When most people think of “metric” these days they think of the SI system. For some applications (especially in the laboratory) the SI system is impractical because of the magnitude of the units. In these cases the CGS system is more practical and easier to use. The following is an overview of the CGS system, from Units of Measurement of Physical Quantities by Chertov:
The cgs system was developed by British scientists on the basis of a proposal advanced by Thomson. It was adopted as an international system at the First International Congress of Electricians in 1881. The term cgs stems from the initial letters of the fundamental units. The word physical is added because the units in this system are used mainly in physics.
FUNDAMENTAL UNITS IN THE CGS SYSTEM
The fundamental units in the cgs system are:
- The centimeter (cm)—the unit of length. The centimeter is one hundredth of a meter.
- The gram (g)—the unit of mass. The gram is one thousandth of a kilogram.
- The second (sec)—the unit of time.
DERIVED UNITS IN THE CGS SYSTEM
The derived units and their dimensions in the cgs system can be obtained in the same manner as indicated for the MKS (SI) system. The sequence of the fundamental equations is shown in Table 2. The structure of the cgs system is similar to that of the MKS system, since in both systems the fundamental quantities are length, mass, and time.
You can download Chertov’s book to look at how the MKS system is derived.