虽然昼夜等长不会发生在秋分日，但这并不意味着入秋第一日的特殊性会大打折扣。
The length of day and night may not be equal on the equinox, but that doesn't make the first day of fall any less special.
如果太阳只发出很小一点的光，并且地球周围不存在大气层，那么在春分这天，昼夜等长，都是12个小时。
If the sun were just a tiny point of light and Earth had no atmosphere, then day and night would each be exactly 12 hours long on a spring equinox day.
如果想要昼夜在春秋分日达到精确地12小时等长，除非太阳是个单点光源或者地球上没有大气层。
Day and night would each be exactly 12 hours long on a spring or fall equinox only if the sun were a single point of light and Earth had no atmosphere.
“这些因素结合起来就造成了昼夜12小时等长的一天不可能是春秋分日，”切斯特说。
"Those factors all combine to make the day of the equinox not the day when we have 12 hours [each] of light and darkness," Chester said.
“这些因素结合起来就造成了昼夜12小时等长的一天不可能是春秋分日，”切斯特说。
"Those factors all combine to make the day of the equinox not the day when we have 12 hours [each] of light and darkness," Chester said.
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