I’ve been reading an amazing book, a little bit every night in bed:
• Edmund Whittaker, A History of the Theories of Aether and Electricity, Two Volumes Bound As One. Volume I: The Classical Theories. Vol. II: The Modern Theories, 1900-1926. Dover, 1989, 753 pages.
How in the world did our species figure out the laws governing the electric field, magnetic field, and charged particles? A lot started with pure luck. Two unusual stones played a key role: amber and lodestone.
The first, really fossilized tree sap, easily acquires an electric charge if you rub it against wool or silk. This was one of human’s introductions to the electric field, and electrons. Indeed, the ancient Greek word for amber was ēlektron. The second, called magnetite, is naturally magnetic.
How odd that of all the minerals in nature, there were two with peculiar abilities to attract and repel! This duality foreshadowed the duality between electric and magnetic fields, now understood mathematically using the Hodge star operator. Who could have guessed that a pair of stones would eventually lead to such deep discoveries?
Isaac Newton caught a glimpse of it. In the early 1700s he commented about both amber and lodestones in the third book of his Opticks, called simply The Queries. He was imagining challenging someone skeptical of the existence of aether:
Let him also tell me, how an electrick Body can by Friction emit an Exhalation so rare and subtile, and yet so potent, as by its Emission to cause no sensible Diminution of the weight of the electrick Body, and to be expanded through a Sphere, whose Diameter is above two Feet, and yet to be able to agitate and carry up Leaf Copper, or Leaf Gold, at the distance of above a Foot from the electrick Body? And how the Effluvia of a Magnet can be so rare and subtile, as to pass through a Plate of Glass without any Resistance or Diminution of their Force, and yet so potent as to turn a magnetick Needle beyond the Glass?
While these are brilliant questions, he and some later thinkers had to struggle for a long time to sort out the relation between what we’d later call electrons and the electric field. It’s easy to see why, since they’re so intimately related.
As it turns out, electrons are not emitted but absorbed by amber when it rubs against wool. Later there were long arguments about whether there were two kinds of ‘electrical fluid’, positively and negatively charged, or just one. But maybe the ‘exhalation’ he mentions is really the electric field, just as the ‘effluvia’ of a magnet are the magnetic field.
There is a lot more to say about all this, but I think I’ll do it in short bits, to avoid writing a 753-page tome like Whittaker’s.