Clock

A clock or chronometer is a device that measures and shows time. It is one of the oldest human inventions, made to measure short periods instead of using natural units like the day, the lunar month, and the year. Early examples include the sundial, which uses the position of a shadow, and the hourglass, which uses flowing sand to track time.

The first mechanical clocks appeared around 1300 in Europe, using a verge escapement and balance wheels. A big improvement came in 1656 when Christiaan Huygens invented the pendulum clock, which was much more accurate. As travel became more important, the need for precise timekeeping grew, leading to many changes in clock design.

Today, all modern clocks use a harmonic oscillator, such as a pendulum, balance wheel, tuning fork, quartz crystal, or even the vibrations of electrons in atoms. Clocks can show time in two main ways: analog clocks with hands on a clock face, and digital clocks that show numbers. Some clocks, like speaking clocks, are made for people who cannot see the display.

Etymology

The word clock comes from an old Latin word meaning 'bell,' called clocca. Many languages in Europe have similar words. Clocks came to England from the Low Countries. The English word changed over time from words like Klocke in Middle Low German and Middle Dutch, as well as clokke in Middle English, cloque in Old North French. All these words meant 'bell'.

History of time-measuring devices

Main article: History of timekeeping devices

The Sun looks different in the sky during the day because the Earth turns. Shadows from objects move during the day, and we can use these shadows to tell the time. A sundial shows the time by using a shadow on a flat surface with marks for the hours. Sundials can be flat on the ground, on walls, or other shapes. People used sundials a lot in ancient times. If you know where you are on Earth, a good sundial can show the right time, usually within a minute or two.

Many tools can help us know how much time has passed, even if they don’t show the exact hour or minute. Examples are candle clocks, incense clocks, and the hourglass. Candle clocks and incense clocks work because they use up a substance at a steady rate. The sand in an hourglass slowly moves through a tiny hole, showing when a certain amount of time has passed.

Water clocks may be almost as old as sundials. We are not sure when or where the first water clock was made. The simplest water clock is a bowl that lets water flow out, and we know these existed in Babylon and Egypt around the 16th century BC. Other places, like India and China, also had early water clocks, but we do not know exactly when.

The Macedonian astronomer Andronicus of Cyrrhus built the Tower of the Winds in Athens in the 1st century BC. It had a large water clock inside and sundials on the outside. The Greek and Roman people made water clocks better. These ideas moved through Byzantine and Islamic times and back to Europe. China also made advanced water clocks by the year 725 AD.

Some water clocks were made separately in different places, and some ideas moved because of trade. In the past, people did not need clocks to be as exact as we do today. Water clocks were mainly used for astrological reasons. These water clocks were made to match the Sun’s position. They were not as exact as modern clocks, but they were the best clocks people had for thousands of years until the pendulum clock was made in Europe in the 1600s.

The first known geared clock was made by the scientist Archimedes around the year 3rd century BC. His clock could tell the time and even make birds move and sing every hour. The clock used weights, strings, and water to keep working.

In Europe, between the years 1280 and 1320, people wrote more about clocks in church records. This shows that a new kind of clock was made. These clocks did not use water but used weights that moved down. This made the clock tick, and it came from ideas used to ring bells. This way of making clocks tick is called the escapement.

A very big water clock called the ‘Cosmic Engine’ was made by the Chinese scientist Su Song in the year 1092. This clock tower was about ten metres tall and used falling water and liquid mercury to move a model of the sky that could solve problems about space and time.

Spring-driven clocks were made in the 1400s. Making smaller clocks was hard, and making them exact and reliable was also hard. Clocks could be beautiful works of art or cheaper clocks made for homes. The escapement was very important for how exact the clock was, so people tried many different ways to make it work.

The next big step in making clocks exact happened after 1656 with the pendulum clock. Galileo thought of using a swing to keep time earlier, but Christiaan Huygens is usually given credit. He worked out the math and made the first pendulum clock in 1657 in the Hague. In England, the longcase clock or grandfather clock was made to hold the pendulum, by William Clement in 1670 or 1671.

In 1675, Huygens and Robert Hooke invented the spiral balance spring, to control how fast the clock’s wheels moved. This helped make small, exact pocket watches possible.

Better clocks were very important for ships at sea, because knowing the exact time helped figure out where the ship was.

For many years, Britain made most of the best clocks, but in the United States, people learned how to make many clocks quickly by using interchangeable parts. In 1816, Eli Terry and other clockmakers in Connecticut made this happen.

In 1815, the English scientist Francis Ronalds made the first electric clock that used dry pile batteries. In 1840, Alexander Bain, a Scottish clockmaker, got a patent for an electric clock. These clocks used electricity to wind their springs.

In 1880, people found that a type of crystal called quartz could work with electricity. The first quartz clock was built in 1927 in Canada by Warren Marrison and J.W. Horton at Bell Telephone Laboratories. Quartz clocks became very popular because they were exact and cheap.

Today, the most exact clocks are atomic clocks. The idea for them began with Lord Kelvin in 1879. The first exact atomic clock, using the atom caesium-133, was built by Louis Essen in 1955 at the National Physical Laboratory in the UK.

Operation

The invention of the mechanical clock in the 13th century changed how people kept track of time. Instead of using shadows on sundials or water flowing in a water clock, clocks began to use regular swings or vibrations. These could be more accurate. All modern clocks work on the idea of regular swings or vibrations.

Clocks have several key parts. An oscillator moves back and forth at a steady rate. A controller keeps the oscillator moving and changes its motion into pulses. A counter adds up these pulses, turning them into seconds, minutes, and hours. Finally, an indicator shows this information in a way people can read. Power sources for clocks include weights and springs in mechanical clocks, and batteries or electricity in electric clocks. The timekeeping part of a clock, called an oscillator, can be a pendulum, a balance wheel, a tuning fork, a quartz crystal, or even the vibrations of atoms in atomic clocks. Some clocks get their time from more accurate external sources.

Types

Clocks can be grouped by how they show time and how they keep time.

Time display methods

Analog

Analog clocks show time with moving pointers called "hands" on a circle with numbers. The most common type has an hour hand and a minute hand. Some also have a second hand. Another type is the sundial, which uses the sun's shadow to show time.

Digital

Main article: Digital clock

Digital clocks show time with numbers. They can use a 24-hour format (00–23) or a 12-hour format with AM/PM. Many digital clocks use electronic screens, but some flip clocks change physical pages to show new numbers each minute.

Hybrid (analog-digital)

Some clocks mix styles, showing hours and minutes like analog clocks but displaying seconds digitally.

Auditory

Main article: Talking clock

Auditory clocks speak the time aloud, either in words or by sounds, helping people who are far away or unable to see the display.

Word

Word clocks show time using sentences, like "It's about three o'clock."

Projection

Main article: Projection clock

Projection clocks shine a bright image of the time onto a wall or ceiling, making it easy to read from a distance.

Tactile

Some clocks are designed for people who cannot see. These may use touch or Braille to show the time.

Multi-display

Some clocks show time in many ways at once, like having several faces or showing different time zones.

Purposes

Clocks are found in many places, such as homes, offices, and public spaces like railway stations and churches. Smaller clocks, called watches, are worn on the wrist or kept in pockets. Computers, mobile phones, and MP3 players often show the time in a small corner of the screen.

The main purpose of a clock is to show the current time. Some clocks, called alarm clocks, can make a loud sound at a set time, such as to wake someone up. These alarms might start softly and get louder, or they can be paused briefly. Special clocks called training clocks help children learn to tell time by using visual cues. Clocks can also control other devices based on time, like heating systems or recording devices. Computers use a steady signal called a clock signal to keep everything running smoothly.

Time standards

For scientific work, very accurate time measurement is important. Atomic clocks, which use the stable vibrations of atoms, provide the most precise timekeeping. These clocks are large and expensive, but they help set the standard for all other clocks.

Navigation

In the past, sailors needed accurate clocks to know their position at sea. This need led to the invention of precise marine chronometers by John Harrison. Today, satellite navigation systems like GPS provide very accurate time information from satellites.

Sports and games

Clocks are also important in sports and games. Stopwatches time athletes, chess clocks limit how long players have to make moves, and various game clocks track the length of sports games or specific actions within them.

Culture

In the United Kingdom, clocks have been part of many interesting beliefs and stories. Some legends say that clocks have stopped on their own when someone important nearby passed away.

In Chinese culture, giving a clock as a gift is often avoided, especially to older people. This is because the word for "giving a clock" sounds similar to the phrase meaning "attending a funeral."

Specific types

Clocks come in many forms and are used in many ways. From simple sundials of long ago to the precise atomic clocks of today, these devices help us measure and keep track of time. There are many different kinds of clocks, each with its own special way of showing time.

You can find clocks everywhere — on walls, in pockets, in computers, and even in vehicles. They all share the same basic purpose: to show us the time in a way that is easy to understand.

Awards

Some special awards for clocks and watch making include the Grand Prix d'Horlogerie de Genève (GPHG) and the Goldene Unruh. These awards celebrate great design and skill in making timepieces.