08.26.04
The Eclipse and the Pendulum
It happens that your attention is grabbed by a misleading combination of signals. What’s interesting is how frequently this results in noticing something that is itself interesting.
A case in point. Spotting ‘Allais’ and ‘Foucault’s Pendulum’ in an article clearly signified, to me, Umberto Eco. There is Eco’s novel, for starters. Then there is my awareness that Eco has written frequently about Alphonse Allais, one of his favourite authors.
Well, as it turned out, the article recounted the curious observations of Maurice Allais in 1954, when he recorded the behaviour of a pendulum over the course of 30 days. This included a solar eclipse when, to his astonishment, the pendulum appeared to speed up slightly.
This, the ‘Allais Effect’, seems to run counter to the general theory of relativity, which has the anomolists hyperventilating with glee, and the scientists running to conduct experiments at every eclipse they can find, like this.
The latest evidence (warning: PDF) seems to be that the eclipse causes an almost instantaneous temperature drop in the air, which causes air mass movement significant enough to affect the pendulum. This isn’t, in and of itself, significant enough to explain the whole of the Allais Effect. On the other hand, the measurement of the Allais Effect is itself controversial, suggesting that, not for the first time, a solution may have been found for a problem that never really existed.