Clock

Long before mechanical clocks, people sought ways to measure time. Sundials used the Sun’s position to indicate the hour, while water clocks measured intervals through a controlled flow of water. Mechanical clocks appeared in Europe in the late Middle Ages, from the late 13th century onward.

A key invention was the escapement, which released the gears in regular steps and controlled their motion. Early public clocks mainly announced the hours and were much less precise than modern ones. Their spread helped communities organize activities around a shared measure of time. Clockmaking became more precise.

In 1656, Christiaan Huygens built the first practical pendulum clock, using the regular swing of a pendulum to regulate its mechanism. Pendulum clocks greatly improved accuracy, although temperature and other factors could affect them. During the 20th century, quartz clocks became widespread. A vibrating quartz crystal provides a very stable frequency that electronic circuits can count.

Today, atomic clocks provide an extremely precise reference. They use natural frequencies associated with atoms such as cesium. Since 1967, the SI second has been defined using a specific transition in the cesium-133 atom. This precision is essential for telecommunications, satellite navigation, scientific measurements and technologies that depend on accurate synchronization.