March 25, 1791 (, Xinhai February 21), the French definition of "meters" as the basic unit of length.


meters is the world's most widely used unit of length. In the International System of Units, 1 meter is equal to 100 cm, equal to one thousandth of one kilometer, or 3 Shichi or 6 feet 8 inches. However, we may not know the units meters (Lssdjt.com) length appear with the French Revolution, and close ties with the circumference of the earth, and now we have to understand about hiding them interesting.
We start with the French Revolution to begin with, in 1791, a famous scientist with revolutionary ideas Lagrange, was elected as the President of the French Committee for Weights and Measures. In his efforts to promote an impact the world of the length of the units - meters surfaced. French authorities provisions: the Earth's meridian through Paris is warp length 1/40000000-defined, 1 m. In layman's terms, l m is from the Earth's North Pole to the equator distance of 1,000 parts per million, March 25, 1791, the French National Assembly decided to adopt a metering system based only on a basic unit of length "m". Global international unit of length meters, thereby regulations come.
remaining question is how to measure the length of the Earth's meridian. Even though we all know this is an arduous trek, but also so careless, you need to carefully survey. The astronomers Joseph Delambre and Andre Mei Shangjian decided to accept this arduous task. They agreed that the departure from Paris, facing away from the line to complete the measurements from Dunkirk to Paris, then to Barcelona this period of the Earth's meridian. Delambre erudite, go north from Paris; careful plum still go south from Paris. Once the two men reach their respective destinations - Dunkirk and Barcelona, ​​began measuring the distance between each other. Finally, according to the measurement data calculated to draw length of 1 m. However, in France, at the time, is in the frenzy of the bourgeois revolution, social shambles. So, the two scientists often to take the risk of being pursued. In the outskirts of Paris, Delambre several escape fanatical crowd hunt, and several times came close to being guillotined. In the fierce battle of France and Spain, Mechain the detention has been used as a French spy. After seven years
trek, Delambre and plum still to cercal Carcassonne in southern France finally rendezvous. With a surveyor to return to Paris, Napoleon Bonaparte has become the new rulers of the Banque de France, political restore calm. Paris masses like to meet the heroes welcome them. Advocating science Napoleon also give them very high marks: "Victory as solo, but this achievement will last forever. "At the Paris International Scientific Committee, a 1-meter-long metal rod to commemorate the adventures of two scientists also made of pure platinum. (Lssjt.cn)
France metrology Committee using the measurement results of the two scientists using a platinum-iridium alloy, made of a cross-sectional view of the H-shaped standard meterstick filed as the original device. The Committee also decided that the promulgation of France from 1812 metric, and enforced in the country in 1837, the metric first to take root in France. 1875, that is, 80 years after the birth of the metric system, the International Committee for Weights and Measures, meeting in Paris. The 17 countries of France, Germany, the United States, Russia and other government representatives signed the Metric Convention, agreed to the establishment of the International Bureau of Weights and Measures. And generally accepted metric is the birth of one of the greatest scientific career in the French Revolution, the to determine meters standard international unit of length, still in use today.
Unfortunately, the measuring work astronomers little failures, resulting in a length of 1 meter 0.02 mm shorter than the length of the definition. Later, it was discovered through precise measurements of the satellite from the Earth the warp long pole to the equator is 10,002,290 meters and 10,000,000 meters, not a plum is still measured, that the short length of 1 m length standard unit than the prescribed 0.02 mm. Well-known science writer Ken Auld was disclosed in the measure of all things "the plum still return to Paris after he measurement error, because two summers, the measurement results are not consistent with him in the same place. This failure to produce the guilt has been haunted Mechain Mechain night of restless spirit almost to the verge of collapse. To correct the error, he again went to the field measurements, the result of deaths due to malaria died en route. [? V history today?? Com]
Ken Alder believes that this error caused slight wear of the surface of the measuring instruments. Moreover, even if there is no measurement error, Mechain and Delambre the goals can not be achieved, because they believe that the Earth is the rules of the sphere assumption is wrong. Earth is not a standard ball off, plus the surface there are ups and downs. However, Mei is still set for ourselves, too harsh, so the tragedy could have been avoided.
era of progress, to make people aware of the basis of the standard meter stick kind, and increasingly difficult to meet the needs of precise measurements, so that would not damage the natural benchmark came into being. 11th International General Conference of Weights and Measures in 1960, the scientific community to re-define meters. New standards required in vacuo, krypton, 86 (krypton an isotope) issued isotropic orange wavelength 1,650,763 times of 1 m. It is more accurate than the platinum-iridium alloy standard meter stick. In 1983, the International Bureau of Weights and Measures in turn meters is defined as: light in vacuum, by the stroke of the sky within a fraction of a second in the 299,792.458 1 meter. Natural wavelengths of light to define the basic unit of length, not only to make the "m" more the spirit of the times, more accurate, and more to adapt to the needs of the development of science and technology. So the scientific community as a measurement of a milestone in the history of science.