We have walked on the moon and peered into the deep past of the universe, yet over 99% of our own planet remains unexplored. In this documentary, Naked Science journeys 4,000 miles down to the Earth’s core—a place as hot as the surface of the sun and under enough pressure to implode a human head instantly. We examine the “Geodynamo” that creates our magnetic field and ask: Is the Earth’s engine dying?