Electromagnetic radiation—observed and imagined

Abstract In Chapter 2 it was shown that electromagnetic fields can be propagated through space at the speed of light and that the field in this dynamic form is known as electromagnetic radiation. The identification of electromagnetic radiation with light, combined with the direct observation of radio waves and the measurement of the velocity of these waves by Hertz (Heinrich Rudolf Hertz, 1857–94), generated some serious conceptual problems. The speed at which the light was moving would be expected to depend on the relative movement of the source and the observer.