
Unification is a successful concept in physics to disentangle the variety of natural phenomena. It is a surprising and encouraging fact, that our outside world can not only be described by a pilingup of observation results. Natural phenomena can be arranged in groups, which are based on the same action principle.
The trajectory of a thrown stone and the motions of planets were explained by one common principle: gravitation (Newton 1687 “Philosophiae Naturalis Principia Mathematica”). Electricity and magnetism were united by Maxwell to one equation system, which is the basis for the description of many phenomena: telegraphy, telephone, radio, televison, microwaves, infrared, light, UV and Xrays (Maxwell 1873 “A Treatise on Electricity and Magnetism”). Einstein succeded in a fusion of space and time as well as energy and mass with his special relativity theory, with his general relativity theory mass attraction and inertia force became the same phenomenon.
At the beginning of the 20th century another program of unification started: the unified field theory, first of all trying to unify gravity and electromagnetism. It was successfull in unifying the weak interaction with electromagnetism and resulted in the endeavour to include also the strong interaction (GUT).
In a restricted sense the Unified Filed Theory is the classical unification of gravity and electromagnetism, which was begun by Weyl, Nordström, Kaluza and Einstein. Wether is was successfull or failed, shall be investigated later on. Here we refer to its contents:
Th. Kaluza, “On the unity problem of physics”, meeting report of the Preussian Akademy of Science, phys.math. class, 966972 (1921)
“... the unmistakable formal correspondence in the construction of the gravitational and electromagnetic equations demands veritably ... to rouse oneself to come to the strongly strange decision to make use of a new, fifth world dimension.”
A.Einstein, “On Kaluza´s theory of the connection between gravitation and electromagnetism”, meeting report of the Preussian Akademy of Science, phys.math. class, 2330 (1927)
“Summarizing one can say that Kaluza´s idea in the frame of general relativity gives a rational foundation for Maxwell´s electromagnetic equations and combines them with the gravitiational equations to a formal whole.”
Before we go into a perhaps possible derivation of Maxwell´s equations from a five dimensional relativity principle and concern further consequences we first set up a hypothesis on the existence of a fifth physical dimension and prove it scientifically. 
