Kaluza -Klein Theory
* In 1919, Theodor Kaluza unified Maxwell's Electromagnetism and Einstein's Theory of General Relativity & Gravity by adding a fifth dimension. The idea came from Hermann Minkowski who had successfully used the fourth dimension to solve the "space-time continuum." In 1921, Kaluza published his theory, with Albert Einstein's encouragement.
Kaluza's Theory became the framework for Einstein's Theory on General Relativity.
* In 1926, Oskar Klein applied Kaluza's Theory to quantum theory, which is used in modern string theory. Over the past seventy years, scientists have had a difficulty correlating the Kaluza-Klein Theory to physical reality. They have modified the assumptions, evaluated compactified, and used extra dimensions. The String & Super String Theories, which have resulted, do not giving acceptable solutions to the physical world.
* In 1998, Overduin & Wesson successfully demonstrated that the fifth dimension would solve the Space-Time-Matter Continuum by eliminated the cylindrical assumption from Kaluza-Klein Theory. In Wesson's book, "Space-Time-Matter, Modern Kaluza-Klein Theory," there are numerous examples that correlate Modern Kaluza-Klein Theory to the physical reality including general relativity and elementary particle physics.