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Kaluza’s theory this fifth dimension was introduced only in order to obtain new components of the metric tensor representing the electromagnetic field. [Our emphasis. ] If Kaluza’s attempt is a real step forward, then it is because of the introduction of the five dimensional space. There have been many attempts to retain the essential formal results obtained by Kaluza without sacrificing the four dimensional character of the physical space. This shows distinctly how vividly our physical intuition resists the introduction of the fifth dimension. But by considering and comparing all these attempts one must come to the conclusion that all these endeavors did not improve the situation. It seems impossible to formulate Kaluza’s idea in a simple way without introducing the fifth dimension. We have, therefore, to take the fifth dimension seriously although we are not encouraged to do so by plain experience. If, therefore, the space structure seems to force acceptance of the five dimensional space theory upon us we must ask whether it is sensible to assume the rigorous reducibility to four dimensional space. We believe that the answer should be “no”, provided that it is possible to understand, in another way, the quasi-four dimensional character of the physical space by taking as a basis the five dimensional continuum and to simplify hereby the basic geometrical assumptions.[...] The most essential point of our theory is the replacing of ...rigorous cylindricity by the assumption that space is closed (or periodic).[...] Kaluza’s five dimensional theory of the physical space provides a unitary representation of gravitation and electromagnetism. [...] It is much more satisfactory to introduce the fifth dimension not only formally, but to assign to it some physical meaning. [Einstein, A, Bergmann, P., Annals of Mathematics, Vol. 38, No. 3, July 1938. Emphases, ours.] Notice particularly Einstein’s remark about the assumption that space is “periodic”. We believe that Einstein was following a path that was later to prove very fruitful even if, shortly after, Einstein publicly repudiated this idea. When Einstein describes space as “periodic”, he have physical meaning seriously. Physics has stagnated in the period since Einstein made such a daring proposal. Might one of the reasons lie in our refusal to take such “outlandish” ideas as serious hypotheses for further research? The universe has already shown itself to be much more “unbelievable” than scientists working prior to Einstein and Dirac might ever have imagined. If we continue to draw the line a priori over 387 High Strangeness — Part Four Einstein was somewhat nervous about this idea, but he followed it anyway, writing in his paper: means that it loops back upon itself. We think that we should take the idea these mathematical formalisms