The moment of inertia depends on the mass distribution in relation to the axis of rotation. The further away a mass element is from the axis of rotation, the more it contributes to the moment of inertia; the distance enters quadratically. If the density of the body increases toward the axis of rotation, its moment of inertia is smaller than if its mass were homogeneously distributed in the same volume. Therefore, for rapidly rotating planets, the flattening can be used to infer the density gradient. Examples, high wire artists with balancing rods In tightrope walking, long poles are preferably used as balancing aids. Compared to a compact body of the same weight, such as a sandbag, such a pole has a very large moment of inertia. Tipping to the side is not prevented, but slowed down so that the performer has enough time for a balancing movement. Rolf