The physics of a dowsing pendulum

Oct 1990

DOWSING, the art of searching for water or minerals using a hand-held pendulum, may really work, according to an Australian engineer. Frank Irons of the University of New South Wales has analysed the chaotic swings of dowsing pendulums. His analysis shows that diviners might be able to detect ore deposits by the variations in the force of gravity they produce (European Journal of Physics, vol 11, p 107).
Dowsers rely on changes in the swings of their pendulum to tell them when they are standing above minerals or water. When the pendulum merely swings back and forth, this indicates nothing special. A circular motion, on the other hand, signals success.
According to Irons, dowsers report a characteristic sequence of changes in the behaviour of pendulums when they are held above ore deposits. First the direction of the swings starts to rotate, then the swings turn into an elliptical motion. Finally, the pendulum traces out a circle.
Irons explains this sequence by looking at the forces which drive pendulums. For instance, the steady swinging of a pendulum needs a rhythmic push from the dowser's fingertips to keep it going. Irons says this push can be so small as to be imperceptible even to the dowser.
When it is swinging steadily, the combination of the force of gravity and the drive from the dowser's fingers makes the pendulum sensitive to small changes in the forces acting on it. He believes that the transition from plain swings to the significant circular motion could then be caused either by a slight increase in the tempo of the dowser's rhythmic push or, more importantly, a small fall in the force of gravity. 'An increasingly positive dowsing reaction . . . might occur either from an increase in the rate of oscillation of the fingertips . . . or conceivably (and this may be relevant in some instances) from a decrease in the acceleration due to gravity as might occur when traversing an ore body,' says Irons.
According to Irons, it would be easy for charlatans to fractionally increase the tempo of their pushes to give the same effect as a change in the force of gravity. He suggests that further studies could identify whether dowsers use finger muscles to alter the pendulum's swing.
Irons' work follows a surge of interest in dowsing-type pendulums because of their chaotic behaviour. In some cases, the motion of a pendulum can become truly unpredictable, and the swinging has become a metaphor for chaos. From issue 1737 of New Scientist magazine, 06 October 1990, page