Question

What are the Kepler’s three laws?

Answer 1

We know that the planets revolve around the sun, and the motion of the planets around the sun was described by Johannes Kepler. He gave a set of three laws called the Kepler’s law of planetary motion. This was the modified version of the heliocentric theory proposed by Nicolaus Copernicus.

Complete answer:
It was believed for a very long time, that the earth was at the centre of the solar system and all the other planets including the sun, revolved around the earth. This was the heliocentric theory proposed by Nicolaus Copernicus.
However, later, Johannes Kepler proposed that the sun was at the center of the solar system and all other planets including earth, would revolve around the sun in elliptical paths, called orbits. He also gave a set of three laws called the Kepler’s law of planetary motion, which are as follows:
1. The planets orbit around the sun in an elliptical path, where the sun is at one of the foci.
2. A line segment joining the sun and the planet at any time instant will sweep equal areas at equal time intervals.
3. The square of the time period of the planet’s orbit is proportional to the cube of the length of the planet along the semi-major axis.

Note:
The above was further modified by Isaac Newton, who applied his laws of motion to Kepler's law of planetary motion to give the law of universal gravitation. This led to the famous relationship of the inverse square law of gravitation and the conservation of angular momentum of the planets.