 Contrary to his ATG, Whitehead’s AQT soon became obsolete. Experiments revealed that there are more elementary particles than electrons and protons. And, of course, the new quantum mechanics (of Schrödinger, Heisenberg, Dirac, Pauli, and many others) emerged. As Whitehead focused on philosophy when at Harvard, his knowledge of physics began to be out of date. His own theory, however, showed some similarities with the new quantum mechanics. Whitehead’s standing electromagnetic waves, in a sense, foreshadowed Schrödinger’s wave mechanics. And whereas the discovery of the quantum of action was the “physicist’s nightmare” (Whitehead 2021:93), Whitehead was happy with the increasing importance of the notion of ‘action’ in physics. Action is an activity through time, and hence confirms Whitehead’s idea that processes, and not instantaneous configurations of inactive masses, are fundamental in nature. Moreover, since there is a minimum quantum of action, Whitehead interpreted the equation, action equals the product of energy and period (which is a duration), by saying: “concentration of time increases energy” (2021: 93). This statement of Whitehead, in a sense, foreshadowed Heisenberg’s uncertainty principle with respect to energy and time, which was formulated two years later. As his AQT thus foreshadowed the new quantum mechanics in two respects, one wonders what he thought of this new theory when it emerged. Charles Hartshorne wrote that Whitehead definitely saw “Heisenberg’s famous article of 1927 on the Uncertainty Principle” (2010: 28). Hartshorne was sure about this, because it was he himself who showed it to Whitehead. But there is (as yet) no evidence that Whitehead seriously studied this paper in particular, or the new quantum mechanics in general.