Ellis, however, remains skeptical. Many experiments have looked for particles traveling faster than light speed in the past and have come up empty-handed, he says. Most troubling for OPERA is a separate analysis of a pulse of neutrinos from a nearby supernova known as 1987a. If the speeds seen by OPERA were achievable by all neutrinos, then the pulse from the supernova would have shown up years earlier than the exploding star's flash of light; instead, they arrived within hours of each other. "It's difficult to reconcile with what OPERA is seeing," Ellis says.
Ereditato says that he welcomes skepticism from outsiders, but adds that the researchers have been unable to find any other explanation for their remarkable result. "Whenever you are in these conditions, then you have to go to the community," he says.
This article is reproduced with permission from the magazine Nature. The article was first published on September 22, 2011.