The proportionality constant in Newton's Law of Universal Gravitation. The gravitational force F between two point masses m1 and m2 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 m1 in the gravimeter):
g is the vector sum of the effect of all the masses (e.g., the masses in the Earth).