Τι (ποιος) είναι cgram - ορισμός
![The [[International Prototype of the Kilogram]], whose mass was defined to be one kilogram from 1889 to 2019.](https://commons.wikimedia.org/wiki/Special:FilePath/International prototype of the kilogram aka Le Grand K.jpg?width=200 "The [[International Prototype of the Kilogram]], whose mass was defined to be one kilogram from 1889 to 2019.")
![SI system]] after the 2019 redefinition: the kilogram is now fixed in terms of the [[second]], the [[speed of light]] and the [[Planck constant]]; furthermore the [[ampere]] no longer depends on the kilogram](https://commons.wikimedia.org/wiki/Special:FilePath/Unit relations in the new SI.svg?width=200 "SI system]] after the 2019 redefinition: the kilogram is now fixed in terms of the [[second]], the [[speed of light]] and the [[Planck constant]]; furthermore the [[ampere]] no longer depends on the kilogram")
![A [[Kibble balance]], which was originally used to measure the [[Planck constant]] in terms of the IPK, can now be used to calibrate secondary standard weights for practical use.](https://commons.wikimedia.org/wiki/Special:FilePath/Watt balance, large view.jpg?width=200 "A [[Kibble balance]], which was originally used to measure the [[Planck constant]] in terms of the IPK, can now be used to calibrate secondary standard weights for practical use.")
Βικιπαίδεια
The kilogram (also kilogramme) is the base unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially. It means 'one thousand grams'.
The kilogram is defined in terms of the second and the metre, both of which are based on fundamental physical constants. This allows a properly equipped metrology laboratory to calibrate a mass measurement instrument such as a Kibble balance as the primary standard to determine an exact kilogram mass.
The kilogram was originally defined in 1795 during the French Revolution as the mass of one litre of water. The current definition of a kilogram agrees with this original definition to within 30 parts per million. In 1799, the platinum Kilogramme des Archives replaced it as the standard of mass. In 1889, a cylinder of platinum-iridium, the International Prototype of the Kilogram (IPK), became the standard of the unit of mass for the metric system and remained so for 130 years, before the current standard was adopted in 2019.
