electrostatic self energy and the mass–energy scale of the electron. Discussion The electron radius occurs in the classical limit of modern theories as well, such as non-relativistic Thomson scattering and the relativistic Klein–Nishina formula. Also, is roughly the length scale at which renormalization becomes important in quantum electrodynamics. That is, at short-enough distances, quantum fluctuations within the vacuum of space surrounding an electron begin to have calculable effects that have measurable consequences in atomic and particle physics. Based on the assumption of a simple mechanical model, attempts to model the electron as a non-point particle have been described by some as ill-conceived and counter-pedagogic. See also Electromagnetic mass References Further reading Arthur N. Cox, Ed. "Allen's Astrophysical Quantities", 4th Ed, Springer, 1999. External links Length Scales in Physics: the Classical Electron Radius Physical constants Atomic physics Electron