Modern Era
Hubble's Expanding Universe (1929): Galaxies Rushing Apart
Hubble's velocity-distance relation provided the key evidence that the universe is expanding, the foundation of Big Bang cosmology.
Era · c. 1800 – 1945
Modern Era
Industry, science and global conflict: the century and a half that built the modern world.
Modern Era
Wall Street Crash of 1929: Black Tuesday and the Global Slump
Share prices collapsed, wiping out tens of billions of dollars in paper wealth; the crash was followed by the Great Depression, though historians debate how far it caused it.
Modern Era
Great Depression in the United States (1929-1939)
Output fell by about a quarter and unemployment reached about 25 per cent by 1933; recovery began under the New Deal but was completed only with Second World War mobilisation.
Modern Era
Discovery of Pluto (1930): Clyde Tombaugh Finds Planet X
Pluto was discovered and counted as the ninth planet until the International Astronomical Union reclassified it as a dwarf planet in 2006.
Modern Era
Salt March (1930): Gandhi's Walk to Dandi Against British Rule
Gandhi broke the salt law at Dandi, launching a nationwide civil disobedience campaign that led to tens of thousands of arrests and the Gandhi-Irwin Pact of 1931.
Modern Era
Dust Bowl (1930s): Drought and Dust Storms on the Great Plains
Severe drought and wind erosion stripped topsoil from millions of acres, drove hundreds of thousands of people from the Plains and led to lasting federal soil conservation programmes.
Modern Era
Mukden Incident (1931): How Japan Seized Manchuria
Japan's Kwantung Army occupied Manchuria and created the puppet state of Manchukuo, and Japan left the League of Nations after being condemned.
Modern Era
Hawke's Bay Earthquake (1931): New Zealand's Deadliest Quake
The earthquake killed 256 people, destroyed central Napier and Hastings, raised about 40 square kilometres of seabed and led to Napier's Art Deco rebuilding.
Modern Era
1931 China Floods: The Yangtze and Huai River Catastrophe
Floods covered roughly 180,000 square kilometres, affected tens of millions of people and caused somewhere between about 150,000 and 2 million or more deaths from drowning, famine and disease.
Modern Era
Holodomor (1932-1933): The Great Famine in Soviet Ukraine
An estimated 3.5 to 5 million people died in Ukraine; the famine was concealed by the Soviet state and is now recognised by Ukraine and many other countries as genocide.
Modern Era
Bonus Army (1932): First World War Veterans March on Washington
Congress refused early payment and the army forcibly cleared the camps on 28 July 1932; the bonus was finally paid in 1936.
Modern Era
Chaco War (1932-1935): Bolivia and Paraguay's Desert War
Paraguay won and the 1938 peace settlement gave it most of the disputed Chaco Boreal; both countries suffered heavy losses and political upheaval.