$$\require{cancel}$$
We describe these four equations in this chapter, and, in passing, we also mention Poisson's and Laplace's equations. We also show how Maxwell's equations predict the existence of electromagnetic waves that travel at a speed of $$3 \times 10^8\, \text{m} \,\text{s}^{-1}$$. This is the speed at which light is measured to move, and one of the most important bases of our belief that light is an electromagnetic wave.