"Most theorists believe that nothing can travel faster than the speed of light. So if this is true, it would rock the foundations of physics," said Stephen Parke, head of the theoretical physics department at the U.S. government-run Fermilab near Chicago, Illinois.

(Related: "Proton Smaller Than Thought—May Rewrite Laws of Physics.")

The existence of faster-than-light particles would also wreak havoc on scientific theories of cause and effect.

"If things travel faster than the speed of light, A can cause B, [but] B can also cause A," Parke said.

"If that happens, the concept of causality becomes ambiguous, and that would cause a great deal of trouble."

Members of the Oscillation Project with Emulsion-tRacking Apparatus, or OPERA, at the European Center for Nuclear