煎蛋小学堂:英语百科(视频+中英字幕) 第1课:夜空为什么是黑的_百科

煎蛋小学堂:英语百科(视频+中英字幕) 第1课:夜空为什么是黑的

Why is the sky dark at night? 夜空为什么是黑的？

You might think the answer is obvious - the sun isnt up! But the only reason the sky looks blue during the day is that sunlight scatters off of the atmosphere - if we didnt have an atmosphere (like on the moon), the sky would always be dark, even when the sun is shining. So lets rephrase the question - why is space dark? 你可能认为答案很简单——因为没有太阳嘛！但白天的天空之所以是蓝色的，完全因为大气层把阳光散射了。而如果没有大气层，就比如月球，那么天空就一直都是黑的，即便有太阳照射，那就让我们换种问法——为什么太空是黑色的？

I mean, space is full of stars - countless stars which are all about as bright as the sun, and in an infinite eternal universe, no matter what direction you picked, if you looked far enough in that direction, you would see a star or galaxy. So the whole sky should be as bright as the sun, night and day! 太空里充满了各种各样的恒星，每一颗的亮度都和太阳一样，而在无穷无尽的宇宙中，不管你选择任何一个方向，只要你走得足够远，你都能遇到一颗恒星，或者一个星系，于是天空就应该是亮如白昼的，不论白天还是黑夜。 And since its not, does the darkness of the night sky mean that theres some distance away from us when stars and galaxies just… stop? A boundary between something and nothing? 但是事实却并非如此，那么，黑色的夜空是否告诉了我们，在一定的距离以外，就没有恒星或者星系了吗？是不是存在一个有星星和没有星星的边界？