In a terse, peremptory-sounding paper posted online on September 29, Andrew Cohen and Sheldon Glashow of Boston University calculate that any neutrinos traveling faster than light would radiate energy away, leaving a wake of slower particles analogous to the sonic boom of a supersonic fighter jet. Their findings cast doubt on the veracity of measurements recently announced at CERN (and posted online here) that clocked neutrinos going a sliver faster than light.
For someone who may have just helped to save the edifice of modern physics (if it was ever really at risk of crumbling down), Cohen is not especially upbeat or relieved. “On the contrary, I am saddened and disappointed,” he says. After all, a lot physicists would love the shocking measurement to be correct. For the experimentalists who made it, it could mean that they had made the discovery of the century. For theorists, it could be the start of an exciting period of creative upheaval. “It gets boring if [nature] always works the same way you expected,” Cohen says.
The result announced at CERN on September 23 (although the news had leaked out ahead of time) was certainly unexpected. By now, if you haven’t heard of it, you must have been a straggler from the Imperial Japanese Army coming out of Iwo Jima’s tunnels. Anyway, to recap, the war in the Pacific is over, and a team of physicists has released data on neutrinos they beamed through the Earth’s crust, from Geneva to the Gran Sasso Massif, near Rome, in an experiment known as OPERA. According to the physicists’ estimates, the neutrinos arrived at destination around 60 nanoseconds too fast, violating the cosmic speed limit set by Albert Einstein’s theory of relativity.
Experts urged caution, especially because another measurement of neutrino velocity—one done in 1987 by detecting particles from a supernova that had gone off in the Magellanic Cloud, just outside our Milky Way—indicated to high precision and accuracy that neutrinos do respect the cosmic speed limit.