Most people assume that the earth has a spherical shape. It is actually more of an ellipsoid shape, but not an exact ellipsoid, since there are numerous mountains and valleys. Researchers have found that a datum, or a reference ellipsoid, that is offset from the center of the earth can be used to accurately map different regions. According to one datum, called the Geodetic Reference System 1980, this reference ellipsoid assumes an equatorial radius of 6,378,137 m and a polar radius of 6,356,752.3141 m. The ellipsoid is rotated about the polar axis. Use the result of Exercise 26 to estimate the volume of the earth.