Studying seismograms of earthquakes in New Zealand, the Danish seismologist Inge Lehmann noticed seismic waves arriving where none should be if the Earth's core were a single liquid ball. In 1936 she concluded that there is a solid inner core inside the liquid outer core, with a radius of about 1,200 km. Her paper, only a few pages long and titled simply 'P prime', was confirmed in the 1970s by computer analysis. The inner core, mostly iron and nickel, is about as hot as the surface of the Sun.
Before and after
- 1936Great Purge
- 1936Construction of Fallingwater
- 1936Origins of American Hockey League
- 1936Establishment of Jim Corbett National Park
- 1936Inge Lehmann discovers the Earth's inner core
- 1936Alan Turing defines the universal machine
- 28 January 1936Birth of Ismail Kadare
- 27 February 1936Death of Ivan Pavlov
- 4 March 1936First flight of LZ 129 Hindenburg
More in Science & technology
- 2 November 1920KDKA begins the first commercial radio broadcasts
- 1931Kurt Godel proves his incompleteness theorems
- 1933Karl Jansky detects radio waves from the Milky Way
- 1 February 1942Launch of Voice of America
- October 1943Streptomycin, the first antibiotic that works against tuberculosis, is discovered
- 1944Avery, MacLeod and McCarty show that DNA carries genes
The era
This moment belongs to the Modern era (1914 CE to 1945 CE), world wars and a changing world. You can also browse everything in the 20th century.