- #1
Alfi
Just stumbled on this in Wiki and wondered.
The kilogram or kilogramme (symbol: kg) is the base unit of mass in the International System of Units (known also by its French-language initials “SI”). The kilogram is defined as being equal to the mass of the International Prototype Kilogram (IPK; known also by its French-language name Le Grand K), which is almost exactly equal to the mass of one liter of water.[1] It is the only SI base unit with an SI prefix as part of its name. It is also the only SI unit that is still defined in relation to an artifact rather than to a fundamental physical property that can be reproduced in different laboratories.
Certainly a lot of diets are. :)I found this bit further down the page interesting.
Ultimately, the watt balance would define the kilogram in terms of the Planck constant, which is a measure that relates the energy of photons to their frequency. The Planck constant would be fixed, where h = 6.62606896 × 10–34 J·s (from the 2006 CODATA value of 6.62606896(33) × 10–34 J·s) and the kilogram would be defined as “the mass of a body at rest whose equivalent energy equals the energy of photons whose frequencies sum to 1.356392733 × 1050 Hz.”[29]
The kilogram or kilogramme (symbol: kg) is the base unit of mass in the International System of Units (known also by its French-language initials “SI”). The kilogram is defined as being equal to the mass of the International Prototype Kilogram (IPK; known also by its French-language name Le Grand K), which is almost exactly equal to the mass of one liter of water.[1] It is the only SI base unit with an SI prefix as part of its name. It is also the only SI unit that is still defined in relation to an artifact rather than to a fundamental physical property that can be reproduced in different laboratories.
Is there a good reason why. A lot of measurements are based on this artifact.It is also the only SI unit that is still defined in relation to an artifact rather than to a fundamental physical property
Certainly a lot of diets are. :)I found this bit further down the page interesting.
Ultimately, the watt balance would define the kilogram in terms of the Planck constant, which is a measure that relates the energy of photons to their frequency. The Planck constant would be fixed, where h = 6.62606896 × 10–34 J·s (from the 2006 CODATA value of 6.62606896(33) × 10–34 J·s) and the kilogram would be defined as “the mass of a body at rest whose equivalent energy equals the energy of photons whose frequencies sum to 1.356392733 × 1050 Hz.”[29]
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