Superficially at least the forces of electricity and magnetism seem to present the same kind of problem as gravitation. Experiment shows that two electrically charged bodies attract one another (or repel if their charges are of the same kind) with a force which conforms to the same mathematical law as the force of gravitation - both forces fall off inversely as the inverse square of the distance. The same is true of the magnetic force also; two magnetic poles attract or repel one another with a force which again follows the law of the inverse square of the distance.

The human race, whose intelligence dates back only a single tick of the astronomical clock, could hardly hope to understand so soon what it all means.

Gravitational force is simple, and a thing by itself, as also are electric and magnetic forces as long as the electric and magnetic poles stand at rest. But as…

The motion of the stars over our heads is as much an illusion as that of the cows, trees and churches that flash past the windows of our train.

Whence do you have it that the terrestrial globe is so heavy? For my part, either I do not know what heaviness is, or the terrestrial globe is neither heavy no…

if a shower of electrons is shot on to a zinc sulphide screen, a number of flashes are produced - one for each electron - and we may picture the electrons as b…

To every action there is always opposed an equal reaction; or, the mutual actions of two bodies upon each other are always equal, and directed to contrary part…