Luego de presentar los trabajos de Heisenberg y Schrodinger, como ejemplos de dos métodos distintos aplicados al mismo problema físico, Dirac nos recuerda la gran influencia de la relatividad en aquellos tiempos (la tercera década del siglo XX):
In order to understand the atmosphere in which theoretical physicists were then working, one must appreciate the enormous influence of relativity. Relativity had burst into the world of scientific thought with a tremendous impact, at the end of a long and difficult war. Everyone wanted to get away from the strain of war and eagerly seized on the new mode of thought and new philosophy. The excitement was quite unprecedented in the history of science.
Against this background of excitement, physicists were trying to understand the mystery of the stability of atoms. Schrodinger, like everyone else, was caught up by the new ideas, and so he tried to set up a quantum mechanics within the framework of relativity. Everything had to be expressed in terms of vectors and tensors in space-time. This was unfortunate, as the time was not ripe for a relativistic quantum mechanics, and Schrodinger's discovery was delayed in consequence.
Ciertamente, Schrodinger podría haber llegado antes a sus resultados si relajaba la cuestión relativista.
Schrodinger was working from a beautiful idea of de Broglie connecting waves and particles in a relativistic way. De Broglie's idea applied only to free particles, and Schrodinger tried to generalize it to an electron bound in an atom. Eventually he succeeded, keeping within the relativistic framework. But when he applied his theory to the hydrogen atom, he found it did not agree with experiment. The discrepancy was due to his not having taken the spin of the electron into account. It was not then known. Schrodinger subsequently noticed that his theory was correct in the nonrelativistic approximation, and he had to reconcile himself to publishing this degraded version of his work, which he did after some month's delay.
The moral of this story is that one should not try to accomplish too much in one go. One should separate the difficulties in physics one from another as far as possible, and then dispose of them one by one.
Sería principalmente Dirac el que agregaría de forma adecuada el marco relativista a la nueva mecánica cuántica. Desde sus años de estudiante, Dirac siempre trataba de generalizar teorías para que fueran compatibles con la relatividad especial de Einstein, y de paso, dando cuenta del spin del electrón (la historia del spin vale varios post aparte).
Angel "Java" Lopez