Ask a Physicist Answers

There seems to be a lot of debate about how accurately CERN measured the departure of their neutrinos. Could they not aim them at some other neutrino detector in the world and just use the difference in distance and time from the readings in Italy as this would eliminate the error in not knowing exactly when the neutrinos left CERN?

OPERA detector

General view of the OPERA Detector
Image from the OPERA experiment.

MINOS detector

Picture of the MINOS detector in the Soudan Underground Mine State Park, during (re)construction.
Image courtesy of Jon 'ShakataGaNai' Davis

Answer: Using another neutrino detector is not feasible right now. Neutrino detectors are not scattered plentifully about the landscape. They are complicated pieces of equipment that have to be shielded in underground laboratories. The OPERA experiment that made this measurement only has one of them at its disposal.

However, a version of your idea is actually being used by another neutrino experiment, MINOS, based in Fermilab outside of Chicago. They have two neutrino detectors, one at Fermilab itself (the “near” detector) and one in a mine about 450 miles away (the “far” detector). They are therefore able to measure the time difference between detection of the beam in the near and far detectors, so in principle they can determine both the departure and arrival times of the neutrinos. The MINOS experiment will probably be the one to replicate the OPERA experiment and see if they, too, measure a speed faster than light.

Answered by:

Alan Chodos, PhD
Associate Executive Officer
The American Physical Society

Submitted by:

Adam Dougall from Wymondham