A sundial showed very precise time .

日晷上显示的时间非常精确。

A sundial measures the movement of the sun across the sky each day .

日晷测量每天太阳跨过天空的运动。

Yet , to the north at alexandria , a sundial cast a shadow even at the solstice midday , because the sun was not directly overhead there .

而在北边的亚历山大城，日晷会投下一个影子，因为在正午太阳并不在头顶正上方。

Eratosthenes knew that at noon on the day of the summer solstice , the sun was observed to be directly overhead at syene ( modern-day aswan ) : you could see it from the bottom of a deep well , and a sundial cast no shadow .

埃拉托色尼知道在夏至的中午，西奈城（现在的阿斯旺）的太阳处在观测者的正上方：也就是说你可以从一口深井的底部看到太阳，日晷也不会有影子。

Forbidden cit beijing china chinese travel tiananmen qing dynasty history eight nation alliance empire empress ming museum palace dowager cixi ballustrades ancient sundial .

故宫中国天安门北京清朝历史八国联军帝国皇后明朝故宫博物馆慈禧太后玉石栏古日晷紫禁城乾隆。