两个世界，两个八字
(原标题: Two Worlds, Two Analemmas)
2025-06-21
浏览次数: 16
当然，当你在一年中每天同一时间标记太阳在地球天空中的位置时，你得到的8字形曲线被称为8字曲线。左图是2011年12月至2012年12月期间拍摄的广角数字图像，通过结合这些图像绘制出了地球的8字曲线。但是，八字曲线的形状取决于行星轨道的偏心率和旋转轴的倾斜程度，因此，不同的世界的八字曲线可能看起来不同。以火星为例。这颗红色行星的轴向倾斜与地球相似，但它围绕同一个太阳的轨道比地球的轨道更偏心（不那么圆）。从火星表面看，右侧面板上的八字曲线形状更像一滴泪珠。机遇号火星探测器捕捉到的火星年的图像与地球的2006年7月至2008年6月相对应。当然，每个世界的夏至日期仍然位于其不同的八字曲线的顶部和底部。上一次火星北方夏至是在2025年5月29日。我们美丽的星球的2025年北方夏至是在6月21日2:42 UTC。
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Sure, that figure-8 shaped curve you get when you mark the position of the Sun in Earth's sky at the same time each day over one year is called an analemma. On the left, Earth's figure-8 analemma was traced by combining wide-angle digital images recorded during the year from December 2011 through December 2012. But the shape of an analemma depends on the eccentricity of a planet's orbit and the tilt of its axis of rotation, so analemma curves can look different for different worlds. Take Mars for example. The Red Planet's axial tilt is similar to Earth's, but its orbit around the same sun is more eccentric (less circular) than Earth's orbit. As seen from the Martian surface, the analemma traced in the right hand panel is shaped more like a tear drop. The Mars rover Opportunity captured the images used over the Martian year corresponding to Earth dates July 2006 to June 2008. Of course, each world's solstice dates still lie at the top and bottom of their different analemma curves. The last Mars northern summer solstice was May 29, 2025. Our fair planet's 2025 northern summer solstice is at June 21, 2:42 UTC.
© Tunc Tezel