squareCircleZ on Biorhythms

In squareCircleZ » Trig graphs – how do you feel today?, Murray Bourne at squareCircleZ has a nice Flash gizmo to show biorhythm graphs and links to a site debunking their validity. Actually I think a nice lesson based on this would be to use a similar gizmo to support a demonstration of how sensitive the timing of coincidences between the different cycles is to small perturbations in their frequencies (most of those who experience biological cycles know that they usually aren’t entirely regular!). This might also lead to discussion of other more real biological cycles and periodicities – including nontrig ones like junebug and locust populations – and to the fact that astronomical regularities do have such unearthly precision that they can in fact be followed for many hundreds of cycles to make predictions about coincidences which are actually observed.