https://motherboard.vice.com/en_us/article/mbya58/antarctic-neutrinos-are-being-used-to-weigh-the-earths-core

Although some people argue that our oceans are the least-understood regions of our planet, there may be a better contender for that title: the core of the earth. But that may be about to change.

Scientists from the University of València in Spain have figured out to use neutrino particle data—the smallest, most abundant particle in the universe—from Antarctica’s “IceCube” observatory at the South Pole in to order to calculate the mass of the Earth, the mass of the earth’s core, prove that the core is denser than the mantle, and determine earth’s moment of inertia (oppositional force during rotation). They published their results in Nature this week.