When quantum theory was developed a few years later it became clear that Weyl’s theory was in conflict with experience in an even more fundamental way since there is a direct relation between clock rates and masses of particles in quantum theory. A particle with a certain rest mass \(m\) possesses a natural frequency which is a function of its rest mass, the speed of light \(c\), and Planck’s constant \(h\). This means that in a Weyl geometry not only clocks would depend on their histori