How did Kepler explain planetary orbits?
I revealed that planetary orbits are not perfect circles, but ellipses, with the Sun positioned at one of the two foci. This central idea, the elliptical nature of planetary paths, is the cornerstone of my first law of planetary motion. It was a significant departure from the ancient Aristotelian and Ptolemaic view of celestial perfection. My second law further elucidates this by stating that a line connecting a planet to the Sun sweeps out equal areas in equal times. This means planets move faster when they are closer to the Sun and slower when they are farther away, a consequence of the conservation of angular momentum. My work in *Astronomia nova* demonstrated that the heavens follow precise, measurable laws, not whims.
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