Earth's circumference

Another Look at Eratosthenes' and Posidonius' Determinations of the Earth's Circumference, Ql. J. of the Royal Astron. Soc., Vol. 16, p.152. John Freely,

was in fact defined as one ten millionth of one quarter of the earth's circumference at sea-level.' Joseph Needham, Science and Civilisation in China

球是圆的，这种理论很快就传遍了希腊地区。公元前330年，亚里士多德第一次使用基础物理学和观测证据在著作中估计了地球的周长（英语：Earth's circumference）。更为精准的测量来自埃拉托斯特尼于公元前240年的测算。公元2世纪，克劳狄乌斯·托勒密在地理學指南中将地球描述为一个球体，并且

Willmann-Bell, 1998) 238. See Ellipse#Circumference. The formula by Ramanujan is accurate enough.[來源請求] Williams, David R. Earth Fact Sheet. NASA. 2004-09-01 [2007-03-17]

was in fact defined as one ten millionth of one quarter of the earth's circumference at sea-level.' Joseph Needham, Science and Civilisation in China