Why the Earth has a liquid core

Under the tremendous pressure and at the incredible temperatures of the Earth’s deep interior, there’s a thick layer of liquid: our outer core. But why is it so?

“If you ever drop your keys into a river of molten lava, let ‘em go, because, man, they’re gone.” -Jack Handey

Take a look at our home planet, Earth, and one of the things you’ll notice is that over 70% of the surface is coated in water.

Image credit: NASA / Johnson Space Center / Apollo 17 mission.

We all know why this is, of course: it’s because the Earth’s oceans float atop the rocks and dirt that make up what we know as land.

This concept of flotation and buoyancy — where the less dense objects rise above the denser ones, which sink to the bottom — does much more than just explain the oceans.

Image credit: IceDream Project Director, Dassault Systemes, via http://www.workingknowledge.com/blog/innovation-in-3d-ice-dream-dscc11/.

This same principle explains why ice floats on water, why a helium balloon rises through the atmosphere or why stones sink to the bottom of a lake, the last…