Many devices can be used to mark the passage of time without respect to reference time (time of day, hours, minutes, etc.) and can be useful for measuring duration or intervals. Devices that measure duration, elapsed time and intervals The flow of sand in an hourglass can be used to keep track of elapsed time. Sundials continued to be used to monitor the performance of clocks until the 1830s, when the use of the telegraph and trains standardized time and time zones between cities. With knowledge of latitude, a well-constructed sundial can measure local solar time with reasonable accuracy, within a minute or two. Sundials were widely used in ancient times. Sundials can be horizontal, vertical, or in other orientations. A sundial shows the time by displaying the position of a shadow on a (usually) flat surface that has markings that correspond to the hours. Shadows cast by stationary objects move correspondingly, so their positions can be used to indicate the time of day. The apparent position of the Sun in the sky changes over the course of each day, reflecting the rotation of the Earth. The word derives from the Middle English clokke, Old North French cloque, or Middle Dutch clocke, all of which mean 'bell'.
Clocks spread to England from the Low Countries, so the English word came from the Middle Low German and Middle Dutch Klocke. The word clock derives from the medieval Latin word for 'bell'- clocca-and has cognates in many European languages. There are also clocks for the blind that have displays that can be read by touch. For the blind and for use over telephones, speaking clocks state the time audibly in words. Most digital clocks use electronic mechanisms and LCD, LED, or VFD displays. Two numbering systems are in use: 12-hour time notation and 24-hour notation. Digital clocks display a numeric representation of time. Analog clocks indicate time with a traditional clock face and moving hands.
This object can be a pendulum, a tuning fork, a quartz crystal, or the vibration of electrons in atoms as they emit microwaves, the last of which is so precise that it serves as the definition of the second.Ĭlocks have different ways of displaying the time. The timekeeping element in every modern clock is a harmonic oscillator, a physical object ( resonator) that vibrates or oscillates at a particular frequency. The electric clock was patented in 1840, and electronic clocks were introduced in the 20th century, becoming widespread with the development of small battery-powered semiconductor devices.
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The mechanism of a timepiece with a series of gears driven by a spring or weights is referred to as clockwork the term is used by extension for a similar mechanism not used in a timepiece. A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation. The next development in accuracy occurred after 1656 with the invention of the pendulum clock by Christiaan Huygens. During the 15th and 16th centuries, clockmaking flourished. Spring-driven clocks appeared during the 15th century. Watches and other timepieces that can be carried on one's person are usually not referred to as clocks. Traditionally, in horology (the study of timekeeping), the term clock was used for a striking clock, while a clock that did not strike the hours audibly was called a timepiece. A major advance occurred with the invention of the verge escapement, which made possible the first mechanical clocks around 1300 in Europe, which kept time with oscillating timekeepers like balance wheels. Water clocks, along with sundials, are possibly the oldest time-measuring instruments. There is a range of duration timers, a well-known example being the hourglass. Some predecessors to the modern clock may be considered "clocks" that are based on movement in nature: A sundial shows the time by displaying the position of a shadow on a flat surface. Devices operating on several physical processes have been used over the millennia. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, and the year. The Shepherd Gate Clock at the Royal Observatory, Greenwich Digital clock radio 24-hour clock face in FlorenceĪ clock, or a timepiece, is a device used to measure and indicate time.
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