# Kepler's Explanation for Spacing of Planets/Historical Note

## Historical Note on Kepler's Explanation for Spacing of Planets

Johannes Kepler's conjecture on the spacing of the planets was made in his $1596$ work Mysterium Cosmographicum.

The earth's orbit is the measure of all things; circumscribe around it a dodecahedron, and the circle containing this will be Mars: circumscribe around Mars a tetrahedron, and the circle containing this will be Jupiter: circumscribe around Jupiter a cube, and the circle containing this will be Saturn. Now inscribe within the earth an icosahedron, and the circle contained in it will be Venus; inscribe within Venus an octahedron, and the circle contained within it will be Mercury. You now have the reason for the number of planets.

His model, however ingenious, did not agree well with observations, particularly in light of subsequent, more accurate, observational data.

However, it made his reputation as an imaginative thinker and keen astronomer, and importantly this was one of the first theses based on a heliocentric universe.

He brought him to the attention of the scientific community, including Galileo Galilei, and soon he was offered a position working for Tycho Brahe.