According to Stephen Hawking in his book ‘On The Shoulders Of Giants’, Kepler discovered how planets orbited and he paved the way for the later Isaac Newton to discover why. Kepler’s work focused on the five Platonic solids, their harmonic ratios, and how these shapes correlated with planetary orbits and sound frequencies. He found the musical tones of individual planets, and the musical scales of planetary movements. He was even able to determine that "…four kinds of voice are expressed in the planets: soprano, contralto, tenor, and bass." (Stephen Hawking). Basically, Kepler had found the music of the cosmos, and that the same harmonic principles found in the stars, and life forms on earth are musical.