According to the use and the context in which it is used, the term Metro has several references.
The most widespread says that meter is the main unit of length in the International System of Units. According to what the International Office of Weights and Measures tells us, the great specialist in this regard, a meter is the distance that light travels in a vacuum during an interval of 1 / 299,792,458 of a second
Originally this unit of longitude was created at the request of the French Academy of Sciences in 1791 and opportunely defined as the ten millionth part of the distance that separates the pole from the line corresponding to the Earth's equator.
On the other hand, also with the word meter, the measuring instrument that has the length of this unit and its dividers marked. Also known as tape measure, the meter is used in distance measurement and is built either in a thin sheet of chrome steel, aluminum, or, the most modern, by means of a weft of carbon fibers joined through a Teflon polymer. The most used meters are those of 5, 10, 15, 20, 25, 30, 50 and 100 meters.
The 50 and 100 meter meters are also known as surveyors and are made only of steel, since the force used to tension them is such that otherwise, if they were made of a material less resistant to steel, it could produce the extension of the same, an effect of course detrimental when it comes to achieving the objective that is accuracy in the measurement. In addition, they are marked with copper or bronze rivets fixed to the tape every 2 dm, while, on the contrary, the smallest ones are centimeter and millimeter with the marks and numbers painted or engraved on the surface of the tape.
Also, the word Metro turns out to be the shorthand for the term railway and subway and therefore it is popularly used to refer to these means of transport so popular in most of the large cities of the world.
Therefore, the mass passenger transport rail systems that operate in large cities to link various areas of their municipal territory and also of their closest surroundings are called metro. This type of transport is characterized mainly by the large number of passengers that it allows to transport and by the high frequency of schedules they have so that people at any time can move without inconvenience to their homes, jobs or study centers, among others. places.
