The way in which the subway has become

The way in which the subway has become One can tell if one is in the world systems of a specific measure. There is the English system used by the United States, which uses pounds and feet measuring, and then there is a parameter that is more accepted in other parts of the so-called civilized world. Although there are three types of units in use today, the most popular by far is the Inteational System of Units (SI or Systeme Inteational d'unites). A measure of this system in particular as regards the length in meters / meter. Changes in meters are prefixes such as kilometers and millimeters. The word has Greek roots, its origin is metron, meaning "a measure". The meter follows a calendar that goes back to the eighteenth century, when two approaches to the definition of standard units of length have been addressed. The first approach defined the meter as the length of a pendulum with a second half period. The other approach suggested that the meter was one quarter of the circumference of the polar soil. On 8 May 1790, the French National Assembly adopted the first approach: its length is equal to the length of a pendulum with a second half period. Just one year later, March 30 1791, this series has accepted the new proposal from the French Academy of Sciences, which has acceded to the second question: the new definition of the meter would be equal to one quarter of the circumference of the polar world. It should be noted that the circumference of the Earth, if measured through the poles is approximately forty million meters. On 10 December 1799, the French National Assembly then specified that the latter would, in effect, according to meters built on the bar of platinum 23 June 1799 and currently deposited in the National Archives. In 1870 a series of inteational conferences that were held to develop new metric standards. E 'was the Meter Convention of 1875 which mandated the creation of a permanent Inteational of Weights and Measures (or BIPM, for Bureau Inteational des Poids et Mesures), based in France. It 'was this organization that was responsible for defending the new prototype meter and kilogram when constructed. This will also keep the comparison between the distributed metric prototypes and the lack of metric measurement standards. Nearly a decade later, September 28 1889 the CGPM defined the length as the distance between two lines in a standard bar of an alloy of platinum with ten percent iridium. This distance is measured at the melting point of ice. This definition fits with the passing years. It was in 1893 when Albert A. Michelson, the inventor of the interferometer, measured the level meter with the device. Not until 1925 when interferometry would be regularly used by the BIPM. On 21 October 1983 the seventeenth CGPM definition of a meter equaled the length traveled by light in vacuum in 1 / 299 2972, 458 of a second. Scientists agree that if the definition is based on the physical properties of light, so it is infinitely more accurate and reproducible. This is due to the fact that the properties associated with the light is universally regarded as a constant.