Why there are two measurement systems in the world?
Human growth is measured in centimeters, and the diagonal of the TV screen is in inches. Why? The reason is simple – the presence of two measurement systems in the world. So you have to keep in my head, that 1 inch is 2.5 cm.
In fact, previously measures were even more. Moreover, in one country there could be several of them. In medieval Europe, each relatively large city has its own measures. So, Thomas Petrushevsky in "General Metrology" described 97 (!) European "inches" size from 20 to 56.76 mm.
One of the few exceptions on this background was the United Kingdom, where a more or less unified system of measures was established in the XIII century. It was called Imperial and was also used in the colonies of Great Britain, including in North America.
In France, as in other European countries, chaos reigned with systems. In the landfit existed several names of the area of the square, different in various provinces. The problem was that the same quantities were not always hidden behind them, and this led to conflicts between farmers and feudal. Due to the varnotes, the development of trade, industry and total farms in general. Therefore, in 1790, a question of measures and scales was raised in the Constituent Assembly on the agenda.
Several projects were offered for consideration, but the preference was decided to give the project Talleyran, which later became the Minister of Internal Affairs. He wished to reform international character and proposed to create a universal metric system.
The transition to the metric system stretched for two hundred years
However, technical problems, inertia of thinking and organizational complexities of such a large-scale reform, led to the fact that the metric convention was signed only on May 20, 1875. The first to have made 17 states, among which, in addition to France, were Russia, Australia, Germany, Italy, Finland. Other countries have joined them gradually. The transition to the metric system was stretched for two hundred years.
In particular, the introduction of a meter in our country ended only in 1927. And the United Kingdom along with their colonies and the United States, although they signed the Convention, I did not rush to introduce meter at all. As for the United States, initially the reason was the stretched relations with France, which were between countries in the XVIII century, and financial considerations. The leadership of the country simply did not understand what these spending.
But when in 1865, civil war ended in the USA, it turned out that most European countries have already moved to a decimal metric system. Ignore this fact was further impossible. True, due to the fact that the transition to the metric system was still called preferred, and not mandatory, the process was delayed to this day.
Thus, the allegiance of the tradition of an inch system of measures today has retained the United States, Myanmar, Liberia and several dwarf island states. In the UK since 1995, the official system is considered to be the metric system, but … inches and pounds continue to be used.
The reasons for that two. First, the financial costs that are required to rewar technical drawings, software and documentation. Secondly, conservatism. So who knows how much time will need for the final transition to a unified measurement system. However, the two measures are easy to make friends easier than 12 types of outlets existing in the world. About how it happened, read in our material "Why on all continents is different outlets?".