# Centimetre–gram–second system of units

**Centimetre–gram–second system of units** (**CGS**) is a system of physical units that is based on three fundamental units: the centimetre for length, the gram for mass, and the second for time. The CGS system has been largely supplanted by the International System of Units (SI), which is based on the metre, kilogram, and second, but it remains in use in some scientific contexts, particularly in electromagnetism and fluid dynamics.

## History[edit | edit source]

The CGS system was developed in the 19th century as scientists sought to standardize measurements. It was officially adopted at the first General Conference on Weights and Measures (CGPM) in 1881. The system was designed to simplify the units of measurement for scientific work by using the metric system's centimetre and gram, combined with the second, as the base units for length, mass, and time, respectively.

## Units[edit | edit source]

The CGS system includes several derived units for physical quantities like force, energy, and pressure. These are derived from the base units using physical laws.

### Derived Units[edit | edit source]

**Dyne**(dyn): The unit of force in the CGS system. It is defined as the force required to accelerate a mass of one gram at a rate of one centimetre per second squared.**Erg**: The unit of energy or work in the CGS system. One erg is the work done by a force of one dyne acting over a distance of one centimetre.**Barye**(Ba): The unit of pressure in the CGS system. It is equivalent to one dyne per square centimetre.

## Advantages and Disadvantages[edit | edit source]

The CGS system offers simplicity for certain theoretical and experimental physics calculations, particularly in electromagnetism where the units can lead to simpler equations without conversion factors. However, the system has disadvantages, including the lack of coherence with the SI system, which can lead to confusion and conversion errors. The use of gram as the base unit of mass is also considered impractical for many applications due to its small size.

## Conversion to SI Units[edit | edit source]

Conversion from CGS to SI units involves scaling factors. For example, to convert from dynes to the SI unit of force (newtons), one must multiply by 10^-5 (1 dyne = 10^-5 newtons).

## Current Use[edit | edit source]

While the SI system is the standard in most scientific and engineering contexts, the CGS system is still used in some areas of physics, such as astrophysics and particle physics. It is also common in academic literature and textbooks related to these fields.

## See Also[edit | edit source]

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Contributors: Prab R. Tumpati, MD