LOG#222. The New SI.

By the time we will find new physics, we have already redefined the SI in terms of base units and fundamental constants.

The definition of the new SI is the next one: the SI is the system in which the following constants are taken to be exact

• The unperturbed ground state hyperfine splitting (transition) frequency of the caesium-133 atom is exactly

Thus, frequency is fundamental, and the time is a base unit from frequency. One second is the time

and 1 Hz is the reciprocal of the above quantity, exactly too.

• The speed of light in vacuum is exactly the quantity

Using the previous and this definition, you can define the meter to be exactly the amount of length

• The elementary charge is exactly the quantity

Thus, the old electric current unit, base unit, the ampère, is the unit in which you can express charge into current, in corresponding units, with the next conversion constants:

• The Planck constant is exactly defined to be

and thus the kilogram is defined in terms of fundamental constants as

• The Boltzmann constant is exactly

so (with and then

• The Avogadro constant is defined exactly to be

so the mole is

• The luminous efficacy of monochromatic radiation of frequency THz is exactly defined to be 683 . Thus, as stereradian is dimensionless, and the candela definition holds exactly to be as well

See you in another blog post!

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