First we have to construct a pendulum with the bottle.
Them we cut the base and make a couple of holes in one of the sides in order to pass the rope and another hole in the stopper to exit the sand filled.
If the bottle is away from the position of equilibrium it begins to oscillate, describing a trajectory that will be recorded in the soil by the stroke that left the sand that falls from the bottle.
Depending of the length of the rope and on the relationship between distances, we can get different figures.
The figures obtained are known as Lissajous figures, names after French scientist Jules Antoine Lissajous, who first observed this in 1857.
by Anabel and Teresa