Magnetism

The effects of magnetism, or, to be more precise, electromagnetism, have been known for a long time. In both early Chinese and early Greek civilisations it was known that pieces of certain materials, when allowed to hang freely, always pointed in a certain direction; the fact was used as an aid to the navigation of ships. Electricity and magnetism are in fact related, magnetism being caused by the movement of electric charge (as we shall discuss shortly) but the connection between the two was not suggested before the seventeeenth century and was not completely verified until the twentieth century.