Concept
Theodor Franz Eduard Kaluza (kaˈluːt͡sa; 9 November 1885 – 19 January 1954) was a German mathematician and physicist known for the Kaluza–Klein theory, involving field equations in five-dimensional space-time. His idea that fundamental forces can be unified by introducing additional dimensions were reused much later for string theory. Kaluza was born to a Roman Catholic family from the town of Ratibor (present-day Racibórz in Poland) in the German Empire's Prussian Province of Silesia. Kaluza himself was born in Wilhelmsthal (a village that was incorporated into Oppeln (presently Opole) in 1899). He spent his youth in Königsberg, where his father, Maximilian "Max" Kaluza, was a professor of the English language. He entered the University of Königsberg to study mathematics and gained his doctorate with a thesis on Tschirnhaus transformations. Kaluza was primarily a mathematician but began studying relativity. In April 1919 Kaluza noticed that when he solved Albert Einstein's equations for general relativity using five dimensions, then Maxwellian equations for electromagnetism resulted spontaneously. Kaluza wrote to Einstein who, in turn, encouraged him to publish. Kaluza's theory was published in 1921 in a paper "Zum Unitätsproblem der Physik" with Einstein's support in Sitzungsberichte Preußische Akademie der Wissenschaften 966–972 (1921). Kaluza's insight is remembered as the Kaluza–Klein theory (named also after physicist Oskar Klein). However, the work was neglected for many years, as attention was directed towards quantum mechanics. His idea that fundamental forces can be explained by additional dimensions was not reused until string theory was developed. It is, however, also notable that many of the aspects of this body of work were already published in 1914 by Gunnar Nordström, but his work also went unnoticed and was not recognized when the ideas were reused. For the rest of his career Kaluza continued to produce ideas about relativity and about models of the atomic nucleus.
