Inge Lehmann discovered that the Earth’s inner core is solid surrounded by a molten outer core. Her interest in parts of the Earth started when she would read cardboard cards with information regarding earthquakes in different parts of the world. She studied shock waves and theorized that waves travelled a distance into the central core and bounded off a boundary. Her findings were later confirmed in the 1970s’ with a seismograph that interpreted waves bouncing off of the solid inner core. In 1971, she was honored with the William Bowie Medal — the highest distinction of the American Geophysical Union. She lived to be 105 years old.