What is the Gravitational Constant?

by Alexander FufaeV

Gravitational constant is a physical constant and determines how strongly masses attract each other. It therefore determines the strength of gravity. It is abbreviated with the letter $G$ and has the following value:

Value of the gravitational constant

$$ \begin{align} G ~\approx~ 6.674 \, 30 ~\cdot~ 10^{-11} \, \frac{ \mathrm{m}^3 }{ \mathrm{kg} \, \mathrm{s}^2 } \end{align} $$

The unit of the gravitational constant $G$ is for example Newton square meter per kilogram squared or cubic meter per kilogram second squared:

$$ \begin{align} \frac{\mathrm{N} \, \mathrm{m}^2}{\mathrm{kg}^2} ~=~ \frac{\mathrm{m}^3}{\mathrm{kg} \, \mathrm{s}^2} \end{align} $$

The gravitational constant occurs in the Newton law of gravity and Einstein field equations, which describe the interaction between masses.

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The gravitational force between two masses is determined in particular by the gravitational constant.

Because of the small value of the gravitational constant (see equation 1) gravity is one of the weakest fundamental forces of nature. The gravitational constant only plays a significant role when large masses are involved, such as the mass of the Earth.

The gravitational constant is difficult to measure accurately compared to other constants of nature. This is simply because any mass around the experiment will affect the measurement. The gravitational constant can be approximately determined, for example, with the Cavendish experiment.