How many gears does it have?
The remaining fragments of the Antikythera Mechanism contain 30 gears. Most of these (27) are to be found in Fragment A. Fragments B, C and D contain one gear each. These gears are not sufficient for the mechanism to fulfil its known functions, and a further 5 gears are required. However, this scheme leaves a lone unused gear in Fragment D. This is probably part of the missing epicycle gearing that modeled Hipparchos’s solar model, and the planetary mechanisms. The total number of gears in the Mechanism depends upon how many planets the mechanism modelled, and how accurately their motions were modelled.