Question

was a mathematician who showed that the orbits of the planets were elliptical.

Answer 1

The mathematician you are referring to is Johannes Kepler. He formulated the three laws of planetary motion, with his first law stating that the orbits of planets around the Sun are ellipses, with the Sun located at one of the foci. Kepler's work was crucial in the development of celestial mechanics and laid the groundwork for Isaac Newton's law of universal gravitation.