Question

Kepler's Laws and Newton 's law of gravity allows for comparison of conditions on exoplanets and planets in the Solar system,

why?

Answer 1

It's interesting to know that Kepler's laws were initially defined to explain (fit) the observational results of Galileo. Similarly, Newton's also first formed his gravitational law with reference to earth moon system. Hence they are used to well describe the motion of planets and exoplanets in our solar system.

Kepler's first law tells us about the shape of the orbits, second law about the area of orbit and time of sweeping the area and third law describes the relation between the distance of planets from sun and it's orbital time period. Thus motion of any planet can be well understood using Kepler's 3 laws.