Re: G-Force Platinum V3.7.5-full Full Versionl
Katja Gains
Early the kilogram was defined as the mass of a cubic decimeter water. Since 1901 is the kilogram a block of platinum-iridium saved in France. One liter water weights according the present norms 0.998 kg.
The mass has a strange unit, because in the unit is a prefix. This is due to the history of the SI. The unit supposed to be equal to one liter of water. This would be called a grave. The volume unit liter is derived from the unit of length. The French thought that the unit was too big and thought that it could give problems with trading and daily use. That is why they have rejected the grave and introduced a new unit. This unit is equal to one milliliter of water. That is 1/1000 of the liter. This new unit got the name gram. This did not seem to be so practical at all and that is why they wanted go back to the grave, but with a new name. The gram was exactly one thousandth of a grave, so the new unit was kilogram, in other words: 1000 gram. That is why there is a prefix in the SI. Later the definition was rejected, because is was not so exact. Nowadays the kilogram is a block of platinum-iridium that is kept in Sèvres, France. This is not in line with the conditions. It is an instable unit, because is isn't based on a nature constant. There is a risk that the value of the kilogram could change. That is why scientists are holding up with the precise definition, but that is very difficult, because it is too difficult to refer on a nature constant.