Newton's Law of Universal Gravitation states that two point masses attract each other with a force proportional to the product of their masses and inversely proportional to the square of the distance between them:
$$F_{1}=F_{2}=G\frac{m_{1}m_{2}}{r^{2}}$$
where,
G— gravitational constant,
m1— mass of the first object,
m2— mass of the second object,
r— separation between the masses.
Gravitational constant (symbol G, also known as the universal gravitational constant, Newton's gravitational constant, or Cavendish's gravitational constant) is a physics constant that characterizes the strength of the gravitational force. Its value is:
$$G=6.67430(15) \times 10^{-11} \frac{N\times m^{2}}{kg^{-2}}$$
The first indirect measurement of the gravitational constant is attributed to Henry Cavendish in 1798.