The Earth has a crust, a mantle, and a core

What actually happened

Nobody has been anywhere near any of this. The deepest hole ever drilled, the Kola Superdeep Borehole, reached about 12.2 kilometers, which is roughly one third of the way through continental crust and nothing at all on the scale of a 6,371 kilometer radius. Everything we know about the interior comes from seismic waves, which change speed and direction at boundaries and effectively let earthquakes X-ray the planet.

The innermost inner core was found by Thanh-Son Phạm and Hrvoje Tkalčić at the Australian National University, using waves that bounce back and forth across the entire planet up to five times. Anisotropy, the direction-dependence of wave speed, differs in the innermost region, suggesting iron crystals aligned along a different axis. That likely records a change in how the core was solidifying, meaning it is a fossil of an event deep in Earth's history.

The layers were never as tidy as the diagram anyway. The mantle has its own divisions and a transition zone, the lithosphere cuts across the crust-mantle boundary, and slabs of subducted plate sink far into it. The 2023 result is a refinement rather than a reversal, but it means the cutaway you memorized is missing a layer.