As is well known, Earth is not a perfect sphere. Because of its rotation, the centrifugal effect makes it bulge slightly at the equator and slightly squashed at the poles, to produce what we refer to as an ‘oblate spheroid’. However, the centrifugal effect also applies to a body on the Earth’s surface as it rotates about Earth’s rotation axis. This force appears to modify the effect of pure gravity and tends to reduce slightly the quantity we call ‘weight’. Click here to access the article: A_Subtlety_of_Earths_Gravity

This article provides an elementary introduction to the effect of oblateness and the centrifugal force on Earth’s gravity for non-Earth scientists, students and other interested readers. Software written in the R language is provided for those who wish to reproduce the calculations and graphs presented here: Gravity_R_Code