a series of BIG BANG THEORY TV SHOW SCIENCE posts for the general public. With two physicists in the family, we're huge fans of the show.
c. 2012 Lois Gresh
There are many theories that can explain the CERN results without violating relativity. I don't believe we can go faster than the speed of light, but we can probably go around it: http://www.science20.com/alpha_meme/million_times_speed_light-83202
ReplyDeleteDear Anonymous,
ReplyDeleteThanks for your comment and the link. Very interesting.
The article refers to a theory in which the neutrinos -- during their creation -- jump a certain distance at approx 10 times the speed of light for a short period of time. Then they continue to travel below the speed of light.
To get ahead by 60 ns, the neutrinos would have to travel at 10 times light speed for a period of 6 ns. At about a foot per ns, this means they only travel much faster than light during the first 60 feet.
If this specific theory were accurate, then there would be no contradiction between the Supernova result and the OPERA result.
Imo, this is a big stretch because there's no reason to think this "FTL jump" theory is accurate. Is there mathematical evidence to support the idea that the neutrinos jump approx 10 times the speed of light for the first 6 ns after creation?
The OPERA experiment has one far neutrino detector. OPERA measures the
time of their neutrino interactions with respect to the time profile of the proton beam that hits the target.
MINOS and T2K both have a near neutrino detector and a far neutrino detector. They measure the time the neutrinos interact in the near detector with respect to those in the far detector. Therefore, if the "FTL jump" happens to neutrinos when they are created, MINOS and T2K would only measure the velocity of the neutrinos after "the jump" and would see no effect.