that’s my point, thought, it’s totally post hoc. but the second is also a fundamentally arbitrary division of time. at least a day has some natural justification, even if the rotational period of the earth doesn’t remain constant forever.
as far of the meter goes, they could have defined that based off of the kilogram (some amount of palladium iirc), and relationship between volume and weight of water. no need to cesium involved.
ETA, look at this bullshit:
The kilogram (also kilogramme [1]) is the base unit of mass in the International System of Units (SI), the metric system, 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.
The kilogram was originally defined in 1795 as the mass of one litre of water. Modern superseding definitions of a kilogram agree 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 until 2019.[2] The kilogram was the last of the SI units to be defined by a physical artefact.
The kilogram is now defined in terms of the second and the metre, based on fixed fundamental constants of nature.[3] 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, although the IPK and other precision kilogram masses remain in use as secondary standards for all ordinary purposes.
The kilogram is defined in terms of three fundamental physical constants: The speed of light c, a specific atomic transition frequency Δ ν Cs, and the Planck constant h. The formal definition is:
The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34 when expressed in the unit J⋅s, which is equal to kg⋅m2⋅s−1, where the metre and the second are defined in terms of c and Δ ν Cs.[4][5]
This definition makes the kilogram consistent with the older definitions: the mass remains within 30 ppm of the mass of one litre of water.
