Kepler's Laws of Planetary Motion – GCSE Astronomy Edexcel Revision

Kepler’s Laws of Planetary Motion

Johannes Kepler was a German astronomer of the 17th century.
He is best known for his formulation of the three laws of planetary motion, based on detailed astronomical observations by Tycho Brahe.

Kepler’s first law states that planets orbit the Sun in elliptical paths, with the Sun at one focus of the ellipse.
This was a significant departure from the previous model, which assumed that planets moved in perfect circles.

According to Kepler’s second law, a line connecting a planet to the Sun sweeps out equal areas in equal times.
This means that planets move more quickly when they are closer to the Sun, and more slowly when they are further away, due to the elliptical nature of the orbits.

The third law, also known as the law of harmonics, relates the orbital period of a planet to its average distance from the Sun.
It states that the square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.
This law allows us to calculate the distance of a planet from the Sun if we know the length of its orbital period, or vice versa.

Kepler’s laws provided a new and more accurate description of the movements of the planets in the solar system.
They formed the foundation for Newton’s theory of universal gravitation.
Kepler’s laws are still used today in fields such as space travel and satellite deployment.

Johannes Kepler formulated three laws of planetary motion, based on observations by Tycho Brahe.
The first law states that the planets orbit the Sun in elliptical paths.
The second law states a line connecting a planet to the Sun sweeps out equal areas in equal times, resulting in varying speeds of the planet.
The third law predicts a planet’s distance from the Sun, based on its orbital period.
Kepler’s laws laid the groundwork for Newton’s theory of gravitation and are fundamental in modern space exploration.