Khalid ibn Abd al-Malik al-Marwarrudhi

Khālid ibn ʿAbd al‐Malik al‐Marwarrūdhī (Template:Langx) was a 9th-century Baghdadi astronomer.Template:Sfn

In 827, Marwarrūdhī, together with the astronomer ʿAlī ibn ʿĪsā al-Asṭurlābī and a party of surveyors, measured the length of a meridian arc of one degree of latitude. The party travelled to the Nineveh Plains in the valley of the Tigris,Template:Sfn at 35 degrees north latitude. The measurement they obtained enabled the astronomers to obtain a value of for the circumference of the Earth, (or, according to other sources, ). The two researchers measured in Arabian , and determined the geographical latitudes of the end points they used from the star altitudes in a celestial horizontal coordinate system. As it is thought that one Arabian represented , they found the length of 1° of meridian to be , which differs from the true value by .

Marwarrūdhī was chosen by the geometer Al-Abbās ibn Said al-Jawharī to organize a new observatory on Mount Qasioun. Despite encountering technical difficulties caused by the distortion of the astronomical instruments, in c. Template:Trim he spent a year obtaining of solar and lunar observations of the Sun and the Moon. He played a role in the project c. Template:Trim determine the length of the spring season by means of astronomical observations.Template:Sfn

Marwarrūdhī was the first of three generations of astronomers.Template:Sfn

Sources

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