An
equator is the intersection of a
sphere's surface with the
plane perpendicular to the sphere's
axis of rotation and midway between the poles. The
Equator usually refers to the
Earth's equator: an imaginary line on the Earth's surface equidistant from the
North Pole and
South Pole, dividing the Earth into the
Northern Hemisphere and
Southern Hemisphere. Other
planets and astronomical bodies have equators similarly defined. Earth's equator is about long; 78.7% is across water and 21.3% is over land.