Angel "Java" Lopez en Blog

Publicado el 19 de Agosto, 2015, 7:41

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Comienza el tema del desarrollo de la mecánica cuántica:

Let us pass on to consider the development of quantum mechanics. This started with a brilliant idea of Heisenberg. Heisenberg's idea was that one should try to construct a theory in terms of quantities which are provided by experiment, rather than building it up, as people had done previously, from an atomic model with involved many quantities which could not be observed. By this brilliant idea Heisenberg really started a new philosophy, a philosophy that physics - physical theory - should keep close to the experimentally obtained data and should not depart into the use of quantities which are only very remotely connected with observation.

Dirac comienza por MECANICA cuántica, mas que por la teoría cuántica antigua, que llevaba un cuarto de siglo desarrollándose cuando en 1925 Heisenberg publica las ideas mencionadas arriba. Estoy escribiendo del tema en: Entendiendo a Heisenberg. Es un tema fascinante, por un lado toda la historia que lo precede, los distintos caminos tomados en la actividad científica, los modelos propuestos, los actores que intervienen, y por otro, sencillamente entender el "paper" de Heisenberg, que pega varios "saltos mágicos" en su razonamiento. El tema de la nueva "filosofía" es para discutir, pero es interesante. Heisenberg siempre insistió en eso, pero no es evidente que la física tenga que avanzar de esa manera. Conceptos como posición no fueron abandonados, sino refinados en la nueva teoría.

This was a wonderful idea of Heisenberg's and, in putting together the various experimentally provided data concerned with atomic spectra, he was led to matrices, and then was led to consider that matrices represent the physical variables ocuyrring in an atom, physical variables like the positions and velocities of the electrons. Heisenberg had not proceeded very far with this idea before he notices that it would lead to his physical quantities not satisfying the commutative law of multiplication. Two such quantities A and B would usually be such that A multiplied by B is different from B multiplied by A.

Este punto es el que destaca Dirac, y con razón: la no conmutabilidad de algunas expresiones relacionadas con las variables físicas. Para Heisenberg, las variables dejaron de ser simples números y comienzan a ser matrices. Su multiplicación es multiplicación de matricas, que no es conmutativa. Curiosamente, Heisenberg no conocía lo que era una matriz en matemática.

Now when Heisenberg noticed that he was really scared. It was such a foreign idea. Physicists from the earliest times had always thought of the variables that they were using as quantities satisfying the ordinary laws of algebra. It was wuit inconceivable that two physical things when multiplied in one order should not give the same result as when multiplied in the other order. It was thus most disturbing to Heisenberg. He was afraid this was a fundamental blemish in his theory and that probably the whole beautiful idea would have to be given up.

Pero Heisenberg siguió adelante. Ese fue su mérito. En el próximo post veremos cómo Dirac recibe y evalúa el trabajo de Heisenberg en tiempos tempranos.

Nos leemos!

Angel "Java" Lopez
http://www.ajlopez.com
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Por ajlopez, en: Ciencia