飞机的窗户，原来藏着这种心机！

There are roughly 102,465 commercial flights each day which, over a year, equates to about four billion air passengers per year.

世界上每天都有大概102,465个班次的商业航班，换算成一年，差不多就是40亿人次。

That's over half of the world's population who've sat on a flight, often for hours on end, and had time to think about planes and ask questions about them.

这所有坐过飞机的人已经超过地球人口的一半了，而且他们通常一坐就是几小时，有充足的时间来思考飞机的方方面面并对它们提出问题。

If you've ever stared out the window as your plane takes off, you will have seen a tiny hole in your window.

如果你曾经在飞机起飞的时候盯着窗外看，你会发现窗子上是有小洞的。

At first, it may seem like a weird addition, especially in something that's carrying a lot of people at a great height, but they're there for a very important reason: to stop the cabin from depressuring.

乍看之下，这个细节很诡异，尤其是它还出现在一个载着这么多人、飞得这么高的东西上，但其实它是有重要作用的：防止机舱减压。

As the plane gains altitude, the air pressure outside drops compared to the regulated air pressure inside the cabin.

随着飞机的飞行高度增加，飞机外面的气压会低于飞机内收到调控的气压。

The difference between the two puts physical stress on the windows - made up of three panes of glass.

两侧的气压差会对窗户造成物理压力。(飞机的窗子是由3层玻璃组成的)

There's a small air gap in between the middle and outer panes and the hole is actually in the middle pane.

在中层玻璃和外层玻璃之间有一个空气层，而这些小洞实际上是位于中层玻璃上的。

If you ever wondered what it's called - it's a "breather" or "bleed hole" - and it balances the pressure between the cabin and the air gap.

你可能好奇过它们叫什么。它们被称为“呼吸孔”或者“出血孔”——它们能平衡机舱与空气层之间的压力。

The outer pane takes the pressure, whereas the middle pane acts as a fail-safe just in case that trusty outer pane fails. Perish the thought.

承受压力的是外层玻璃，而中层玻璃则是一层保险，以防那层可靠的外层玻璃突然时效了。不过你还是打消这个想法吧。

So we now know the crucial function of those tiny holes in aeroplane windows which previously might have made you panic mildly.

好，现在我们已经知道飞机窗户上那些小洞有多么重要的作用了，而这玩意以前可能会给你带来点小恐慌。