◀ ▲ ▶History / Early-middle-ages / Person: Ibn Yunus, Abu'l-Hasan Ali Ibn Abd al-Rahman
Person: Ibn Yunus, Abu'l-Hasan Ali Ibn Abd al-Rahman
Ibn Yunus was an Islamic mathematician known for his astronomical observations and for his many trigonometrical and astronomical tables.
Mathematical Profile (Excerpt):
- Ibn Yunus was closely connected with the Fatimids and two Caliphs supported his scientific work.
- Although there is uncertainty about the instruments that ibn Yunus used, it is claimed by early writers that al-Aziz provided ibn Yunus with at least some instruments.
- Famed for his astronomical observations, ibn Yunus was also an astrologer but he is most famous for his many trigonometrical and astronomical tables.
- Of course it was very reasonable for a Caliph to support the type of astronomical work that ibn Yunus was undertaking.
- For most of his 20 year reign he worked towards this aim while ibn Yunus toiled on his astronomical work.
- Certainly al-Hakim supported ibn Yunus in his astronomical work, although it is hard to determine the strength of that support.
- Perhaps al-Hakim's interest in astrology meant that he favoured ibn Yunus who is reported by his biographers to have devoted considerable amounts of time to making astrological predictions.
- Ibn Yunus and al-Hakim were both eccentrics, although al-Hakim's eccentricities were more damaging, while ibn Yunus's sound rather typical of someone totally absorbed in academic pursuits.
- However, probably because of his interest in astrology, al-Hakim kept some astronomical instruments in his house overlooking Cairo and we know that on at least one occasion ibn Yunus observed Venus from al-Hakim's house.
- Ibn Yunus's major work, an astronomical handbook, was al-Zij al-Hakimi al-kabir.
- 'Al-kabir' means 'large' which is apt and 'al-Hakimi' means that the work is dedicated to Caliph al-Hakim who certainly supported ibn Yunus.
- There are lists of observations made by Yunus and also observations made by his predecessors.
- We can confirm, using modern knowledge of the positions of the planets, that ibn Yunus was exactly right in his description and that the distance of one third of a degree that he gives is again exactly right.
- We gathered to observe this eclipse at al-Qarafa, in the Mosque of Ibn Nasr al Maghribi.
- Ibn Yunus gives tables to convert dates between these calendars.
- Many other tables have been attriributed to ibn Yunus.
- Ibn Yunus's tables, if such they are, contain over 34000 entries ...
- The author notes that ibn Yunus used data for these tables that he had collected for the Hakimi Zij.
- The high degree of accuracy displayed by these tables suggests to D A King that ibn Yunus used systems of nonlinear interpolation.
- Perhaps it is worth mentioning that, contrary to claims which are often made, there is no evidence to suggest that ibn Yunus used a pendulum for time measurements.
- Ibn Yunus predicted the date of his own death to be in seven days time when he was in good health.
Born 950, Egypt. Died 1009, Fustat, Egypt.
View full biography at MacTutor
Tags relevant for this person:
African, Ancient Arab, Astronomy, Origin Egypt
Thank you to the contributors under CC BY-SA 4.0! 
- Github:
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- non-Github:
- @J-J-O'Connor
- @E-F-Robertson
References
Adapted from other CC BY-SA 4.0 Sources:
- O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive
