Glossary term: 夜
Description: 黑夜是指太阳低于地平线的一段黑暗时间。黑夜从日落持续到日出。在地球的大部分地区，每 24 小时就有一个夜晚。然而，在北极圈以北和南极圈以南，冬至前后会出现极夜持续数月的黑暗期。这些地区在夏至前后没有则是极昼。
太阳刚刚落到地平线以下的时期称为黄昏。在黄昏期间，太阳仍能照亮部分天空。黄昏分为三个相等的时段：民用晨昏蒙影（Civil Twilight），航海晨昏蒙影（Nautical Twilight），天文晨昏蒙影（Astronomical Twilight）。民用晨昏蒙影--太阳在地平线下 0 到 6 度时--天空相对明亮，因此通常不需要街道照明等人工照明。航海晨昏蒙影--当太阳位于地平线下 6 至 12 度时--既能看到明亮的星星，天空也足够明亮，即使在无月之夜也能看到地平线。这样，水手就可以使用天体导航进行航行。天文晨昏蒙影是指太阳位于地平线下 12 至 18 度的时候。
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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher The translation of this term and its definition is still awaiting approval
The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".
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