Universal Law of Gravitation given by Newton is called Newton’s Law of Gravitation. This law states that, “Every object in the universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.”
Suppose two bodies A and B of mass m1 and m2 be at distance r from each other.
So, according to Newton’s law of gravitation,
F ∝ m1 x m2..... ….1
And F ∝ \(\frac{1}{r^2}\) ......….2
Thus, combining equations 1 and 2 we get,
F =G \(\frac{m_1\times m_2}{r^2}\)
Where, G = Universal Gravitational Constant
G = 6.67 x 10-11 Nm2kg-2
Newton’s law of gravitation is called universal law of gravitation because it is applicable to all bodies having mass: whether big or small; whether the bodies are terrestrial (which are on earth) or celestial (which are in outer space) such as stones, planets and satellites.