For a planetary surface to boast extensive areas of both land and water, a delicate balance must be struck between the volume of water it retains, and the depth and height of its valleys and mountains. With too much water, sea levels will be above the highest point on the planet. But if a planet doesn't have enough water, it will be quasi-desert.
The Earth has both continents and oceans. Is there any natural process that makes this situation probable, or were we just lucky?
ICCUB researcher Fergus Simpson has explained in a recent paper, noticed and commented on the prestigious US National Public Radio (NPR), why the Earth has a nearly equal coverage of land and water mass: it is a form of natural selection.
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