PDF File The Special Theory of Relativity. 1 Introduction: What is Relativity? Until the end of the 19th century it was believed that Newton’s three Laws of Motion and the associated ideas about the properties of space and time provided a basis on which the motion of matter could be completely understood. However, the formulation by Maxwell of a unified theory of electromagnetism disrupted this comfortable state of affairs – the theory was extraordinarily successful, yet at a fundamental level it seemed to be inconsistent with certain aspects of the Newtonian ideas of space and time. Ultimately, a radical modification of these latter concepts, and consequently of Newton’s equations themselves, was found to be necessary.