Se qualcosa dovesse andare più veloce della luce verrà fuori. Per il momento forse è più opportuno controllare i circuiti di calcolo, misurare bene la distanza tra il Cern e il Gran Sasso in modo proporzionato al nanosecondo. Lanciare un segnale radio in triangolazione con un satellite nel momento in cui il neutrino lascia il Cern implica dover prendere in considerazione ciò che può influenzare il viaggio come la presenza di campi magnetici. E questi non sempre sono prevedibilissimi. Einstein può rilassarsi (probabilmente) secondo quanto sostiene il prof. Frank Close di Oxford.
Di sicuro al momento c’è solo che se la Gelmini lo avesse scavato realmente, il tunnel, avremo meno dubbi sulla reale distanza.
Measuring the time to accuracies of nanoseconds involves accounting for the time that electronic signals take to pass through circuits, into readouts and onwards to further parts of the complex of counters, computer chips and the myriad pathways of the nanoworld. If you have all of these measured, and if they are indeed everything you need to know, then you can determine the time elapsed – with some uncertainty. This they have done. However, if there is some unexpected bottleneck, unrecognised and hence unaccounted for, the timing might be a few nanoseconds amiss.
Then there is the measurement of the distance. Determining this to an accuracy of about 10 centimetres in 730km is required – and, apparently, is possible by geodesy. But precisely how this is done is, to me at least, still one of the many mysteries in this experiment. You certainly don’t do it with a tape measure, even if you had one that was accurate to atomic sizes. Sending a radio signal up to a satellite, at the instant the neutrino leaves Cern, which then passes it on down to the receiver in Rome, and comparing which arrives first, and by how much, has its own difficulties. The speed of radio waves through the atmosphere is affected by magnetic fields, and by other phenomena; it is far from simply a radio beam passing through a vacuum at “the speed of light”.