Editing Aswan (section)

=== Northern Tropic boundary ===
The [[latitude]] of the city that would become Aswan – located at 24° 5′ 23″ – was an object of great interest to the ancient geographers and mathematicians.<ref name="Venturi">Venturi, Jacir J.. [https://www.educacional.com.br/articulistas/outrosOutros_artigo.asp?artigo=jacir0003 Eratóstenes e a Esfericidade da Terra] {{Webarchive|url=https://web.archive.org/web/20220127203232/https://www.educacional.com.br/articulistas/outrosOutros_artigo.asp?artigo=jacir0003 |date=2022-01-27 }}. Revista Articulistas.[s/d].</ref> They believed that it was seated immediately under the [[Tropic of Cancer|tropic]], and that on the day of the [[summer solstice]], a vertically positioned staff cast no shadow.<ref name="Venturi"/> They noted that the sun's disc was reflected in a deep well (or pit) at noon.<ref name="Venturi"/> This statement is only approximately correct;<ref name="Venturi"/> at the summer solstice, the shadow was only {{frac|400}} of the staff, and so could scarcely be discerned, and the northern limb of the Sun's disc would be nearly vertical.{{Citation needed|date=April 2020|reason=Eratosthenes did not use any assumption in the latitude of Aswan, so if no other geographer from antiquity did, the whole paragraph should be removed}} More than 2200 years ago, Greek polymath [[Eratosthenes]] used this information to calculate [[Earth's circumference]].<ref name="Venturi"/>