Ahmad al-Farghani (approximate dates 798-861) is one of the largest medieval scientists of the 9th century, a Central Asian astronomer, mathematician and geographer. A native of the Fergana Valley. In Europe it was known under the Latinized name Alfraganus.
Ahmad al Ferghani, and a group of scientists under the leadership of the head of the House of Wisdom, mathematician and astronomer Al-Khorezmi, have made a large number of discoveries over the years, including: calculating the magnitude of the earth's meridian, calculating the circumference of the Earth, (tables of the starry sky), containing the exact coordinates and descriptions of thousands of celestial bodies. One of the most famous treatises of Al-Farghani is "The book of astronomical movements and a summary of the science of the stars." The work was available not only in Arabic, but also in several European languages and was the most studied in the Middle Ages. The scientific work was published in 1493 and was used by students as a teaching aid. It is curious that in 1669 Al-Farghani's work was re-translated and published by the Dutch scientist Jacob Golius. During his work in Egypt, he created the famous "Cairo measuring instrument of the Nile, Nilometer", which was the measuring instrument of the Nile waters, which has not lost its scientific value to this day. In addition, with difficulty Alfraganus was familiar with Dante Alighieri. There is an assumption that the author of the "Divine Comedy" made the journey of his hero through purgatory, based on the description of Al-Farghani of the Southern Hemisphere of the Earth, the scientist, according to his calculations, concluded that there may be an unknown continent in the West, which was later discovered by Amerigo Vispucci.