The moons of Jupiter. 17th century diagram showing how the changes in the observed positions of the moons of Jupiter could be explained by their relative orbits. The diagram includes times during which each moon might be eclipsed by Jupiter (shadow toward upper left). The diagram was published just four years after the moons of Jupiter were first observed by Galileo. This woodcut illustration comes from Disquisitiones mathematicae by Christoph Scheiner, published at Ingolstadt in 1614.