History
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The decisions, accidents and people that shaped now.
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How Eratosthenes measured the whole Earth with a stick and a shadow
Around 240 BC, Eratosthenes, head of the Library of Alexandria, measured the size of the whole Earth with a stick and a shadow. At noon on midsummer, sticks in…
How sailors found longitude before satellites: a race against the clock
Latitude is easy: measure the height of the Sun or the Pole Star. Longitude is hard, because the Earth turns one degree every four minutes. To know how far…