In early days, people were observing the heavenly bodies like sun, moon, stars, planets etc, and their movement. It was the Italian physicist Galileo,
(1564-1642), who recognised all the heavenly bodies like the sun, planets, the moon etc., are moving around the earth which is stationary and was taken as the centre of the universe.
The earliest recorded model for planetary motions proposed by Ptolemy about 2000 years ago was a geocentric model. It states that the description of the cosmos where the earth is at the orbital centre of all celestial bodies.
However, a more elegant model in which the sun was the centre around which the planet revolved the heliocentric model. This theory was later on supported by Galileo from his experimental study on the moon and other planets.
Tycho Brahe (1546-1601) spent his entire lifetime recording observations of the planets with the naked eyes. His assistants Johannes Kepler compiled his a and analysed. He extracted three elegant laws that are now known as Kepler’s law.