Ibn Yunus

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Egyptian mathematician (c. 950–1009)

Ibn Yunus' records of the solar eclipses of 993 and 1004 as well as the lunar eclipses of 1001 and 1002.

Abu al-Hasan 'Ali ibn 'Abd al-Rahman ibn Ahmad ibn Yunus al-Sadafi al-Misri (Arabic: ابن يونس; c. 950 – 1009) was an important Egyptian astronomer and mathematician, whose works are noted for being ahead of their time, having been based on meticulous calculations and attention to detail.

The crater Ibn Yunus on the Moon is named after him.

1 Life
2 Works
- 2.1 Astrology
- 2.2 Astronomy
- 2.3 Pendulum
3 References
4 External links

Life

Information regarding his early life and education is uncertain. He was born in Egypt between 950 and 952 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 traveller 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 *ociate of the noted legal scholar Imam 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, al-Zij al-Kabir al-Hakimi, to the latter.

As well as for his mathematics, Ibn Yunus was also known as an eccentric and a poet.

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, al-Zij al-Kabir al-Hakimi (c. 1000), was a 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".

Yunus expressed the solutions in his zij without mathematical symbols, but Delambre noted in his 1819 translation of the Hakemite tables that two of Ibn Yunus' methods for determining the time from solar or stellar al*ude were equivalent to the trigonometric iden*y 2 cos ⁡ ( a ) cos ⁡ ( b ) = cos ⁡ ( a + b ) + cos ⁡ ( a − b ) {displaystyle 2cos(a)cos(b)=cos(a+b)+cos(a-b)} identified in Johannes Werner's 16th-century m*cript on conic sections. Now recognized as one of Werner's formulas, it was essential for the development of prosthaphaeresis and logarithms decades later.

Ibn Yunus described 40 planetary conjunctions and 30 lunar eclipses. For example, he accurately describes the planetary conjunction that occurred in the year 1000 as follows:

A conjunction of Venus and Mercury in Gemini, observed in the western sky: The two planets were in conjunction after sunset on the night . The time was approximately eight equinoctial hours after midday on Sunday ... . Mercury was north of Venus and their la*ude difference was a third of a degree.

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. Ibn Yunus's observations on conjunctions and eclipses were used in Richard Dunthorne and Simon Newcombs' respective calculations of the secular acceleration of the moon.

Pendulum

Recent encyclopaedias and popular accounts claim that the tenth century astronomer Ibn Yunus used a pendulum for time measurement, despite the fact that it has been known for nearly a hundred years that this is based on nothing more than an error made in 1684 by the Savilian Professor of Astronomy at Oxford Edward Bernard.

References

External links

King, David A. (2007). "Ibn Yūnus: Abū al‐Ḥasan ҁʿAlī ibn ʿAbd al‐Raḥmān ibn Aḥmad ibn Yūnus al‐Ṣadafī". In Thomas Hockey; et:al. (eds.). The Biographical Encyclopedia of Astronomers. New York: Springer. pp.:573–4. ISBN:978-0-387-31022-0. (PDF version)
O'Connor, John J.; Robertson, Edmund F., "Abu'l-Hasan Ali ibn Abd al-Rahman ibn Yunus", MacTutor History of Mathematics archive, University of St Andrews
King, David A. (2008) . "Ibn Yūnus, AbuʿL-Hasan ʿAlī Ibn ʿ Abd Al-Rahmān Ibn Yūnus Al Sadafī". Complete Dictionary of Scientific Biography. Encyclopedia.com.
Ibn Yunus Biography

Instruments

Alidade
*og computer
Aperture
Armillary sphere
Astrolabe
Astronomical clock
Celestial globe
Comp*
Comp* rose
Dioptra
Equatorial ring
Equatorium
Globe
Graph paper
Magnifying gl*
Mural instrument
Navigational astrolabe
Nebula
Octant
Planisphere
Quadrant
Sextant
Shadow square
Sundial
Schema for horizontal sundials
Triquetrum

Concepts

Almucantar
Apogee
Astrology in medieval Islam
Astrophysics
Axial tilt
Azimuth
Celestial mechanics
Celestial spheres
Circular orbit
Deferent and epicycle
Earth's rotation
Eccentricity
Ecliptic
Elliptic orbit
Equant
Galaxy
Geocentrism
Gravitational energy
Gravity
Heliocentrism
Inertia
Islamic cosmology
Moonlight
Multiverse
Muwaqqit
Obliquity
Parallax
Precession
Qibla
Salah times
Specific gravity
Spherical Earth
Sublunary sphere
Sunlight
Supernova
Temporal finitism
Trepidation
Triangulation
Tusi couple
Universe

Ins*utions

Al-Azhar University
House of Knowledge
House of Wisdom
University of al-Qarawiyyin
Observatories
- Constantinople (Taqi al-Din)
- Maragheh
- Samarkand (Ulugh Beg)

Influences

Babylonian astronomy
Egyptian astronomy
Hellenistic astronomy
Indian astronomy

Influenced

Byzantine science
Chinese astronomy
Medieval European science
Indian astronomy

Mathematical
works

The Compendious Book on Calculation by Completion and Balancing
De Gradibus
Principles of Hindu Reckoning
Book of Optics
The Book of Healing
Almanac
Encyclopedia of the Brethren of Purity
Toledan Tables
Tabula Rogeriana
Zij