PUBLISHED ONMay 08, 2016 5:32 PMByChris Baraniuk
We are told that nothing can travel faster than light. This is how we know it is true.
It was September 2011 and physicist Antonio Ereditato had just shocked the world.
The announcement he had made promised to overturn our understanding of the Universe. If the data gathered by 160 scientists working on the OPERA project were correct, the unthinkable had been observed.
Particles - in this case, neutrinos - had travelled faster than light.
According to Einstein's theories of relativity, this should not have been possible. And the implications for showing it had happened were vast. Many bits of physics might have to be reconsidered.
Although Ereditato said that he and his team had "high confidence" in their result, they did not claim that they knew it was completely accurate. In fact, they were asking for other scientists to help them understand what had happened.
In the end, it turned out the OPERA result was wrong. A timing problem had been caused by a poorly connected cable that should have been transmitting accurate signals from GPS satellites.
There was an unexpected delay in the signal. As a consequence, the measurements of how long the neutrinos took to travel the given distance were off by about 73 nanoseconds, making it look as though they had whizzed along more quickly than light could have done.
Despite months of careful checks prior to the experiment, and plentiful double-checking of the data afterwards, this time the scientists got it wrong. Ereditato resigned, though many pointed out that mistakes like these happen all the time in the hugely complex machinery of particle accelerators.
Why was it such a big deal to suggest - even as a possibility - that something had travelled faster than light? And are we really sure that nothing can?
Let's take the second of those questions first.
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