February 21, 1993, died #OTD, Danish seismologist Inge Lehman. Based on her research on seismic waves, she argued that the #Earth has a solid inner core & announced her discovery with the shortest title for a paper ever: P'-after a seismic discontinuity🌍

https://vox.com/2015/5/13/8595157/inge-lehmann?fbclid=IwAR2VWf_8C_Lk2qKSyBk2h-AtV7j7SBAXz2meiboFNrIyejkyGTfrQPfzbM8