Cross section of the varying layers of the Earth . (Yuri Arcurs via Getty images)
When especially interesting new planets are discovered in the cosmos, scientists around the world begin the process of identifying their characteristics — their orbit, their mass and density, their composition, their thermal properties and much more. It’s all part of a drive that seems to be innate in humans to learn about the workings of the world (or worlds) around us.
This began millennia ago when our distant ancestors started to learn about the make-up and processes of Earth. We now know enormous amounts about our planet, but I was recently introduced to a domain where our knowledge has some substantial holes. The area of the Earth least well understood is, not surprisingly, what lies deep below us, in the mantle — the inner 2,900 kilometers (2000 miles) of the planet between the outer crust and the iron core.
The on-going exploration of this vast region — made up substances including some which cannot remain intact on the Earth’s surface — struck me as in some ways comparable to the study of exoplanets. It’s also a realm where scientific observation is limited, but what knowledge ...