Repeating the experiment: Alan Garner and the faster-than-light neutrinos

The recent experimental result showing that one type of neutrino can apparently travel faster than light is looking rather dubious. The result was first reported in September from the Gran Sasso lab in Italy, which claimed to have detected neutrinos from CERN a few billionths of a second quicker than was predicted. It’s fair to say there’s a lot of scepticism in the physics community about the result (Professor Jim Al-Khalili offered to eat his boxer shorts on live TV if the result is correct), and the researchers at Gran Sasso are being suitably cautious about it all. Even other teams working out of the same lab disagree with the result.

If the result stands, then Einstein’s theory of special relativity with its prohibition on faster-than-light travel, will need to be reworked. The theory states that nothing can be accelerated beyond the speed of light. And because of the absolute and constant value of this speed, it is intimately connected with the nature of space and time itself. As the speed of an object increases and approaches the speed of light, time slows down. At the speed of light itself, time stops. So photons, or light particles, live in an eternal present moment with no past or future. Theoretical particles such as tachyons which travel faster than the speed of light, travel backwards through time. So, to break through this barrier could mean that time travel into the past is possible; which means curtains for causality. Hence the fascination and concern around Gran Sasso’s result.

How will we know for sure whether this result is correct? The only way is to repeat it, using different experimental set-ups, at different times and in different locations. Why is this repetition so important? Because it’s the best way we know of trying to understand the hidden errors that may have affected the outcome. Scientists are good at measuring random errors that impact upon the (un)certainty of their results. What is much more difficult is identifying and quantifying systematic problems – things that may have gone wrong in the design and execution of the experiment. For example, this experiment relies on measuring the speed of the neutrinos to a certain accuracy. To measure a speed, you need to measure both the time taken and distance travelled. The team at Gran Sasso cannot rule out the possibility that the clocks measuring the start and end of the neutrinos’ journey are not properly synchronised. It’s not trivial to measure the distance (about 730 km) to the required accuracy of a few centimetres either.

Repetition is essential to establishing a scientific reality, then. Yet we don’t give repetition much thought in other areas of our lives. For example, apart from a nice column in the Guardian, rereading books seems to be an unremarked-on activity. Alan Garner is one of my favourite authors and when I was about 11 or 12, I must have reread his book ‘The Owl Service’ about thirty times. It’s based on a story in the Mabinogion, about two men and a woman who is created out of flowers to satisfy their desires, and whose infidelity leads to the downfall of all three. ‘The Owl Service’ takes this tale and turns it into a cyclical event that must be repeated by subsequent generations of a family. The novel cleverly layers events happening at different times, so that the reader realises just how vivid the past is in the minds of the people in the present. Time is not uniform in this book. The past and present happen at the same time and are all muddled up. The inevitability of the repeating events implies an apparent lack of free will in this universe, at least until the characters learn to abandon their prejudices and fears and break the cycle.

I reread it now to learn from it, and to try and understand how Garner tells such a complex, sophisticated story so succinctly (it’s only about 150 pages long). But every time I read it I get lost on a Welsh mountain, frightened of the woman who has turned into an owl.