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The most important and common simple time measuring device was the sundial - the only one of the listed types of clocks based on the Sun's daily movement. Ancient man realized the relationship between the length and position of the Sun's shadow from objects and the position of the Sun in the sky, and therefore navigated the current time by the Sun. The first clocks were solar devices for measuring the current time in units smaller than one day. The exact date of the appearance of the sundial, which in its original form had the shape of an obelisk - a gnomon, is unknown. The message about them in the manuscript of the Chinese Chiu-pi from about 1100 BC is considered the very first mention of a sundial. The sundial used the constant periodic process of the Earth's rotation.

The gnomon, a vertical obelisk with a scale applied to the ground or a flat stone - a kadran, was the first sundial that measured time by the length of the cast shadow. But the sundial worked only during the day and in clear weather, when the Sun was shining, and even then not accurately enough.

Sundial in the Forbidden City, Beijing

Water clocks, fire clocks - candles with divisions, and hourglasses could work at any time of day and in any weather. They provided an accuracy of time measurement of ± 15-20 minutes.

Clepsydra

Clepsydra - the most ancient clock. A hole is drilled in the bottom of a vessel with water, into which a small diameter tube is inserted. Water slowly flows down it and falls into another vessel, on the walls of which divisions are applied. The water level plays the role of the hour hand. The higher it rises, the more time has "flowed". Ctesibius (c. 2-1 centuries BC) - an ancient Greek mechanic from Alexandria invented a water float clock. It has a dial and one hand. A steady stream of water flowed into a 3-meter-high vessel, in which a float rose - a figurine with an arrow - a stick in his hand. The stick was directed at the dial, where the current time could be counted. Ctesibius's Water Clock. An hourglass is the simplest device for counting time intervals. It consists of two vessels connected by a narrow neck, one of which is partially filled with sand. The time it takes for the sand to pour through the neck into the other vessel can range from a few seconds to several hours.

Hourglass

Candles were used as so-called "fire" clocks, on which marks were evenly applied. The distance between the marks served as a unit of time.

The church primarily needed reliable clocks to clarify the time of worship. At first, sundials coped with this task more or less successfully; over time, they were replaced by tower clocks with a chime.

The next stage in measuring time, the invention of mechanical tower wheel clocks, is attributed to the monk Gerbert of Aurillac, who later became Pope Sylvester II (950-1003). Mechanical clocks used a constant periodic process of pendulum oscillations. The clock was driven by a weight that created a continuous traction force. Through a wheel transmission, the weight was set in motion by a rotating rocker. The balance of such clocks did not have a period of oscillation, so they were not very accurate.

On the dials of such clocks, there was only one hand - the hour hand, and these clocks also struck a bell every hour (the English word "clock" comes from the Latin "clocca" - "bell"). Later, a second hand - the minute hand - was added to the hour hand. The clock goes clockwise - from left to right - because this is the direction in which the shadow of the sundial moves. However, there are clocks whose hands move "counterclockwise".

In 1288, there were already iron tower Westminster chimes.

Big Ben Clock in London

(Big Ben is not the name of the tower, but of the 13-ton bell that rings inside.) In the middle of the 14th century, city bell towers with clocks were built in European cities. Their bells struck church hours, the time of commercial transactions, and the work of artisans. It was also necessary to know the time in manufactories, where the result of the work depended on the exact observance of the duration of individual technological processes.

Mechanical wheel clocks worked reliably only on land; they were unsuitable for sea travel.

In 1657, the Dutch scientist Christiaan Huygens made a mechanical clock with a pendulum. The clock's accuracy increased significantly, but it was still impossible to transport such a clock. In 1670, the anchor escapement was invented, which ensured a uniform movement of the clock mechanism.

Compact portable mechanical chronometers became possible after Huygens invented the rotary balance wheel in 1675 and used a spring instead of weights. The combination of a torsion pendulum, a spiral spring, and an anchor escapement opened the way to creating mass-produced small-sized clocks, marine chronometers, and significantly increased the accuracy of astronomical observations.

Accurate watches—chronometers—were necessary for sea navigation. The Englishman John Harrison made them in 1735. Their accuracy was ± 5 seconds per day, and they were already quite suitable for sea travel. In 1764, the inventor increased the accuracy of his chronometer to ± 1 second per day. At this point, the capabilities of mechanical watches were exhausted.

Antique mechanical pocket watches by Moser

At the beginning of the 19th century, postal services faced the problem of keeping Time, trying to ensure the movement of mail carriages on schedule. As a result, they acquired watches that they could carry with them. And with the advent of railways, train conductors also received watches. The more actively transatlantic communication developed, the more important it was to ensure the unity of timekeeping on different ocean sides. In this situation, mechanical watches were no longer suitable. And then electricity came to the rescue. Electric watches solved the problem of synchronization over large distances - first on the continents, and then between them. In 1851, a cable was laid along the bottom of the English Channel, in 1860 - the Mediterranean Sea, and 1865 - the Atlantic Ocean. And since 1899, the transmission of precise time signals by radio began.

Electric clocks were invented in 1847 by the Englishman Alexander Bain. They were based on a contact controlled by a pendulum swung by an electromagnet. The oscillations were summed up by an electromagnetic counter connected by a gear train to the hands on the dial.

At the beginning of the 20th century, electric clocks finally replaced mechanical ones in systems for storing and transmitting precise Time. The William Shortt clock, installed in 1921 at the Edinburgh Observatory, was the most accurate clock based on free electromagnetic pendulums. Its accuracy was 1 sec/year.

Quartz clocks

In 1918, the first quartz clock was built. In 1937, quartz clocks developed by Lewis Essen were installed at the Greenwich Observatory; their accuracy was about 2 ms/day. In 1944, the accuracy of quartz clocks increased to 0.1 ms/day.

In the second half of the 20th century, electronic clocks replaced mechanical ones. They are based on counting the oscillation periods of a stable quartz generator (resonator) using counters—dividers and displaying readings on an electronic display: electroluminescent-vacuum, LED, or liquid crystal, using decoders. Instead of making electrical contact, they used a transistor, and a quartz resonator performed the pendulum functions.

Today, it is quartz resonators in wristwatches, personal computers, washing machines, cars, and cell phones that form the Time with an accuracy significantly exceeding the accuracy of mechanical clocks: mechanical clocks are wrong by a second per day, and household electronic ones by a second per 1 year! High accuracy, sufficient for household appliances.

There are TV watches, radio watches, telephone watches, GPS watch receivers, computer watches, weather station watches, compass watches, and depth gauge watches.

1972 the world's first electronic watch with a liquid crystal display appeared. At the beginning of the 21st century, more than 1 billion watch movements were produced annually. Most of the watches produced are quartz watches with a dial and hands. But watches with a liquid crystal digital display are much more informative - they indicate the calendar day, day of the week, current month, and much more. And the reading accuracy of digital watches is higher than that of hands. But, despite this, the share of purely electronic watches with a liquid crystal digital time indicator is only about 10% - over hundreds of years, people have become accustomed to watches with hands.

Therefore, most electronic watches are electromechanical, with a quartz resonator and a dial with moving hands. They are driven by a miniature stepper motor. A system of gears transmits the rotation of the motor to the hands. The energy source for electronic watches is miniature "watch" batteries, which last for at least a year.

Only 18 million purely mechanical clocks were produced.

Atom clocks

But astronomy and space flights to distant worlds required much greater accuracy. In 1949, the first atomic clock was built, where the source of oscillations was not a pendulum or a quartz generator, but signals associated with the quantum transition of an electron between two energy levels of an atom. This electromagnetic wave, that is, a photon of radio emission, is characterized by very high stability of energy and oscillation frequency. 1955 the first atomic clock based on cesium atoms appeared; hydrogen and rubidium atoms are used.

Since the invention of atomic clocks, their accuracy has increased, on average, by half every two years. This process continues today.

In 1967, they switched to an atomic time standard.

In the 21st century, electronic Greenwich time appeared on the Internet. On January 1, 2001, the British government officially announced a new time standard, Greenwich e-time (GET).

The head of Microsoft, Bill Gates, is also introducing a new technology for transmitting personal information to wristwatches: SPOT (Smart Personal Objects Technology) - watches, receiving radio signals of the exact Time in the FM range, are able to adjust the Time in accordance with the location automatically.