Foucault's Pendulum

On Sunday we watched Foucault's Pendulum keep time with the earth at Cosmo Caixa in Barcelona. It was like being hypnotised into a meditative state, and then woken abruptly when one of the metal sticks was knocked down, marking time.
Someone has put a rope in the trees above Petit Paris. It is hard to meditate on movement however, when one of your children is the ball, and you cannot be sure of the stength of the knots.