Decades of meticulous investigation have revealed many features of the 1st Century BC Antikythera Mechanism, a portable planetarium that demonstrated the motion of celestial objects. But we must question researchers’ conclusion that the Mechanism incorrectly represented the orbit of Mars, in particular, by roughly 30 degrees during retrograde motion1.
This discrepancy seems anomalous in a sophisticated device that otherwise exhibited a much smaller range of error. So maybe there is some other explanation.