Final answer:
The 127 gear on the Antikythera Mechanism tracks the celestial equator.
Step-by-step explanation:
The significance of the 127 gear on the Antikythera Mechanism is that it tracks the celestial equator. The celestial equator is an imaginary circle on the celestial sphere directly above the Earth's equator. It is a reference point for measuring the declination (angular distance north or south) of celestial objects. By tracking the celestial equator, the 127 gear on the Antikythera Mechanism helps determine the positions of stars and other celestial objects in the sky.