Ulug Beg: the astronomer king

Religion disperses like a fog, kingdoms perish, but the works of scholars remain for an eternity.
Ulug Beg

Not content with their earthly domains, kings have often looked to the stars for confirmation of their divine right to rule, and indications of what the future might bring.Their patronage and personal interest in astronomy have driven forward our understanding of not only our own solar system but also the planets beyond.

Astronomy had been a royal pursuit for thousands of years: the ancient Egyptians aligned their pyramids to the stars and were able to accurately predict the flooding of the Nile by sightings of Sirius and the summer solstice, whilst the Babylonians were producing star catalogues as long ago as 1200 bc. It would be the medieval Emperor Ulug Beg (1394-1449) who would take astronomy into the modern age, however, building a vast observatory and producing the most detailed star catalogue before that of Tycho Brahe. Ulug Beg was born in Samarkand in 1394 and was the grandson of Amir Timur. He lacked the political skills of his predecessors but instead focused on turning his capital into an intellectual centre for scholars from across the Islamic world. Having travelled to both India and the Middle East as a child, he was well aware of scientific developments in both those regions, and was determined to build upon them in Samarkand. The young Ulug Beg constructed a huge madrassa on the Registan square and invited numerous astronomers and mathematicians to study there.

Although Ulug Beg was himself a fine mathematician, his real interest lay in astronomy.The observatory he built, the Gurkhani Zij, contained a sextant 11 m long and with a radius of 40.4m. It was the largest such instrument in the world and had to be kept underground to protect it from earthquakes. Long before the invention of the telescope, this instrument enabled Ulug Beg to accurately position over 1,000 stars, determine the year with such accuracy that it would even surpass Copernicus' calculations, and to work out the exact tilt of the earth's axis.

Given that Ulug Beg and his astronomers were working without optics, the accuracy of their calculations is unnerving. Even today we do not have a more accurate calculation of the earth's axial tilt than Ulug Beg's 23.52°, and his assertion that the year is 365 days, six hours, ten minutes and eight seconds in length is only one minute longer than modern electronic calculations.

Had Ulug Beg and his astronomers had more time to study the stars, they may yet have been more impressive, but fate was to intervene: the observatory was destroyed by religious fanatics in 1449 and would lie forgotten underground until it was rediscovered by an archaeologist in 1908. Ulug Beg himself hardly met a more glamorous fate: he was beheaded by his own son en route to Mecca and his remains were interred in Timur's tomb.