What is the difference between sidereal and solar time? How many hours are there in a day

The annual motion of our planet around the Sun is called the annual motion of the Earth; its consequence is the change of seasons.

So, for example, in the northern hemisphere, astronomical summer begins on June 21 or 22 - in summer solstice day, when the rising and setting of the Sun on the horizon and its height at noon hardly change for several days close to this date; At this time the day length is the longest of the year. Astronomical winter begins on December 22 or 23; The length of the day is the shortest of the year. In the southern hemisphere, it’s the other way around: astronomical winter begins on June 21–22, and summer begins on December 22–23.

§ 5. Sidereal day and sidereal time

When solving astronomical problems they use sidereal day. A sidereal day is the period of time between two successive upper culminations on the same geographical meridian of the same star or vernal equinox. A sidereal day is divided into 24 sidereal hours, each hour into 60 sidereal minutes, and each minute into 60 sidereal seconds. A sidereal day is made up of sidereal year. The tropical year is shorter than the sidereal year - the true period of the Earth's revolution around the Sun - by 1224 seconds, or 20.4 minutes. The beginning of the sidereal day for points of each meridian is taken to be the moment of the upper culmination of the vernal equinox.

The closest star to north pole world is the relatively bright Polaris from the constellation Ursa Minor, which to the naked eye seems to always be in one place and almost exactly above the north point, and all the other stars describe circles of different radii around Polaris (more precisely, around the celestial pole). The further a star is from the celestial pole, the larger the circle it describes. Stars located on the celestial equator describe the largest circles. For measuring sidereal time they use sidereal clocks located in astronomical observatories and adjusted so that they go forward every day against ordinary clocks and 3 minutes 56 seconds (see p. 18).

§ 6. True solar and mean solar (civil) time. Equation of time

The time interval between two successive eponymous (upper or lower) culminations of the center of the solar disk is called true sunny days. It is inconvenient to use this unit of time for two reasons. The apparent movement of the Sun occurs not along the celestial equator, but along the ecliptic, inclined to it by 23°27′, and this movement is uneven, since the Earth’s orbit has an elliptical shape, which is why the speed of its movement is not the same at different times of the year. Therefore, the duration of the true solar day varies somewhat from day to day.

In practical life (in science, technology and production), the basic unit of time is taken to be average solar day.

When establishing the duration of the average solar day, instead of the center of the true Sun, they use a point that moves evenly along the celestial equator, making a full revolution throughout the year. Such an imaginary point is called the average sun. The average solar day is the time interval between two successive culminations of the average sun of the same name; their length is always the same and equal to 24 average hours, amounting to approximately 1/365.24 of a year. The Sun is one of the most common stars that make up our Galaxy. Its difference from all other stars is that it is measurably closer to us. Therefore, due to the movement of the Earth, in one day the Sun moves against the background of the rest, “fixed” stars, and the Earth still needs to turn for the Sun to “come” to the same meridian. As a result, the average solar day is 3 minutes 56 seconds longer than the sidereal day! (the star returns to the same meridian before the Sun). Just as in the sidereal day, each hour of the average solar day is divided into 60 minutes, and a minute into 60 seconds.

Until 1956, the value of a second was taken to be 1:86,400 parts of the average solar day, determined by the rotation of the Earth around its axis. To more accurately determine the second in 1960, the XI General Conference on Weights and Measures approved its value, recommended by the IX MAC Congress in 1955, as 1:315 569 25.9747 part of the tropical year, as it was at the beginning of 1900. Such a second was named ephemeris; it is determined with an error of up to (2–5) 10 - 9 . The beginning of the average solar day is taken to be the moment of the lower culmination of the average sun. This kind of time counting is called civil time.

In the USSR, civil time has been used in the national economy since 1919, and in astronomy since 1925. The clocks we use are adjusted not according to true time, but according to mean solar time. Since the speed of the average sun is the same and it passes through the meridian earlier or later than the true Sun, then, consequently, the average day can occur earlier or later than the true ones.

Rice. 4. Equation of Time Graph

Difference between true And mean solar time η called equation of time. Therefore, at any moment the average solar time Tm equal to true solar time T o plus equation of time η , i.e.

Tm = T o + η ,

Where η has a positive value when the true Sun is ahead of the average Sun on the ecliptic, and negative when the average Sun is ahead of the true Sun. (The sign Θ in astronomy denotes the Sun.)

In Fig. Figure 4 shows a graph of changes in the equation of time over the course of a year in half a month. The equation of time is zero around April 15, June 14, August 31, and December 25, when true solar time is almost identical to mean solar time; on these days, clocks set according to mean solar time will show 12 o'clock at noon. The largest (in absolute value) negative value of the equation of time (see Fig. 4), η = - 16.5 minutes, occurs around November 4, and the greatest positive, η = + 14.3 minutes, - February 12.

§ 7. Local and universal time

From the definition of mean solar time it follows that it refers to the place where observations are made. Consequently, mean solar time has its own value for each meridian on Earth and therefore it is also called local mean time .

For any point of the same meridian, local time is preserved constant value, but as the longitude of the observation site changes, the local mean time also changes. When it’s noon in Moscow, then opposite side globe, i.e. 180° west or east of Moscow, at this moment it will be midnight. Within one hour, the celestial sphere in its apparent motion rotates by 1/24 of its full revolution, which in angular units corresponds to 360°: 24 = 15°. Therefore, two points on Earth that have a longitude difference of 15° will have a local time that differs by 1 hour. If you move from the original observation location in longitude, for example, 30° (i.e., two hours) to the east or west, then in the first case the Sun will obviously pass through the meridian of the new observation location two hours earlier, and in in the second case, on the contrary, two hours later than at the original point. Consequently, by the difference in clock readings running in local time at different points on the Earth, one can judge the difference in longitude of these points.

In accordance with the international agreement (Rome, 1883), the Greenwich meridian with a longitude equal to 0°00′00″ was adopted as the prime meridian for calculating geographic longitudes on our planet, and the local Greenwich time, counted from midnight, was agreed to be called worldwide or world time (T o). Therefore, when midnight arrives in Greenwich (near London), i.e. 00:00:00 from local mean time, the local mean time of any point on our planet will be equal to the longitude of that point, expressed in hourly units. In other words, the difference in longitude of two points is equal to the difference in local times at these points at the same moment. This is what the measurement of longitude is based on.

§ 8. Standard time. Maternity time

The presence of different local times at different points lying on different meridians led to many inconveniences.

In 1878, Canadian engineer S. Fleming proposed the so-called standard time ( T p), which was adopted at the International Astronomical Congress in 1884. According to S. Fleming's idea, the entire surface of the globe is conventionally divided by meridians into 24 time zones, each 15° (1 hour) long in longitude. At all points in each time zone, the time corresponding to the middle meridian of that zone is set.

Each of the 24 time zones is assigned a corresponding number from 0 (zero) to 23. The zone whose middle meridian is Greenwich is taken as zero, from which the belts are numbered from west to east. The middle meridian of the first belt is located 15° east of the Greenwich meridian, or 1 hour in time; the middle meridian of the second zone has an eastern longitude of 30°, and its local time differs from universal time (Greenwich) by 2 hours, etc. Thus, the number of each time zone shows how many whole hours the time of this zone differs from universal time ( ahead of him); at the same time, the minutes and seconds in all zones remain the same. Hence, standard time when moving from one zone to an adjacent one, it changes abruptly by 1 hour. If you designate the belt number using n, then standard time is equal to world time T o plus n, i.e.

T n = T o + n.

Standard time in some time zones has special names. So, for example, the time of the zero zone is called Western European, the first zone - Central European, the second zone - Eastern European.

Standard time was first introduced in 1883 in Canada and the USA; at the beginning of the 20th century they began to be used in some European countries.

In our country, they first switched to standard time on July 1, 1919, in accordance with the Decree of the Council of People's Commissars of the RSFSR of February 8, 1918, and at first it was used only for shipping purposes.

The territory of the USSR has 11 time zones, from 2nd to 12th; at the same time, Moscow is classified in the second time zone, although only a small western part of the city is located in the second zone, and most of it lies east of the meridian separating the second and third zones. Thus, it turned out that local time in Moscow is half an hour ahead of standard time - Moscow time. In general, the boundaries of time zones are drawn along the boundaries of administrative units - regions, territories, republics.

In our country, at first, the time of the second zone was used only on railways and telegraphs. By decree of the Council of People's Commissars of the USSR dated January 17, 1924, standard time was introduced everywhere throughout the entire territory of the USSR.

In order to make better use of natural light, i.e., the symmetrical arrangement of the working day relative to half a day, and for some economic reasons, in the summer in many countries of the world, clocks are moved forward relative to standard time by one or more hours, thereby establishing the so-called summer time.

This, for example, was done in France in April 1916, and then some other countries followed suit.

In our country, summer time was also introduced several times. The last time was on June 16, 1930, when, in accordance with the Decree of the Council of People's Commissars of the USSR, the clock hands in all zones of the country were moved forward against standard time by one hour. However, subsequently the hands were not moved back, and since then such time, which differs from standard time by one hour, is called maternity time, and it was in effect all year round until April 1, 1981. However, by decision of the State Commission of Unified Time and Standard Frequencies of the USSR, some regions of the USSR did not introduce maternity time, remaining to live on the same time as Moscow. As a result of this, the autonomous republics of Dagestan, Kabardino-Balkarian, Kalmyk, Komi, Mari, Mordovian, North Ossetian, Tatar, Checheno-Ingush, Chuvash, Krasnodar and Stavropol territories and the regions of Arkhangelsk, Vladimir, Vologda, Voronezh, Gorky, Ivanovo, Kostroma , Lipetsk, Penza, Rostov, Ryazan, Tambov, Tyumen, Yaroslavl, as well as the Nenets and Evenki Autonomous Okrugs and the Khatanga region of the Taimyr Autonomous Okrug continued to live according to maternity time of the 2nd zone (according to the so-called Moscow time) throughout the year, although , for example, the Komi Autonomous Soviet Socialist Republic is located in the 4th time zone, i.e., it was two hours behind its local time.

All this led to the fact that several of the largest industrial regions were simultaneously connected to the country’s power grid, which led to a colossal increase in the load on the power system during peak hours.

In recent years there have been significant changes in the economy of the North, Far East, Siberia and Kazakhstan. In these regions, the population increased quite noticeably, new cities and powerful territorial-industrial complexes appeared, which made it possible to create large industrial centers, and if previously on the map of time zones, for example, the border between the sixth and seventh time zones ( Eastern Siberia) was drawn in a straight line (along the meridian) and divided the Evenki Autonomous Okrug into two parts, this caused a lot of inconvenience. To eliminate this drawback, from October 1, 1981, new time zone boundaries were established on the map of the USSR (Fig. 5; different lines indicate: 1 - time zone boundaries introduced in 1981, 2 - boundaries that existed before 10/01/81 , 3 - meridians). In addition, in accordance with this, at the end of the day on April 1, 1981, after the Kremlin chimes, as always, counted out 12 strikes, an announcement was made on the radio that at that time it was one in the morning in the capital of our Motherland, Moscow. After this announcement, the hands of all clocks in our country were moved forward exactly one hour, and the transition to daylight saving time was implemented. However, on October 1, 1981, the clock hands were not turned in the opposite direction everywhere. This made it possible to streamline the calculation of time within all time zones and restore the calculation of standard time throughout the entire territory of the USSR.

Now in the USSR, every year on the last Sunday in March, the clock hands are moved forward one hour, and on the last Sunday in September one hour back, i.e., there is a regular transition from maternity (winter) time to summer time and vice versa.

The point of introducing daylight saving time is to “carve out” an extra hour during daylight hours and thus make more efficient use of the morning light. According to experts, one “summer” hour in our huge country with its powerful industry saves more than two billion kilowatt-hours annually, which will provide electricity to several million apartments. Maternity time and summer time together can save approximately 7 billion kilowatt-hours per year.

According to doctors' conclusions, based on specially conducted studies, moving the clock hand forward does not affect people's well-being. On the contrary, “an extra hour” daylight reduces the so-called “light starvation”, in particular, less stress falls on vision. The transition from summer to winter time also does not introduce any inconvenience into people’s daily lives. As for railway transport, long-distance telephone and telegraph communications, they operate according to Moscow time throughout the entire territory of the USSR.

Rice. 5. Time zones on the territory of the USSR

§ 9. Date line

At every point on the globe, a new calendar date, otherwise known as a calendar date, begins at midnight. And since in different places On our planet, midnight comes at different times; in some places the new calendar date comes earlier, and in others later. This situation, especially when traveling around the world, previously often led to misunderstandings, expressed in the “loss” or “gain” of an entire day.

For example, the sailors of the flotilla of Ferdinand Magellan (c. 1480–1521), returning in 1522 from a voyage around the world to Spain from the east and stopping in Santiago Bay, discovered a discrepancy of one day between their count of days, which they carefully kept in the ship's register. magazine) and the account kept by local residents, and had to bring church repentance for violating the dates religious holidays. The secret of such a “loss” is that they traveled around the world in the direction opposite to the rotation of the Earth around its axis. Moving from east to west, when returning to their starting point, the travelers spent one day less on the road (that is, they saw one less sunrise) than the days that had passed at their starting point. (If you travel around the world from west to east, then for travelers it will be one day more than at the starting point. Russian explorers who discovered and developed the west coast of North America, having met with local residents who populated the country from the east, celebrated Sunday on that day , when the locals had Saturday.

The meridian, whose longitude is 180°, or 12 hours, is on Earth the boundary between the western and eastern hemispheres. If from the Greenwich meridian one ship goes east and the other west, then on the first of them, when crossing a meridian with a longitude of 180°, the time will be 12 hours ahead of Greenwich, and on the second - 12 hours behind Greenwich.

Rice. 6. Date line

To avoid confusion in the dates of the month, according to international agreement, it was established date line, which for the most part runs along the meridian with a longitude of 180° (12 hours). This is where the new calendar date (day of the month) begins first. In Fig. Figure 6 shows part of the date line.

The crew of a ship crossing the date line from west to east must count the same day twice so as not to gain in the number of days, and vice versa, when crossing this line from east to west, it is necessary to skip one day so as not to gain This is a waste of a day. Related to this is the problem formulated by Ya. I. Perelman, “How many Fridays are there in February?” For the crew of a ship sailing, for example, between Chukotka and Alaska, there may be ten Fridays in February of a leap year if it passes the international date line at midnight from Friday to Saturday from west to east, and not a single Friday if the ship passes this line at midnight from Thursday to Friday heading west.

§ 10. Measurement of time in ancient times

The history of the development of watches - means for measuring time - is one of the most interesting pages in the struggle of human genius for understanding and mastering the forces of nature.

The first clock was the Sun. The higher it rose in the sky, the closer to noon, and the lower it descended to the horizon, the closer to evening, and at first people identified only four “hours” in each day: morning, noon, evening and night.

Rice. 7. Gnomon

Sundial. The first instruments for measuring time were sundials. People have long noticed that the longest shadows from objects illuminated by the Sun occur in the morning, by noon they shorten, and by evening they lengthen again. They also noticed that shadows change not only their size but also their direction throughout the day. This phenomenon was used to create the simplest sundial - gnomon. The dial of such a watch is a flat horizontal platform, on which a pole (rod, plate) is vertically mounted, casting a shadow (Fig. 7). In the morning the shadow of the gnomon faces west, at noon in our northern hemisphere it faces north, and in the evening it faces east. True solar time is determined by the position of the shadow. However, the shadow of the gnomon in such a clock describes not a circle during the day, but a more complex curve, which does not remain constant not only in different months of the year, but changes from day to day.

To rid sundials of this drawback, they began to make their dial from several lines with divisions, each of which was intended for a specific month of the year. So, for example, the ancient Greek astronomer Aristarchus of Samos (late 4th - first half of the 3rd century BC) for his sundial made a bowl-shaped dial with a network of lines drawn on its inner surface, and the clock of the ancient Greek astronomer Eudoxus (c. 408 - ca. 355 BC) had a very complex network of lines on a flat dial, called “arachnea”, which means “spider”.

Rice. 8. Equatorial sundial

Later, astronomers realized that in order to increase the accuracy of the sundial, their pointer should be directed to the celestial pole, i.e., to that point in the vault of heaven that appears motionless when the Earth rotates. If the plane of the dial is placed parallel to the plane of the celestial equator, i.e., perpendicular to the rod, then the end of the shadow of the rod will describe a circle. The speed of movement of the shadow will be uniform, and therefore on such a dial the distances around the circle between the hour markers (strokes) will be equal, and they can be determined on the basis of 360° = 24 hours. This is how they were created equatorial sundial, in which the board with the dial was installed obliquely to the horizon at an angle α = 90° - φ , Where φ - geographical latitude of the place where the clock is installed. On them, the divisions are marked on both sides of the dial (top and bottom), and the pointer is pierced through (Fig. 8). So, for example, in the manufacture of equatorial sundials for latitude φ = 55°47′ the dial angle should be α = 34°13′. In such a watch, during one part of the year (in the northern hemisphere from March to September), the shadow from the rod falls on the dial from above, and during the other part from below, and therefore the watch is suitable for all days of the year. However, timing when a shadow falls from below is difficult.

To eliminate this drawback, sundials began to be made with a horizontal dial with divisions applied based on tg x= tg t sin φ , Where x- angle at the center of the dial between noon line(north-south line) and this division, t = T o- 12 h - hour angle the sun, and φ - geographic latitude of the watch location. On such a dial, the line passing through the strokes corresponding to 6 and 18 o'clock will be perpendicular to the noon line. The pointer in such a watch is a triangle (Fig. 9) with an acute angle equal to the latitude of the given area φ .

Rice. 9. Sundial with a horizontal dial

It was installed so that its plane was perpendicular to the plane of the dial and coincided with the north-south direction. In such watches, the speed of movement of the shadow from the triangle is uneven, and therefore the angles on the dial corresponding to hourly periods of time are unequal.

In ancient times, sundials were widespread. In Egypt, tall obelisks were taken for the gnomon of a sundial. Pilgrims in India used staves with miniature sundials embedded in them.

In 10 BC. e. By order of Emperor Augustus (63 BC - 14 AD), in honor of the victory over Egypt, a large sundial was created in Rome, the gnomon of which was a granite obelisk about 22 m high and weighing 250 tons. On the dial of this clock measuring 170 by 80 m, the shadow of the obelisk fell on 12 sectors from zodiac signs(Fig. 10); This type of clock was used to determine not only the time of day, but also the date and season of the year.

Zodiac in Ancient Greece called the belt in the sky, including 12 constellations located along the ecliptic. In ancient times, the zodiac belt was divided into parts of 30°; they had the names of those constellations through which the ecliptic passed. In each such part - a zodiac sign - the Sun, during its annual movement, was for one month: in the sign of Aquarius - in January - February, in the sign of Pisces - in February - March, in the sign of Aries - in March - April, in the sign of Taurus - in April - May, in the sign of Gemini - in May - June, in the sign of Cancer - in June - July, in the sign of Leo - in July - August, in the sign of Virgo - in August - September, in the sign of Libra - in September - October, in the sign of Scorpio - in October - November, in the sign of Sagittarius - in November - December, in the sign of Capricorn - in December - January. Since the beginning of our era, the point of the vernal equinox, due to precession, has shifted by almost 30°, and the Sun in December - January passes through the constellation Sagittarius, in January - February - through the constellation Capricorn, etc., but the signs of the zodiac remain the same. Now they have no practical significance, but in ancient times they were used to compile horoscopes.

Rice. 20. Zodiac signs

In 1278, the Chinese Emperor Koshu King, trying to improve the accuracy of the sundial, built a gnomon in Beijing, the height of which was equal to 40 steps. In Samarkand, the Uzbek astronomer Ulugbek (1394–1449), grandson of the famous conqueror Tamerlane (1336–1405), trying to increase the accuracy of determining time using a sundial, erected a gnomon in 1430, the rod of which reached a height of 175 steps (about 50 m).

There are known sundials in which noon was marked by ringing. In another clock, by means of a suitably positioned and directed burning glass, the sun's ray controlled the cannon, causing it to fire at a certain time.

The sundial did not require winding, it did not stop and even “moved” more correctly than some current clocks, but with two significant caveats: only in the daytime and in cloudless weather. They continued to be built until the 17th and even 18th centuries.

Sundials, both stationary and portable, have been widely used in social practice by various peoples of our country for a long time. Stationary clocks were made of stone (mainly), less often of metal and wood and, as a rule, of large sizes, which made it possible to increase their accuracy and see them at a considerable distance. Many of them have been preserved not only in museums, but also at the site of their original installation.

Portable sundials, distinguished by their relatively small size, were most often made of metal (brass, bronze, silver), expensive types of wood, and even ivory or tortoiseshell. For orientation to the cardinal points, they were usually equipped with a magnetic needle.

Until recently, the appearance of the first sundial in Rus' was attributed to the 15th century. However, during the renovation of the Transfiguration Cathedral in Chernigov, built in 1031–1036, decor was discovered, the shallow niches of which with a peculiar ornament represented, as historian G.I. Petrash established, elements of a unique cylindrical sundial.

From surviving documents it is known that in 1614 Tsar Mikhail Fedorovich purchased a sundial from a Moscow merchant, and later in the 17th century. “a sundial painted with paints” was installed in the Izmailovo palace complex (near Moscow). A sundial has also been preserved in the village of Kolomenskoye (the estate of the Russian tsars near Moscow), installed at about the same time. At the beginning of the 18th century. used a sundial mounted on the bell tower of the Cathedral of the Svyatogorsk Monastery, but the time of its installation is not known.

Our compatriots who sailed the northern seas used the so-called “uterus”, which was a kind of portable sundial equipped with a compass, which made it possible to navigate the sea. Evidence of the widespread use by our sailors of sundials of various devices are six sundials found by Soviet scientists in 1940 on the northern coast of the Taimyr Peninsula, left there in 1617 by a Russian commercial and industrial expedition.

The Leningrad Museum of the Arctic and Antarctic houses three sundials discovered during excavations in the city of Mangazeya in Siberia. The document, first published by M.I. Belyaev in 1952, notes that in the “list of goods” transported “down the Lena and by sea to the Indigirka River and to the Kolyma and other third-party rivers”, “thirteen queens in bones” are mentioned "

Among the property left by the famous educational figure Feofan Prokopovich (1681–1736), several sundials were discovered, which he used at his observatory near Peterhof (now Petrodvorets), and at the observatory of L. D. Menshikov (1673–1729), producing astronomical observations.

Great attention was paid to sundials by Peter I (1672–1725) and statesman J. W. Bruce (1670–1735); They personally made several watches, which were used at the astronomical observatory, located between Peterhof and Oranienbaum (now Lomonosov), and at the observatory of Prince A.D. Menshikov they also organized the training of watchmakers. A sundial that was once installed on the building of the former cadet corps (on Vasilievsky Island in Leningrad), built in 1738–1753, has recently been restored. Two marble mileposts (former Tsarskoye Selo and Peterhof roads) with sundials, representing square marble slabs with hour scales and a gnomon, have also survived to this day, and in the city of Pushkin (near Leningrad) there are now obelisks with sundials. More advanced sundials, taking into account the change in the height of the Sun during the day, were demonstrated in 1879 at the Council of Moscow University by the famous ethnographer E.I. Yakushin (1826–1905), obtained by him from the Yaroslavl province (see the book “Sundials and calendar systems peoples of the USSR"). Until the 40s of our century, there were several sundials installed at different times in the parks of Leningrad and its environs. Many sundials were built in the 17th–18th centuries. in different cities, towns, villages of our country, especially in Siberia and the northern regions. The original sundial on the stand was built in 1833 in Taganrog in front of the stairs leading to the sea; they have survived to this day. There were many of them in Moscow and its environs. For example, clocks have been preserved on the buildings of the Historical and Archival Institute, the Novodevichy Convent (built in 1525), in the Arkhangelskoye museum-estate... On the territory of the house-museum of the father of Russian aviation N. E. Zhukovsky (1847–1921) in the village of Glukhovo In the Vladimir region, a stone stand with a sundial, which he used until 1919, has been preserved.

In 1795, Prince G. A. Potemkin (1739–1791) founded a sundial factory in the town of Dubrovka in Belarus, which was transferred in the same year to the village of Kupavna near Moscow; it trained sundial masters from serfs.

The most recent sundial in our country was built in 1947 for the 800th anniversary of Moscow on the site of the Moscow Planetarium. The clock shows Moscow time from May to September.

In connection with the 750th anniversary of the city of Siauliai (Lithuanian SSR), an architectural and sculptural ensemble is being created in it - the triad “Time - Sun - Shooter”, awarded the Gold Medal of the USSR Academy of Arts, designed by A. Cherniauskas, R. Jurela, A. Visniunas and S. Kuzma. The central part of the ensemble is a square paved with paving stones and is the dial of a sundial with the numbers 12, 3 and 6, symbolizing the year the city was founded (1236). The clock hand is a reinforced concrete 18-meter column with a gilded figure of the arrow.

Interest in sundials is evident in different countries and in our time. For example, in the GDR there are 1150 hours of sunshine; Of these, about 500 of these “chronometers” are still in use, while others are preserved as cultural and historical monuments. Several dozen monument clocks have survived in the Czechoslovak Socialist Republic; they served until the end of the 16th century, and some are still in use today. The latter includes the clock on the facade of the Schwarzenberg Palace, in the garden of the former Strahov Monastery.

Due to the lack of electricity during the siege of Leningrad in 1941–1944. On the initiative of V.I. Pryanishnikov, a sundial was installed on the edge of the lawn near Bolshoy Prospekt and the Ninth Line on Vasilievsky Island. They were used until the end of the Great Patriotic War.

At noon sunny day and now in Leningrad you can check the clock on the section of Herzen Street from the General Staff Arch to Nevsky Prospekt, since this section of the street is located exactly along the noon line (see in the book “Sundial ...”).

Rice. 11. Hourglass

Hourglass. Later the hourglass was invented. They could be used at any time of the day and regardless of weather conditions. They were more often made in the form of two funnel-shaped glass vessels placed one on top of the other (Fig. 11). The upper one was filled with sand to a certain level. The duration of pouring sand into the lower vessel served as a measure of time. Such clocks were made not only from two, but also from a larger number of vessels. So, for example, in one watch, which consisted of four vessels, the first vessel was emptied in 15, the second in 30, the third in 45 minutes, and the fourth in 1 hour. Then the vessels were turned by a person specially assigned to them and the time was counted down again, and the person serving them noted the elapsed hours.

Hourglasses were widely used on ships - the so-called “ship flasks”, which served sailors to set the time of watch changes and rest. In the 13th century The granular mass for the hourglass was prepared from a mixture of sand and marble dust, boiled with wine and lemon juice, repeating this operation up to ten times and removing the resulting scale. This mixture of bulk material made it possible to slightly increase the accuracy of determining time. Now hourglasses are widely used mainly in medical practice.

Rice. 12. Fire clock

Fire clock. Fire clocks, which were widely used, were more convenient and did not require constant supervision.

One of the fire clocks used by the miners of the ancient world was a clay vessel with enough oil to burn the lamp for 10 hours. As the oil burned out in the vessel, the miner finished his work in the mine.

In China, for fire clocks, dough was prepared from special types of wood, ground into powder, along with incense, from which sticks of various shapes were made, or more often long, several meters in a spiral (Fig. 12). Such sticks (spirals) could burn for months without requiring maintenance personnel.

There are known fire clocks that are also an alarm clock (Fig. 13). For such watches, and they first appeared in China, to the spiral or sticks in certain places metal balls were suspended, which, when the spiral (sticks) burned, fell into a porcelain vase, producing a loud ringing sound.

The European version of the fire clock, which was especially often used in monasteries, consisted of candles on which marks were applied. The combustion of the candle segment between the marks corresponded to a certain period of time.

However, the accuracy of fire watches, regardless of their design, was very low and largely depended on the condition environment- access to fresh air, wind and other factors.

Rice. 13. Fire alarm clock

Water clock. More advanced were water clock, which, unlike fiery ones, did not require systematic renewal. Water clocks were known and widely used in Ancient Egypt, Judea, Babylon, and China. In Greece they were called “clepsydras” (“water thieves”).

The first water clock was a vessel with a hole from which water flowed out over a certain period of time. So, for example, in Africa, where there was a shortage of water, the person in charge of its distribution (“ukil-el-ma”), releasing water into the peasant’s field, simultaneously filled the vessel. When the water flowed out of the vessel, the water supply to the peasant’s field was stopped; she was allowed into the fields of another farmer.

Subsequently, water clocks of various designs were created, and time was determined using such clocks by the speed of water flowing from one vessel to another. The vessels had marks that were used to count periods of time. Clepsydra were used not only in everyday life (especially at night), but also to regulate the time for speakers to speak in public meetings and courts, when changing guards and in other cases.

The accuracy of determining time using sun, sand, fire and water clocks did not exceed several minutes or even tens of minutes per day, which, however, was sufficient for the economic and social needs of that time.

A unique hand-held “water” clock with high precision was created in our time at the University of Texas (USA). Their source of energy is salted water. Once a week, a few drops of water are poured into a special hole. The watch is advertised to operate without failure for ten years if water is kept in the watch at all times.

§ 11. Mechanical watches

As the productive forces developed and cities grew, the requirements for instruments for measuring time increased, with the help of which it would be possible to regulate the economic, cultural and scientific activities of not only cities, but also entire countries. To solve this problem at the end of the 11th - beginning of the 12th centuries. mechanical watches with wheels and weights were invented, marking an entire era. K. Marx wrote to F. Engels on January 26, 1863: “A watch is the first automatic machine used for practical purposes. The whole theory developed on their basis producing uniform motion". A huge amount of energy, knowledge, wit and art was spent on the creation of mechanical watches in the modern sense.

The invention of purely mechanical watches, the first mention of which dates back to Byzantine sources at the end of the 6th century. n. e., some authors attribute it to Pacificus of Verona (IX century), and others to Pope Sylvester II (X century) (formerly monk Herbert), who allegedly made a tower clock with weights for the city of Magdeburg (now in the GDR). Only four centuries later did watches appear in which the rotation of the wheels was carried out using a spindle - a roller rotating under the influence of a load suspended from it. This clock is from the 16th century. had only an hour hand, and their accuracy did not exceed a quarter of an hour per day. They already had basically all the components of modern wall clock.

The original weight spindle chimes with moving figures were installed in 1354 in Strasbourg (France) on the cathedral building. They had indicators of mean solar and sidereal time, a perpetual calendar with holidays, showed the time of sunrise and sunset, the phases of the Magnifier and eclipses. There are known clocks installed in the 12th century. on the 97-meter bell tower of the Cathedral of St. Rombaud in Brussels. They are automatically connected to the system of the famous 49 bells with a “crimson” ringing. In Stockholm, each district of the city has its own chimes.

However, a very noticeable step forward in the creation of mechanical watches was made by Galileo Galilei (1564–1642), who discovered the phenomenon of isochronism of a pendulum with small oscillations, i.e., the independence of the oscillation period from the amplitude. This served as the basis for him to propose in 1640 the design of a pendulum clock, in which the oscillations of the pendulum and their counting were carried out automatically. This design was not implemented.

The inventor of modern pendulum clocks is considered to be the physicist Christian Huygens (1629–1695), who proposed them in 1657 and improved them in 1673 and 1675. Huygens used a balance instead of a spindle device, which significantly increased the accuracy of the clock.

The clock installed on the tower of the town hall on Old Town Square in Prague is very famous. Their two dials, painted by the outstanding Czech artist I. Manes, are decorated with zodiac signs and moving figures. They were created, according to legend, by the famous astronomer and mathematician Hanus from Ruzha. So that nowhere could there be a watch more beautiful than this wonderful creation, their creator was allegedly blinded.

The tower clock in Shumen (Bulgaria) with hammers and two bells striking 144 times a day (every 10 minutes!) is very original. On a marble slab at the base of the tower, part of an ancient Turkish inscription reads: “On this clock, Venus will be a pendulum, the Universe will be a wheel, and God’s Sun will be a bell...”.

The tower clock in Bernburg (GDR), installed in 1875 on the local town hall, has 23 dials, which can now be used to determine the exact time of many capitals of the world, the location of the planets of the solar system, and one of the hands indicating the date makes a full turnover for four years.

On one of the towers near San Francisco there is a clock that every hour makes a sound reminiscent of the mooing of a cow, and at noon and midnight the mooing of an entire herd can be heard. One of the largest clocks in Europe was recently installed in France on the building of one of the railway stations in Saint-Christophe; the diameter of their dial is 10 m. There is a unique clock weighing 16 tons, located on Alexanderplatz in the capital of the GDR and showing world time.

The Portuguese Amando Jose Ribeiro created a mechanical watch weighing 150 kg the size of a telephone booth, which uses combinations of 16 thousand letters and numbers, which also allow you to determine the day of the week and the date of Easter; they indicate the phases of the moon, contain a thermometer and barometer, and can serve as an alarm clock.

In Russia, the first mechanical clocks were also tower clocks, created by the hands of their own watchmakers and which became widespread in the 15th–17th centuries. The first of them were made in 1404 for the Moscow Kremlin by the monk Lazar Serbin. According to historians, the first chimes on the Spasskaya Tower were installed around 1491, shortly after its construction. In the chronicles of the 16th century. The watchmakers who serviced these watches are already mentioned. In 1624, the mechanic Galloway installed a mechanical chime clock on the Spasskaya Tower instead of the previous ones, and at the end of the 17th century. Such clocks appeared on three more towers of the Moscow Kremlin.

In 1706, a new clock was installed on the Spasskaya Tower, made by order of Peter I in Holland, with a dial of 12 numbers. In the same year, the dial was remade by Russian craftsmen, but for some unknown reason this watch eventually fell into complete disrepair. Instead, large chimes were installed, discovered in 1763 in the Chamber of Facets. After the retreat of Napoleon's army from Moscow, the clock was restored by Y. Lebedev, for which he was awarded the honorary title of Master of the Spassky Clock. In 1851–1852 The clocks were repaired and modernized by famous masters, immigrants from Holland, brothers Ivan and Nikolai Butenop.

The mechanism of the Moscow Kremlin clock - the main clock of our country - is located on three floors of the tower; they have one main bell that strikes full hours, and ten quarter bells. The mechanism of this watch has been updated three times to this day. Twice a day the clock is wound and the accuracy of its movement is checked using transmitted signals.

During the Seven Years' War, Peter I ordered all the bells to be cast into cannons, but according to the surviving legend, he did not touch the chimes in the bell tower of the St. Sophia Cathedral in Vologda, since he liked the skillful performance of the “Kamarinskaya” melody by the bell ringer on them. Currently, these chimes, being a decoration of the city, serve as a standard of time. The weights of the chimes are pulled up by a special collar.

More than 100 years ago, a tower clock was built in the monastery in Verkola, transported in the 30s to Karpogory (Arkhangelsk region) and installed on a wooden building. For more than 20 years they have been emitting a melodious chime and indicating fairly accurate time; they were repaired by the driver Z. Kokorin, who exercises constant control over them.

On the tower of the railway station in Riga there are chimes weighing 4 tons, and in Izhevsk there are miniature chimes with a “raspberry” ringing, made by mechanic P. Luchinkin according to the model of the chimes he made at one time for the ancient tower of the Izhmash plant. , of which he was the caretaker.

In Leningrad, on the tower of one of the buildings of the All-Union Scientific Research Institute. D.I. Mendeleev (formerly the Chamber of Weights and Measures) installed the most accurate mechanical clocks in the city. This is the only clock that did not stop for a minute during the entire period of the siege. They are daily set in motion by a multi-pound weight lifted by a special collar, which was selflessly performed by the oldest worker of the institute, I. F. Fedotov, who worked with D. I. Mendeleev.

In October 1917, V.D. Bonch-Bruevich "(1873–1955), wanting to accurately record the time of the capture of the Winter Palace by the revolutionary masses, turned from Smolny by telephone to the Chamber of Weights and Measures to the sailor on duty there, who, according to the words of the guardian scientist Chambers - reported: “One hour forty minutes twenty-two seconds.” The readings of the clock on the tower were verified with the readings of the time service clock located in the Chamber.

The youngest chimes in our country are the electronic-mechanical hybrid clock created by V. Strukov and his son, installed in Voronezh on the tower of the Voronezh Hotel for the city’s four hundredth anniversary (1977). Their dials, facing on three sides, show not only hours and minutes, but also seconds. They are distinguished by their high precision: at any time of the year in a month they go ahead or lag behind by no more than six seconds; every half hour they emit a melodious ringing, reminiscent of bells, and at night their loud chime is automatically turned off by a special electronic device. The original clock is installed on the Carillon Tower in the city of Salzburg (Austria): the hours of the day are shown by a large hand, and the minutes by a small hand, which misleads tourists.

The youngest electronic chimes of the original design are installed on the roof of the high-rise hotel "Yoshkar-Ola" in the capital of the Mari Autonomous Soviet Socialist Republic. They were made by students of the Mari Polytechnic Institute under the guidance of the head of the department P. Lavrentiev. Every 15 minutes, one of the 18 melodies stored in the watch’s memory floats over the city.

But the most original clock - the miracle chimes designed by V. M. Kalmanson - is installed above the entrance to the State Order of the Red Banner of Labor Central Puppet Theater in Moscow. Above the clock dial there is a large rooster, around which there are twelve houses. The rooster accompanies each chiming hour with loud singing, turning and flapping its wings. At the same time, one of the houses opens, from which the doll comes out. When the clock strikes twelve o'clock, the doors of all the houses open, a bear, a goat, an owl, a crow, a hare, a fox, a monkey, a cat, a ram, a pig, a goat and a wolf come out of them and dance to the music.

In the 90s of the XVIII century. Russian self-taught mechanic, inventor I.P. Kulibin (1735–1818), who also went down in history as a watchmaker, created original design pocket watches are slightly smaller in size goose egg containing more than 1000 parts. They have a built-in mechanism that plays at noon a hymn composed by Kulibin himself. He also created a “planetary” pocket watch, which, in addition to time in seconds, shows the seasons, months and days of the week, phases of the Moon, sunrise and sunset. The wall clock of I.P. Kulibin, which he used, is also known.

The Japanese company Kesio has released three modifications of electronic table clocks with pictures. On the panel of this clock, where the time is displayed, every hour an image of a dolphin playing with a ball, an owl with blinking eyes and a windmill appears. Another Japanese company, Sitezen, produces watches that, in response to the owner’s question, not only show the time, but also perform 31 operations upon a voice command, for example, show the date and time at points located in two different time zones.

In the second half of the 80s, a “perpetual” clock was installed on the lawn of Tokyo’s Hibiya Park, the dial of which is a horizontal plate, and the mechanism is driven by solar panels. The desktop “Population Clock” made by Seiko Instruments is of great interest. In addition to the time of day, days of the week, months and years, they show the total population on Earth and in UN member countries. The clock was created in connection with the birth of the five billionth inhabitant of the planet and reflects the change in the number of inhabitants every minute in accordance with the forecasts of UN experts. In 1987, the director of the United Nations Population Fund presented the watch to Secretary General UN Perez de Cuellar.

Interest in collecting unique watches continues. So, for example, for exclusively high price At an auction in Geneva in 1983, a watch made in 1650 by the remarkable watchmaker J. Kremsdorf was purchased for 1.87 million Swiss francs. Their case and dial are covered with enamel, and the numbers are decorated with diamonds. In 1987, at a trade fair in Basel (Switzerland), three mechanical wrist watches were demonstrated, all the parts of which were made by hand by the Englishman D. Daniel; the cheapest are priced at $160,000. In Taiwan, a lot of attention of visitors to the 1987 fair was attracted by gigantic wooden clocks designed to decorate the interior of a home. Also in 1987, an interesting fair and exhibition was held in Turin (Italy) under the motto “Honor to Watches,” in which 65 Italian organizations and individuals took part, presenting the “Signors of Time,” as watches are called in Italy. Such “hour-long meetings” are expected to be held regularly and made international.

In recent years, Swiss watchmakers have been looking for unusual materials: for example, the case of the Roquogue model watch is made of granite, and the Meteorite model has a dial made of real meteorite iron. Recently, in the same country, a clock without a dial or hands appeared; their mechanism is enclosed in a sealed tube and they show the time when a button is pressed. Recently, watches were produced here specifically for women, the mechanism of which can be inserted into buttons, brooches, and earrings. Despite the inconvenience of use, watches are in great demand.

The private collection of watchmaker F. Feldman (Dresden, German Democratic Republic) contains 500 watches mainly from German, Swiss and French masters; the oldest of them is a pocket watch from 1780, and the newest is a mechanical chronometer made in the GDR in the 80s of our century. The Vienna Clock Museum displays more than a thousand time keepers of different designs and purposes. Among them, a unique mechanical astronomical calendar made in Austria in 1815 attracts the attention of visitors. The private collection of the Roman television journalist Alessandro di Paolo, which contains copies of all known in the 18th–20th centuries, is famous. hours.

But the most popular mechanical clock is still the cuckoo clock. They, as legend has it, were invented in 1720 (according to other sources - in the middle of the 16th century by the German mechanic A. Ketter) in Germany to cheer up a princess of a sad disposition. One of the first cuckoo clocks is in a private collection in Zittau (GDR), where more than 500 mechanical clocks are collected, including clocks made of wood in 1470 by Russian craftsmen, as well as various “walkers” and special watches for couriers . IN Lately In the USA, mechanical clocks appeared in which the cuckoo not only sticks out, but comes out of the door.

The Central Military History Museum (Leningrad) exhibits a two-meter-high watch made by the serf peasant of the Yaroslavl province L. S. Nechaev in 1837–1851. They attract attention with a massive, unusually designed pendulum and many dials, by which you can determine not only the time, but also the year, month, date, day of the week, length of day and night, increase and decrease of the day (in minutes and seconds), sunrise and sunset and the Moon, and also find out whether it is a simple year or a leap year. In the upper arc-shaped cutout of the main dial, with sunrise, a metal disk-luminary appears moving along this cutout, which hides at sunset. Its rising and setting are accompanied by the melodies of Russian folk songs.

In 1848, there was a melodious ringing of a chiming clock with a half-meter dial installed on the city cathedral in Chermoz (Perm region), with an indicator of the numbers of the month and phases of the moon. This watch was created by craftsman Egorka Epishkin, a worker at the Chermoz sheet rolling plant - the son of a serf assigned to the plant.

In 1851, serf Vasily Rysov made a chiming clock installed on a 66-meter bell tower in the town of Slobodskoye (Kirov region), which residents still use today. IN local history museum This city has an interesting and very rich collection of mechanical watches, and among them, the watches of talented Vyatka craftsmen attract special attention.

The watch made by Vyatka cabinetmaker Semyon Bronnikov from wood and distinguished by its grace and precision is of great surprise. Their case and case are made of burl, the hands are made of honeysuckle, the hairs and springs are made of hardened bamboo, and the entire mechanism and dial are made of palm. Several copies of such watches were made, and they are stored in museums in different cities of our country and in the Armory Chamber of the Moscow Kremlin. The museum also displays a calendar clock that shows not only the time, but also the names of the months, days of the week, day of the month and phases of the moon. The hands of Russian masters created mechanical watches of various types and purposes. For example, there is a known table clock made by M. Perkhin. They are a golden vase with a bouquet of lilies carved from matte white onyx. In them, the dial is a uniformly moving enamel ring with Roman numerals, and the hand is fixed motionless in front of it.

The State United Historical and Revolutionary Museum of Ivanovo exhibits the world's only universal astronomical clock, which is the art of the hands of the Parisian mechanic Albert Billet, made in 1873. They simultaneously show about a hundred different variables, indices and names: the movement of the Earth and other planets around The Sun, the apparent daily movement of the Sun, Moon and stars of the northern hemisphere. The other part of the clock consists of mechanical calendars showing the Gregorian, Julian, Jewish and Mohammedan calendars (see Chapter 3). In the third part, on 37 dials, standard time is calculated for different cities in Europe, Asia, South and North America, Africa and Australia, the time of sunrise and sunset, the length of day and night, the dates of the equinoxes and some other astronomical values. After they were restored in 1943 by Associate Professor of the Ivanovo Pedagogical Institute A.V. Pototsky, they continue to work to this day.

At the Museum of Ethnography and Arts of the Academy of Sciences of the Ukrainian SSR (Lvov), an exhibition opened in 1974 displays more than 300 tower, mantel, table, wall, pocket and hand clocks created in different countries. Here, visitors’ special attention is drawn to bronze watches made four centuries ago. There are five dials on their body, from which, in addition to the time of day, you can determine the phases of the moon, the month and days of the week and other data.

The Museum of Klaipeda (Lithuanian SSR) contains a variety of sand, sun and mechanical clocks of various sizes and purposes, from different times and peoples, starting with those created in the 15th–17th centuries. Tula masters and ending with watches from domestic factories of our time. Among them, the watches of the 16th century are especially noteworthy, on the dial of which there is a scale with the phases of the moon and the signs of the zodiac; they were used by sailors of that time.

Since 1967, a permanent exhibition has been opened in Angarsk containing more than 150 antique mechanical watches made by Russian craftsmen, and all of them are working. The watches that were in space on board the Salyut-6 station together with the pilot-cosmonaut, twice Hero of the Soviet Union G. M. Grechko are also on display here.

A rich private collection containing 500 mechanical watches of various brands and types - German, French, Italian, English, Swiss and other companies, was collected by V. A. Chubatov in the city of Kolchinsk (Omsk region).

The collection of antique watches of the ship mechanic from Tallinn A. Prokopchuk, numbering about 150 pieces, is interesting; Among them, especially noteworthy are the table clocks by the English master Elef Deighton and the original pocket watches of the 17th century.

In recent years, the Yaroslavl Museum-Reserve has been replenished with original mechanical table clocks made at the beginning of the 18th century. and representing a rare example of decorative applied arts. They were decorated using casting, carving, chasing and copper inlay on tortoiseshell. There is also a clock there that has been silent for a long time, but is now active. mid-18th century c., recently repaired by the doctor R. Fomin and supplemented by him with a decorative pendulum arrow.

In 1986, a collection of time keepers was opened in the Vladimir-Suzdal Museum-Reserve under the motto “Tempus fugit” (time flies), including more than 500 working clocks.

One of the halls of the Polytechnic Museum in Moscow houses the most complete collection of a wide variety of watches in the USSR, presented in their historical development. It includes “guardians of time” from the first primitive to the most complex modern automatic mechanisms created at different times. Among its exhibits, various watches by Russian masters deserve special attention. For example, a unique watch with an annual winding, which has 14 dials, showing, in addition to the time of day, the months, dates and days of the week, the time of sunset and sunrise, and the phases of the moon. It took 25 years to create this watch. A very original clock made in 1885 by the peasant F. T. Skorodubov from wood, wire and nails with weights from four-pound stones. An outstanding evidence of the development of science and technology is the watch of the famous Ukrainian master N. S. Syadristy, representing a life-size dragonfly made of glass and gold, in one eye of which the world's smallest electronic watch is mounted. In 1985, the museum's collection was replenished with original grandfather clocks, individual parts of the running parts of which are a copy of the Kremlin chimes. To improve the accuracy of these watches, master I. Butenop, whom we have already discussed, used the achievements of chronometry technology from the mid-19th century. and made his own improvements.

In Russia, the first astronomical clock was created by mechanic T.I. Voloskov (1712–1806), the son of a Rzhev (formerly Tver province) merchant, which was distinguished by high accuracy for its time. The clock contained, according to the author, “in the aggregate everything that is connected in nature by a continuous connection.” The watch was a complex and very ingenious mechanism that surprised contemporaries with its design and accuracy. In them, one wheel rotated around its axis only once in four years. They had several dials and showed, with an accuracy of seconds, not only local time, but also time in all points of the globe, months of the year, the position of the Sun, Moon and stars. by them for a long time used by astronomers, for example, when calculating the coordinates of stars. On the dial of the watch there were inscriptions: “The moon flies across the sky”, “The globe is shining”, “Rzhev merchant Terenty Ivanovich Voloskov”. T.I. Voloskov's watch was, as it were, composed of watches he had previously designed, some of which showed the position of the Sun in the sky, others, in addition to hours and minutes, showed the number of the month (with 28 days in February of a common month and 29 days in February of a leap year years), and on the third - a change in the phases of the moon. Until 1941, Voloskov's astronomical clock was exhibited in the Rzhev Museum of Local Lore; they disappeared during the occupation.

At the beginning of the 20th century. In Russia, Riefler’s single-pendulum mechanical clocks, proposed by him in late XIX century, and Short's two-pendulum clock, created in Great Britain in 1920. One of the pendulums, called “free” or “primary,” is enclosed in a copper cylinder with air evacuated from it. Random errors in the daily course of such clocks did not exceed several thousandths of a second.

A watch of a similar design was made according to the design of F. M. Fedchenko at the Leningrad Etalon plant with a “free” pendulum made of invar (an alloy of steel and nickel), which almost does not respond to changes in temperature, air pressure and various vibrations. The clocks were used for a long time at astronomical observatories and were quite accurate; their daily variation did not exceed ± (0.003–0.004) seconds.

In 1952–1955 F. M. Fedchenko designed the high-precision astronomical pendulum clock AUF-1. The AUF-2 clock and, finally, the AUF-3 model clock became even more accurate with a root-mean-square variation of the daily cycle of 0.2–0.3 s, or in relative terms (2–3)·10 -9; it was the most accurate pendulum clock in the world. Accuracy was ensured by a special thermal compensation system for the pendulum. Power was provided by a mercury oxide cell designed for continuous operation for three to four years. They are stored under the hood of a pressure chamber in which a pressure of 3–5 mm Hg (400–670 Pascals) is maintained.

In 1986, watchmaker H. Pekli (Germany) created an original combine watch with an astronomical chronometer: it shows the time of any time zone, sunrise and sunset, moon phases and keeps track of days and weeks.

§ 12. Quartz and atomic clocks

Observations of the Sun, planets and stars make it possible to determine secular fluctuations in the Earth's rotation period. However, astronomers are also interested in short-period oscillations.

With the current development of science and technology, it is necessary to measure time accurately to thousandths and even millionths and billionths of a second.

Increasing requirements for the accuracy of time determination is necessary, for example, in automatic control systems for production and technological processes in industry and on all types of transport, when studying ultra-fast processes occurring in the atomic nucleus, when establishing efficiency technical means communications between continents, during spacecraft launches and space flights. Ultra-precise time is used to verify results at optical observation stations for artificial Earth satellites and in many other cases. Even this far from complete list confirms the wide and versatile scope of applications of instruments for determining precise time and shows how extensive the range of tasks performed with their help is. Solving such problems requires more accurate watches than those produced for these purposes by the Etalon plant.

More accurate clocks that replaced pendulum clocks in the 1930s were quartz clocks. Instead of a pendulum, they used elastic piezoelectric vibrations of quartz plates, i.e., deformations of these plates when an alternating electric current was applied to their faces. Under certain conditions, such quartz vibrations are absolutely stable, independent of the force of gravity, earthquakes and other natural phenomena.

For quartz clocks, which keep time accurate to 10 -10 seconds for several months, the variation of their daily rate is stable (up to several millionths of a second) and it is a thousand times less than that of pendulum clocks. But a quartz plate “ages” relatively quickly, so the difference in the readings of two quartz watches can reach ten seconds over the course of several years. Nevertheless, with the help of quartz watches, which were part of the first State Standard of Time and Frequency in the USSR, changes were discovered in the speed of rotation of the Earth - the natural standard of time, which turned out to be unstable.

Quartz clocks, the error of which does not exceed microseconds per day, are used as primary ones for the electronic station in Hamburg, which guarantees synchronous work all electronic clocks included in the system; the station can manage a network of approximately 20,000 secondary electronic clocks.

The art clock factory in Moscow began producing quartz cuckoo wall clocks, which are distinguished by high precision.

The watch industry of the USSR mastered the production of electronic quartz wristwatches, characterized by high precision; per day they can lag behind or go ahead by no more than two seconds.

After the development of highly stable vibration generators by academicians N. G. Basov and L. M. Prokhorov in 1954, a clock was created in which the pendulum was the vibration of ammonia molecules. Such clocks are called “quantum” or “atomic”, and sometimes “molecular”. They allow you to obtain "atomic seconds". The time measured by such a clock is called atomic. 24 atomic hours constitute an atomic day containing 86,400 atomic seconds, which are not related to either the rotation of the Earth or time determined astronomically.

Research has shown that atomic clocks can be accurate to a millionth of a second per day, meaning they can be one second behind astronomically determined time in only 500,000 years. The operation of such clocks, which are a complex of complex devices, is controlled by a quantum generator. The atomic clocks are kept in the All-Union Order of the Red Banner of Labor Research Institute of Physical, Technical and Radio Engineering Measurements (VNIIFTRI) near Moscow. They are the center of time and frequency of the USSR; their official name is “State Primary Time and Frequency Standard”. For such clocks that keep accurate time, installed in a deep basement, a special mode is provided; they need absolute peace. They are protected from fluctuations in temperature, humidity, pressure, vibration and other external influences; even minor vibrations are damped by the special design of their foundation. It is from them that six short signals are transmitted every hour on the radio in our country: information about the exact time that millions of people hear every day.

The high accuracy of atomic clocks made it possible to determine the seasonal irregularities in the rotation of the Earth from the difference between universal and atomic time, which is the cause of instability in the length of the day, in the annual and semi-annual periods, amounting to 0.0005 and 0.0003 seconds, respectively. It has been established that, for example, in July a day is shorter than in April and November by approximately 0.001 seconds. However, despite the high accuracy of atomic time calculation, the need for time determined astronomically remains when solving a number of problems in astronomy, geodesy and other sciences.

At the XIII International Conference on Weights and Measures, held in 1967, it was recommended to take “the duration of 9,192,631,770 oscillations of radiation corresponding to the resonant frequency of the transition between two levels of the hyperfine structure of the ground state of the cesium-133 atom in the absence of disturbances” as a unit of time - a second from external fields." After this, the USSR and all developed countries adopted the “atomic second” as the standard of time. It, as studies have shown, coincides with the second of mean solar time, representing 1/86,400 of the mean solar day, with an accuracy of the order of 10 -8. The atomic second, which caused a real revolution in matters of determining exact time in the intervals between astronomical definitions, was the standard time in the USSR until 1983.

However, the development of the scientific and technological revolution required determining time with even greater accuracy, thereby stimulating work to improve the State Primary Standard of Time and Frequency. Therefore, since 1983, the USSR has used a new primary time standard, which is based on two metrological cesium frequency references, each of which reproduces the “size” of a second in the SI system. This standard is significantly superior in its metrological characteristics to the 1967 standard, and in accuracy - all known frequency standards; it is one of the three best primary time and frequency standards in the world.

In recent years, scientists at the Institute of Thermophysics of the Siberian Branch of the USSR Academy of Sciences have created even more accurate clocks. In them, the “pendulum” is replaced by the only stable laser in the world. It produces a million billion vibrations - rhythmic flashes of light in one second of time, and a clock with such a “pendulum” - optical clock- characterized by an error of one second per 10 million years. Based on such a laser, it seems possible to create a single standard of time - frequency - length, understanding the latter meter as “the length of the path traversed by a flat electromagnetic wave in a vacuum in 1/299,792,485 seconds." This definition of the meter was recommended in 1983 by the Advisory Committee of the International Bureau of Weights and Measures. Although such a standard, such watches are still in the stage of improvement, but “... still they no longer live in dreams, not in plans, but in reality, “in hardware.”

In France, in the port city of Le Havre, a new clock of gigantic proportions has been installed, showing, as residents of the city believe, the most accurate time on Earth and which has no analogue in the world, or, at least, in France. They allow a lag of one second per 250,000 years, which is achieved thanks to the “atomic synchronizer”. Their special device receives, via satellite communications, constant signals from one of the observatories in Switzerland, which has an atomic clock.

On the building of a large cultural center (the Pompidou Center) in Paris, an electronic clock installed several years ago continuously counts down the seconds remaining until the year 2000. On the indicator of this watch, intended to mark beginning of XXI century, 0 seconds will be on the night of December 31, 1999 to January 1, 2000, while it should be a year later, since the 21st century begins on January 1, 2001.

The Japanese company Seiko Instrument has created an original “watch-recorder” on liquid crystals with two memory blocks that reproduces a person’s voice for 8 seconds.

Currently, there is significant overproduction on the world market wristwatch. Therefore, competing companies create watches that not only differ in size and materials from which the case is made, but also contain additional devices in addition to the clock mechanism - calculators, heart rate meters, moisture meters, etc.

§ 13. International time service

The decision of a number of scientific and technical problems requires knowledge of the exact time. For example, many years of careful measurements of the distance between the same points located in Europe and in North America, allowed us to determine the change in this distance. It turned out that the continents are moving closer together, and the speed of this approach at latitude 45° is about 65 cm per year. This shift of continents corresponds to a change in local time of 0.002 seconds, which confirms the need to measure time in individual cases (for example, to determine the longitude of a place) with very high accuracy.

Precise definition longitude of points located on our planet requires the solution of two auxiliary problems: carrying out special astronomical observations of the Sun or stars and receiving the transmission of exact time (without losing accuracy) from those places where it is received and stored using high-precision clocks.

Receiving precise time moments was carried out until recently in astronomical observatories by their time services. The invention of radio radically changed the nature and methods of work of time services. Already the first experiments in transmitting precise time signals via radio, carried out at the beginning of the 20th century, showed the need to create international organization to coordinate the supply of radio time signals and determine their errors. In 1912, at the proposal of the Bureau of Longitudes, an international conference of representatives of 16 countries was held in Paris, at which a special committee was elected under the chairmanship of Academician O. A. Backlund (1846–1916), then director of the Pulkovo Observatory, but the World War of 1914 interrupted the work of this committee. And only in 1919, at a conference in Brussels, the International Astronomical Union was created - MAC, and one of the first decisions of the Special Commission of this union was the establishment in Paris of a permanent International Time Bureau (IBI), whose activities began on January 1, 1920; Its task is to coordinate the work and summarize the results of all time services in the world.

§ 14. USSR Time Service

Now the exact time is learned mainly from the radio. When there was no radio, watches were checked by watchmakers who checked the time on a telegraph.

In 1863, for the first time, the exact time determined at the Pulkovo Observatory from astronomical observations was transmitted by wire to the Main St. Petersburg Telegraph Office, with whose clock the time in all telegraph institutions in Russia was checked.

In our country, meeting the needs National economy High-precision time and reference frequencies are carried out by the State Time and Frequency Service of the USSR, the reference base of which includes a primary standard stored in VNIIFTRI and a number of secondary standards located in various cities of the USSR.

In our country, the organization of time services, which is now represented by the State Commission of Unified Time and Standard Frequencies of the USSR, essentially began only after the Great October Socialist Revolution. The beginning of its organization should be considered regular, starting from December 1, 1920, daily broadcasts of radio signals of the exact time through the Petrograd radio station “New Holland”, first at 19 hours 30 minutes, and from July 1921 - at 19 hours universal time, coming from astronomical clock of the Pulkovo Observatory. Since May 1921, precise time signals have been transmitted through the Oktyabrskaya radio station in Moscow every day at 22:00 universal time.

In 1924, the Interdepartmental Committee of the Time Service was created at the Pulkovo Observatory, which in 1925 began issuing bulletins with a schedule of transmissions of precise time signals by both domestic and foreign radio stations with an accuracy of approximately a few hundredths of a second.

Since 1952, transmissions of time and frequency signals have been carried out through a whole network of shortwave and longwave radio stations from high-precision clocks through special equipment, which has significantly increased the accuracy of such transmissions.

In the USSR, time services were created at the Tashkent Astronomical Observatory (1928), at the State Astronomical Institute named after. P.K. Sternberg in Moscow (1929), and then in Kharkov (1935), Nikolaev (1938), Leningrad (1947), Riga (1951), Irkutsk (1953) , Novosibirsk (1957) and other places. Currently, there are 12 time services in the USSR.

At the beginning of the Great Patriotic War some time services (Pulkovskaya, Kharkovskaya, etc.) stopped working, and the time services of the State Astronomical Institute named after. P.K. Sternberg (SAI) and at the Central Research Institute of Geodesy, Aerial Photography and Cartography (TsNIIGAiK) were evacuated - the first to Sverdlovsk, and the second to Dzhambul Kazakh SSR and, together with the Tashkent Time Service, which did not stop its activities, carried out all the work to provide accurate time for all country requests.

Since 1964, the time services of the SAI and TsNIIGAiK were transformed into one united time service in Moscow.

In 1948, the functions of the Interdepartmental Committee were transferred to the Interdepartmental Commission of the Unified Time Service under the Committee on Measures and Measuring Instruments under the Council of Ministers of the USSR, transformed into the State Commission of Unified Time and Standard Frequencies of the USSR and the Central Research Bureau of the Unified Time Service, whose task was includes resolving issues related to the transmission of precise time signals, coordinating the work of various departments in the field of time services and resolving issues related to the zone time counting system - the boundaries of time zones on the territory of the USSR. The next step is to resolve the issue related to a single time for both terrestrial and space instruments, and for this, experts suggest, the time standard can be signals from neutron stars - pulsars, against which ultra-precise terrestrial clocks should be checked.

The time service's transmission of time signals over any distance with high accuracy makes it easy to compare the results obtained from each of them with similar results from other time services.

Notes:

Lenin V.I. Full collection Op. - T. 18.- P. 181.

Engels F. Anti-Dühring.- M.: Gospolitizdat, 1948.- P. 49.

Marx K., Engels F. Op. - 2nd ed. - T. 23. - P. 522; interlinear note 5.

The equinoxes sometimes shift to adjacent dates (for example, the spring equinox occurs on March 20). Therefore, the duration of the summer “half-year” can be 187, and the winter - 178 days.

Astronomical yearbooks give the equation of time for each day of the year.

To facilitate the calculation of local time, in 1967, in the English magazine New Scientist, it was proposed that instead of dividing the day into 24 hours, count 10 hours in them, dividing each such hour into 100 minutes, and a minute into 100 seconds. In this regard, it was proposed to divide the arc of the earth's equator not into 360°, but into 1000 degrees; in this case the relations 1 hour = 100°, 1° = 1 min would be fulfilled.

Of these, nine are located in Siberia and the Far East.

Perelman Ya. I. Entertaining astronomy. - Ed. 6th. - M.: Fizmatgiz, 1961, - P. 56.

The gnomon itself is a vertically mounted rod. The first sundials in India, China and Egypt were used about 3000 years ago (see the book “Sundials and calendar systems of the peoples of the USSR”, listed in the list of references).

The gnomon, despite the simplicity of its design, was used in ancient times to determine the latitude of its installation location and the inclination of the ecliptic to the equator; By comparing the length of the shadow from the pole with its length, they determined the height of the Sun above the horizon and solved other problems.

During excavations of ancient settlements in Shalesi (Albania), a well-preserved sundial weighing 2.5 kg, made in the 4th century, was discovered. BC e. from alabaster. Their dial is divided into 12 equal parts.

Marx K., Engels F. Op. - 2nd ed. - T. 30. - P. 263.

History notes an interesting case when a mechanical clock installed in the city of Görlitz (GDR) saved senators from being kidnapped by conspirators in 1253 as they left the city hall. The conceived plan failed, as one of the conspirators, repenting at the last moment, moved the clock forward seven minutes. The conspirators, who gathered “on time” in front of the town hall, were captured. Since then, this clock, in memory of what happened, has invariably moved seven minutes ahead.

According to some information, Bürgi from Kassel (now in Germany) created a pendulum clock even earlier - in 1612.

At their house in Moscow, an original clock made by the name was installed, which played the melody “Kol glorified...”.

Kept in the Leningrad Hermitage.

They were sold by Kulibin's wife to organize the funeral of their creator; Subsequently, the watch was acquired by the Polytechnic Museum in Moscow, where it is still kept.

Their work was awarded the Lenin Prize in 1959.

In 1970, at the World Exhibition in Osaka (Japan), “ZKSPO-70”, a precision time system was demonstrated, the center of which was an atomic clock mounted on a tower 19 m high; their error in timing, as experts advertised, was one second in a thousand years.

In 1978, the creators of such a laser, corresponding member of the USSR Academy of Sciences V.P. Chebotaev and Professor V.S. Letokhov, who worked independently of each other, were awarded the Lenin Prize.

Soviet Union became a member of the International Astronomical Union in 1935.

Based on observations of the daily rotation of the sky and the annual movement of the Sun, i.e. The measurement of time is based on the rotation of the Earth around its axis and on the revolution of the Earth around the Sun.

The rotation of the Earth around its axis occurs almost uniformly, with a period equal to the period of rotation of the firmament, which can be determined quite accurately from observations. Therefore, by the angle of rotation of the Earth from a certain initial position, one can judge the elapsed time. The initial position of the Earth is taken to be the moment of passage of the plane of the earth's meridian of the observation site through a selected point in the sky, or, which is the same thing, the moment of the upper (or lower) culmination of this point on a given meridian.

The duration of the basic unit of time, called a day, depends on the selected point in the sky. In astronomy, such points are taken to be: a) the point of the vernal equinox; b) the center of the visible disk of the Sun (the true Sun); c) “average sun” - fictitious point, whose position in the sky can be calculated theoretically for any moment in time.

The three different units of time defined by these points are called respectively sidereal, true solar and mean solar days, and the time measured by them is sidereal, true solar and mean solar time.

tropical year is the time interval between two successive passages of the center of the true Sun through the vernal equinox.

3.2. Sidereal day. sidereal time

The time interval between two successive culminations of the vernal equinox on the same geographic meridian is called the sidereal day.

The beginning of the sidereal day on a given meridian is taken to be the moment of the upper culmination of the vernal equinox.

The angle by which the Earth will rotate from the moment of the upper culmination of the vernal equinox to some other moment is equal to the hourly angle of the vernal equinox at that moment. Consequently, sidereal time s on a given meridian at any moment is numerically equal to the hour angle of the vernal equinox point t, expressed in hourly measure, i.e.

s = t . (1.14)

The vernal equinox point in the sky is not marked by anything. It is impossible to directly measure its hour angle or notice the moment it passes through the meridian. Therefore, in practice, to establish the beginning of the sidereal day or sidereal time at any moment, it is necessary to measure the hour angle t of some luminary M, whose right ascension known (Fig. 12).

Then, since t = Qm =m, and the hour angle of the vernal equinox point t = Q and, by definition, is equal to sidereal time s,

s = t = +t, (1.15)

those. sidereal time at any moment is equal to the right ascension of any luminary plus its hour angle.

At the moment of the upper culmination of the luminary its hour angle t = 0, and then

s = . (1.16)

At the moment of the lower culmination of the luminary, its hour angle t = 12h, and sidereal time

s = +12h. (1.17)

Measuring time by sidereal days and their fractions is the simplest and therefore very beneficial in solving many astronomical problems. But in everyday life, using sidereal time is extremely inconvenient. The daily routine of human life is associated with the visible position of the Sun above the horizon, with its rising, culmination and setting, and not with the position of the fictitious point of the vernal equinox. And since mutual arrangement The sun and the points of the vernal equinox continuously change throughout the year, then, for example, the upper culmination of the Sun (noon) on different days of the year occurs at different moments of the sidereal day. Indeed, only once a year, when the Sun passes through the vernal equinox, i.e. when its right ascension = 0h, it will culminate along with the vernal equinox at noon, at 0h sidereal time. After one sidereal day, the point of the vernal equinox will again be at the upper culmination, and the Sun will arrive at the meridian only after approximately 4 minutes, since in one sidereal day it will shift east relative to the point of the vernal equinox by almost 1°, and its right ascension will be narrower equals =0h4m. After another sidereal day, the right ascension of the Sun will again increase by 4m, i.e. noon will begin at approximately 0h8m sidereal time, etc. Thus, the sidereal time of the solar culmination continuously increases, and noon occurs at different moments of the sidereal day. The inconvenience is quite obvious.

In the last article I mentioned the term “sidereal day”. And since it will occur many more times, and not everyone knows the difference between sidereal and solar days, sidereal and solar time, this article will be just about that.

True, in that article I also talked about the “solar wind”, but that will be in the next post.

So, for any celestial body there are two times. Although, maybe more, for example, about black hole Over time, the devil knows what’s going on, but we’re talking about simple and understandable astronomical concepts here. About sidereal and solar time.

The solar day of the Earth is a day known to all of us. In which 24 hours. They are equal to one complete rotation of the Earth around its axis. Naturally, the Sun is taken as the reference point.

But because The Earth not only rotates around its axis, but also moves around the Sun, then after the planet has turned once, it has traveled some distance in its orbit. This means it has shifted relative to the Sun. As a result, in order to catch up with the reference point, the Earth needs to rotate around its axis a little more.

In addition, since the movement does not proceed in a circle, but along an eleptic orbit, the solar day is by no means a constant value. During the year they can decrease and increase. And 24 hours is simply their average.

But for astronomical calculations, on which, for example, it depends how and where it will fly space rocket this average value is not enough. Therefore, “sidereal time” was created, or better said, approved.

Sidereal time

A sidereal day is one rotation of the planet, but not relative to the Sun, but relative to the fixed stars. Simply put, the little bit by which the Earth rotates to catch up with the Sun is removed from the calculations.

So, a sidereal day is the period of time between two successive upper culminations on the same geographical meridian of the same star. Or, what astronomers prefer, the vernal equinox.

The vernal equinox point is the point of intersection of the ecliptic with the celestial equator, which the Sun passes when moving from southern hemisphere to the north, around March 21. From this moment on, spring begins in the northern hemisphere of the globe.

The duration of these sidereal days is 23 hours 56 minutes and 4.090530833 seconds of solar time. But our “fixed” point of the spring equinox is not so stationary.

Due to the orbital motion of the Earth, it is constantly shifting by a small amount. Therefore, astronomers came up with the so-called celestial ephemeris beginning for the reference point and a day relative to this point lasts 23 hours 56 minutes and 4.0989036 seconds.

Time is the most important philosophical, scientific and practical category. The choice of a method for measuring time has interested man since ancient times, when practical life began to be associated with the periods of revolution of the sun and moon. Despite the fact that the first clock, the sundial, appeared three and a half millennia BC, this problem remains quite complex. Often answering the simplest question related to it, for example, “how many hours are there in a day,” is not so simple.

History of time calculation

The alternation of light and dark times of the day, periods of sleep and wakefulness, work and rest began to mean the passage of time for people back in primitive times. Every day the sun moved across the sky during the day, from sunrise to sunset, and the moon moved at night. It is logical that the period between identical phases of the movement of the luminaries became a unit of time calculation. Day and night gradually formed into a day - a concept that defines the change of date. On their basis, shorter units of time appeared - hours, minutes and seconds.

For the first time, they began to determine how many hours there are in a day in ancient times. The development of knowledge in astronomy led to the fact that day and night began to be divided into equal periods associated with the rise of certain constellations to the celestial equator. And the Greeks adopted the sexagesimal number system from the ancient Sumerians, who considered it the most practical.

Why 60 minutes and 24 hours?

To count something, ancient man used what was usually always at hand - his fingers. This is where the decimal number system adopted in most countries originates. Another method, based on the phalanges of the four fingers of the open palm of the left hand, reached its peak in Egypt and Babylon. In the culture and science of the Sumerians and other peoples of Mesopotamia, the number 60 became sacred. In many cases, the presence of many divisors, one of which is 12, made it possible to divide it without a remainder.

The mathematical concept of how many hours there are in a day originates in Ancient Greece. The Greeks at one time took into account only the daylight hours in the calendar and divided the time from sunrise to sunset into twelve equal intervals. Then they did the same with night time, resulting in a 24-part division of the day. Greek scientists knew that the length of the day changes throughout the year, so for a long time there were day and night hours, which were the same only on the days of the equinox.

From the Sumerians, the Greeks also adopted the division of a circle into 360 degrees, on the basis of which a system of geographical coordinates and the division of the hour into minutes (minuta prima (Latin) - “reduced first part” (of the hour)) and seconds (secunda divisio (Latin)) were developed. - “second division” (of the hour)).

Sunny day

The meaning of a day in relation to the interaction of celestial objects is the period of time during which the Earth makes a complete revolution around its axis of rotation. Astronomers usually make several clarifications. They distinguish solar days - the beginning and end of a revolution are calculated by the location of the Sun at the same point on the celestial sphere - and divide them into true and average.

It is impossible to say, down to the second, how many hours there are in a day, which are called true solar hours, without specifying a specific date. During the year, their duration periodically changes by almost a minute. This is due to the unevenness and complex trajectory of the movement of the star along the celestial sphere - the axis of rotation of the planet has an inclination of about 23 degrees relative to the plane of the celestial equator.

We can more or less accurately say how many hours and minutes there are in a day, which experts call average solar. These are the usual calendar periods of time used in everyday life that define a specific date. It is believed that their duration is constant, that they are exactly 24 hours, or 1440 minutes, or 86,400 seconds. But this statement is conditional. It is known that the speed of rotation of the Earth decreases (a day lengthens by 0.0017 seconds per hundred years). The intensity of the planet's rotation is influenced by complex gravitational cosmic interactions and spontaneous geological processes inside her.

Sidereal day

Modern requirements for calculations in space ballistics, navigation, etc. are such that the question of how many hours a day lasts requires a solution with an accuracy of nanoseconds. For this purpose, more stable reference points are selected than nearby celestial bodies. If you calculate the complete revolution of the globe, taking as the initial moment its position relative to the point of the vernal equinox, you can obtain the length of the day, called sidereal.

Modern science establishes exactly how many hours there are in a day that bears the beautiful name of sidereal hours - 23 hours 56 minutes 4 seconds. Moreover, in some cases their duration is further specified: the true number of seconds is 4.0905308333. But this scale of refinement is also insufficient: the constancy of the reference point is affected by the unevenness of the orbital motion of the planet. To exclude this factor, a special, ephemeris origin associated with extragalactic radio sources is selected.

Time and calendar

The final version of determining how many hours there are in a day, close to the modern one, was adopted in Ancient Rome, with the introduction of the Julian calendar. Unlike the ancient Greek system of time calculation, the day was divided into 24 equal intervals, regardless of the time of day or season.

Different cultures use their own calendars, which have specific events, most often of a religious nature, as their starting point. But the length of the average solar day is the same throughout the Earth.

And the sundial was mentioned that the time varies. So let's try to figure it out.

Solar noon has also already been written about - this is the highest point at which the sun appears during the day. And they also say the passage of the sun through the meridian (north-south direction). And also the upper culmination of the sun. It is worth noting that there is also a lower culmination - the lowest point of the sun above the horizon at this point the sun is in the north. In the middle latitudes this point is not visible, but in the subpolar latitudes, on a polar day you can clearly see how the sun rises at noon at highest point in the south at noon and drops to its lowest point at midnight in the north.

The most obvious thing is that a day is the time from one solar noon to another. They decided to divide this day into 24 hours. Most likely this is a Babylonian idea, from a predilection for duodecimal and sexagesimal number systems. Because 12 is conveniently divided into parts 2, 3, 4, 6. And 60 is also for 5 and for and for 10 and for 12 and for 15 and for 30. Well, it doesn’t matter. This sunny day.

The same thing can be observed with stars. From one upper culmination of any selected star to the next upper culmination of the same star - same day, only sidereal.

Already the most ancient (possibly still cave) astronomers noticed that sidereal days are not equal to solar days. This is visible and by indirect evidence: Every night all the constellations move slightly to the west. And in a year they make a full revolution. In a month they move approximately 30 degrees. You can see if you look every day which stars and constellations are visible in the south at the same time, for example at 22.00.

And by direct signs– with each total solar eclipse (when stars are visible during the day), the sun is in a different constellation.

Observations show that the sun lags behind the movement of the stars by 3 minutes. 56 seconds per day. This slow motion of the sun against the background of stars leads to the fact that 365 solar days and 366 sidereal days pass in a year.

This has 2 interesting consequences.

• Over the course of a year, the sun passes through the entire circle of the zodiac constellations.
• Over the course of a year, sidereal noon (the culmination of one star we have chosen) occurs sequentially at different hours and minutes of all 24 solar hours.

Zodiac constellations- those that are located in the plane of rotation of the sun and through which the sun successively passes throughout the year. The sun never passes through the other constellations.

The picture shows the path of the sun among the stars.

Means sunny afternoon may be during the day when the sun is at its highest position. Sidereal noon (for the star we have chosen) can be at any time of the day according to the sundial. And it is inconvenient to use such time in everyday life. But it is convenient for astronomical observations and, accordingly, orientation by the stars.

Astronomical observatories use clocks that follow sidereal time.

Sidereal time is also used for orientation, but it is recalculated from solar time. Because carrying an accurate sidereal clock with you is problematic.

To tell the truth, using sunny days is also not convenient. Finest Hours, minutes, seconds - at least uniform. And solar ones are different throughout the year.

The unevenness consists of many reasons, including those of a random nature (for example, random redistribution of water masses on the surface of the earth, which leads to a change in the speed of rotation and, therefore, a change in the length of the day). But these are minor things compared to the two main ones.

1. The Earth moves around the Sun in an ellipse, so at the point closest to the Sun, the Sun moves faster against the background of the constellations. At the farthest point of the orbit it is slower.
2. The apparent plane of movement of the sun against the background of the constellations is inclined to the plane of the celestial equator at an angle of 23.4 degrees. Therefore, the speed of movement of the sun among the stars is divided into 2 components - vertical - the change in the declination of the sun and horizontal - movement along the celestial equator.

The figure shows that the path of the Sun is a curve, a sinusoid. The direction of movement changes, which means the horizontal and vertical components of the speed change their magnitude, and the vertical component also changes the direction of movement (the sign changes from plus to minus).

In the good old days, when there was no transport, no computers, no instant communication. It didn't matter. We lived by the sundial.

But with the advent of all of the above, problems began.

For example, a telegram across the Atlantic Ocean arrives in a split second, but the time differs by 5-6 hours. Or train schedules even within England based on the sundials of various cities turn into a nightmare.

Therefore, we decided to look for something more uniform.

• It would be nice... if the earth rotated around the sun in a circle - the speed was constant. But if we replace the real ellipse with a circle, we get only 4 exact match points.
• It would be nice if the sun rotated in the plane of the celestial equator... The shadows would move strictly in the east-west direction. And this happens 2 times a year - on the days of the equinoxes.

Two uniform rhythms would work so well for navigation and transport. And it’s much easier to make a clock with a uniform speed than experimenting with eccentric elliptical gears. And it is easier to recalculate uniform virtual time into uniform sidereal time.

Well, since everyone is happy, then they did so. :-) We simulated uniform motion (around the circle) and in the plane of the celestial equator of a conditional point. This time was called mean solar time. Beauty. There are exactly 24 uniform hours in a day. Uniform movement conditional point – facilitates astronomical calculations. It is easier to make clocks with a uniform rate.

True, this average time at each specific moment differs from the true solar one. But if you need to find out by the average clock solar hour, you can use the yearly chart, which gives an amendment for any day. And reflect the rule:

True solar time = mean time + correction.

It’s worth noting right away that this chart is simply not suitable for a sundial. Because the sundial IMMEDIATELY shows true solar time. To obtain the average time from the readings of a sundial, the above-mentioned formula must be rewritten as: average time = true time - correction. That is, the correction must be SUBTRACTED from solar time. Or redraw the graph in a mirror image. You should always carefully read the caption to the chart to see what time the correction from the chart gives. There is confusion about this even in reference books and eccyclopedias.

Because the above-mentioned amendment was defined differently.

Until 1834, all events in maritime yearbooks were indicated in SOLAR time. Because the main clock on the ship was the solar clock.

By 1834, accurate marine chronometers keeping MEAN time had already become a rule of good form. And after this date, all events in naval yearbooks began to be indicated in MEAN time.

Accordingly, the correction of the equation of time BEFORE and AFTER the mentioned date was indicated differently.

As you can see, 4 times a year the average time coincides with the solar time (crosses line 0 on the graph). But these are not memorable dates like March 21, June 22, September 23 or December 22.

In everyday life, the work of transport, these translations are not needed. But also up to certain limits. In the UK, trains can still run without any problems on London time.

But on the territory of Russia... “It’s 15 o’clock in Moscow, in Petropavlovsk-Kamchatsky it’s midnight...”. Until October 17, they made do with what was available on the entire railway network - St. Petersburg time, and in each specific city - the local average solar time - according to the latitude of the location. That's what they said - station time and city time.

After 1818, they decided to join international agreements and set not any local time, but only 24 possible hours on a global scale (and 9 on a Russian scale).

The essence of this international agreement is to divide the earth into 24 time zones, 15 degrees each. Within 1 zone, the time on all watches is the same, in the next zone it differs by exactly an hour.

But in the light of subsequent reforms, this strict and logical system did not survive... But more on that another time.

And also about when sunny time is needed. Needed - in navigation. When determining the height of the sun, they want to get their coordinates in the sea. Measuring the height of the sun, in particular local noon – we determine solar time. To determine longitude, you need to know Greenwich Time at the same moment. To compare with local and calculate longitude. But in Grivich the clocks run according to mean time. Therefore, the true solar time determined by the sun is converted to mean local time using a graph of the equation of time. After this, time in some units is compared with Greenwich. And they get the longitude.

Sometimes the graph of the equation of time is drawn in a more elegant and more informative form:

On such a graph, in addition to the correction of the equation of time, you can also see the declination of the sun for each day. In addition, it is clear that the sign of the correction is opposite to that given by the above-mentioned graph in the form of a sinusoid. This graph can be immediately drawn on a sundial. The rule on the graph clearly states:

The correction is added to the true solar time to obtain the true one.

You can also use this mnemonic rule:

This is to determine what type of graph you are dealing with in the book or reference book.

Find out more about the meaning of this rule. Date at 12 noon according to solar hours on February 14th. Correction of the equation of time -14 minutes. This means the average time at this moment is only 11.46. And you will have to watch the sundial for another 14 long minutes until the girl’s watch shows 12 noon according to average time.

If you look at this figure eight graph on a large scale

Then you can see 4 periods when the digit of the equation of time changes very slowly, less than a minute in 3 weeks:

In approximate calculations, for emergency situations, during these periods the correction of the time equation can be considered constant.

In addition, this graph shows 4 dates, near which the correction to the equation of time is equal to zero. And it does not need to be taken into account in the calculations:

When making accurate calculations, it is taken into account that the correction of the equation of time changes continuously even during the day.

“NEAR” the mentioned dates should be understood in the sense that this schedule should be shifted by 6 hours every year in a leap cycle of 4 years. And in a leap year until February 29, the error occurs on 1 day. Therefore, the graph is constructed as an average, giving the minimum possible error in any of the 4 years of the leap cycle. Graphs of increased accuracy would have to be built for each year of the cycle and used four consecutively.