Well, it turns out that Einstein and Kaluza and many others worked on trying to refine this framework and apply it to the physics of the universe as was understood at the time, and, in detail, it didn't work.
Bueno, resulta que Einstein, Kaluza y muchos otros trabajaron para tratar de refinar este esquema y aplicarlo a la física del universo tal y como se entendía en ese tiempo, y no funcionó.