Equator

The equator is the great circle farthest from the north-south spin axis of Earth. The equator is everywhere equidistant from the North and South poles on the surface of Earth, which is a sphere or a reference ellipsoid.

Although the equator is easy to define, it is not easily found and marked on Earth. The gravitational force is lower along the equator since it is the circle on the ellipsoid farthest from the center of mass of Earth. The equator marks the line above which the Coriolis force deflects movement toward the left of the direction of travel and below which the deflection is to the right. While these effects are real and influence weather patterns, ocean currents, and aircraft flight, they are so weak as ...