送交者: 008 于 2005-1-12, 21:58:02:
回答: 同时不是关键,同经才是. 由 outsider 于 2005-1-12, 18:07:47:
He pointed out that there are many cities where sunlight can reach the bottome of a well on the summer solstice. To solve this problem one more constraint is needed: either force them to be at the same longitude, or do a measurement at exactly the same time. Why do yo think one is 关键 the other one is not?
There's actually another 关键: what if the well is not straight? What is "straight" anyway?