The scientist who headed a European research team that last year measured particles travelling faster than light has resigned, weeks after a rival team cast doubt on the accuracy of those readings.
Italy's National Institute of Nuclear Physics said today that Antonio Ereditato had stepped down from the leadership of the OPERA experiment, whose measurements on the speed of neutrinos were widely questioned when they were announced in September.
Mr Ereditato confirmed his resignation in an email but declined to comment further.
The OPERA team itself had cautioned in September that the measurements needed to be checked by independent researchers because they appeared to go against a key tenet of modern physics - that nothing can travel faster than light.
Breaking that rule, which underlies Albert Einstein's famous special theory of relativity, could have opened the door to a new kind of physics in which time travel and warp speeds might be possible.
In February, the OPERA team acknowledged that it had found a flaw in the technical set-up of its experiment that could have affected the measurements, but held off on calling them wrong.
Then, earlier this month, a rival team called ICARUS clocked neutrino speeds using a different experiment and found they behaved just as expected. They travelled at, but no faster than, light speed.
OPERA, ICARUS and two other teams will try to settle the issue once and for all by conducting further tests at the European Organisation for Nuclear Research, or CERN, in May.