Michael Faraday studied the lines that iron filings formed by magnets and saw lines of force spreading across the universe.
He thought other forces, like gravity, electricity, and even light, all acted with these lines of force. He was right, but he could not work out the mathematical proof, or description, of his theory.
James Clerk Maxwell put together the model and the mathematical equations that proved Faraday’s theory.
First, Maxwell showed that magnetic fields and electric fields always exist together, so the field is really an electromagnetic field.
Maxwell’s model for this electromagnetic field that spreads out in all directions in the universe is complicated. It can best be described as a series of rotating cylinders separated by small spheres.
When one cylinder turns, the motion is transmitted through the spheres so that all the cylinders turn like a whirlpool. The field is a loop around the universe with no starting or ending point.
Maxwell’s equations are even more complicated, but they basically have to do with measurable electrical and magnetic quantities of mass, distance, and time.
He found that electric waves and magnetic waves travel because of the effects they have on each other. His equations also revealed that electromagnetic waves travel at the speed of light.
Maxwell concluded that light itself was electromagnetic radiation and he suggested that there were probably many other forms of electromagnetic radiation, that we cannot see.
The German physicist Heinrich Hertz discovered the first of these, radio waves, in 1888.
James Clerk Maxwell drew this diagram showing the lines of force of three different size objects. Maxwell’s theories were most often expressed in mathematical formulas that eventually related the three main fields of physics, electricity, magnetism and light, to one another.
When Albert Einstein drew his new picture of the universe in the twentieth century, he started with Maxwell’s model of electromagnetic fields.