De Magnete

A highly influential and successful book, it exerted an immediate influence on many contemporary writers, including Francis Godwin and Mark Ridley.

Gilbert made the claim that gravity was due to the same force and he believed that this held the Moon in orbit around the Earth.

Amber is called elektron in Greek, and electrum in Latin, so Gilbert decided to refer to the phenomenon by the adjective electricus.

An amber stick when rubbed affects a rotating needle made of any type of metal (a versorium) and attracts paper, leaves and even water.

He shows the effects of cutting a spherical lodestone (which he calls a terrella) through the poles and equator and the direction of attraction at different points.

Heraclides and others held that the Earth rotates from west to east and this is supported by Copernicus (the "restorer of astronomy"), but Aristotle said otherwise.

"If the rotations of the earth seems headlong and not to be permitted by nature because of its rapidity, then worse than insane, both as regards itself and the whole universe is the motion of the primum mobile."

He states that "the cause of the diurnal motion are to be found in the magnetic energy and the alliance of bodies" but offers no further guidance.

He also argues for the extreme variability of the distance to the various heavenly bodies and states that situated "in thinnest aether, or in the most subtle fifth essence, or in vacuity – how shall the stars keep their places in the mighty swirl of these enormous spheres composed of a substance of which no one knows aught?".