What is Gravity ?

Gravity is the force, that attracts a body towards the centre of the earth, or towards any other physical body having mass.

In 4th century BC Aristotle proposes that stones fall to the ground simply because they are heavy, and that smoke rises because it is light.

In 1604 Italian scientist Galileo Galilei investigates how objects fall to Earth. He showed that all objects fall at the same speed, no matter what their weight.

In 17th century English physicist Isaac Newton publishes his Law of Gravitation, perhaps inspired by seeing an apple fall from a tree. He wrote the book "The Mathematical Principles of Natural Philosophy ".