CGSSystem

cgsSystem refers to the CGS (centimeter-gram-second) system of physical units, based on centimeters, grams, and seconds. It is an early coherent metric framework that predates the modern SI system and was widely used in physics, astronomy, and chemistry. In CGS, many quantities are expressed in base units such as centimeter, gram, and second, with derived units like the dyne for force and the erg for energy.

Within CGS, electromagnetism has several sub-systems, notably CGS-ESU (electrostatic units) and CGS-EMU (electromagnetic units). Gaussian (also called CGS-Gaussian) units blur the boundary between electric and magnetic quantities to simplify Maxwell's equations. These variants differ in how forces, charges, fields, and constants are defined, leading to different unit conventions for E, D, H, B, and Q.

Common CGS units include dyne, erg, and erg per cubic centimeter; in these systems, 1 dyne equals 1 g·cm/s^2 and 1 erg equals 1 g·cm^2/s^2. In electromagnetism CGS variants, charges are expressed as statcoulombs, fields in gauss and oersteds, and the relationship to SI involves the speed of light and large conversion factors (for example, 1 C ≈ 2.9979×10^9 statC and 1 gauss = 10^-4 tesla).

Today the CGS system is largely supplanted by SI in most disciplines, but it persists in certain areas of theoretical physics, astrophysics, and historical literature. Some software packages or libraries expose a cgsSystem configuration to enable CGS unit handling or to convert CGS quantities to SI representations.