Nature and Destiny of the Moon (1 May 1841)

[1.1] Now, as far as the moon is concerned, it is a solid world-body, even more than your earth, and is in a certain way a child of the earth, i.e. it is formed from the constituent parts of the earth.

[1.2] It is attached to the earth so that it catches the magnetic force flowing out from the earth and then returns it to the earth as needed, for which reason it's course around the earth is also just as extensive; for this always depends on the greater or lesser quantity of the magnetic presence on the earth; and on the contrary, however, also the course of the moon, as a carrier of this substance, depends on the possible need of the earth for this natural life-substance. This is the main function of the moon.

[1.3] If a planet is smaller than the earth, it does not need a moon, and the place of the moon is taken by very high mountains, which is the case, for example, with Venus, Mercury and Mars and some other much smaller planets; but what the larger planets are, they must be provided with one or also several moons in order to render the already known service to their planet.