A closer look
Until 1936, scientists thought the Earth was just a hollow shell of rock filled with a big, slushy magma center. Enter Inge Lehmann, a brilliant Danish seismologist who spent her days staring at the squiggly lines of earthquake shockwaves. She noticed that specific seismic waves were bouncing off something solid deep inside the Earth instead of passing straight through the liquid center. Through sheer mathematical stubbornness, she proved that our planet actually has a solid, super-dense iron-nickel heart spinning inside that liquid core. She fundamentally rewrote geophysics and lived to be 104, probably out of sheer spite.
