Johannes Kepler (1571-1630), German mathematician and astronomer in 17th Century had propagated that planets orbit the Sun in Elliptical path rather than circular one.
Kepler finding revolutionized the world of astronomy. He coined three laws of planetary motion. Kepler’s work had opened new vistas in the understanding of cosmic world.
Prior to Kepler’s discoveries, the predominate theory of the solar system was an Earth-centered geometry as described by Ptolemy. A Sun-centered theory had been proposed by Copernicus, but its predictions were plagued with inaccuracies.
Kepler’s Laws of Planetary Motion
There are three scientific laws which defines the motion of planets around the sun. In astronomy, these are famously known as Kepler’s Laws of Planetary Motion. These are as follow:
a) Kepler’s First Law – The Law of Ellipses (1609): Planets orbit the Sun in elliptical paths. It explains that the Sun is located at one of the two foci of the ellipse. Perihelion is the point when a planet is close to the Sun. Aphelion is the point at which the planet is positioned farthest from the Sun.
b) Kepler’s Second Law – Law of Equal Areas (1609): The line connecting the planet to the Sun sweeps equal areas in equal times.
c) Kepler’s Third Law – Law of Harmonies (The Law of Periods) (1619): The square of a planet’s orbital period is proportional to the cube of its semi-major axis. Kepler challenged the view of Copernicus which states that planets orbit in a circular way around the Sun.
Kepler findings reveals that the planets orbit the Sun in elliptical path.
Features of Kepler’s Ellipses
1. Elliptical Shape: Planets orbit the Sun in elliptical paths, not circular ones.
2. Foci: The Sun is located at one of the two foci of the ellipse.
3. Major Axis: The longest diameter of the ellipse.
4. Minor Axis: The shortest diameter of the ellipse.
5. Eccentricity: Measures the ellipse’s deviation from a circle.
Importance of Kepler’s Discovery
a) Accurate Predictions about : Enabled precise forecasts of planetary positions.
b) Understanding Planetary Motion: Laid the groundwork for Sir Isaac Newton’s laws of motion and universal gravitation.
c) Fundamental Shift: Changed the understanding of the solar system from geocentric to heliocentric.
Kepler is remembered as “cracking the codes” that describe the orbit of the planets.