In an earlier chapter we have seen that charges create electric fields. In this chapter we have seen that moving charges, that is, currents, create magnetic fields and that changing magnetic fields produce electric fields. In the 1860s Scottish physicist James Clerk Maxwell (1831-1879) added a crucial additional connection: changing electric fields can produce magnetic fields.

With that idea Maxwell recognized that these relationships meant that electric and magnetic fields could move through space. The fields move through space as transverse waves that are perpendicular to each other. Maxwell calculated the speed and found that it was equal to the speed of light. He published his results in 1864 and a textbook on electromagnetism in 1873. In 1881 Oliver Heaviside wrote Maxwell’s famous four equations in the form they are used today.

In 1888 Heinrich Hertz (1857-1894) transmitted electromagnetic waves across his laboratory, confirming Maxwell’s theoretical work.