Clocks

A clock is a device that measures and displays time. It tracks the passage of time and presents it in units such as hours, minutes, and seconds. Clocks are typically stationary and larger than watches, though both share the same underlying purpose of timekeeping.

The history of clocks spans sundials and water clocks, with mechanical clocks appearing in Europe during the 13th and 14th centuries. The invention of the escapement and gear trains enabled more precise regulation of motion. The pendulum, introduced in the 17th century, further improved accuracy, and in the 20th century electronic and quartz timekeeping emerged. Today, atomic clocks provide the highest accuracy and underpin international time standards.

Clocks differ in mechanism and display. Mechanical clocks use gears powered by a weight or mainspring and regulate motion with an escapement, often aided by a pendulum or balance wheel. Quartz clocks rely on the stable oscillations of a quartz crystal controlled by an electronic circuit. Atomic clocks measure time by the consistent frequencies of atomic transitions. Display formats include analog faces with hands and digital readouts.

Modern timekeeping centers on international standards. Atomic clocks define the most precise time, coordinated globally through networks such as GPS and satellite time signals. Coordinated Universal Time (UTC) serves as the civil time standard, with leap seconds occasionally added to keep it aligned with Earth's rotation. Clocks serve everyday life, industry, transportation, science, and culture, and may include alarms, calendars, and synchronization features.

Common forms include grandfather clocks, wall clocks, mantel clocks, and wristwatches. Some clocks, such as astronomical clocks, display additional information about celestial events. Public clocks and institutional timekeepers reflect historical methods of measuring and coordinating time.