Appel à candidatures pour le Prix Maurice Allais de Science Economique 2019

Call for applications for 2019 Maurice Allais Economics Prize

Maurice Allais’s experimental research in optics: sightings at marks and collimators

By Jean-Bernard DELOLY

This research was carried out between 1958 and 1960 and was cut short at the same time as Maurice Allais’s other experimental research projects: see the account of these projects (Click HERE) and the table “Experiments conducted by Maurice Allais of under his direction” (Click HERE).

▪ The observations consisted in monitoring the deviations detected during sightings at marks (sightings at a vertical target mark using a telescope) or at collimators (sightings at the vertical line of the reticle, illuminated by a bulb mounted in the place of the eyepiece, of a telescope focussed at infinity and therefore used as a collimator).

These elements were mounted on two columns directed along an approximately north-south axis and duplicated (the columns remaining the same) so as to permit both north-south sightings and south-north sightings.

As for the pendulum, the observations involved were conducted continuously (one series of sightings every twenty minutes) for a period close to one month.

▪ Two programmes of experiments were conducted: the first in June-July 1958 at Saint-Germain by Maurice Allais, in tandem with an other programme making simultaneous use of two anisotropic pendulums (Proceedings of the Académie des Sciences, vol. 247, 3 Novembers 1958, n° 18, p. 1428-1431 – Click HERE), and which used only sightings at marks, and the second in February-March 1959 at the IGN [National Geographic Institute – Translator], by an IGN team, following directions given by Maurice Allais; this one included both sightings at marks and sightings at collimators.

Only partial use could be made of these experiments owing to various fine tuning issues. Moreover, in contrast to the meticulous practice observed for the pendulum, the published accounts of these experiments do not include any analysis of possible perturbation factors.

Nonetheless they provided a number of results remarkable enough for us to regret that it was not possible to continue them:

a) From analysis of the slow deviations detected over the month – deviations the scale of which was considerably greater than any possible errors of measurement – it emerged that:

– whereas for the sightings at marks the deviations were of the same amplitude and in the same direction for the South-North sightings as for the North-South sightings, both at Saint-Germain and at the IGN, for the sightings at collimators they were of the same amplitude but in opposite directions, their amplitude being this time 2.5 times as great as that detected for the sightings at marks – and this notwithstanding the fact that the marks and the collimators were fixed on the same columns.

This seems to rule out the possibility that these deviations were due to deformations of the support: hence the effects detected can be attributed only to modifications of the space between the telescopes and the marks (or collimators), i.e. to an anisotropy of optical space, while the difference in behaviour between the mark and the collimator sightings can be explained only by the fact that the physical phenomena involved are not exactly the same.

If this phenomenon were confirmed it would be quite a remarkable discovery.

Strangely, however, so far no one has come forward to repeat the experiment.

– in all cases they displayed a close approximation to being the sum of a linear “drift” (of the order of 10-6 rd per day) with a highly significant sinusoidal variation (of amplitude approximately 10-5 rd) and period of about 1 month – a period corresponding a priori to a lunar influence.

It would appear in fact that it is a monthly lunar sidereal component, as for the pendulum (the adjustments are better than for a monthly synodic component).

– as with the pendulum azimuths, efforts to explain the drifts detected over a month in terms of the presence of a half-yearly component find that its extrema are close to the solstices and equinoxes.

b) The investigation of diurnal variations, the amplitude of which was considerably less (of the order of 10-6 rd), was seriously disturbed by various difficulties:

– with regard to the Saint-Germain experiments (so only sightings at marks), only the last two weeks were able to be fully exploited.

As with the slow deviations, the deviations appeared with the same amplitude and in the same direction, both for the 24 hour component and for the 24 h 50 component.

– turning to the IGN, the research report concludes against the presence of significant diurnal cycles, but this conclusion seems to owe a great deal to the very high number of observers (26), who also took over from another at regular times (leading to a bias in favour of a 24 h cycle) and to the methods of correcting the “personal equations” of the observers.

c) Moreover a highly remarkable phenomenon noted during the June-July 1958 observations was the phase agreement (within a five minute margin) of the lunar diurnal components of 24 h 50 and the half-sum of the readings of the two telescopes (these results having been obtained by making use of the 2 weeks during which the sightings at marks were exploitable for the determination of diurnal variations).

It should be recalled that one of the two pendulums was installed far underground in a quarry, thereby excluding any temperature influence.

This agreement makes it highly probable that this lunar diurnal component does indeed exist and that a connection was indeed detected between two phenomena entirely different in nature: the one mechanical and the other optical.