I've been thinking about Earth. Typically we think of the Earth as being a perfect sphere as represented by those silly globes from grade school. In reality, due to concentrations of magma, mountains and deep sea trenches, the Earth is anything but a perfect sphere. Not only does this distort our concept of a perfectly spherical planet, but it also distorts the Earth's gravitational field, causing regional anomalies. Visualization helps. Here are a few images of the Earth's gravitational anomalies in relief: