Johannes Kepler

Kepler grew up in a family that faced financial uncertainty and frequent change. Poor health affected him as a child, but he developed a strong interest in mathematics and the sky.

Explain planetary motion accurately enough to match Tycho Brahe’s observations, even when the traditional circular-orbit model failed.

Kepler abandoned perfect circles and discovered that planets move in ellipses, then identified mathematical relationships that became his three laws of planetary motion.

His laws made planetary motion predictable and became foundational to orbital mechanics.

Modern satellite and spacecraft orbit calculations still rely on the same physical geometry Kepler helped reveal.