Hence a substantial body of physical theory developed since Planck's 1899 paper suggests normalizing not G but 4 π G (or 8 π G) to 1. Doing so would introduce a factor of ⁠ 1 / 4 π ⁠ (or ⁠ 1 / 8 π ⁠) into the nondimensionalized form of the law of universal gravitation, consistent with the modern rationalized formulation of Coulomb's law in terms of the vacuum permittivity. In fact, alternative normalizations frequently preserve the factor of ⁠ 1 / 4 π ⁠ in the nondimensionalized form of Coulomb's law as well, so that the nondimensionalized Maxwell's equations for electromagnetism and gravitoelectromagnetism both take the same form as those for electromagnetism in SI, which do not have any factors of 4 π. When this is applied to electromagnetic constants, ε 0, this unit system is called " rationalized ". When applied additionally to gravitation and Planck units, these are called rationalized Planck units and are seen in high-energy physics.