The recurring action of a mechanical clock depends on the swing of a pendulum, or the oscillation of a balance wheel and balance spring or hairspring, or the vibration of a tuning fork, mechanisms capable of repeating their cyclic movements with great regularity. A counting mechanism, consisting of a gear train with calibrated dial and indicating hands, sometimes with a striking mechanism, marks the number of oscillations that have occurred, although the graduations are in seconds, minutes, and hours. A weight or spring ordinarily supplies power to operate the oscillating and the counting mechanisms. However, temperature changes, accelerations, automatic windings, or electricity may provide the power.
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In physics, Huygens studied pendulums, making the first practical pendulum clocks, and the nature of light. In 1678, Huygens presented his wave theory of light, saying light behaves much like an ocean wave moving through the sea. Later work by Thomas Young confirmed that light acts as a wave.
<u>Pendulum Clock</u>This practical aspect of Huygens’s work is also manifested in the great time and energy he devoted to the perfection of the pendulum clock. Although he had been working on it for some years, Huygens first described his successful application of the pendulum to the escapement mechanism of the standard mechanical clock in 1658.Sometime after he had produced the first pendulum clock, Huygens became interested in its obvious application to the problem of determining longitude at sea. One of the simplest solutions to this important navigation problem involved the construction of an extremely accurate time keeping device with which local time could be compared with a standard time at, say, Paris or London. Although the pendulum clock was the most accurate such device then available, its motion was easily disturbed by the movement of the ship at sea. In an effort to overcome this difficulty, Huygens invented a pendulum whose period of oscillation was independent of the amplitude of its swing (for regular pendulums this isochronous property exists only for very small amplitudes). Although the discovery of a pendulum whose path was a cycloidal arc provided such an isochronous device, it did not solve the problem of constructing a marine clock or chronometer whose accuracy would not be affected by the pitching of a ship.