My older kids (now 24 and 16) learned in school that it is an oblate sphere. Both of them asked the teacher why then all of the pictures show them a round ball. The teacher's answer was something like "Everybody is so used to this image, it would confuse them to show an oblate sphere now". This was not only confusing but rather irritation for my kids.... even more so, because me and my husband had no satisfiying answers for them either - when we went to school it was still supposed to be a ball-round-sphere...