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The Antikythera Mechanism I

With Java animations by Bill Casselman

Java-animation of The Sun-Moon Assembly

This java animation shows the operation of the Sun-Moon assembly, that part of the gearing of the Antikythera Mechanism marked in color on page 3. The linkage between the (yellow) sun gear and the (white) moon gear, determined by the number of teeth in each gear in the assembly, makes the moon gear turn 254/19 times as fast as the sun. This is an excellent approximation of the actual ratio of their apparent speeds around the zodiac. In this animation, each step corresponds to about 7 hours of real time. It is not known what tokens were used in the Antikythera Mechanism to represent the sun and the moon on the dials, nor how they were attached to their gears. In this simulation the sun is represented by a yellow disc, the moon by a white. The moon's motion follows the position of the moon gear exactly. The sun moves just like the sun gear, but in the opposite directon. In the original this was accomplished by linking a second sun gear to the first by a vertical, cylindrical gear.

Back to 2. The Sun-Moon Assembly