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Our planet has a terminator.
我们的星球有一位终结者。
No, not a time traveling humanoid robot, but a line where its light and dark side meet.
不，它并非一个穿越时空的人形机器人，而是光明与黑暗的交界线。
On Earth we see the Sun rise from the East and set in the West.
在地球上，我们看到太阳从东边升起，从西边落下。
But if you were looking straight down from space, you would see half the planet lit,
但如果你从太空垂直向下看，你会看到地球只点亮了一半，
and the other half in total darkness. That's the terminator.
而另一半则完全处在黑暗中。那就是“终结者”。
The terminator, also called solar terminator or the “twilight zone” moves around our planet once a day.
这位“终结者”，又称“太阳终结者”或“暮色地带”，每天绕地一周。
The Earth is constantly rotating, and it's got a little tilt to it.
地球一直在旋转，而且略微倾斜。
Our planet orbits the sun at a 23.5 degree angle.
我们地球的黄赤交角是23.5度。
That axial tilt causes one pole to be facing the Sun, and the other pole facing away, which gives our planet its four seasons.
这种轴向倾斜，使得地球一个磁极面向太阳，而另一个磁极背向太阳，由此形成了四季。
The terminator is a guide for solar-powered low earth orbit satellites.
这位“终结者”是太阳能低地球轨道卫星运行的基准。
They ride the line in total sunlight to take pictures of Earth.
它们在全日光照射下，沿晨昏线，拍摄地球照片。
That constant sunlight is useful for collecting images, monitoring weather and gathering data on climate change.
这种持续不断的日照非常有用，有了它我们可以收集图像，监测天气，还可以收集气候变化数据。
So while the terminator doesn't really do anything, it is good for science!
所以虽然“终结者”（看似）什么都没有做，却助力了科学（研究）！
You can watch new episodes of Space Crafts right here every Wednesday.
每周三，你可以在这里观看最新一集的Space Crafts。
In this edition, we break out everyone's favorite elementary school science experiment to explain how galactic ice volcanoes erupt on Enceladus.
在这期节目中，我们深入大家喜爱的小学科学实验课，来为大家阐释银河系中的冰火山，如何在土卫二上爆发。
Thanks for watching and make sure to subscribe!
感谢观看，欢迎订阅！
