为了在白天追踪时间，发明家发明了日晷，它通过太阳阴影的长度或方向来指示时间。
In order to track temporal hours during the day, inventors created sundials, which indicate time by the length or direction of the sun's shadow.
这条黑夜与白天分界线的形状随着季节的变化面变化，它代表着不同的白天时间长度和不同的阳光照射量。
The shape of this line between night and day varies with the seasons, which means different lengths of days and differing amounts of warming sunshine.
在一年里这两个时间点上，太阳出现在赤道的正上方，并且在地球上绝大多数地方，白天与夜间的长度是相同的。
At these times of the year, the sun appears to be directly over Earth's equator, and the lengths of the day and the night are equal over most of the planet.
一年之中只有两次，白天和夜晚的长度一样，即春分和秋分。
It was only at two points in the year that the night and the day were of equal length and that was at the spring or fall equinox.
一年中出现两次的日子，这一天中午太阳直射赤道，并且白天和晚上有相同时间长度。
One of the two dates each year when at noon the Sun is directly overhead at the equator and day and night are of equal length.
有多少个夜晚，就有多少个白天，在年的长度里，夜晚和白天一样漫长。
There are as many nights as days, and the one is just as long as the other in the year'scourse.
有多少个夜晚，就有多少个白天，在年的长度里，夜晚和白天一样漫长。
There are as many nights as days, and the one is just as long as the other in the year'scourse.
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