There are roughly 102,465 commercial flights each day which, over a year, equates¹ 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 weird² 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 panes³ 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 pane⁴.

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 previously⁵ 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。

And if you've ever wondered why aeroplane seats aren't always aligned⁶ with the windows, then there's an answer for that too.

不过你可能还好奇过：为什么不是所有的飞机座位都和窗子对齐？这也是有答案的。

It's nothing to do with safety either.

这个其实和安全问题无关。

While the entire design and engineering of planes is done to ensure passenger safety, this does not extend to seat alignment⁷.

虽然整个飞机的外观设计和工程学设计都是为了保证乘客的安全，但这并不包括飞机座位的对齐方式。

Some don't even have a window view.

有些座位甚至看不到窗子。（面壁的）

Airlines are essentially⁸ business who want to make money - and they make money by getting as many bums⁹ on seats as possible.

航空公司基本都是做生意赚钱的，而显然，坐到他们飞机上的屁股越多，他们就越赚钱。