The fifth dimension: Theodor Kaluza's ground-breaking idea



Theodor Kaluza (1885–1954) attracted the attention of the physical community since 1921 with his unified field theory of gravitation and electromagnetism in five dimensions. Despite Einstein's great interest in Kaluza's theory, 50 years elapsed before it contributed toward a paradigm shift in modern theoretical physics. The biography of this still unknown scientist is briefly presented along with an outline of his work in physics. A short history of the theories of unification and the dimensionality of space-time is followed by a discussion of the significance of Kaluza's five-dimensional unified theory in modern physics from the point of view of superstring and M-theory.