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Alfi

## Main Question or Discussion Point

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”).

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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