Kepler’s contribution to Physics

Karla Ramos Calixto

Johannes Kepler was born in Weilder Stadt, Germany on December 27, 1571 and died in Ratisbona, Germany on November 15, 1630. He was an astronomer and mathematician. Kepler dedicated a great part of his life trying to understand and explain the movement of the planets. Most of Kepler's enthusiasm for the Copernican system was based on his theological convictions of the connection between the physical and the spiritual things. “The universe itself was an image of God, with the Sun corresponding to the Father, the stellar sphere to the Son, and the intervening space between to the Holy Spirit”. His first writing of Mysterium contained an extensive part that relates the heliocentrism to the Biblical passages that apparently supported the geocentrism.

At the beginning of his research, Kepler thought that the movement of the planets was based on the pitagorical laws of harmony and that the distance of the planets in relation to the sun were given by the spheres within the interior of the perfect polyhedrons. In the year 1600, he began collaboration with astronomer Tycho Brahe, which had the best astronomy observation center at the time. Kepler was unable to access the data and observations made by Tycho because they did not trust each other. Kepler was able to study the data after Tycho’s death in 1620. Kepler was able to discover that the planets movements could not be defined by the polyhedrons and harmony model, Based on the ideas that the planets were simple geometrical figures, he decided to experiment with combinations of circles and ovals, He saw that it was impossible with circles. Without any other options, he decided to use eclipses and had a breakthrough. Based on this data, he then developed the three laws that describe the movement of the planets. They were published in his book Nova Astronomy in the year 1609.

These laws were: First Law (1609): All planets move around the sun showing elliptical orbits, being the sun within its focus. The Second Law (1609): The radio vector that joins the planet and the sun covers the same areas within the same time range. The laws of area are equivalent to the constancy of the angular moment, when the planet is further from the sun (aphelion) its velocity is less than it is when it is nearer to the sun (perihelion). At the aphelion and the perihelion, the angular moment L is the product of the planets mass, speed and distance to the center of the sun. Third law (1618): For any given planet, the cube of its orbital period (the time that the planets take to circle once around the sun) is directly proportionate to the cube of the media distance with the sun. These laws permitted Kepler to be classified as the greatest astronomer of his time.

Three centuries later, his intuition about the planets being described as simple figures was confirmed by Einstein which was confirmed and proven with his Relativity Theory which demonstrated that the celestial bodies follow rectal lines.