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Time

the Science and technics
 
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Rotation of the Earth and the Moon defines duration of years, seasons, months and days. Once such division of time was enough for the organisation people of the ability to live, but today we cannot present the life without hours.

The Cycle of rotation of the Earth round the Sun makes one year. In this time one stars replace others in the night sky, and in weather there are seasonal changes. As soon as such sequence of events has been found out, people have learnt to derive practical benefit from the supervision. For example, occurrence of a certain star meant that there has come sowing time. Ancient Egyptians knew that annual floods of Nile always began soon after occurrence over horizon of a star Sirius.


the Juliansky calendar

Duration of days is defined by rotation of the Earth about the axis, and it seems to us that the Sun ascends and comes. Complexity at calendar drawing up is connected by that year lasts not the whole quantity of days, and approximately 365,25 days. In 15 year to the item e. July Caesar has solved this problem and has entered a calendar in which behind three years, but 365 days 366-day leap-year followed.


the Gregorian calendar

Gregorian calendar First to julianskomu to a calendar of claims was not, but it became gradually clear that year lasts for 11 minutes less, than have counted. This error has been eliminated in 1582 by daddy Grigory XIII who have published the decree according to whom put on October, 5th followed consider on October, 15th. Otherwise calendar dates would not coincide with certain seasons more and more. To exclude such error in the future, he also has disposed to consider century years leap only when they share on 400 without the rest. This Gregorian calendar is still used in the western countries.

Day and night were the shortest periods of time known our far ancestors. More exact calendar has appeared about 4000 years to and. e., when ancient Egyptians have broken time of days for hours. The first chronometre were a sundial consisting in basic from the column-index (gnomona) which was stuck in the earth so that to reject a shade on a scale with hour divisions. When the sun moved on a sky, the shade from gnomona moved on a scale and showed time.


Water, sand and wax

The Main lack of a sundial consisted that they could not use at night and cloudy days. This problem finally managed to be solved about 1500 to and. e., when Egyptians have invented klepsidru, or a water-clock. The elementary kind of such hours represented a vessel with a small aperture in the bottom part. The water filled in in a vessel slowly followed through an aperture, and the water level concerning the marked scale showed expired time.

On change to a sundial have come sand to which sand was strewed through suzhenuju a part of a glass vessel, showing the expiration of the certain period of time, more often a half an hour or hour.

For time readout also widely used a burning candle. Notches on wax showed, how many has passed hours from the moment of candle ignition.


the Mechanical clock

Mechanical clock the First mechanical clock has appeared in Europe about 1275, however the name of the inventor is not known to us. The cargo suspended on a cord rotated a wheel putting in action the mechanism of hours, which each hour published a ring. Soon hours had arrows and a dial.

The Important detail of hours - a course regulator, the device limiting speed of the mechanism at the expense of step-by-step rotation of a cogwheel. A course regulator the timer providing the necessary speed of a course of hours operates.

The Course of an ancient mechanical clock was regulated "¶юышю=юь" - the balance weight consisting of a cross-beam fastening on a vertical core with counterbalances on both ends. The balance weight was shaken backwards-forward, its fluctuations were transferred to a course regulator, and that regulated speed of rotation of the mechanism.


the Striking clock

About 1330 in Italy a striking clock in which the quantity of blows corresponded to each hour have been created. And approximately in 1475 hours with spring factory have been invented. It has led to working out of portable hours that was unreal for mechanisms with weights.

Till XVI century hours had only one, hour, to an arrow. Shares of hour could be defined only approximately. It suited the majority of people. But astronomers required more exact registration of the supervision. As a result there were hours with minute, and some even with a second hand. The hours, which course it was regulated foliotom, went it is inexact, but with occurrence in a XVII-th century of a pendulum clock accuracy of calendar has considerably improved.


Accuracy of the pendular mechanism

In 1580th the Italian physicist and astronomer Galileo Galilej (1564-1642) has opened izohronnost pendulum fluctuations. In 1641 it has made the plan of use of a pendulum for regulation of a course of hours, but a year later has died, and only in 1649 his son Vinchentso and the mechanic by name of Balestri. At last, have made hours Galilee. More perfect design of such hours has been developed by the Dutch scientist Hristianom Gjujgensom in the end of 1650th thanks to what the pendulum has proved as an exact regulator of a course, and the daily error of hours has decreased since several minutes to ten seconds.

Other kind of a regulator of a course of hours has been created in 1658 when Robert Huk has invented a balance weight spring, or voloskovuju pruzhinku. This fenny screw spring fastened to the so-called balance weight. The spring twisted serially and untwisted depending on a direction of movement of the balance weight. This movement allowed to operate a course regulator. The main advantage of the balance weight in comparison with a pendulum consisted that its work was influenced much less by moving of hours. So there was possible a manufacturing smaller on the size and more exact pocket and a watch.

To the beginning of XVIII item new geographical opening and as result, world trade expansion have led to sharp increase in quantity of long voyages. The exact method of definition of a site of the vessel was necessary for successful swimming for seamen. It was most difficult to define a longitude - number in degree to the east or the West from Greenwich meridian. The exact hours showing time across Greenwich (England) for this purpose were required. But rolling of courts broke pendulum work, and hours with balansirnym a course regulator went is inexact in the conditions of the extreme temperatures negatively affecting work thin voloskovoj of a spring.


the Award for accuracy

The Given problem was so serious that in 1714 the government of England has established the award in 20 thousand pounds sterling to the one who can, offer a method of exact definition of a longitude during navigation. Thus demanded accuracy was so high that if it was a question of hours, their daily error should not exceed three seconds within six weeks. The award has got to carpenter John Garrisonu who has designed of some chronometres - exact hours for the purposes morehodstva. In 1760 t. Competition was won by its fourth model. During one navigation the error of its hours has made only 54 seconds for 156 days, Garrison has found a way at which temperature fluctuations changed effective length voloskovoj springs, providing automatic indemnification before available errors.


Modern hours

A Number modern stationary and a watch are issued with a mechanical drive, however the increasing distribution receive electric and electronic clock. In many electric clock the course of arrows provides a motor working from a network of an alternating current by frequency of 50-60 Hz. A similar principle of work and at some digital electronic clock, but they show time for a digital light board. The regulator of a course is necessary for an electronic watch, and this role is played often by the quartz crystal providing almost constant frequency of vibration under the influence of an electricity. The vibrating crystal generates electric impulses precisely measured on time which operate indication of electronic figures or movement of mechanical arrows. Some stationary hours also work on quartz crystals.

The Quartz watch gives very much a split-hair accuracy - about 1/30 seconds a day, but also it "тёхЁр°эшщ фхэі" in comparison with an atomic clock using frequency of radiation of atoms of certain elements (for example, caesium) and providing electronic indication of time with a margin error less than one second for one thousand years. Such hours are used in the experiments demanding exact readout of time and for definition of time: today second is defined as an interval of time for which atoms of caesium-133 radiate 9 192 631 770 impulses in certain concrete conditions.