The earth is not spherical. The diameter of the earth through the equator is more than the diameter through the poles, because of its angular velocity. See http

The earth is not spherical. The diameter of the earth through the equator is more than the diameter through the poles, because of its angular velocity. See http://en.wikipedia.org/wiki/Figure_of_the_Earth http://en.wikipedia.org/wiki/Figure_of_the_Earth