【英语时差8,16】天空变成绿色时

It sounds like something from a fairy tale.   If you look at the horizon at sunset–exactly as the last sliver¹ of sun disappears–you might see a flash of brilliant green blaze across the sky. Indeed, an old Scottish proverb maintains that whoever sees this flash will always be lucky in love. While we can't confirm the lucky-in-love part of this, there is a scientific explanation for the flash of green light.

As sunlight enters our atmosphere, it bends slightly. This is due to refraction, the same thing that makes a pencil look slightly askew² when you stick it half way into a glass of water. The atmospheric³ bending of light rays is greatest when the sun is right along the horizon, at sunrise or sunset.

How does bending sunlight create a green flash? When sunlight is bent⁴ by refraction, it separates into different colors, just like light through a prism. While a prism can make a dramatic rainbow, atmospheric refraction isn't that strong. It doesn't turn the sun into a rainbow, but it makes the lowest part of the sun seem a bit more red, and the top of the sun seem greenish blue. The effect is so subtle, you'd never notice it.

Except, of course, at sunset or sunrise. For a split second, when most of the sun's globe is below the horizon, the only part showing is that blue-green sliver along the top. Blue light is scattered⁵ by the atmosphere, so what's left is a brief flash of green, the only illumination in the sky!

Please remember, this happens immediately after a sunset. Never look directly at the setting sun.  

1 sliver   

n.裂片，细片，梳毛；v.纵切，切成长片，剖开

参考例句：

• There was only one sliver of light in the darkness.黑暗中只有一点零星的光亮。
• Then,one night,Monica saw a thin sliver of the moon reappear.之后的一天晚上，莫尼卡看到了一个月牙。

2 askew   

adv.斜地；adj.歪斜的

参考例句：

• His glasses had been knocked askew by the blow.他的眼镜一下子被打歪了。
• Her hat was slightly askew.她的帽子戴得有点斜。

3 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。

4 bent   

n.爱好，癖好；adj.弯的；决心的，一心的

参考例句：

• He was fully bent upon the project.他一心扑在这项计划上。
• We bent over backward to help them.我们尽了最大努力帮助他们。

5 scattered   

adj.分散的，稀疏的；散步的；疏疏落落的

参考例句：

• Gathering up his scattered papers,he pushed them into his case.他把散乱的文件收拾起来，塞进文件夹里。