The International System of Units is a structure based on the use of mass in kilograms and length in meters. Since its inception, there have been various variations of it. The difference between them was in the choice of key indicators. Today, many countries use units of measurement in the SI system. In it, the elements are the same for all states (with the exception of the USA, Liberia, Burma). This system is widely used in various fields - from everyday life to scientific research.

## Features

The metric system of measures is an ordered set of parameters. This significantly distinguishes it from the previously used traditional methods for determining certain units. To designate any value, the metric system of measures uses only one main indicator, the value of which can vary in multiples (achievedusing decimal prefixes). The main advantage of this approach is that it is easier to use. This eliminates a huge number of different unnecessary units (feet, miles, inches and others).

## Timing parameters

For a long period, attempts have been made by a number of scientists to represent time in metric units. It was proposed to divide the day into smaller elements - millidays, and the angles - into 400 degrees or take a full cycle of revolution as 1000 milliturns. Over time, due to inconvenience in use, this idea had to be abandoned. Today, SI time is denoted by seconds (consisting of milliseconds) and radians.

## History of occurrence

It is believed that the modern metric system was born in France. In the period from 1791 to 1795, a number of important legislative acts were adopted in this country. They were aimed at determining the status of the meter - one ten-millionth of a 1/4 meridian from the equator to the North Pole. July 4, 1837 adopted a special document. According to him, the mandatory use of the elements that made up the metric system of measures was officially approved in all economic transactions carried out in France. In the future, the adopted structure began to spread to neighboring European countries. Due to its simplicity and convenience, the metric system of measures gradually replaced most of the national ones used earlier. It can also be used in the US and UK.

## Basicquantities

The founders of the system, as noted above, took a meter as a unit of length. Gram became the element of mass - the weight of one millionth m3 of water at its standard density. For more convenient use of the units of the new system, the creators have come up with a way to make them more accessible - by making metal standards. These models are made with perfect fidelity. Where are the standards of the metric system, will be discussed below. Later, when using these models, people realized that it is much easier and more convenient to compare the desired value with them than, for example, with a quarter of the meridian. At the same time, when determining the mass of the desired body, it became obvious that it is much more convenient to evaluate it by the standard than by the corresponding amount of water.

## "Archive" samples

A decision of the International Commission in 1872 adopted a specially made meter as the standard for measuring length. At the same time, the members of the commission decided to take a special kilogram as the standard for measuring mass. It was made from platinum and iridium alloys. "Archival" meter and kilogram are permanently stored in Paris. In 1885, on May 20, a special Convention was signed by representatives of seventeen countries. As part of it, the procedure for determining and using measurement standards in scientific research and work was regulated. This required special organizations. These include, in particular, the International Bureau of Weights and Measures. Within the framework of the newly createdorganization began the development of samples of mass and length, with the subsequent transfer of their copies to all participating countries.

## Metric system of measures in Russia

More and more countries used the accepted designs. Under the circumstances, Russia could not ignore the emergence of a new system. Therefore, by the Law of July 4, 1899 (author and developer - D. I. Mendeleev), it was allowed for use on an optional basis. It became obligatory only after the adoption by the Provisional Government of the corresponding decree of 1917. Later, its use was enshrined in the decree of the Council of People's Commissars of the USSR of July 21, 1925. In the twentieth century, most countries switched to measurements in the international system of units SI. Its final version was developed and approved by the XI General Conference in 1960.

## Post-Soviet times

The collapse of the USSR coincided with the moment of rapid development of computer and household appliances, the main production of which is concentrated in Asian countries. Huge consignments of goods from these manufacturers began to be imported into the territory of the Russian Federation. At the same time, the Asian states did not think about the possible problems and inconvenience of the operation of their goods by the Russian-speaking population and supplied their products with universal (in their opinion) instructions in English, using American parameters. In everyday life, the designation of quantities in the metric system began to be replaced by elements used in the United States. For example, sizescomputer disks, monitor diagonals and other components are indicated in inches. At the same time, initially the parameters of these components were designated strictly in terms of the metric system (the width of a CD and DVD, for example, is 120 mm).

## International use

Currently, the most common on planet Earth is the metric system of measures. The table of masses, lengths, distances and other parameters makes it easy to translate one indicator into another. There are fewer and fewer countries that, for certain reasons, have not switched to this system every year. States that continue to use their own parameters include the United States, Burma, and Liberia. America uses the SI system in the branches of scientific production. All others used American parameters. The UK and Saint Lucia have not yet switched to the world SI system. But, I must say that the process is in an active stage. The last of the countries to finally switch to the metric system in 2005 was Ireland. Antigua and Guyana are only making the transition, but the pace is very slow. An interesting situation is in China, which officially switched to the metric system, but at the same time, the use of ancient Chinese units continues on its territory.

## Aviation parameters

The metric system of measures is recognized almost everywhere. But there are certain industries in which it has not taken root. Aviation still uses a measurement system based onthere are such units as feet and miles. The use of this system in this area has developed historically. The position of the International Civil Aviation Organization is unequivocal - a transition to metric values ​​\u200b\u200bmust be made. However, only a few countries strictly adhere to these recommendations. Among them are Russia, China and Sweden. Moreover, the civil aviation structure of the Russian Federation, in order to avoid confusion with international control centers, in 2011 partially adopted a system of measures, the main unit of which is foot.