By the early 1920s, the quantum pioneers had made great headway in understanding the microscopic universe. However, by the time physicists from far and wide converged on Goettingen for the Bohrfest, they had squeezed just about all they could from the quantum postulates they had developed. Their efforts to date had been brilliant, but had only produced a patchwork of solutions to the disparate problems.
Their work was still incomplete. There remained a plethora of mysteries, from the rules that governed the filling of electron shells to the bizarre dual personality of light. Try as they may, however, the breakthroughs had stopped coming. “Old” quantum physics, as the early works of Planck, Einstein, and Bohr is now known, ...