The Observatory of Ulugh Beg

Ulugh Beg built his revolutionary observatory in 1428, more than a hundred years before the birth of Galileo. In its prime, the observatory consisted of three great astronomical instruments contained within a three-story cylindrical building. The main instrument, the sextant, which remains mostly intact, is a monumental meridian arc, now called the Fakhri sextant. Its forty metre curving stone arch was once used by the astronomers of the time to measure the angle and elevation of bright celestial objects. With this instrument, Ulugh Beg and his fellow astronomers could determine the time of noon each day and the angle between the Earths rotational axis and the plane of its orbit around the sun.

The sextant worked by allowing light to pour in through a window and fall on a specific point on the arch that depended on the height of the object in the sky. In fact, the astronomers at the Ulugh Beg observatory were able to measure the length of a year to with in twenty-five seconds of its actual value, and determined the axial tilt of the Earth so accurately that their number falls with in modern ranges. They we able to achieve this because the meridian arch of the sextant was the largest of its kind ever built. Following the death of Ulugh Beg the observatory was razed to the ground by his son and skilled scientists driven away from Samarkand. The site was rediscovered in 1908 by Russian archaeologist Vassily Vyatkin.