He found the radius of the earth to be 6339.6 km, a value not obtained in the West until the 16th century. His Masudic canon contains a table giving the coordinates of six hundred places, almost all of which he had direct knowledge. Not all, however, were measured by al-Biruni himself, some being taken from a similar table given by al-Khwarizmi. al-Biruni seemed to realise that for places given by both al-Khwarizmi and Ptolemy, the value obtained by al-Khwarizmi is the more accurate. Al-Biruni also wrote a treatise on time-keeping, wrote several treatises on the astrolabe and describes a mechanical calendar. He makes interesting observations on the velocity of light, stating that its velocity is immense compared with that of sound.
He also describes the Milky Way as.. a collection of countless fragments of the nature of nebulous stars.

Abu Arrayhan Muhammad ibn Ahmad al-Biruni
Born: 15 Sept 973 in Kath, Khwarazm (now Kara-Kalpakskaya, Uzbekistan)
Died: 13 Dec 1048 in Ghazna (now Ghazni, Afganistan)