HOW THE METRO IS BORN

A few centuries ago, measuring was very complicated. As we said, to measure is simply to compare, and each person, each town, each country compared things with what most seemed to him. For example, they used the hand measurement to measure distances, and even today many people, when they do not have a ruler or a tape measure, measure the width of the door with their hands or the length of the yard with steps. The problem with this is obvious: all human beings do not have feet or hands of the same size, that is, also a problem of measures.

The most rare systems of measurement coexisted until the French Revolution, around 1789. In this time of turmoil and great changes, the French, inflamed by their desire to change and order the world, decided they had to found a system of measurements rational and unique that was superior to all others. While the politicians dedicated themselves to sending their enemies to the guillotine, the National Assembly (French) entrusted him in 1790 to the Academy of Sciences to create this new system.

The new system and its “MUST HAVE”:

-Be based on things that remain stable in nature. No, for example, the length of a foot, because as you know the length of the feet, like the noses, varies from person to person.

-Be based on few ways of measuring that connect with each other logically. For example, once the centimeter is defined, the liter is defined as the volume of something that enters a cube of 10 cm on each side, and the kilogram is defined as the weight of a liter of water.

-It should be a decimal system, that is, where the multiples of the units will vary from 10 to 10. Thus, one decameter equals 10 meters, one hectometer equals 10 decameters, and so on.

After much thought, the scientists of the time agreed that the unit of measurement should have to do with the planet Earth. And he proposed: why not make the unit of length be ten millionth of a quarter of Earth's meridian ?.

For a terrestrial meridian is the distance that goes from the North Pole to the South Pole and back to the North Pole, that is, a complete return to the planet through both poles. The Academy of Sciences, entrusted a group of adventurers who were to measure, not a whole meridian, which is very long, but a quarter of a meridian, which is still quite. These meters measured the distance from the city of Dunkirk, France, to that of Barcelona, ​​Spain.

From that measurement and by astronomical observations it was possible to calculate the length of the quarter of the terrestrial meridian. That number was divided by ten million. The length that resulted from that account was used to make a platinum bar baptizing it with the name of meter.

Then, several copies of the pattern meter were made and stored in a security vault, protected from rust, cold, heat and thieves. It was also decided that the kilogram would, by definition, be the weight of the water that fits in a cube one tenth of a meter on the side (that is, 10 centimeters). A standard weight of exactly one kilogram was also built and stored along with the meter. From that moment, all the measurements were comparisons with that bar and that platinum weight.

The picture says: Definition given on september 1889.

The distance between two lines arched in a rod of iridium and 10% platinum that is kept in the International Office of Weights and Measures of Sevres (Paris). The meter pattern weighs 3 kilograms and its measurements are: 102 centimeters long and 2 centimeters wide and 2 centimeters high.