Note from the Editor: A version of this article was originally featured in CNN's Wonder Theory science newsletter. Want it delivered straight to your inbox? Subscribe for free here. Deep within our planet, an enduring enigma continues to intrigue scientists: Earth’s inner core. Comprised primarily of iron and nickel, this intensely hot, solid sphere is roughly 70% the size of our moon. A recent study suggested that the core has reversed its rotation, and now, researchers have discovered