Introduction: Classical Electrodynamics in Modern Times

Classical electrodynamics is still based on the same equations as in the late 19th century. In the meantime, however, their physical interpretation has changed substantially. Maxwell and his contemporaries did not doubt that all space was filled with a strange substance called ether. In his days, matter’s electrical and atomic structure was utterly unknown, just like quantum mechanics and relativity. This chapter will summarise some of the key discoveries of the 20th century that changed the interpretation of Maxwell’s equations. The resulting conjectures on electromagnetism will be stated at the end. They will form the basis for all the following chapters.