Gravity
One of the four fundamental forces of nature. The origin of the gravitational force is mass, and it is always an attractive force. Although much weaker than the electromagnetic and nuclear forces, gravity dominates most of what occurs in the universe. It controls the motions of planets around stars, the motions of stars in galaxies, and the evolution of the universe itself.
The strength of the gravitational force is related to the masses and to the
distance between them:
