### Jitter

Here’s an old riddle, that some of you may have heard.

François lives in Lyons, and has two girlfriends: one in Marseilles and another in Paris. He can’t seem to choose between them, so he decides on the following strategy. The trains to Paris and to Marseilles both run once-an-hour. He decides to show up at the railroad station at random times, and takes whichever train comes first.

After several weeks, François finds that, on average, 9 times out of 10, he ends up visiting the girlfriend in Marseilles. Clearly, the Fates have chosen for him, so he dumps the girlfriend in Paris and proposes to the girl in Marseilles.

What’s going on?

The answer, if you think about it, is obvious. Both trains run once an hour. But the one to Marseilles leaves on the hour, while the one to Paris leaves at 6 minutes past the hour. If François arrives at random times (a uniform distribution) during the hour, he is 9 times more likely to find that the next train is the one to Marseilles.

The OPERA experiment has released a revised version of their “superluminal” paper. Among the improvements, they give more details on their timing. One factoid jumps out at us: their clock runs at 20 MHz, which means that there’s an irreducible jitter (or granularity) in their timing of events, of 50 ns. Tomasso Dorigo asks if there’s an effect which could bias that jitter in one direction.

I suggest that he consult with François.

## Re: Jitter

The truly unfortunate thing is that the public will now think that the experiments have been validated, which of course they haven’t. Independent reproduction anyone?