The cycloid is the evolute of an identical cycloid . This means that if a thread supporting a weight is forced to move along a cycloid, then the weight supported by the thread describes another cycloid. However, because the time a body takes to reach point A on the cycloid is independent from its starting point, (tautochron curve ),it follows that the period of suspension is independent from the amplitude of oscillation. The exhibit shows the difference between a cycloidal pendulum, which is perfectly isochronic, and an ordinary pendulum.