# Gravitational Constant and Universal Law of Gravitation, Universal Law of Gravitation (For CBSE, ICSE, IAS, NET, NRA 2022)

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# Gravitational Constant and Universal Law of Gravitation

## Universal Law of Gravitation

- Newton՚s law of universal gravitation is usually called as that every particle attracts every other particle in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
- The publication of the theory has become known as the “first great unification,” as it marked the unification of the previously described phenomena of gravity on Earth with known astronomical behaviors.
- According to Newton՚s Universal Law of Gravitation, the force exerted between two objects, by each other is given by the following relation.

Where,

- G = gravitational force between two bodies
- = mass of one object
- = mass of the second object
- r = distance between the centers of two objects

## Gravitational Constant

Actual force exerted between two bodies can be given by the following equation

Where,

- G = the universal gravitational constant with a value of;
- G = an empirical constant of proportionality.
- Even though it is Newton՚s Universal Law of Gravitation, the value of G wasn՚t given by him.
- This was calculated by Henry Cavendish in 1798 through a series of experiments and observations.
- It is hypothesized the influence of the earth՚s core on the experiments alters its rotational inertia because of which the value of G given is not always constant throughout the globe.
- Other theory regarding the universal gravitational constant is that, if it is true that the universe is expanding since the Big Bang, then the value of G will keep decreasing!
- The universal gravitational constant is used in Newton՚s Universal Law of Gravitation, Einstein՚s General Theory of Relativity and Kepler՚s Third Law of Planetary Motion, to calculate the time period of a planet to complete one full revolution in its orbit.