The survey was also essential in determining the arc measurement, i.e., the length of meridian arc，although Yi Xing, who did not know the Earth was spherical, did not conceptualize his measurements in these terms.
自己去看看别人怎么说的吧，别一边脑补一边乱举例子
【 在 defeatyou 的大作中提到: 】
: 随你说
英国的世界史教材就是写的一行测量子午线长度
我上面也写了，你也可以说祖冲之算的是直径一丈圆的周长，不是圆周率
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FROM 222.129.6.*