Gravity and Gravitation

Gravity and Gravitation  

The force by which planet or any heavenly bodies attracts towards its centre is called its gravity. For example: A stone falling down towards the centre of earth. 
The force of mutual attraction between two masses is called gravitation. For example:The attraction between sun and earth. 
Before 16th century, it was believed that the earth was at the center of universe around which planets, sun and other heavenly bodies revolve around it. This model was assumed as geocentric model. Later on Nicholas Copernicus introduced a heliocentric model which assumed that the sun lies at the center and all the planets and heavenly bodies revolve around it in a fix orbit. Newton try to find out the reason why these planets revolve around the sun and he began to investigate on it. During his observation he propounded the famous law of gravitation in 1687 AD by which the force of gravitation between two bodies could be measured.