- May 5 City-wide fire burns for over 100 hours in Hamburg, Germany
- May 8 Versailles to Paris train catches fire; 50 die
- May 14 Illustrated London News; the world's first illustrated weekly newspaper, begins publication
- May 22 Farmers Lester Howe and Henry Wetsel discover Howe Caverns in New York state when they stumble upon a large gaping hole in the ground
Doppler Effect
May 25 Christian Doppler presents his idea, now known as the Doppler Effect (through the changing colors of binary stars), to the Royal Bohemian Society, Prague
Assassination Attempt on Queen Victoria
May 30 John Francis attempts to assassinate Queen Victoria
Authors
Dictators
Explorers
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Queens
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