Harmonices Mundi, or 'The Harmony of the World', is a seminal work by the mathematician and astronomer Johannes Kepler, published in 1619. In this book, Kepler explores the relationship between music, geometry, and the cosmos, proposing that the movements of celestial bodies are governed by harmonic principles. He famously introduced the idea of the 'music of the spheres', suggesting that the planets produce a form of music through their orbits. Kepler's work laid the foundation for the field of harmonics and influenced later thinkers in both science and philosophy. By connecting the physical universe with musical harmony, Harmonices Mundi reflects the Renaissance belief in the interconnectedness of all things, bridging the gap between art and science.