27 December - Johannes Kepler birth anniversary

 

Johannes Kepler (1571–1630) was a German mathematician, astronomer, and astrologer who played a key role in the scientific revolution of the 17th century. He made significant contributions to the fields of astronomy and mathematics, and his work laid the foundation for many later developments in these disciplines. 

He was born on 27 December 1571, in Weil der Stadt, in the Holy Roman Empire (now in Germany). He passed away on 15 November 1630  in Regensburg, also in the Holy Roman Empire. 

1. Laws of Planetary Motion: Kepler's most famous work is his formulation of the laws governing the motion of planets around the sun. These laws, known as Kepler's Laws of Planetary Motion, were derived based on careful observations made by Tycho Brahe. The three laws are:

   • First Law (Law of Ellipses): The orbit of a planet around the sun is an ellipse with the sun at one of the two foci.
   • Second Law (Law of Equal Areas): A line segment joining a planet and the sun sweeps out equal areas during equal intervals of time.
   • Third Law (Harmonic Law): The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

2. Astronomia nova (New Astronomy): In this work published in 1609, Kepler presented his first two laws of planetary motion. He also discussed the concept of elliptical orbits, moving away from the traditional belief in perfect circular orbits.

3. Harmonices Mundi (Harmony of the World): Published in 1619, this work continued Kepler's exploration of the relationships between planetary orbits and musical harmony. He proposed a connection between the distances of the planets from the sun and musical intervals.

4. Rudolphine Tables: Kepler worked on and completed the Rudolphine Tables, a set of astronomical tables based on Tycho Brahe's observations. These tables were named in honor of his patron, Holy Roman Emperor Rudolph II.

Kepler's work laid the groundwork for Isaac Newton's later development of the law of universal gravitation. His contributions were instrumental in advancing the understanding of celestial mechanics and paved the way for a more accurate description of planetary motion.