  The attraction of the Moon on objects at the surface of the Earth gives rise
to a so-called tidal force which is of the order of 1/10,000,000 times the
gravitational force of the Earth. For instance, when the Moon is located
between the Earth and the Sun (new moon) the distance from a given terrestrial
location to the Moon is shorter at noon than at midnight. This reduces the
gravitational acceleration and therefore increases the period of a simple
pendulum by a small amount. Although the change is of the order of 100
nanoseconds it appears that it can be detected. We give some preliminary
results and discuss how the accuracy can be further improved. It is hoped that
the present paper will encourage new experiments in this direction.
