# Dictionary:Gravitational constant

The proportionality constant in **Newton's Law of Universal Gravitation**. The gravitational force *F* between two point masses *m*_{1} and *m*_{2} can be related to the distance *r* between them:

has the value . The force is a vector directed toward the attracting mass. The gravitational field *g* (also a vector, often called the **acceleration of gravity**) is the force per unit mass (measured by the force on the mass *m*_{1} in the gravimeter):

*g* is the vector sum of the effect of all the masses (e.g., the masses in the Earth).