Ciro Santilli @cirosantilli  40

Ciro Santilli appreciates this concept of "remembering the suffering of others" a lot due to Ciro Santilli's self perceived compassionate personality and Ciro Santilli's cheapness.

Bibliography:

Great overview of the earlier history of unit standardization.

Gives particular emphasis to the invention of gauge blocks.

Starting in the 2019 redefinition of the SI base units, the elementary charge is assigned a fixed number, and the Ampere is based on it and on the second, which is beautiful.

This choice is not because we attempt to count individual electrons going through a wire, as it would be far too many to count!

Rather, it is because because there are two crazy quantum mechanical effects that give us macroscopic measures that are directly related to the electron charge. www.nist.gov/si-redefinition/ampere/ampere-quantum-metrology-triangle by the NIST explains that the two effects are:

Those effect work because they also involve dividing by the Planck constant, the fundamental constant of quantum mechanics, which is also tiny, and thus brings values into a much more measurable order of size.

Unit of electric current.

Affected by the ampere in the 2019 redefinition of the SI base units.

Unit of mass.

Defined in the 2019 redefinition of the SI base units via the Planck constant. This was possible due to the development of the Kibble balance.

A series of systems usually derived from the International System of Units that are more convenient for certain applications.