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One of the most enlightening high school courses, no doubt for many readers and your secretary, was the series of physics courses in which SI units were explained. This glorious feeling of seeing the order of the universe unlocked into a nested series of units whose definitions could all be derived in terms of a series of basic units was mind-blowing. in the early years of adolescence, and even if the explanations could have a level for children who was ejected from the water through later learning layers is still a foundation that will serve everything to along with an engineer or a scientist.
The definitions of SI base units have evolved with scientific progress, to the point where they are no longer related to their physical entity origin definitions. Among all the basic units, there remains one that has resisted the desire to move away from the physical: the kilogram (giving it the French spelling to preserve the context) is always defined in terms of metal cylinder in a laboratory located at the gates of Paris. Hard kilograms do not have much time to hang on to their platinum-iridium alloy because a new definition has been adopted in which it is derived from the Planck constant. Starting next May, this will become the official kilogram. At this stage, concerns about microscopic erosion of the metal standard will become unnecessary and one kilogram of IS will be replicated by any laboratory with the necessary means.
The apparatus that makes this definition possible is Kibble equilibrium, an equilibrium in which the force required to overcome the effect of gravitational force on a given mass is measured in terms of the electrical power required to do so. The gravitational force at a given point can be measured accurately and is defined in terms of other SI units, while electrical power can come from a Josephson junction, a superconducting junction whose current is defined in terms of the Planck constant . As a result, the kilogram can be measured only in terms of constant and other SI units, the metal cylinder being recorded in the history.
This high-end metrology and physics are interesting to read, but it is quite obvious that the de facto kilogram we use all will not change. Our daily measurements of everything from sugar to PLA filament will be the same today as next May. But that's not the point, daily measurements do not need the extreme accuracy and reproducibility of a lab. The purpose of all this lies in still unanticipated applications, for example, the ability to synchronize synchronization to create a GPS or a digital radio would have been possible if the second still had to be defined in terms of astronomical movements rather than the same. atomic states.
Standard kilogram replica shot: 88 Japs [CC BY-SA 3.0]
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