Superluminary Neutrinos Turn Out to be a Letdown

By Calvin Leung, 11th Grade, Fremont, CA

Last month, the OPERA team based in Italy announced they had measured neutrinos traveling faster than the speed of light. Following this announcement, the experiment has come under intense scientific scrutiny for errors that could be responsible for such startling results. One paper, New Constraints on Neutrino Velocities, published by Cohen and Glasgow, may finally ironically turn this breakthrough into yet another reinforcement of the concept that light sets for universe a universal speed limit.

Turns out that a particle which moves faster than light does emits a special type of electromagnetic radiation called Cherenkov radiation, which is responsible for the alien glow commonly associated with nuclear reactors. Cherenkov radiation is somewhat like a sonic boom—when a particle travels faster than light, the electromagnetic waves it emits “pile up” much like sound waves do in the case of supersonic aircraft. This shock wave excites electrons to a higher energy level, and the resulting drop back to the ground state causes the release of electromagnetic radiation. This jostling of electrons in the surrounding medium rapidly reduces the energy of the neutrinos to a terminal energy (somewhat like terminal velocity due to air resistance), and as a result, only a few neutrinos having more than terminal energy should reach Gran Sasso.
Since the OPERA team repeatedly failed to detect any Cherenkov radiation from superluminary particles, and an unusually high number of high-energy neutrinos were detected, Cohen and Glasgow conclude that said neutrinos could not have been moving faster than light.

An earlier article featured on this website cautioning readers to remain hopefully skeptical made an important point—the universal speed limit has been tested in countless experiments over the past century, and it is highly unlikely for a single experiment to overturn a century of experimentation.
A. G. Cohen and S. L. Glashow, New Constraints on Neutrino Velocities, arXiv:1109.6562.