Kepler's Planetary Laws

If there’s one person to give credit to for their incredible contribution to the world of orbital mechanics, Kepler would be an ideal choice. Born in 1571, Kepler managed to pick up an area of maths that had seemingly been left largely untouched since the Ancient Greeks, conic sections, and use it to create 3 laws that laid the foundations of our understanding of orbital mechanics.

Despite being deeply religious, Kepler’s research was too controversial for the church at the time, and as the church became stricter, Kepler was excommunicated from his hometown. However, perhaps this was a blessing in disguise, as he then found a job working as assistant for Tycho Brahe, a well-known Danish astronomer. Tycho had been gifted an island by the Danish King, and on it built an observatory that would prove incredibly useful for collecting accurate observations to use in calculations. When Tycho then died, Kepler was able to use these readings for his own purposes, and soon became appointed Imperial Mathematician

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. His alternative way of astronomy, coming up with theories and testing them, paired nicely with Tycho’s diligent and accurate data collection methods, leading to much progress

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The beginning of Kepler’s great discoveries and laws was through his use of Tycho’s observations of Mars’ orbit. Despite years of detailed records, Kepler had to complete many calculations to calculate the orbit of Mars, and the thought that Mars’ orbit was circular added greatly to the difficulties Kepler faced in trying to plot it

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. However, once complete, he came to the conclusion that the orbit of Mars around the Sun was in fact not a circle but an ellipse, and the Sun was at one of the foci. This would soon be proved true for all planets orbiting a Sun, and became Kepler’s First Law. Kepler’s Second Law stated that an imaginary line connecting a Sun and the orbiting planet would sweep out equal amounts of area in equal amounts of time, i.e. a planet travels faster closer to the Sun and slower further away.

Kepler’s legacy will not be forgotten for a long time, as he laid the groundwork for the more famous Newton’s Law of Gravitation, which were actually discovered after Kepler’s work - making it even more impressive.