Light, Electricity, and Magnetism

Abstract

In the first two chapters, we reexamined such basic concepts as space and time from the very start, things that the philosopher Kant thought to be built into our brain to be able to grasp the world around us. Then how did Einstein get the idea for his theory of special relativity? There was a road map at hand, a blueprint of what was to be expected: That was, and still is, the theory of moving electrical charges, that is, electrodynamics. The reason is simple: While mass, time, and length change with speed relative to the observer, electrical charge is absolute, like the speed of light. We will demonstrate this at a simple example, a straight wire carrying an electric current. We will see why the magnetic field around this wire shows relativity in everyday life. This example was the starting point for the theory of special relativity.