Why didn't the US switch to the metric system? Metric system of measures In which countries the metric system of measurement is used.

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Metric system (SI International System)

Metric system of measures (SI International System)

For residents of the United States or another country that does not use the metric system, it is sometimes difficult to understand how the rest of the world lives in and navigates it. But in fact, the SI system is much simpler than all traditional national measurement systems.

The principles of the metric system are very simple.

The structure of the international system of SI units

The metric system was developed in France in the 18th century. The new system was intended to replace the chaotic collection of different units of measurement then in use with a single common standard with simple decimal coefficients.

The standard unit of length was defined as one ten-millionth of the distance from the Earth's north pole to the equator. The resulting value was called meter. The definition of meter was later refined several times. The modern and most accurate definition of a meter is: “the distance that light travels in a vacuum in 1/299,792,458 of a second.” Standards for the remaining measurements were established in a similar manner.

The metric system or International System of Units (SI) is based on seven basic units for seven basic dimensions, independent of each other. These measurements and units are: length (meter), mass (kilogram), time (second), electric current (ampere), thermodynamic temperature (kelvin), amount of substance (mole) and radiation intensity (candela). All other units are derived from the base ones.

All units of a specific measurement are built on the basis of the base unit by adding universal ones metric prefixes. A table of metric prefixes is shown below.

Metric prefixes

Metric prefixes simple and very convenient. It is not necessary to understand the nature of the unit in order to convert a value from, for example, kilo units to mega units. All metric prefixes are powers of 10. The most commonly used prefixes are highlighted in the table.

By the way, on the Fractions and Percentages page you can easily convert a value from one metric prefix to another.

Even in countries that use the metric system, most people only know the most common prefixes, such as kilo, milli, mega. These prefixes are highlighted in the table. The remaining prefixes are used mainly in science.

On the facade of the Ministry of Justice in Paris, under one of the windows, a horizontal line and the inscription “meter” are carved in marble. Such a tiny detail is barely noticeable against the backdrop of the majestic Ministry building and Place Vendôme, but this line is the only one remaining in the city of “meter standards”, which were placed throughout the city more than 200 years ago in an attempt to introduce the people to a new universal system of measures - metric.

We often take a system of measures for granted and don’t even think about what story lies behind its creation. The metric system, which was invented in France, is official throughout the world, with the exception of three countries: the United States, Liberia and Myanmar, although in these countries it is used in some areas such as international trade.

Can you imagine what our world would be like if the system of measures was different everywhere, like the situation with currencies that we are familiar with? But everything was like this before the French Revolution, which flared up at the end of the 18th century: then the units of weights and measures were different not only between individual states, but even within the same country. Almost every French province had its own units of measures and weights, incomparable with the units used by their neighbors.

The revolution brought a wind of change to this area: in the period from 1789 to 1799, activists sought to overturn not only the government regime, but also to fundamentally change society, changing traditional foundations and habits. For example, in order to limit the influence of the church on public life, the revolutionaries introduced a new Republican calendar in 1793: it consisted of ten-hour days, one hour equaled 100 minutes, one minute equaled 100 seconds. This calendar was fully consistent with the new government's desire to introduce a decimal system in France. This approach to calculating time never caught on, but people came to like the decimal system of measures, which was based on meters and kilograms.

The first scientific minds of the Republic worked on the development of a new system of measures. Scientists set out to invent a system that would obey logic, and not local traditions or the wishes of authorities. Then they decided to rely on what nature had given us - the standard meter should be equal to one ten-millionth of the distance from the North Pole to the equator. This distance was measured along the Paris meridian, which passed through the building of the Paris Observatory and divided it into two equal parts.

In 1792, scientists Jean-Baptiste Joseph Delambre and Pierre Méchain set out along the meridian: the former's destination was the city of Dunkirk in northern France, the latter followed south to Barcelona. Using the latest equipment and the mathematical process of triangulation (a method of constructing a geodetic network in the form of triangles in which their angles and some of their sides are measured), they hoped to measure the meridian arc between two cities located at sea level. Then, using the method of extrapolation (a method of scientific research consisting of extending conclusions drawn from observations of one part of a phenomenon to another part of it), they intended to calculate the distance between the pole and the equator. According to the initial plan, scientists planned to spend a year on all measurements and the creation of a new universal system of measures, but in the end the process lasted for seven years.

Astronomers were faced with the fact that in those turbulent times people often perceived them with great caution and even hostility. In addition, without the support of the local population, scientists were often not allowed to work; There were cases when they were injured while climbing the highest points in the area, such as church domes.

From the top of the dome of the Pantheon, Delambre took measurements of the territory of Paris. Initially, King Louis XV erected the Pantheon building for the church, but the Republicans equipped it as the central geodetic station of the city. Today the Pantheon serves as a mausoleum for the heroes of the Revolution: Voltaire, René Descartes, Victor Hugo, etc. In those days, the building also served as a museum - all the old standards of weights and measures were stored there, which were sent by residents of all of France in anticipation of a new perfect system.

Unfortunately, despite all the efforts scientists spent on developing a worthy replacement for the old units of measurement, no one wanted to use the new system. People refused to forget the usual methods of measurement, which were often closely related to local traditions, rituals and way of life. For example, the el, a unit of measurement for cloth, was usually equal to the size of the looms, and the size of arable land was calculated solely in the days that had to be spent on cultivating it.

Parisian authorities were so outraged by residents' refusal to use the new system that they often sent police to local markets to force it into use. Napoleon eventually abandoned the policy of introducing the metric system in 1812 - it was still taught in schools, but people were allowed to use the usual units of measurement until 1840, when the policy was renewed.

It took France almost a hundred years to fully adopt the metric system. This finally succeeded, but not thanks to the persistence of the government: France was rapidly moving towards the industrial revolution. In addition, it was necessary to improve terrain maps for military purposes - this process required accuracy, which was not possible without a universal system of measures. France confidently entered the international market: in 1851, the first International Fair was held in Paris, at which event participants shared their achievements in the field of science and industry. The metric system was simply necessary to avoid confusion. The construction of the Eiffel Tower, 324 meters high, was timed to coincide with the International Fair in Paris in 1889 - then it became the tallest man-made structure in the world.

In 1875, the International Bureau of Weights and Measures was established, with its headquarters located in a quiet suburb of Paris - in the city of Sèvres. The Bureau maintains international standards and the unity of the seven measures: meter, kilogram, second, ampere, Kelvin, Mole and Candela. A platinum meter standard is kept there, from which standard copies were previously carefully made and sent to other countries as a sample. In 1960, the General Conference of Weights and Measures adopted a definition of the meter based on the wavelength of light—thus bringing the standard even closer to nature.

The Bureau's headquarters also houses the kilogram standard: it is housed in an underground storage facility under three glass bells. The standard is made in the form of a cylinder made of an alloy of platinum and iridium; in November 2018, the standard will be revised and redefined using the quantum Planck constant. The resolution on the revision of the International System of Units was adopted back in 2011, however, due to some technical features of the procedure, its implementation was not possible until recently.

Determining units of weights and measures is a very labor-intensive process, which is accompanied by various difficulties: from the nuances of conducting experiments to financing. The metric system underlies progress in many fields: science, economics, medicine, etc., and is vital for further research, globalization and improving our understanding of the universe.

Universal measure

An original proposal was once made by S. Pudlovsky, a professor at the University of Krakow. His idea was that as a single measure we should take the length of the pendulum that makes a full swing in one second. This proposal was published in the book “Universal Measure”, published in Vilna in 1675 by his student T. Buratini. He also suggested calling meter unit of length.

Somewhat earlier, in 1673, the Dutch scientist H. Huygens published a brilliant work “Pendulum Clocks”, where he developed the theory of oscillations and described the designs of pendulum clocks. Based on this work, Huygens proposed his own universal measure of length, which he called hour foot, and the hour foot was equal to 1/3 the length of the second pendulum. “This measure can not only be determined everywhere in the world, but can always be restored for all future centuries,” Huygens wrote proudly.

However, there was one circumstance that confused scientists. The period of oscillation of a pendulum with the same length was different depending on the geographic latitude, i.e., strictly speaking, the measure was not universal.

Huygens' idea was promoted by the French surveyor C. Condamine, who proposed to base the measurement system on a unit of length corresponding to the length of a pendulum swinging once per second at the equator.

The French astronomer and mathematician G. Mouton also supported the idea of ​​a second pendulum, but only as a control device, and G. Mouton proposed to base the universal system of measures on the principle of connecting the unit of measurement with the dimensions of the Earth, i.e., taking a part as a unit of length meridian arc length. This scientist also proposed dividing the measured part into tenths, hundredths and thousandths, i.e. using the decimal principle.

Metric system

Projects for reform of systems of measures appeared in different countries, but this issue was especially acute in France for the reasons listed above. Gradually, the idea of ​​creating a system of measures that meets certain requirements emerged:

– the system of measures must be unified and general;

– units of measurement must have strictly defined dimensions;

– there must be standards of units of measurement that are constant over time;

– for each quantity there should be only one unit;

– units of different quantities must be related to each other in a convenient way;

– units must have submultiple and multiple values.

On May 8, 1790, the French National Assembly adopted a decree on the reform of the system of measures and instructed the Paris Academy of Sciences to carry out the necessary work, guided by the above requirements.

Several commissions were formed. One of them, led by academician Lagrange, recommended the decimal division of multiples and submultiples of units.

Another commission, which included scientists Laplace, Monge, Borda and Condors, proposed adopting one forty millionth of the earth's meridian as a unit of length, although the overwhelming majority of experts who knew the essence of the matter thought that the choice would be in favor of the second pendulum.

The decisive factor here was that a stable basis was chosen - the size of the Earth, the correctness and immutability of its shape in the form of a ball.

Commission member C. Borda, a surveyor and hydraulic engineer, proposed calling the unit of length the meter; in 1792, he determined the length of the second pendulum in Paris.

On March 26, 1791, the French National Assembly approved the proposal of the Paris Academy, and a temporary commission was formed to practically implement the decree on the reform of measures.

On April 7, 1795, the French National Convention adopted a law on new weights and measures. It was accepted that meter- one ten-millionth of a quarter of the earth's meridian passing through Paris. but it was especially emphasized that the introduced unit of length in name and size did not coincide with any of the French units of length that existed at that time. Therefore, the possible future argument that France is “pushing” its system of measures as an international one is excluded.

Instead of temporary commissions, commissioners were appointed who were tasked with carrying out work on the experimental determination of units of length and mass. The commissioners included famous scientists Berthollet, Borda, Brisson, Coulomb, Delambre, Haüy, Lagrange, Laplace, Mechain, Monge and others.

Delambre and Méchain resumed work on measuring the length of the meridian arc between Dunkirk and Barcelona, ​​corresponding to the 9°40′ sphere (this arc was later extended from the Shetland Islands to Algeria).

This work was completed by the fall of 1798. Meter and kilogram standards were made of platinum. The meter standard was a platinum bar 1 meter long and with a cross-section of 25 × 4 mm, i.e. it was end measure, and on June 22, 1799, the ceremonial transfer of the prototypes of the meter and kilogram to the Archives of France took place, and since then they have been called archival. But it must be said that even in France the metric system did not take hold immediately; traditions and inertia of thinking had a big impact. Napoleon, who became Emperor of France, did not like the metric system, to put it mildly. He believed: “There is nothing more contrary to the mindset, memory and consideration than what these scientists propose. The good of present generations has been sacrificed to abstractions and empty hopes, because in order to force the old nation to accept new units of weights and measures, it is necessary to redo all administrative rules, all industrial calculations. This kind of work boggles the mind.” In 1812, by decree of Napoleon, the metric system in France was abolished and only in 1840 was it restored again.

Gradually, the metric system was adopted and introduced by Belgium, Holland, Spain, Portugal, Italy, and a number of South American republics. The initiators of the introduction of the metric system in Russia were, of course, scientists, engineers, and researchers, but tailors, seamstresses and milliners played a significant role - by that time, Parisian fashion had conquered high society, and there, mostly craftsmen who came from abroad worked there with their own meters . It was from them that the narrow strips of oilcloth fabric that still exist today - “centimeters”, which are still used today, came from.

At the Paris Exhibition of 1867, the International Committee of Weights, Measures and Coins was created, which compiled a report on the benefits of the metric system. However, the decisive influence on the entire further course of events was exerted by the report compiled in 1869 by academicians O. V. Struve, G. I. Wild and B. S. Jacobi, sent on behalf of the St. Petersburg Academy of Sciences to the Paris Academy. The report argued for the need to introduce an international system of weights and measures based on the metric system.

The proposal was supported by the Paris Academy, and the French government appealed to all interested states with a request to send scientists to the International Metric Commission to solve practical problems. By that time, it became clear that the shape of the Earth is not a sphere, but a three-dimensional spheroid (the average radius of the equator is 6,378,245 meters, the difference between the largest and smallest radii is 213 meters, and the difference between the average radius of the equator and the polar semi-axis is 21,382 meters). In addition, repeated measurements of the arc of the Paris meridian gave a value of the meter slightly smaller compared to the value obtained by Delambre and Méchain. In addition, there is always the possibility that with the creation of more advanced measuring instruments and the emergence of new measurement methods, the measurement results will change. Therefore, the commission made an important decision: “The new prototype of the length measure should be equal in size to the Archival meter,” that is, it should be an artificial standard.

The international commission also made the following decisions.

1) The new prototype meter should be a line measure, it should be made of an alloy of platinum (90%) and iridium (10%) and have an X-shaped cross-section.

2) In order to give the metric system an international character and ensure uniformity of measures, standards should be produced and distributed among the countries concerned.

3) One standard, closest in size to the Archive, should be accepted as international.

4) Entrust practical work on creating standards to the French section of the commission, since archival prototypes are located in Paris.

5) Appoint a permanent international committee of 12 members to supervise the work.

6) Establish the International Bureau of Weights and Measures as a neutral scientific institution based in France.

In accordance with the decision of the commission, practical measures were carried out and in 1875 an international conference was convened in Paris, at the last meeting of which, on May 20, 1875, the Meter Convention was signed. It was signed by 17 countries: Austria-Hungary, Argentina, Belgium, Brazil, Venezuela, Germany, Denmark, Spain, Italy, France, Peru, Portugal, Russia, USA, Turkey, Switzerland, Sweden and Norway (as one country). Three more countries (Great Britain, Holland, Greece), although they participated in the conference, did not sign the Convention due to disagreement on the functions of the International Bureau.

The Bretel Pavilion, located in the Saint-Cloud park in the Paris suburb of Sèvres, was allocated for the International Bureau of Weights and Measures; soon a laboratory building with equipment was built near this pavilion. The activities of the Bureau are carried out at the expense of funds transferred by the member countries of the Convention in proportion to the size of their population. Using these funds, standards for the meter and kilogram (36 and 43, respectively) were ordered in England, which were manufactured in 1889.

Meter standards

The meter standard was a platinum-iridium rod with an X-shaped cross-section, 1020 mm long. On the neutral plane at 0 °C, three strokes were applied on each side, the distance between the middle strokes was 1 meter (Fig. 1.1). The standards were numbered and compared with the Archive Meter. Prototype No. 6 turned out to be the closest to the Archive, and it was approved as an international prototype. Thus, the standard meter became artificial and represented lined measure.

Four more witness standards were added to standard No. 6 and these were retained by the International Bureau. The remaining standards were distributed by lot among the countries that signed the Convention. Russia received standards No. 11 and No. 28, and No. 28 was closer to the international prototype, so it became the national standard of Russia.

By decree of the Council of People's Commissars of the RSFSR of September 11, 1918, prototype No. 28 was approved as the state primary standard of the meter. In 1925, the Council of People's Commissars of the USSR adopted a resolution recognizing the Metric Convention of 1875 as valid for the USSR.

In 1957 - 1958 standard No. 6 was marked with a scale with decimeter divisions, the first decimeter was divided into 10 centimeters, and the first centimeter into 10 millimeters. After applying the strokes, this standard was re-certified by the International Bureau of Weights and Measures.

The error in transmitting a unit of length from the standard to the measuring instruments was 0.1 - 0.2 microns, which with the development of technology is becoming clearly insufficient, therefore, in order to reduce the transmission error and obtain a natural indestructible standard, a new meter standard was created.

Back in 1829, the French physicist J. Babinet proposed taking the length of a certain line in the spectrum as a unit of length. However, the practical implementation of this idea occurred only when the American physicist A. Michelson invented the interferometer. Together with the chemist Morley E. Babinet, J. published the work “On the method of using the wavelength of sodium light as a natural and practical standard of length,” then he moved on to studies of isotopes: mercury - green and cadmium - red line.

In 1927, it was accepted that 1 m was equal to 1553164.13 wavelengths of the red line of cadmium-114, this value was accepted as a standard along with the old prototype meter.

Subsequently, work was continued: the spectrum of mercury was studied in the USA, the spectrum of cadmium was studied in the USSR, krypton was studied in Germany and France.

In 1960, the XI General Conference on Weights and Measures adopted the meter, expressed in wavelengths of light, specifically the inert gas Kr-86, as the standard unit of length. Thus, the standard of the meter again became natural.

Meter– length equal to 1650763.73 wavelengths in vacuum of radiation corresponding to the transition between levels 2p 10 and 5d 5 of the krypton-86 atom. The old definition of the meter is abolished, but the prototypes of the meter remain and are stored under the same conditions.

In accordance with this decision, the State Primary Standard (GOST 8.020-75) was established in the USSR, which included the following components (Fig. 1.2):

1) source of primary reference radiation of krypton-86;

2) a reference interferometer used to study sources of primary reference radiation;

The accuracy of reproduction and transmission of the meter in light units is 1∙10 -8 m.

In 1983, the XVII General Conference on Weights and Measures adopted a new definition of the meter: 1 meter is a unit of length equal to the path traveled by light in a vacuum in 1/299792458 of a second, i.e. the standard of the meter remains natural.

Composition of the meter standard:

1) source of primary reference radiation – a highly frequency-stabilized helium-neon laser;

2) a reference interferometer used to study sources of primary and secondary reference measurements;

3) a standard interferometer used to measure the length of line and end standards (secondary standards).

International decimal system measurements based on the use of units such as the kilogram and meter is called metric. Various options metric system have been developed and used over the past two hundred years, and the differences between them consist mainly in the choice of basic, basic units. At the moment, the so-called International system of units (SI). The elements that are used in it are identical throughout the world, although there are differences in individual details. International system of units is very widely and actively used all over the world, both in everyday life and in scientific research.

For now Metric system used in most countries of the world. There are, however, several large states that still use the English system of measures based on units such as pounds, feet and seconds. These include the UK, USA and Canada. However, these countries have also already adopted several legislative measures aimed at moving towards Metric system.

It itself originated in the middle of the 18th century in France. It was then that scientists decided that they should create system of measures, the basis of which will be units taken from nature. The essence of this approach was that they constantly remain unchanged, and therefore the entire system as a whole will be stable.

Length measures

• 1 kilometer (km) = 1000 meters (m)
• 1 meter (m) = 10 decimeters (dm) = 100 centimeters (cm)
• 1 decimeter (dm) = 10 centimeters (cm)
• 1 centimeter (cm) = 10 millimeters (mm)

Area measures

• 1 sq. kilometer (km 2) = 1,000,000 sq. meters (m 2)
• 1 sq. meter (m2) = 100 sq. decimeters (dm 2) = 10,000 sq. centimeters (cm 2)
• 1 hectare (ha) = 100 aram (a) = 10,000 sq. meters (m 2)
• 1 ar (a) = 100 sq. meters (m 2)

Volume measures

• 1 cu. meter (m 3) = 1000 cubic meters decimeters (dm 3) = 1,000,000 cubic meters. centimeters (cm 3)
• 1 cu. decimeter (dm 3) = 1000 cubic meters. centimeters (cm 3)
• 1 liter (l) = 1 cu. decimeter (dm 3)
• 1 hectoliter (hl) = 100 liters (l)

Weights

• 1 ton (t) = 1000 kilograms (kg)
• 1 quintal (c) = 100 kilograms (kg)
• 1 kilogram (kg) = 1000 grams (g)
• 1 gram (g) = 1000 milligrams (mg)

Metric system

It should be noted that the metric system was not immediately recognized. As for Russia, in our country it was allowed to be used after it signed metric convention. At the same time this system of measures for a long time it was used in parallel with the national one, which was based on units such as pound, fathom and bucket.

Some old Russian measures

Length measures

• 1 verst = 500 fathoms = 1500 arshins = 3500 feet = 1066.8 m
• 1 fathom = 3 arshins = 48 vershoks = 7 feet = 84 inches = 2.1336 m
• 1 arshin = 16 vershok = 71.12 cm
• 1 vershok = 4.450 cm
• 1 foot = 12 inches = 0.3048 m
• 1 inch = 2.540 cm
• 1 nautical mile = 1852.2 m

Weights

• 1 pood = 40 pounds = 16.380 kg
• 1 lb = 0.40951 kg

Main difference Metric system from those previously used is that it uses an ordered set of units of measurement. This means that any physical quantity is characterized by a certain main unit, and all submultiples and multiples are formed according to a single standard, namely, using decimal prefixes.

Introduction of this systems of measures eliminates the inconvenience that previously resulted from the abundance of different units of measurement that have rather complex rules for transformation between themselves. Those in metric system are very simple and boil down to the fact that the original value is multiplied or divided by a power of 10.

Metric system, decimal system of measures, a set of units of physical quantities, which is based on the unit of length - meter. Initially, the Metric system of measures, in addition to the meter, included the following units: area - square meter, volume - cubic meter and mass - kilogram (mass of 1 dm 3 of water at 4 ° C), as well as liter(for capacity), ar(for land area) and ton(1000 kg). An important distinctive feature of the Metric system of measures was the method of formation multiples of units And submultiple units, which are in decimal ratios; To form the names of derived units, prefixes were adopted: kilo, hecto, soundboard, deci, centi And Milli.

The metric system of measures was developed in France during the French Revolution. At the proposal of a commission of major French scientists (J. Borda, J. Condorcet, P. Laplace, G. Monge, etc.), the unit of length - the meter - was adopted as a ten-millionth part of 1/4 of the length of the Parisian geographical meridian. This decision was determined by the desire to base the Metric system of measures on an easily reproducible “natural” unit of length associated with some practically unchanging object of nature. The decree introducing the metric system of measures in France was adopted on April 7, 1795. In 1799, a platinum prototype of the meter was manufactured and approved. The dimensions, names and definitions of other units of the Metric system of measures were chosen so that it was not national in nature and could be adopted by all countries. The metric system of measures acquired a truly international character in 1875, when 17 countries, including Russia, signed metric convention to ensure international unity and improvement of the metric system. The metric system of measures was approved for use in Russia (optional) by the law of June 4, 1899, the draft of which was developed by D. I. Mendeleev, and introduced as mandatory by the decree of the Council of People's Commissars of the RSFSR of September 14, 1918, and for the USSR by decree Council of People's Commissars of the USSR dated July 21, 1925.

Based on the Metric system of measures, a whole series of particular measures arose, covering only certain sections of physics or branches of technology, systems of units and individual non-system units. The development of science and technology, as well as international relations, led to the creation, based on the Metric system of measures, of a unified system of units covering all areas of measurement - International System of Units(SI), which has already been accepted as mandatory or preferred by many countries.