Al-Ashraf Umar II

Al‐Malik A‐Ashraf (Mumahhid Al‐Din) Umar Ibn Yūsuf Ibn Umar Ibn Alī Ibn Rasul (Arabic: عمر بن يوسف بن عمر بن علي بن رسول الغساني), also as Umar Ibn Yusuf (or also Al-Asharaf Umar II) was the third Rasulid sultan and also an Arab mathematician, astronomer and physician.

Umar Ibn Yussuf
Coin of the Rasulids in 1335.
Borncirca 1242
Yemen
Died22 November 1296
Yemen
Scientific career
FieldsAstronomy, Mathematician and Physician

Biography
Al-Ashraf's diagram of the compass and Qibla, copied in Yemen, 1293.[1]

Umar Ibn Yusuf was born in 1242 in Yemen and he died in 1296. [2] He is known for writing the first description of the use of a magnetic compass for determining the qibla.[1] Also, his works on astronomy contain important information on earlier sources.[1]

In a treatise about astrolabes and sundials, al-Ashraf includes several paragraphs on the construction of a compass bowl (ṭāsa). He then uses the compass to determine the north point, the meridian (khaṭṭ niṣf al-nahār), and the Qibla towards Mecca. This is the first mention of a compass in a medieval Islamic scientific text and its earliest known use as a Qibla indicator, although al-Ashraf did not claim to be the first to use it for this purpose.[1]

Notes
  1. Schmidl, Petra G. (1996–97). "Two Early Arabic Sources On The Magnetic Compass". Journal of Arabic and Islamic Studies. 1: 81–132.CS1 maint: ref=harv (link) http://www.uib.no/jais/v001ht/01-081-132schmidl1.htm#_ftn4 Archived 2014-09-02 at the Wayback Machine
  2. Schmidl 2007.

References


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