on 15 November 1999. His tombstone is in section 17 with the grave number 84457. Works Criticism of Maxwell–Lorentz electromagnetic theory Not so well known is the fact that in 1908 Ritz produced a lengthy criticism of Maxwell–Lorentz electromagnetic theory, in which he contended that the theory's connection with the luminescent ether (see Lorentz ether theory) made it "essentially inappropriate to express the comprehensive laws for the propagation of electrodynamic actions." Ritz pointed out seven problems with Maxwell–Lorentz electromagnetic field equations: Electric and magnetic forces really express relations about space and time and should be replaced with non-instantaneous elementary actions. Advanced potentials don't exist (and their erroneous use led to the Rayleigh–Jeans ultraviolet catastrophe). Localization of energy in the ether is vague. It is impossible to reduce gravity to the same notions. The unacceptable inequality of action and reaction is brought about by the concept of absolute motion with respect to the ether. Apparent relativistic mass increase is amenable to different interpretations. The use of absolute coordinates, if independent of all motions of matter, requires throwing away the time honored use of Galilean relativity and our notions of rigid ponderable bodies. Instead he indicated that light is not propagated (in a medium) but is projected. This theory, however, is considered to be refuted. Ritz's method In 1909 Ritz developed a direct method to find an approximate solution for boundary value problems. It converts the often insoluble differential equation into solution of a matrix equation. It is a theoretical preparatory work for the finite element method (FEM). This method is also known Ritz's variation principle and the Rayleigh-Ritz principle. Ritz's combination principle In 1908, Ritz found empirically the Ritz combination principle named after him. After that, the sum or difference of the frequencies of two spectral lines is often the frequency of another line. Which of these calculated frequencies is actually observed was only explained later by selection rules, which follow from quantum mechanical calculations. The basis for this was the spectral line research (Balmer series) by Johann Jakob Balmer. Honors The lunar crater Ritz is named after him. References Jean-Claude Pont (ed.) Le Destin Douloureux de Walther Ritz, physicien théoricien de génie, Sion: Archives de l'Etat de Valais, 2012 (= Proceedings of the International Conference in Honor of Walther Ritz's 100th Anniversary). External links Abbreviated Biographical Sketch of Walter Ritz Critical Researches on General Electrodynamics, Walter Ritz, 1908, English translation