Haber's rule

• Every object in the Universe attracts every other object with a force directed along the line of centers for the two objects that is proportional to the product of their masses and inversely proportional to the square of the separation between the two objects. (See also inverse-square law.)
• Two bodies attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Strictly speaking, this law applies only to point-like objects. If the objects have spatial extent, the true force has to be found by integrating the forces between the various points.

The law expressed as an equation:

$F=G\frac{m_1{m}_2}{r^2}$

where:

• $F$ = gravitational force between two objects
• $m_1$ = mass of first object
• $m_2$ = mass of second object
• $r$ = distance between the center of mass of the objects
• $G$ = universal constant of gravitation

The Gravitational equation that is given above is similar to that of Coulomb's Law which deals with the electrostatic force between two charged particles.