The Great Mathematician and Astronomer
Abd ar-Rahman ibn Yunus al-Misri is an Islamic scholar who calculated the end of his life.
Abd ar-Rahman ibn Yunus al-Misri was a very talented student of Muhammad Abu al-Wafa. He was born in 950 in Fustat in the Abbasid Caliphate and passed away on 31 May 1009 in Cairo in the Fatimid Caliphate. He was a great mathematician and astronomer. He conducted astronomical research at the observatory on Mount Mokaptan near Cairo. The talented researcher Ibn Yunus prepared the then best tables on astronomy, “Zij al-Hakimi”, which were used by astronomers for the next two centuries.
“Zij” by Abd ar-Rahman al-Misri contains 81 chapters. In this book, the author reviews the achievements of his predecessors in this field and the conclusions of Ibn Yunus’s own research. The great Muslim scholar made adjustments to the meaning of the angle of inclination of the ecliptic and the precession of the equinoxes, which had not been changed since the life of the scientist Ptolemy (100-170).
Having analysed the results of studies of eclipses of the Moon and the Sun from 977 to 1007 and revealed a secular acceleration of the average motion of the Moon. He modernised the gnomon (ancient Greek, “pointer”), an ancient astronomical instrument with a vertical object (column or pole), by which the angular height of the sun and the shortest length of its shadow (during the zenith of the sun) were determined, and established that its shadow demonstrates the height above the horizon of the upper edge, and not the centre of the solar disc.
Abd ar-Rahman ibn Yunus expressed his opinions on plane and spherical trigonometry and was the first to find ways to solve spherical triangles by introducing auxiliary angles.
He also wrote “A Treatise on the Method of Determining Two Lines in Kustas” (this was the name for scales with a scale and a sliding weight) and the book “Construction of a Lamp in Which Twelve Lamps Burn, of Which One Lamp Goes Out After One Hour of the Night”.
Ibn Yunus calculated instructions for converting dates among the Muslim Coptic and Syrian calendars, as well as for finding the meridian and determining the qibla (direction of Mecca) and the phases of the Moon. In Islamic culture, the knowledge of astronomers is in great demand in order to accurately calculate the time of prayer and to know the beginning of the month of fasting in Ramadan and when this holiday begins after the end of the fast. And all this is unacceptable without observing the Moon.
Ibn Yunus’s calculations are distinguished by the highest accuracy. This greatest Islamic mathematician and astronomer even calculated the time of his death with amazing accuracy! In 1009, nothing foreshadowed the unexpected, the scientist looked healthy and strong. Nevertheless, he said that he would die in seven days. He retired to his house and read the Holy Koran from morning to evening. A week later, on 31 May 1009, Abd ar-Rahman ibn Yunus died.
In memory of this outstanding Islamic mathematician and astronomer, the International Astronomical Union in 1970 named a crater on the invisible surface of the Moon after Ibn Yunus.
