Analysis of information sources in references of the Wikipedia article "جغرافيا" in Arabic language version.
It was Biruni, not Avicenna, who found a way for a single man, at a single moment, to measure the earth's circumference, by trigonometric calculations based on angles measured from a mountaintop and the plain beneath it – thus improving on Eratosthenes' method of sighting the sun simultaneously from two different sites, applied in the ninth century by astronomers of the Khalif al-Ma'mun.
{{استشهاد بدورية محكمة}}: صيانة الاستشهاد: علامات ترقيم زائدة (link){{استشهاد بدورية محكمة}}: صيانة الاستشهاد: علامات ترقيم زائدة (link)It was Biruni, not Avicenna, who found a way for a single man, at a single moment, to measure the earth's circumference, by trigonometric calculations based on angles measured from a mountaintop and the plain beneath it – thus improving on Eratosthenes' method of sighting the sun simultaneously from two different sites, applied in the ninth century by astronomers of the Khalif al-Ma'mun.
{{استشهاد بدورية محكمة}}: صيانة الاستشهاد: علامات ترقيم زائدة (link){{استشهاد بدورية محكمة}}: صيانة الاستشهاد: علامات ترقيم زائدة (link){{استشهاد بدورية محكمة}}: صيانة الاستشهاد: علامات ترقيم زائدة (link)