Time units. Travel Tips

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Time units. Travel Tips

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Since ancient times as a natural time standard took the period of rotation of the Earth around its axis, allowing a person to navigate quite well on its surface. Until recently, a second was defined as 1:86 of a mean solar day.

Observations over a long period of time have shown that the rotation of the Earth is subject to fluctuations, which do not allow us to consider the period of its revolution as a natural standard of time and deprive the concept of a mean solar day of metrological significance. From 1872 to 1903 the average duration of the day increased by 0,007 seconds, and from 1903 to 1934 it decreased by 0,005 seconds, after which it began to increase again. Thus, the average day is determined with an accuracy of 10-7, this accuracy is completely insufficient with the current state of technology, so it became necessary to choose a new natural time standard that provides greater accuracy in reproducing the unit of time, i.e., the interval between two spring equinoxes, the following one by one is taken as a reference.

The Eleventh General Conference on Weights and Measures approved the modern definition of the basic unit of time, the second 31556925 9747 part of the tropical year for 1900. About January at 12 o'clock ephemeris time (introduced in the USSR by GOSTs 7664-61 and 9867-61), which tie it not to rotation Earth around its axis, but to the movement of the Earth in orbit around the Sun.

The tropical year for 1900 is 365,24219878 days = 31 seconds.

In civilian life, the calendar year is used, which reproduces with great accuracy the duration of the tropical year. The calendar year is 365,2425 days, i.e., 26 seconds longer than the tropical year, which gives a difference of 3300 day in 1 years.

The so-called Gregorian calendar provides for the alternation of simple years (365 days) and leap years (366 days).

In recent years, remarkable results have been achieved in physics in creating new molecular and atomic standards of frequency and time based on the ability of molecules and atoms to emit and absorb energy in strict periodicity.

Molecular and atomic frequency standards open up prospects for further improving the accuracy of frequency and time standards. It has been theoretically established that in "atomic" clocks an accuracy of up to millionths of a second per day is achievable. "Atomic" clocks can be used as a new standard of frequency and time, independent of astronomical observations.

In "atomic" clocks, movements are made much more regularly than in pendulum and quartz astronomical clocks and the Earth-Sun system. Thanks to this, "atomic" clocks make it possible to check the rotation of the Earth around its axis and to detect the unevenness of this rotation, the study of which is of great scientific interest.

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