The Shape of the Earth (and What it has Inside)

The Earth is not a perfect sphere. It is, in fact, an oblate spheroid - a sphere with a bulge around the equator. It is estimated to consist of 32.1% iron , 30% oxygen, 15.1% silicon. Oxygen is present in the atmosphere but also in rocks in the form of oxides. It is useful to ponder related questions. For example, what is the radius of the earth? It is 6,378 km.