The faster growth under Indonesia's Banda Sea hasn't left the core lopsided. Gravity evenly distributes the new growth—iron crystals that form as the molten iron cools—to maintain a spherical inner core that grows in radius by an average of 1 millimeter per year. But the enhanced growth on one side suggests that something in Earth's outer core or mantle under Indonesia is removing heat from the inner core at a faster rate than on the opposite side, under Brazil. Quicker cooling on one side would accelerate iron crystallization and inner core growth on that side. This has implications for Earth's...