Brian Clegg - Physics: A Crash Course

In Newtons day, physics was primarily concerned with forces and movement, with astronomy still pigeonholed in the Greek fashion under mathematics. However, as the discipline became more clearly established, not only would considerations of the universe come into the fold, but other natural phenomena became more clearly identified and added to the remit of physics. Both electricity and magnetism had been known since ancient times, but for many centuries they remained little more than a mystery. Magnets become increasingly useful in compasses, helped by the idea developed in the sixteenth century by English natural philosopher William Gilbert that the Earth itself was a huge magnet and it was this that made compass needles point in a particular direction. Gilbert constructed elegant little magnetic globes known as terrellae to investigate this. Meanwhile, by the eighteenth century, electricity had become an entertainment for the wealthy with displays such as the Flying Boy, where a youth was suspended from silk cords, charged up with static electricity, and used to pick up lightweight objects by electrostatic attraction and to produce sparks from his fingertips.

However, it would be the nineteenth century, as with so much else in science and technology, that saw electricity and magnetism come to the fore as a topic of physics. English scientist Michael Faraday, and other pioneers of the period such as the American Joseph Henry, produced a whole range of electrical and magnetic discoveries, leading to the development of the electric generator and motor. Their work made it clear that magnetism and electricity did not exist in isolation from each other. Moving magnets produced electricity, while electric currents could be used to create electromagnets.

The observed phenomena were pulled together by the Scottish physicist James Clerk Maxwell. He not only gave a mathematical basis for the combined field of electromagnetism, but also showed that electromagnetic waves should existand if they did, they would have to travel at the speed of light, establishing the origin of one of the key aspects of nature.