Volcanoes, water, and the shape of the Earth
Natural disasters, public-health epiphanies, and one Greek who measured the planet with a shadow.
5 questions. Pick an answer to see the explanation. Share your result at the end.
How far away was the 1883 Krakatoa explosion heard?
The fourth explosion of Krakatoa on 27 August 1883 was heard by the chief of police on Rodrigues island in the western Indian Ocean, 4,800 km away — over four hours after the eruption, on the opposite side of the Indian Ocean. It is the loudest sound in recorded human history.
In what year did Mount Tambora — the largest volcanic eruption in 1,300 years — erupt?
Tambora, on the Indonesian island of Sumbawa, erupted catastrophically on 10 April 1815. It killed roughly 71,000 people in the immediate region and cooled the Earth by about half a degree Celsius for two years — producing the Year Without a Summer in 1816. Krakatoa (1883) was about a quarter as powerful, despite being more famous.
Where was the pump that John Snow asked to have shut down during the 1854 London cholera outbreak?
The Broad Street pump — now Broadwick Street in Soho — was the contaminated water source Snow identified by mapping cholera deaths in September 1854. The Board of Guardians of St James's parish removed the pump handle on 8 September. The outbreak had already largely run its course, but the action prevented a second wave. The well was contaminated by a leaking cesspool three metres away.
What was the Antikythera mechanism designed to do?
The Antikythera mechanism — a bronze geared device recovered from a Roman shipwreck in 1900-1901 — was a hand-cranked analog computer for astronomy. Its 37 gears modelled the lunar orbit, predicted solar and lunar eclipses, tracked planetary positions, and included a 4-year Olympiad counter. It is roughly 1,500 years more sophisticated than the next known geared mechanism.
How accurate was Eratosthenes's measurement of the Earth's circumference around 240 BC?
Eratosthenes measured the angle of the noon sun at Alexandria on the summer solstice (about 7°12') and compared it with the well at Syene (where the sun was directly overhead). He calculated the Earth's circumference at 250,000 stadia. Using the Egyptian stadion of 157.5 m — which most scholars now believe is what he used — that's about 39,375 km, against the actual 40,008 km. Under 2% off.