it evolves).  Liouville's theorem can also be construed as the statement that  information is conserved . Joseph Liouville (1809-1882; X 1825).  Liouville's measure. Josiah Willard Gibbs (1839-1903).  "Density in phase". Ludwig Boltzmann (1844-1906). Preservation of Phase Volume & Liouville's Theorem for non-Hamiltonian systems   by Mark Tuckerman Application to Electron Orbits