Astronomical Images : The Earth compared to a magnetic whirl

Johannes Kepler

Astronomical Images

<p style='text-align: justify;'>Johannes Kepler's <i>Epitome astronomiae copernicanae</i> was published in three successive parts from 1617 to 1621. Intended as a new astronomical textbook for students, the <i>Epitome</i> covered much of the material traditionally associated with the <i>Theoricae planetarum</i> and works on spherical astronomy. Despite its title, the <i>Epitome</i> does not draw its information directly from Copernicus' <i>De revolutionibus</i> but is an original synthesis, mainly based on Kepler's own earlier works. It thus presents a comprehensive survey of Kepler's new astronomy. The text is illustrated by an abundance of images, with some figures printed multiple times. This image demonstrates the physical causes of the Earth's motion. In attempting to explain the three movements of the Earth, as well as the reason that the orientation of the poles remains stable throughout its revolution, Kepler represents the Earth as a kind of spinning top. Its body is made of magnetic fibres, which are circular and centred around the Earth's axis. Through the action of 'solar magnetism', the Earth's '<i>species immateriata</i>' materialises and becomes a physical faculty through these magnetic fibres.</p>