The Ibn Yunus crater, on the Moon, is named after him.
Life
Information regarding his early life and education is uncertain. He was born in Egypt between 950 and 952 AD and came from a respected family in Fustat. His father was a historian, biographer and scholar of hadith, who wrote two volumes about the history of Egypt—one about the Egyptians and one based on traveler commentary on Egypt. A prolific writer, Ibn Yunus' father has been described as "Egypt's most celebrated early historian and first known compiler of a biographical dictionary devoted exclusively to Egyptians". His great grandfather had been an associate of the noted legal scholar al-Shafi.
Early in the life of Ibn Yunus, the Fatimid dynasty came to power and the new city of Cairo was founded. In Cairo, he worked as an astronomer for the Fatimid dynasty for twenty-six years, first for the Caliph al-Aziz and then for al-Hakim. Ibn Yunus dedicated his most famous astronomical work, Zij al-Kabir al-Hakimi, to the latter.
Works
Astrology
In astrology, noted for making predictions and having written the Kitab bulugh al-umniyya ("On the Attainment of Desire"), a work concerning the heliacal risings of Sirius, and on predictions concerning what day of the week the Coptic year will start on.Astronomy
Ibn Yunus' most famous work in Islamic astronomy, Zij al-Kabir al-Hakimi (c. 1000 AD), was a Zij handbook of astronomical tables which contained very accurate observations, many of which may have been obtained with very large astronomical instruments. According to N. M. Swerdlow, the Zij al-Kabir al-Hakimi is "a work of outstanding originality of which just over half survives".Ibn Yunus described 40 planetary conjunctions and 30 lunar eclipses. For example, he accurately describes the planetary conjunction that occurred in the year 1000 AD as follows:
Modern knowledge of the positions of the planets confirms that his description and his calculation of the distance being one third of a degree is exactly correct. In the 19th century, Simon Newcomb found Ibn Yunus' observations on conjunctions and eclipses reliable enough to use them in his lunar theory to determine the secular acceleration of the moon. Ibn Yunus' other observations also inspired Laplace's Obliquity of the Ecliptic and Inequalities of Jupiter and Saturn's. Ibn Yunus also observed more than 10,000 entries for the sun's position for many years using a large monumental astrolabe with a diameter of nearly 1.4 metres.
Mathematics
In Islamic mathematics, he performed many careful trigonometric calculations and demonstrated the following trigonometric identity:Poetry
Ibn Yunus is also thought to have been an Arabic poet, and to have used very large instruments in making his observations, though neither assertion is certain.Other works
He is said to have predicted his own death, seven days prior to the event, and without any outward sign of ill health.Ibn Yunus is believed to have described an early type of pendulum in the 10th century. Some claimed that he used it for making measurements of time, like a pendulum clock, but this is now believed to be a misinterpretation on the part of Edward Bernard, an English historian.
References
External links
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Last updated on Wednesday July 23, 2008 at 00:30:51 PDT (GMT -0700)
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