December, 21

• Winter solstice (northern hemisphere) or summer (southern hemisphere)

• 1872 The HMS Challenger sets sail from Portsmouth for a 4-year scientific expedition that will lay the foundations of oceanography

• 1898 Marie and Pierre Curie discover the radio

• 1913 Arthur Wynne's "word-cross", the first crossword puzzle, is published in New York World

• 1923 Nepal passes from a British protectorate to an independent state

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