On Absolute Units, I: Choices

In 1899 Max Planck proposed what he called a system of absolute units, based on the speed of light c, Newton’s gravitational constant G, and his newly minted quantum of action ħ. From these, by taking powers and ratios, one can manufacture units of mass $M Planck ≡ ħ c / G = 2.2 × 10 − 5$ gram, length $L Planck ≡ ħ G / c 3 = 1.6 × 10 − 33$ centimeter, and time $T Planck ≡ ħ G / c 5 = 5.4 × 10 − 44$ second. Upon adopting those units as standards, one can express any physical quantity in purely numerical terms. For example, the near-Earth acceleration due to gravity is g = 9.8 × 10²cm/sec² = 1.8 × 10⁻⁵¹ L _Planck/T _Planck ².

Obviously Planck units are not very handy for practical purposes....