Mole (unit) and growth chamber lighting for plants is sometimes expressed in micromoles per square meter per second, where 1 mol photons = photons. In 2011, the 24th meeting of the General Conference on Weights and Measures (CGPM) agreed to a plan for a possible revision of the SI base unit definitions at an undetermined date. The 26th meeting of the CGPM, in a formal vote on 16 November 2018, approved the proposed redefinition of SI base units mole, kilogram, ampere and kelvin. One mole of a substance will have exactly specified "elementary entities" of that substance. The definition of the mole
Stoic physics Stoic physics Stoic physics is the natural philosophy adopted by the Stoic philosophers of ancient Greece and Rome used to explain the natural processes at work in the universe. To the Stoics, the universe is a single pantheistic God, but one which is also a material substance. The primitive substance of the universe is a divine essence ("pneuma") which is the basis of everything which exists. This "pneuma", which is the active part or reason ("logos") of God, provides form and motion to matter, and is the origin of the elements, life, and human rationality. From their physics, the Stoics