 Forty-two years after young proved that light traveled as a wave, the French physicist Hippolyte Frizzou measured the speed of light to be just under 300,000 km per second. That's 186,000 miles per second. We cover how he did it in the Speed of Light chapter in the How Fast is a video book. Over that period and into the 1860s. People like Michael Faraday, Andre Ampere and James Maxwell and others were studying electric and magnetic fields. Because waves were known to need a medium to propagate through, like water waves, it was assumed that all space was filled with a massless substance that was given the name ether. Then in the mid-1800s Maxwell proposed that the existence of an electric charge filled empty space with an electric field. Here's a NASA picture of small threads suspended in an oil aligned with the electric field of a charge. Accelerating the charge causes the electric field to change. Furthermore, he showed that a changing electric field created a magnetic field. And a changing magnetic field created an electric field. So the accelerated electron creates a disturbance in the electric field that propagates itself through space as an electromagnetic wave. Earlier Faraday had measured the resistance of empty space to the forming of an electric field called permittivity. And Ampere had measured the resistance of empty space to the forming of a magnetic field called permeability. In 1864, using their numbers, Maxwell calculated the speed of his waves. He found that his velocity was in agreement with the Zeus for light. He had demonstrated that light is indeed an electromagnetic wave. The idea of an ether filling otherwise empty space was rendered unneeded for light propagation once electromagnetic radiation was understood. So it faded from our vocabulary, replaced by the idea that empty space supported magnetic and electric fields and light represented a disturbance in the electric field. The exact characteristics of so-called empty space will be a recurring subject for us as we approach our segment on the Higgs boson. Here's a simple wave. It has a repeating cycle, a wavelength, and a frequency in cycles per second. Here we see the full electromagnetic spectrum with visible light in the middle. Radiation with longer wavelengths and smaller frequencies than red light is called infrared. Radiation with longer wavelengths than infrared are called microwaves, and still longer wavelengths are called radio waves. Moving up the energy scale, radiation with shorter wavelengths than violet light is called ultraviolet. Still shorter wavelengths are called x-rays, and the maximum energy radiation is called gamma rays.