Glossary term: 二至点
Description: 地轴并非垂直于地球围绕太阳的轨道平面，而是与垂直方向呈23.4度的倾斜角。因此，在地球轨道的不同位置上，地轴与太阳视线之间的角度在一年内是不同的。这种现象的实际效果是，对于地球上的观测者来说，太阳在一天中达到地平线上最高点的高度会随时间而变化。北半球夏至，同时也是南半球的冬至，大约发生在6月21日，此时太阳在北半球的高度到达一年中的最高点，同时在南半球的高度则到达最低点。而南半球夏至，同时也是北半球的冬至，大约发生在12月21日，此时太阳在南半球的高度到达最高点，同时在北半球的高度则到达最低点。
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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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