SI: kilogram Mystery Cache

The International System of Units (SI), commonly known as the metric system, is the international standard for measurement. The SI plays an essential role in international commerce and is commonly used in scientific and technological research and development. This cache is part of the SI geoart that allows you to learn about the SI units. Visit the introduction cache to learn more about this geoart.

Mass: kilogram (kg)

The kilogram is the SI base unit of mass.

In 1795, the gram was decreed in France to be “the absolute weight of a volume of pure water equal to the cube of the hundredth part of the metre, and at the temperature of melting ice”. Since a mass standard made of water would be inconvenient and unstable, a provisional mass standard was made as a single-piece, metallic artifact one thousand times as massive as the gram - the kilogram.

Since 1889, the magnitude of the kilogram has been defined as the mass of an object called the International Prototype of the Kilogram (IPK).

By definition, the error in the measured value of the IPK’s mass is exactly zero; the mass of the IPK is the kilogram. However, periodic verification of the IPK and its national replicas reveals that the masses of the entire worldwide ensemble of prototypes have been slowly but inexorably diverging from each other. The stability of the IPK is crucial because the kilogram underpins much of the SI system of measurement as it is currently defined and structured. Therefore, in 2018, the International Committee for Weights and Measures (CIPM) approved a redefinition of SI base units, in which the kilogram is precisely defined and expressed in terms of a fundamental physical constant: the Planck constant.

The new definition took effect on 20 May 2019. Since then, the SI system of measurement no longer depends upon the stability of a 140-year-old, golf-ball-sized cylinder of metal stored in a vault in France.

This Geocache

What’s the mass of a 1965 US quarter coin in milligrams? Divide by 10 and add 124 to get ABC.

What’s the mass of a cubic metre of aluminum (room temperature) in kilograms? Add 208, divide by 3, and round to an integer to get DEF.

Final coordinates: N 39° 07.ABC W 077° 08.DEF

You can validate your puzzle solution with certitude.

Cache container is a baby-nano with tiny log sheet. A pair of tweezers is mandatory for log retrieval. To conserve space, please omit the date and write the first two letters of your username only.

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Lists of Caches in SI geoart

0. introduction
1. second and hertz
2. metre
3. kilogram
4. m/s and km/h
5. mole
6. radian and steradian
7. m/s² and newton
8. m² and pascal
9. joule and watt
10. ampere and coulomb
11. volt and farad
12. ohm
13. kelvin
14. candela, lumen, and lux
15. bushel
16. foreword & afterword
17. prize distribution