THINGS ARE SELDOM WHAT THEY SEEM -- CHRISTIAAN HUYGENS , THE PENDULUM AND THE CYCLOID

Christiaan Huygens is universally credited with being the first person to regulate a clock using a pendulum - even though, in fact, his invention was intended to count the swings of a pendulum using a clock mechanism.

At roughly the same time, Huygens and others became aware that the period of the pendulum varied according to the amplitude of its swing. Overcoming that problem of anisochronism has been the bane of clockmakers for the following 350years.

Huygens himself, with good theoretical support, invented a device to solve the problem - the so called cycloidal cheeks. This is a very important passage in the history of science. The associated mathematics became a foundation of kinematics subsequently picked up by Newton and Euler et al.

The "cycloidal pendulum" has long been regarded by clockmakers as the solution to the anisochronism of the pendulum. The literature is littered with confusing and frequently erroneous references to this episode in the history of tools of science.

In this paper Alan will develop a coherent view and also demonstrate that Huygens was wrong about the cycloidal pendulum. Alan is a retired aeronautical engineer. His career included twenty years in the RAAF, four years in the Commonwealth Bureau of Transport Economics, and thirteen years in the Civil Aviation Safety Authority regulating the reliability and durabilty of of the Australian civil aviation fleet. In the 1990s he was an advisor on airworthiness standards and procedures to the International Civil Aviation Organisation. Alan has been involved with horological science and the restoration of clocks as an amateur for some thirty years.