# Gravitation

Have you ever thought why do things fall on earth on being released from a height? Why don't they go upwards? Appears to be a very stupid question to ask. But these small stupid looking questions make the ingredient of genius. One such story is about Sir Issac Newton.

It is said that Newton was sitting under an apple tree when an apple fell. Newton started thinking why this apple fell on the ground? Why did it not fly in the air? No matter how stupid this question appears, but this question made Newton greatest scientist of his time. Actually we don't know wether this story is true or not (most probably it is not), but gravitation is one of the most talked about discoveries of Newton.

Newton gave following Universal law of gravitation:

All the bodies attract each other with a force which is directly proportional to their masses and inversely proportional to square of distance between them:

##### $$F = G{m_1m_2\over d^2}$$

Here, G is called Universal gravitational constant and it's value is $$6.67*10^-11 Nm^2Kg^-2$$