Upon his discoveries and inventions in his time,
Thabit was tasked by Caliph Me’mun with measuring the diameter of the earth.
Measurements set forth by him and other scholars were transferred to Europe
through Andalusia in the following years. It is said that seamen like
Christopher Columbus had found their way by using these measurements.

According to “*Kamus’ul
Alam*” the discovery of “calculus”, which is a branch of mathematics, belongs
to him as well. He named calculus “tefadul”. In another work it is said that
Thabit ibn Qurra discovered the differential calculation before Newton. He did
studies on positive real numbers, integral, calculus, theory of numbers,
spherical trigonometry, astronomy, mechanics and statics. His studies on
parabolas cleared the way for the discovery of integral calculus. Many writers
say that although Qurra was aware of Archimedes’ studies, he did not use them.
He precisely calculated the integral of x and root of x. His calculation was
based on the use of integral sums as exponent and base. He made progress not
only in astronomy but also in medicine and philosophy.

Thabit ibn Qurra’s books were read and analyzed in
East and West and they had been used as sources for new and unique researches.
Thabit’s works, which were read in the Islamic world as well, translated to
Western languages in 12^{th} century. According to what Beyhaki said,
among his followers, his grandson Muhammad bin Cabir el-Harrani el-Battani
(D.929) was the most significant one. Battani is regarded as the most prominent
astronomer and scholar after the reign of Me’mun. The tradition that began with
Thabit ibn Qurra, who was the ancestor of the lineage of Harran scholars, who
had a say in astrologic, medical and mathematical researches, was pursued by
his son, Sinan, and his two grandsons, Thabit and Ibrahim.

**MAIN WORKS:**

*Kindî’ye Reddiye* (Syriac), *Deniz Suyunun Tuzlu Oluşunun Sebebine Dair*, *Calinus’un Gıdalar Üzerine Olan Kitabının Özeti*, *Ay Tutulmasının Belirtileri Üzerine*, *Güneş ve Ay Tutulmasının Nedeni Hakkında*,
*Süryanice ve Arapça’nın Grameri Hakkında*,
*Ölülerin Tekfini Hakkında*, *Sabiîler’in İtikadı Hakkında*, *Taharet ve Necaset Hakkında*, *İbadetlerin Vakitleri Hakkında*.

REFERENCE: Hilmi Ziya Ülken / Uyanış Devirlerinde Tercümenin Rolü (s. 84, 1997), Şinasi Gündüz / Son Gnostikler Sâbiîler (2. baskı, 1999) - Anadolu’da Paganizm Antik Dönemde Harran ve Urfa (s. 43-44, 2005), Doç. Dr. Bayram Ali Çetinkaya (Somuncu Baba Dergisi, Ağustos 2006, s. 36-39), İhsan Işık / Ünlü Bilim Adamları (Türkiye Ünlüleri Ansiklopedisi, c. 2, 2013) - Resimli ve Metin Örnekli Türkiye Edebiyatçılar ve Kültür Adamları Ansiklopedisi (C. 12, 2017).