Numerical simulation of two pendulums with identical masses coupled by a string with a comparable big string constant. After the first pendulum starts moving, the energy periodically (but faster as compared to the experiment with the medium string constant) moves between both pendulums. The lamps above each pendulum indicate the sum of potential and kinetic energy the pendulum below: The energy increases from black via blue to white, and the status (black white) of the upper hemispherical lamp indicates the pendulum with the (at the moment) highest energy.