Terms denoting various units of time measurement. Meter, second, kilogram - the history of origin. day ….2 months
The basis of measuring time by astronomical chronology is the movement of celestial bodies, which reflects three factors: the rotation of the earth on its axis, the revolution of the moon around the earth, and the movement of the earth around Sun. These factors are decisive in the selection of the basic units of time.
First natural unit of time allocated by primitive people, there were days associated with the change of day and night - the time of work and rest.
Day- this is the length of time during which the Earth makes one complete revolution around its axis relative to any point in the sky. Differ stellar and solar day. sidereal day equal to the interval between two successive positions at the same point in the sky of a certain star. solar day determined by the same position of the sun. Since the Sun moves relative to the stars in the same direction as the Earth, sidereal and solar days do not coincide (solar days are longer by about 4 minutes). During the year, the difference between sidereal and solar days reaches about a day. In addition, the Earth moves around the Sun at different speeds, and therefore the solar day is not a constant value. To facilitate the calculation of time, a fictitious concept " mean sun", i.e., the movement of the Sun is considered to be uniform. Therefore, the day has become a constant unit, they are divided into 24 hours, each of which has 60 minutes, in a minute - 60 seconds, in a second - 60 thirds. The emergence of small units of time measurement (hours , minutes, seconds) are associated with the ancient Babylonian duodecimal counting system.In 1792, the French astronomer and mathematician Pierre Simon Laplace proposed a decimal division of the day, i.e. - into 10 hours, 100 minutes each and 100 seconds per minute. But this division was not accepted.
The starting point of the day - midnight - in Russia was established by a decree of the Soviet government, signed by V.I. Lenin in February 1919: "Count the time during the day from 0 to 24 hours, taking midnight as the beginning of the day."
The Earth, rotating around its axis, successively turns to the Sun with different parts of the surface, and the day does not come in all places of the globe at the same time. In the 19th century S. Fleshing suggested standard time- a time counting system based on the division of the Earth's surface into 24 time zones. In 1884, an international conference was held in Washington on the introduction of a single standard time and a single prime meridian. The initial (zero) meridian was the one that passes through the Greenwich Laboratory in the suburbs of London. The local time of time zones located to the east of Greenwich, from zone to zone, increases by an hour, and to the west - by an hour decreases. It was decided to draw time zone boundaries in uninhabited places (oceans, deserts, mountains) along meridians, and in other territories - taking into account physical and geographical features (along large rivers, watersheds) or along interstate and administrative borders. At the same conference, the so-called. "date line" - the meridian of 180º E, located in the opposite part of the globe from the zero Greenwich meridian.
Paying attention to the passage of the various phases of the Moon from one new moon to another, people identified a larger unit of time - lunar (synodic) month(from Greek " synodos"- rapprochement, convergence, since at the time of the new moon the Sun and Moon "approach"). Month - This is the period of the observed alternation of the lunar phases, depending on the movement of the Moon around the Earth. The synodic (lunar) month is 29 days 13 hours 44 minutes 2.9 seconds. Initially, its duration was determined at 30 days.
The establishment of the following unit of time is largely connected with the phases of the moon - seven day week. The counting of days by seven days arose in the Near East and in Egypt several millennia ago. The names of the days of the week are repeated in many languages, and most often indicate the ordinal number in the week. The exception is the word Shabbat, which arose to designate the day of the week in ancient Babylon, where it denoted peace, since the day was considered unlucky, and one should not work, but one had to indulge in peace. There is another option: in the Akkadian language, the word "shabbatum" meant "full moon" or "phase of the moon", which indicates that the seven-day count was associated with the approximate duration of each phase of the moon.
The need to monitor the change of seasons associated with the apparent movement of the Sun (in fact, with the movement of the Earth around the Sun) brought to life the appearance of the solar year. Year astronomically corresponds to the real complete revolution of the Earth around the Sun. The astronomical solar year is called tropical. Twice a year, the Sun and the Earth are in such a mutual position that the sun's rays evenly illuminate the earth's hemispheres, and the day is equal to the night on the entire planet. These days are named spring(21 March) and autumn(23 September) equinoxes. The time interval between successive positions of the Sun at the vernal equinox is called tropical year, e its duration is 365 days 5 hours 48 minutes 46 seconds.
A day, a tropical year, and a synodic month are incommensurable quantities, they cannot be expressed one through the other. Therefore, when highlighting the solar year, the months are conditional units, not connected in any way with the real lunar months.
Century - in ancient Russia, this chronological value was first understood as a long period of time - an epoch. The chronicles indicated: “There are 6 centuries from Adam to this time”, “There were centuries of Trojan, the summers of Yaroslavl passed”, Later, a number of years began to be called a “century”, “how long a person can live”; "that seventy years will transform the age of the human belly." Finally, from the 17th century "age" began to be used in the meaning of "century".
The new age starts from the first year. In 2000, a special explanation was given by the State Committee of the Russian Federation for Standardization and Metrology about when the 21st century and the 3rd millennium begin: "In accordance with the document of the International Organization for Standardization ISO 8601 and Russian GOST 7.64-90, the counting system long periods of time (chronology) is carried out according to the Gregorian calendar, introduced since 1582 and adopted in Russia since February 1918. The counting of years in the Gregorian calendar is made from the 1st year of the new era.Therefore, the 1st century (century) of the new era contains years 1-100 and ends at the end of the year 100. The second century begins in the year 101 and continues until the end of the year 200, etc. Continuing the accepted calendar count of years, we get that on December 31, 2000, the end of the twentieth century will come and the second millennium. Therefore, the 21st century and the third millennium will indeed begin on January 1, 2001."
Eroy is called the starting point of the chronology(from Latin aera- initial moment, initial number), as well as the chronology system itself. Any calendar system needs a starting point. A feature of the era is its conventionality, because. the starting point could be any significant historical or mythological event in the life of a particular nation or state. Depending on the nature of such an event, eras are distinguished political, religious, astronomical. So, for example, the reckoning of the calendar from the birth of Christ or from the creation of the world - religious eras. were widespread and political era, determined, for example, by the time of the reign of certain dynasties: in Egypt - the dynasty of pharaohs, in China and Japan - the dynasty of emperors, in Western Europe, especially in Italy - the dynasty of Roman emperors. There is an opinion that the word "era" (aera) itself is nothing more than a combination of the initial letters of the Latin phrase "Ab exordio regni Augusti" ("From the beginning of the accession of Augustus" (63 BC)). Bashkirs in the 16th century in their Sherezh chronicles, they took the date of the capture of Kazan by Ivan the Terrible as the initial date of the new era, which is also a political era. There are also fictitious and real eras. In real eras, a real historical event is taken as the basis for counting (for example, the fall of Kazan, the era of Diocletian from the moment this emperor came to the throne, etc.). Fictitious eras - from the birth of Christ, because. it is impossible to prove or disprove the reality of the birth of this character, or the Muslim era - Hijra - counted from the unprovable date of Muhammad's flight from Mecca to Medina.
Allocate and so-called. world eras, counting the time since the creation of the world. In Russia, the Byzantine world era was adopted, considering the year of the creation of the world 5508 BC. e. In general, the church dates the creation of the world in the range from 6984 to 3483 BC.
Now the most common in the world is the era from the Nativity of Christ, calculated by the monk Dionysius the Small as starting in 754 from the founding of Rome or in 281 before the beginning of the era of Diocletian. In Russia, this era was introduced by Peter the Great on January 1, 1700.
In 1627, the French scientist Petavius proposed a backward counting method, i.e. "before the birth of Christ" or BC, this account became widely used from the end of the 18th century. It is accepted that the 1st year BC. directly adjoins the 1st year AD. It is also accepted that the number of years BC. increases as you move into the past, but the months, numbers in them and days of the week are considered exactly the same as in the years of our era.
Cycles (circles) are temporary. In the Middle Ages, time is also known in larger time units than the year. The Piskarevsky Chronicler says: “Renewal is all around: the sky is renewed in 100 years, the stars in 50 years, the sun in 28 years, the moon in 19 years, the sea in 60 years, the water in 7 years, the earth in 10 years, the wind in 4 summer, and the high cost for 4 and the indict for 15 years ..., the epacta for 12 years, the base for 19 years. Let's take a look at some of these units:
indict - the serial number of the year within the 15-year cycle (indictikona) (from lat. " indico"- I announce, I appoint). The appearance of the indicative account is associated with the name of the Roman emperor Octavian Augustus, who established the collection of taxes in this order: in the first five years - honey and iron, in the second - silver, in the third - gold. After 3 5- summer cycles (chandeliers) repeated the same order in the collection of taxes. In Byzantium, the indict account was introduced by Emperor Constantine the Great in 312, and from the reign of Emperor Justenian (537), dating by indict became mandatory in Byzantium. The starting point of the indict account is " world creation".
The beginning of the indicative year did not coincide with the beginning of the ecclesiastical or civil year. There are several options for the beginning of the indict:
In ancient Russia, the calculation of time by indicts was borrowed from Byzantium (with the beginning of the indict on September 1), and was used until the 18th century.
Circle of the Moon. In the 5th century BC. Athenian astronomer Meton found that 19 solar years contain 235 full lunar months, and every 19 years there is a repetition of the lunar phases on the same dates of the solar calendar. The 19 year cycle is called lunar or metonic cycle, and the serial number of the year inside this cycle is around the moon. At the same time, it became customary in Athens to put on public display boards with the number of years that have passed since the beginning of the current 19-year lunar cycle indicated in gold letters. Therefore, this number began to be called gold.
Circle of the Sun. The sequence of days in a year repeats periodically every 28 years. This time interval in the Byzantine and Russian medieval chronology was called solar circle, and the ordinal place of the year within it is around the sun.
The circle of the sun is important for determining the days of the week. In the ancient Russian calendars (monthly books), each day of the week from the beginning to the end of the year, starting from March 1, corresponded to one of the 7 letters of the Slavic alphabet. The same letter in the course of the year corresponds to the same day. Vrutseleto (Sunday letter), which corresponds to the Sunday of the given year. After the vrutselet and the circle of the moon of the year are determined, Easter is easily established according to a special table.
Great Indicton – this is the name of the period in 532, since the phases of the moon return to the same numbers of months after 19 years, and the days of the week, taking into account leap years, after 28 years, thus. 19 x 28 = 532 years. All elements return to their former order, and the days of Easter according to the Julian calendar repeat exactly.
All these subtleties are taken into account when translating the dates indicated in the annals to the modern system of chronology, since events are often indicated not with an exact date, but in relation to one or another church holiday, most often Easter. Therefore, it is necessary to navigate the calculation of church holidays.
History is not able to answer the question of when people learned to measure time. Obviously, the first methods of measurement should have been preceded by the development of an abstract idea of time, the emergence of the need to measure it. There is no doubt that these prerequisites appeared in the process of primary collective actions, in labor operations associated with periodic natural phenomena. Finally, in order to measure time, a person already had to be able to count.
The accounting of time, as well as the emergence of counting, can be attributed to the category of convergent phenomena, i.e., those that arose independently of each other among different peoples under the influence of similar conditions and requirements of developing societies. Judging by the perfection of the first calendar systems that appeared among many peoples already in the Neolithic period, the initial stages of the process of counting time should be attributed to earlier periods. This can be indirectly confirmed by the presence of a primary account in the Upper Paleolithic.
The first unit of time measurement was the day, a curious account of days in the 6th century. BC. among the Persians describes Herodotus. King Darius, setting off on a campaign against the Scythians, left to the soldiers guarding the Danube crossing a kind of calendar - a belt with knots tied on it. Untying the knot every day, the soldiers counted the days that had passed since the beginning of the campaign. The remaining knots signified the days until the planned return of the king. Of course, in the era of the Achaemenids, the Persians were also familiar with more advanced systems of counting time, but for ordinary soldiers, the use of such a primitive calendar was more understandable Volodomonov N. Calendar: past, present, future. Page 99.
The calculation of time by the alternation of the phases of the moon also arose very early. But also turnover. The moon, the lunar month, is a comparatively small measure of time. The needs of ancient chronology were satisfied with the appearance of the lunar and solar years in the account. The counting of days within a year, divided into twelve approximately equal periods (months), made it possible to create the simplest devices: wooden, bone, ceramic tables - calendars. Many peoples kept them in everyday life until the beginning of the 20th century, and our modern mobile calendar tables go back to these simplest devices. .
Along with portable devices, monumental calendar devices were also created in antiquity, a kind of stone observatories that made it possible to compare time with astronomical indicators. These are the buildings of the III millennium BC. e. in Stonehenge (England), a stone calendar near Cusco (Peru), etc.
In ancient times, the first methods of measuring time within a day appeared. The very perception of time in the past was significantly different from the modern one. Today we are used to measuring time in minutes and seconds, and medieval clocks had only an hour hand on the dial, the minute appeared in the middle of the 16th century, and Pushkin's contemporaries did not yet know the second.
Different peoples in different eras divided the day in different ways. The modern system of dividing them into 24 hours originated in Babylon, although it was officially introduced by the Alexandrian astronomer Claudius Ptolemy, who lived in the 2nd century BC. AD
The first ways to measure time during the day were associated with the Sun. The oldest and simplest instrument for measuring time by the Sun was the gnomon, a vertical pole. By the length of the shadow cast by it, it was possible to determine the time of day. The first mention of the gnomon dates back to the 6th century. BC e.
A further development of the idea of measuring time according to the Sun is the skafis - a sundial that indicates time by the direction of the shadow cast on a special dial by a vertical axis - an arrow. The first skafis was built by the priest Beros from Babylon in the 3rd century BC. BC e. The improvement of the skafis led to the invention of a horizontal sundial, in which the axis - the arrow is the edge of a right-angled triangle, oriented at an acute angle equal to the latitude of the place where the clock is installed, to the south.
The peoples of Asia have used hourglasses since ancient times, where time was measured by the amount of sand pouring from one vessel to another. Such watches are not connected with the Sun, they measure certain small periods of time, by counting which you can set the time of day. To count short periods of time, the hourglass is still used in medicine today.
In China, the so-called fire clock was used, where the passage of time was determined by the uniform combustion of a special candle. Medieval Europe also knew candles with hour divisions, and in Russia short time periods were measured by the number of burnt torches.
In the I millennium BC. many countries used water clocks or "clepsydras". With the use of these watches, Latin turns of speech that have survived to this day are associated, sounding in Russian as “no need to pour water”, or “since then a lot of water has flowed under the bridge”.
All the described systems did not differ in accuracy, were inconvenient, but up to a certain time they satisfied society. However, with the development of productive forces, with the advent of new tasks, a need arose for more advanced methods of measuring time. An important step in this regard was the transition to mechanical clocks, the first mention of which is found in Byzantine sources in 578. The widespread practical use of mechanical (wheel) clocks in Europe dates back to the 11th-12th centuries. Usually they were installed on the towers of town halls, linking the clock mechanism with a ringing or striking device. The disadvantage of wheel clocks was their bulkiness and low accuracy. In Russia, the first wheel clock was installed in the Moscow Kremlin in 1404. The Spasskaya clock and the Kremlin tower were installed in 1624 under Tsar Mikhail Fedorovich by the mechanic Galloway. In 1706, by order of Peter I, they were replaced by Dutch chimes, which are still in effect today.
Replacing the driven load with a spring in the wheel clock made it possible to create at the beginning of the 16th century. the first portable copies. Finally, in 1640, Galileo proposed the construction of a pendulum clock, which came into use after the death of the scientist 1 .
Pendulum clocks, which increased the accuracy to several seconds a day, became an important tool in the hands of scientists, helped astronomers to make calculations that determined the shape and size of the Earth.
Invention in the middle of the XVIII century. The Englishman D. Harrison of the chronometer made it possible to determine the exact time not only on land, but also at sea, which is very important for finding out the longitude of the ship's location. Most modern household clocks use the chronometer principle.
Currently, quartz, molecular, atomic and other systems of ultraprecise devices are used for special scientific purposes. Modern astronomical clocks can provide an accuracy of up to 0.002 seconds per day. Work is underway to further improve the devices that measure time.
The daily routine of life of the people of the globe is coordinated with the daily course of time. At the same time, the definition of the mean solar day is associated with a specific place for observing the culminations of the Sun. Therefore, the mean solar time has a different value for different meridians of the Earth. This circumstance gives rise to the problem of the so-called local time. Since the celestial sphere makes a complete revolution during the day, and the day consists of 24 hours, then 360 ° can be calculated in angular units: 24 \u003d 15 °, i.e. in an hour the celestial sphere rotates 15°. This means that two points on Earth that are 15° apart from each other in longitude will have a difference in local time of 1 hour.
In 1878, Canadian S. Fleming proposed introducing the so-called standard time. The entire surface of the globe was conditionally subdivided into 24 time zones, limited by meridians drawn at intervals of 15 °. For each zone (from 0 to 23), local time was set corresponding to its average meridian. The zero belt is taken as the middle meridian of which is the Greenwich meridian. To the east of zero lies the first zone, then the second, and so on. Standard time changes jump by 1 hour when moving from one zone to an adjacent one.
Standard time was adopted at the International Astronomical Congress and introduced in 1883 in Canada and the USA, and then in European countries. In the USSR, standard time (from 2 to 12 zones) was introduced by a decree of the Council of People's Commissars of January 17, 1924.
On March 1, 1957, the boundaries of time zones were introduced, following not strictly along the meridian, but coinciding with the borders of the edges and regions.
In many countries, for economic reasons, they introduce amendments to standard time, moving the clock forward by 1 or more hours. In our country, by a decree of the Council of People's Commissars of the USSR of July 16, 1930, in order to make more rational use of the working day and save electricity, the so-called maternity time was also introduced. It is ahead of the belt by 1 hour. Therefore, if in Greenwich (zero zone) it is 20 hours, in Moscow (second zone) the time is: 20 + 2 = 22 hours + 1 daylight saving time = 23 hours.
Since 1981, in addition to the standard time on the territory of the USSR, an annual seasonal shift of the clock hands (from April 1 to October 1) has been introduced 1 hour ahead. Local time in the specified spring-summer period will be ahead of the true standard time by 2 hours Yanin VL Chronology. Page 28.
The so-called date line is also associated with time zones. A new day is everywhere measured from midnight. To avoid confusion in counting days, an international agreement has established: the meridian with a longitude of 180 ° (12 hours), which delimits the western and eastern hemispheres of the Earth, "is considered the date change line. On ships crossing this line from west to" east, one and the same the same day is counted twice, and on ships going in the opposite direction, one calendar day is skipped.
People very early began to use astronomical phenomena to measure time. Much later, they realized that the basic units of such a measurement could not be set arbitrarily, as they depended on certain astronomical laws.
One of the first units of time measurement, of course, was the day, that is, the time during which the Sun, having appeared in the sky, "bypasses" the Earth and reappears at its original point. The division of the day into two parts - day and night facilitated the fixation of this period of time. For different peoples, the time of the change of day was associated with the change of day and night. The Russian word "day" comes from the ancient "stuck", that is, to connect two parts into a whole, in this case, to connect night and day, light and darkness. In ancient times, the beginning of the day was often considered the sunrise (the cult of the Sun), among Muslims it was the sunset (the cult of the Moon), in our time, the most common boundary between the days is midnight, that is, the time conditionally corresponding to the lower climax of the Sun in a given territory.
The rotation of the Earth around its axis occurs uniformly, however, a number of reasons make it difficult to choose a criterion for accurately determining the day. Therefore, there are concepts: sidereal day, true solar and mean solar day.
A sidereal day is defined by the time interval between two successive upper climaxes of the same star. Their value serves as a standard for measuring the so-called sidereal time; there are, respectively, derivatives of the sidereal day (hours, minutes, seconds) and special sidereal hours, without which not a single observatory in the world can do. Astronomy needs to take sidereal time into account.
The usual routine of life is closely connected with other, solar days, with solar time. A solar day is measured by the length of time between successive upper climaxes of the Sun. The duration of a solar day exceeds the stellar day by an average of 4 minutes. In addition, the solar day, due to the uneven movement of the Earth in an elliptical orbit around the Sun, has a variable value. It is inconvenient to use them at home. Therefore, the abstract average solar day, determined by the calculated uniform motion of an imaginary point ("average Sun") along the celestial equator around the Earth with the average speed of the true Sun along the ecliptic, is taken as a standard.
The time interval between two successive climaxes of such an "average Sun" is called the average solar day.
All clocks in everyday life are adjusted to the average time, the average time is also the basis of modern calendars. The mean solar time, counted from midnight, is called civil time.
As a result of the tilt of the ecliptic with respect to the plane of the celestial equator and the tilt of the Earth's axis of rotation with respect to the plane of the Earth's orbit, the length of day and night changes throughout the year. Only during the period of the spring and autumn equinoxes on the entire globe is day equal to night. The rest of the time, the height of the climaxes of the Sun changes daily, reaching a maximum for the northern hemisphere during the summer solstice and a minimum during the winter solstice.
The average solar day, like the sidereal ones, is divided into 24 hours, each of which has 60 minutes, and 60 seconds in minutes.
A more fractional division of the day first arose in ancient Babylon and is based on the sexagesimal counting system Volodomonov N. Calendar: past, present, future. Page 88.
Since a day is a relatively short period of time, larger units of its measurement were gradually developed. At first, counting was done with the help of fingers. As a result, such units of time measurement as ten days (decades) and twenty days appeared. Later, an account based on astronomical phenomena was established. The unit of time was taken as the interval between two identical phases of the moon. Since it was easiest to notice the appearance of a narrow lunar crescent after moonless nights, this moment was considered to be the beginning of a new month. The Greeks called it neomenia, that is, the new moon. The day during which the first setting of the young moon was observed was considered the beginning of the calendar month among the peoples who counted according to the lunar calendar. For chronological calculations, the time interval separating the true new moon from neomenia is important. On average, it is 36 hours.
The average length of a synodic month is 29 days, 12 hours, 44 minutes and 3 seconds. In the practice of constructing calendars, a duration of 29.5 days was used, and the accruing difference was eliminated by the special introduction of additional days.
The months of the solar calendar are not associated with the phases of the moon, so their duration was arbitrary (from 22 to 40 days), but on average it was close (30-31 days) to the duration of the synodic month. This circumstance to some extent contributed to the preservation of the count of days by weeks. The seven-day period of time (week) arose not only because of the worship of the seven gods, corresponding to the seven wandering celestial bodies, but also because seven days made up approximately a fourth of the lunar month.
The number of months in a year accepted in most calendars (twelve) is associated with the twelve zodiacal constellations of the ecliptic. The names of the months often trace their connection with certain seasons, with larger units of time - the seasons.
The third basic unit of time (the year) was less noticeable, especially in the lands closer to the equator, where there is not much difference between the seasons. The value of the solar year, i.e., the period of time during which the Earth makes a revolution around the Sun, was calculated with sufficient accuracy in ancient Egypt, where seasonal changes in nature were of exceptional importance in the economic life of the country. "The need to calculate the periods of rise and fall of the waters of the Nile created Egyptian astronomy."
Gradually, the magnitude of the so-called tropical year, that is, the time interval between two successive passages of the center of the Sun through the vernal equinox, was determined. For modern calculations, the duration of the year is 365 days, 5 hours, 48 minutes and 46 seconds.
In some calendars, years are counted by lunar years, which are associated with a certain number of lunar months and have nothing to do with the tropical year.
In modern practice, the division of the year is widely used not only into months, but also into half-years (6 months) and quarters (3 months).
Try to immediately give a precise definition: what is time? The thought revolves around this concept, trying to grasp, but it is difficult to formulate an unambiguous definition. There are different concepts and interpretations of time in philosophy, physics, metrology.
Classical mechanics and relativity use completely different concepts of time. In the first case, time characterizes the sequence of events occurring in three-dimensional space. In the second, it is also considered as the fourth coordinate.
But first things first. Let's find out how people measured time, why the second is its smallest accepted unit. We will also define the concept of time in physics, consider the phenomena of relativistic and gravitational time dilation.
What is time?
The passage of time is a completely natural phenomenon. Time passes, everything around changes, different events occur. That is why it is worth talking about time from the point of view of physics, first of all, in the context of events.
If nothing was happening around, the concept of time would have no traditional meaning. In other words, without events, time does not exist. So:
Time is a measure of how the world around us changes. Time determines the duration of the existence of objects, the change in their states and the processes taking place in them.
In system SI time is measured in seconds and denoted by the letter t .
How did people measure time?
To measure time, you need some recurring events with the same period. For example, the change of day and night. The sun rises every day in the east and sets in the west, and the moon every synodic month goes through the entire cycle of phases of illumination by the sun - from a thin crescent crescent to a full moon.
A synodic month is the time from one new moon to the next. In a synodic month, the Moon revolves around the Earth.
The ancient people had no choice but to tie the countdown to the movement of celestial bodies and the events associated with it. Namely - to the change of days, nights and seasons of the year.
per year 4 season and 12 months. That is how many times during spring, summer, autumn and winter the moon changes its phases.
With the development of progress, methods for measuring time improved, solar, water, sand, fire, mechanical, electronic and, finally, molecular clocks appeared.
FOCS Clock 1 Clock FOCS 1in Switzerland
measure time with an error of about one second in 30 million years. This is a very accurate clock, but after 30 million years they still have to be "brought down". Why are there 60 minutes in an hour, 60 seconds in a minute, and 24 hours in a day?
Let's make a reservation right away that what is stated below is largely the author's personal assumptions made on the basis of historical information. If our readers have clarifications or questions, we will be glad to see them in the discussions.
The ancient peoples needed some kind of basis to build their number systems. In Babylon, the number was taken as such a basis 60 .
It is thanks to the sexagesimal number system, invented by the Sumerians and later spread in Ancient Babylon, that a circle contains 360 degrees, a degree - 60 minutes, and a minute - 60 seconds.
The year can be represented as a circle containing 360 degrees. Perhaps the number 360 in this context, it came from the fact that in the year 365 days, and this figure was simply rounded up to 360 .
Once upon a time, the shortest unit of time was hour. The ancient Babylonians were strong mathematicians and decided to introduce smaller units of time using their favorite number 60 . Therefore, in the hour 60 minutes, but in a minute 60 seconds.
But why is the day divided into 12 hours? For this we must say thanks to the ancient Egyptians and their duodecimal system. Day and night were divided into 12 early parts, considered different kingdoms of being. Most likely, the original use of the number 12 related to the number of revolutions of the moon around the earth in a year.
The largest unit of time
The largest unit of time is kalpa. Kalpa is a concept from Hinduism and Buddhism. It equals approximately 4,32 billions of years, which coincides with the age of the Earth up to 5% .
How did the ancient Hindus come up with such numbers? We do not know the answer to this question, but the whole system seems to tell us that then people knew a little more about the Universe than we do.
Kalpa in Hinduism is also called the "day of Brahma." Day is replaced by night, equal to it in duration. 30 days and nights make up a month, and a year consists of 12 months. The whole life of Brahma is 100 years, after which the world perishes with him.
If we translate one hundred years of Brahma into our traditional years, we get 311 trillion and 40 billion years! current Brahma 51 year.
Conclusion: if all this is true, then you should not worry - the Universe will exist for a long time.
Kalpa is the largest unit of time according to the Guinness Book of Records.
First watch
At first, a stick was enough, on which you can make notches with a stone ax and thereby count the days that have passed. But it was more of a calendar than a clock.
The first and most ancient clock is solar. Their action is based on the change in the length of the shadow of objects as the sun moves across the sky. Such a watch was a gnomon - a long pole stuck in the ground. The sundial was used in ancient Egypt and China. They were already well known in 1200 year BC.
Then came water, sandy and fiery clock. The work of these mechanisms was not tied to the movement of heavenly bodies. For a long time, the water clock was the main instrument for measuring time.
The first mechanical clocks were made by Chinese craftsmen in 725 year of our era. However, they have become widespread relatively recently.
In medieval Europe, mechanical clocks were installed in the towers of cathedrals and had only one hand - the hour. Pocket watches appeared only in 1675 year (the invention was patented by Huygens), and wrist - much later.
The first wristwatch was exclusively a women's accessory. They were richly decorated products, the accuracy of which was distinguished by huge errors. A self-respecting man could not even think about wearing a wrist watch.
Modern clock
Now everyone has a mechanical or electronic watch. They measure time with relatively small errors. However, the most accurate clocks in the world are atomic clocks. They are also called molecular or quantum.
Big Ben - the famous tower clock As we remember, some periodic process is necessary to determine the unit of time. Once upon a time, the shortest unit was the day. That is, the unit of time was tied to the frequency of sunrise and sunset. Then the hour became the minimum unit, and so on.
FROM 1967 year, according to the international system SI, the definition of one second is tied to the period of electromagnetic radiation that occurs during the transition between hyperfine levels of the ground state of the atom Cesium-133. Namely, one second is equal to 9 192 631 770 such periods.
Time in physics
At the moment, there is no definite and unified concept of the definition of time in physics.
In classical mechanics, time is considered a continuous, a priori and undefined characteristic of the world.
Some periodic sequence of events is used to measure time. In classical physics, time is invariant with respect to any frame of reference. That is, in all systems, events occur simultaneously.
How to find time in physics? The simplest formula that determines the relationship between the distance traveled, speed and time is known to every student and has the form:
This is the time formula for uniform and rectilinear motion. Here t - time, S - distance traveled v - speed.
But the most interesting begins in relativistic physics. Here is a quote from Stephen Hawking, the physicist who wrote a brief history of time.
We have to accept that time is not completely separated from space and is not independent of it, but together with it forms a single object, which is called space-time.
Also in relativistic physics, time ceases to be an invariant and one can speak of the relativity of time. In other words, the course of time depends on the motion of the frame of reference.
This is the so-called relativistic time dilation. If the clock is in a fixed frame of reference, then in a moving body all processes occur more slowly than in a stationary one. That is why an astronaut traveling in space on a super high-speed ship will practically not age compared to his twin brother, who remained on Earth.
In addition to relativistic, there is gravitational time dilation. What it is? Gravitational time dilation is a change in the course of a clock in a gravitational field. The stronger the gravitational field, the stronger the deceleration.
Recall that a second is the time it takes for an atom of a cesium isotope to complete 9 192 631 770 quantum transitions. Depending on where the atom is located (on the ground, in space, away from any object, or near a black hole), the second will have different values.
Therefore, the time of processes associated with a given frame of reference will also differ. So, for an observer at the event horizon of a Schwarzschild black hole, time will practically stop, and for an observer on Earth, everything will happen almost instantly.
People have always been interested in the topic of time travel. We invite you to watch a popular science film on this topic and remind you that if you have absolutely no time for academic affairs, our student service will always help you cope with current tasks and problems.
In theory, time is a continuously changing independent variable. In all processes associated with movement, time plays the role of a determining parameter, since written in the form of an expression x = x (t) - means that the process is completely known to the researcher at all times. Any measurement of time means the establishment of evenly following one after another labels that can be counted. The distance between two such marks in time may be chosen as the unit of time.
The introduction of a uniform time scale was based on the uniform change and invariable rotation of the stars and planets, the periodic change of day and night, the cyclic change of seasons, and so on.
The exact value of the unit of time was required in physical studies of the atomic nucleus and elementary particles. The officially accepted unit of time is based on the methods of atomic physics.
Historically, the division of one part (hour) into 60 minutes, and then already in the 15th century, astronomers defined a second as 1/60 minutes.
Time as a physical the value measured in the processes of control or diagnosing, acts either as a fixed moment corresponding to some event, or as a time interval between events.
In the first case, the date of time serves as a quantitative estimate, and in the second case, the time interval. The natural system for measuring time was originally the rotating globe. In this system, a second was defined as 1/86400 of the period of the Earth's revolution around its axis (mean solar day). However, the period of rotation of the Earth around its axis changes for three reasons:
1. Due to the secular gradual slowdown (obtained on the basis of data on solar eclipses). This led to an increase in the day by 0.0023 s for every 100 years.
2. Due to the periodic (seasonal) change in the length of the day (obtained on the basis of data from astronomical measurements compared with astronomical clocks). Which leads to an inaccuracy equal to ∼ 0.001 s per year.
3. Due to a non-periodic (jump-like) change in the speed of the Earth's rotation (obtained on the basis of data on the irregularity of the motion of the Moon, planets and the Sun). In this case, the error is ~0.0034 s.
Therefore, in 1956, a transition was made from a second based on the "Earth rotating around its axis" clock to a second based on the "Earth rotating around the Sun" clock. In this system, the value of a second is 1/31556925.9747 of a tropical year.
A tropical year is the time interval between two successive passages of the center of the Sun through the vernal equinox. But in this case, the time unit loses its reproducibility. In this connection, the reference second was tied to the duration of 1900.
The error of a second in the latter case became smaller, because it was tied to a year, a value more stable than a day. However, in practical implementation, in this case, the errors remain significant. Taking into account that the molecules and atoms of some substances in an alternating electric field are excited and change their energy state at a resonant frequency characteristic only of the molecules (atoms) of a given substance, in 1967 a new unit of time measurement was adopted - the atomic second. An atomic second is a time interval during which 1420405751.8 energy transitions occur in the hydrogen atom. Thus, at present, there are two systems of time measurement in parallel: the astronomical time measurement system and the atomic time measurement system, which complement each other.
Under the time scale is understood a continuous sequence of time intervals of a certain duration, counted from the initial moment. The time scale can be reproduced by observing the periodic (chronometric) process running continuously.
A measure of time is a means of measuring time, designed to reproduce time intervals of a given duration or given points in time.
Typical time values include the rotation period, the duration of the oscillation period, the half-life of a radioactive substance, the pulse duration, etc.
The second is the only unit of time with which SI prefixes are used to form submultiples and (rarely) multiples. Currently, a second is defined as follows: a second is equal to 9192631770 periods of radiation corresponding to the transition between two hyperfine levels (f = 4 and f = 3) of the ground state of the cesium-133 atom (1967).
To measure longer time intervals, the units of year, month, and week are used, consisting of an integer number of solar days. A year is approximately equal to the period of revolution of the Earth around the Sun (approximately 365.25 days), a month is the period of a complete change in the phases of the Moon (called a synodic month, equal to 29.53 days).
Even larger units of time are a century (100 years) and a millennium (1000 years). A century is sometimes divided into decades. In sciences such as astronomy and geology, which study very long periods of time (millions and billions of years), even larger units of time are sometimes used, such as gigayears (billion years).
According to their functional properties, time instruments and devices are divided into the following groups:
a) current time meters that allow you to set the hour, minute, second;
b) time interval meters (stopwatches, time relays, etc.);
c) meters of temporary physical characteristics (tachometers, revolution counters);
c) program-time sensors of time intervals (timers);
e) sensors of uniform speed (stabilizers of engine speed, clock mechanisms of self-recording instruments, etc.).
When measuring time, as a rule, two main principles are used: the principle of periodic chronometry and the principle of aperiodic chronometry.
The main elements of any time meter are an energy source, an oscillatory system (oscillator), a counter, an output device. The procedure for measuring time is reduced to counting a strictly periodic sequence of pulses generated by oscillations of the oscillator.