Light

Kepler's Laws of Planetary Motion

Definition

Kepler's Laws of Planetary Motion are three scientific laws describing the motion of planets around the Sun. They state that orbits are ellipses with the Sun at one focus; planets sweep out equal areas in equal times; and there is a relationship between a planet's orbital period and its distance from the Sun.

Analogy

Think about spinning a ball on a string around your head - it doesn't go in a perfect circle but more like an oval or ellipse. That’s similar to how planets orbit the sun according to Kepler’s first law. The second law is like sweeping dirt into a dustpan - you try to sweep up an equal amount each time you push your broom. The third law can be compared to running tracks – runners on outer tracks have longer distances to cover than those on inner tracks, just as planets further from the sun have longer orbital periods.

Related terms

Gravity: This is the force by which every mass or particle of matter (including photons) attracts every other mass or particle.

Elliptical Orbit: An elliptical orbit refers to any orbit in shape of an ellipse. According to Kepler's first law, all planetary orbits are elliptical.

Orbital Period: This refers to the time taken for a given object to make one complete orbit around another object.