Orrery, 1910-1920.

UNITED STATES - NOVEMBER 26: This planetary model was made by Laing Planetarium Company in Detroit, Michigan, United States. Called an orrery, or more correctly a tellurium, it is a demonstration model to show the motions of the Earth and Moon around the Sun. Such devices became popular during the 17th century, especially after Sir Isaac Newton (1642-1727) published his universal theory of gravity in 1687. To reproduce the motions of the solar system, this model uses hand driven pulleys with cords on a wooden pedestal stand. This type of model would have been commonly employed in schools or colleges to teach astronomy. (Photo by SSPL/Getty Images)