旋转地球上的春分点
(原标题: Equinox on a Spinning Earth)
2021-09-22
浏览次数: 31
什么时候昼夜之间的界限变得垂直？今天。今天是地球上的春分，一年中白天和黑夜最接近相等的时候。在春分时，地球的分界线——白天和黑夜的分界线——变得垂直，连接南北两极。这个特色的延时视频通过在12秒内展示地球上的一整年来证明这一点。从地球同步轨道上，气象卫星9号每天在当地同一时间记录下这些地球的红外图像。这段视频开始于2010年9月的春分，当时的终点线是垂直的。当地球围绕太阳旋转时，人们看到明暗分界线以某种方式倾斜，从而减少了北半球每天的阳光照射，导致北方进入冬季。随着时间的推移，2011年3月的春分在视频中途到来，随后明暗分界线向另一个方向倾斜，导致南半球进入冬季，北半球进入夏季。拍摄到的这一年又以9月的春分结束，地球已经绕太阳转了数十亿圈，并将继续绕太阳转。
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When does the line between night and day become vertical? Today. Today is an equinox on planet Earth, a time of year when day and night are most nearly equal. At an equinox, the Earth's terminator -- the dividing line between day and night -- becomes vertical and connects the north and south poles. The featured time-lapse video demonstrates this by displaying an entire year on planet Earth in twelve seconds. From geosynchronous orbit, the Meteosat 9 satellite recorded these infrared images of the Earth every day at the same local time. The video started at the September 2010 equinox with the terminator line being vertical. As the Earth revolved around the Sun, the terminator was seen to tilt in a way that provides less daily sunlight to the northern hemisphere, causing winter in the north. As the year progressed, the March 2011 equinox arrived halfway through the video, followed by the terminator tilting the other way, causing winter in the southern hemisphere -- and summer in the north. The captured year ends again with the September equinox, concluding another of billions of trips the Earth has taken -- and will take -- around the Sun.