Which is the only province in the country that uses “kilogram”?

The International Conference on Weights and Measures (General Conference on Weights and Measures) is held in Versailles, France. Representatives from 57 countries will vote on the reform of the kilogram measurement - this is the first time that the kilogram measurement has been changed in more than 100 years. . At present, the kilogram is the only metric unit that is still measured in physical objects. Scientists are preparing to replace the original physical standard with a constant, which is of great significance to the field of measurement. At this point, all members of the measurement unit family have entered a new era.

The foundation of modern measurement can be traced back to the mid-18th century. As international trade gradually developed, the lack of a unified unit for measuring the length of cloth became a problem. For example, in some places, the shoe size of the local earl was regarded as A unit of length. As a result, people began to realize that the country should provide unified units of weights and measures. In the late 18th century, with the approval of King Louis XVI of France, the French Academy of Sciences began to search for a more reasonable measurement method. This activity was also supported by the National Convention after the French Revolution began.

At that time, scientists proposed a measurement system based on nature, a set of measurement standards for "all times, all people". Among them, "kilogram" is defined as the mass of 1 cubic decimeter of pure water at 4°C. In order to make the unit of measurement more practical, the kilogram was upgraded to a physical object, which is the International Prototype Kilogram (IPK).

The plan completed an international system of measurement (SI), including seven basic measurement units: length unit meter (m), time unit second (s), mass unit kilogram (kg), material unit The unit of quantity is mole (mol), the unit of current is ampere (A), the unit of thermodynamic temperature is kelvin (K), and the unit of luminous intensity is candela (cd).

For the past 129 years, the world's official unit of mass has been the International Prototype Kilogram (IPK), affectionately known as "Le Grand K" (Le Grand K). It is a shiny cylinder of platinum-iridium alloy, sealed in a triple bell jar and stored at the International Bureau of Weights and Measures (BIPM) in Paris. In addition, there are many official replicas of the international original kilogram, which are sent to countries around the world to calibrate measurement standards. Every 40 years, these replicas are returned to Paris to inspect the originals for wear and tear.

The big K defines the kilogram, so the mass of the kilogram is fixed, but the mass of the big K itself will vary slightly. During storage, platinum absorbs contaminants from the air and the Big K becomes heavier and heavier. And when it is cleaned, the weight will be reduced because trace amounts of alloy are removed. Such uncertainty makes scientists very distressed.

Stephan Schlamminger, a physicist at the National Institute of Standards and Technology (NIST), said: “If aliens come to Earth, what else can we discuss besides physics? If we want to talk about physics, we have to unify our units, but if we say our unit of mass is determined by a piece of metal placed in Paris, we're making a cosmic joke."