Around 1025 the Persian polymath Abu Rayhan al-Biruni, working in Ghazni in modern Afghanistan and in India, devised a method to calculate the radius of the Earth that, unlike the method of Eratosthenes, did not require walking over long distances. He measured the height of a mountain at Nandana, in the Punjab, and the angle of dip of the horizon from its summit, and used trigonometry to obtain a radius of about 6,340 kilometres, within 1 per cent of the modern value of 6,371. He wrote more than 100 books on astronomy, geography, mathematics, pharmacology and the customs of India, and studied the question of whether the Earth rotates on its axis.
Before and after
- 1020Construction of Wawel Cathedral
- 1021Ibn al-Haytham completes the Book of Optics
- 1021Vikings are at L'Anse aux Meadows in Newfoundland
- 1024The Song dynasty issues the first government paper money
- c. 1020sAl-Biruni measures the size of the Earth
- 1025Avicenna completes the Canon of Medicine
- 8 November 1028Birth of William the Conqueror
- 1031Construction of Krak des Chevaliers
- from 1035 to 1707Kingdom of Aragon
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The era
This moment belongs to the Medieval world (500 CE to 1500 CE), kingdoms, faiths and trade routes. You can also browse everything in the 11th century.