Here's why:

* Latitude lines are imaginary circles that run parallel to the equator. They measure distance north or south of the equator.

* The equator is the largest of these circles, situated at 0 degrees latitude. It divides the Earth into the Northern and Southern Hemispheres.

* The center of a circle is the point equidistant from all points on the circumference. Since all latitude lines are centered on the Earth's axis of rotation, the equator, being centered on that axis, is also the center of all latitude lines.

Therefore, the equator is considered the center of latitude.