The discoverer of the Earth's inner core, Danish geophysicist Inge Lehman, was born on this day in 1888. After studying the shock waves from earthquakes recorded on seismographs, Lehman proposed that Earth has a smaller, solid inner core. She published this theory in 1936 under the title "P", for the three types of waves generated by Pacific temblors. Within a few years, work by others confirmed her hypothesis. Lehman later was the founder and first president of the European Seismological Federation.
[Source: Emily McMurray, Ed., Notable Twentieth Century Scientists (Gale Research Inc., ITP, 1995).]