This is a fairly simple one and rests on the principal that if you have a globe that is heavier on one side than the other, the globe will tend to fall with the heavy side down, kind of like a slice of bread that has been buttered. The buttered side is heavier and always ends up being the side that lands on the floor. The proof follows. If you place some dirt in water, most of the dirt sinks to the bottom of the water. By and large then, dirt is heavier than water.
Land is made up of dirt.
If you look at a map of the world, you will notice that there is more land to the north of the equator. There is, therefore, more dirt north of the equator. That area is therefore heavier than the south side, it falls to the bottom and therefore Australia is on the top, Europe on the bottom. The Related Gravitational Proof Related to the proof immediately above is the related gravitational proof. In this case, we replace dirt with people.