Early Astronomy in the University of Michigan Collections

Dialogo: Woodcut

Using this woodcut, Galileo offers an incredibly straightforward explanation of the heliocentric system. The large circle represents the orbis magnus, drawn on the plane of the ecliptic, which in turn is divided into four equal parts by two diameters, Capricorn-Cancer and Libra-Aries: they represent the four cardinal points, that is, the two solstices and the two equinoxes. In the center of the large circle is the Sun. Around each of the four points are drawn four circles representing the location of the Earth at different times, indicating that the Earth will travel from west to east across the entire circle, that is, through Capricorn, Cancer, Libra, and Aries, for a full year. Thus, for instance, while the Earth is on Capricorn, the Sun will rise on Cancer.



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