[Instant Egghead]

絕對別對啤酒做這件事!

[Clink]

所有麥香和美味的小幸福將全部浪費!

That is a terrible thing to do to a beer.

但是，為何在啤酒罐頂部的敲擊，會引發爆炸般的泡沫，

All that delicious, malty goodness gone to waste.

而和朋友互敲酒瓶飲酒作樂，卻可以安然無恙呢?

But, why should a tap on top trigger a foam explosion,

這和酒瓶的形狀有關

while a clink on the side signals the start of a drink with friends?

當你"碰"酒瓶的頂部，

It has to do with the shape of a beer bottle.

撞擊力道會產生壓力波，從頂部傳經過液體，再傳到底部

When you "bonk" a beer bottle on top,

壓力波到底部時會反射，傳回頂部，

the hit creates pressure waves that travel down through the liquid.

然後再向下傳到底部

These waves bounce off the bottom of the bottle, head back up to the top,

啤酒內壓力的改變，使得氣泡迅速擴大，並使小氣泡結合在一起

and then bounce back down again.

到達顛峰時，氣泡就會爆炸

The changing pressure in the beer rapidly expands and contracts any small bubbles.

產出數以千計的迷你新氣泡

At a certain point, these bubbles burst under the pressure,

這是連鎖反應的開端

creating thousands of tiny new bubbles.

每顆迷你氣泡都佔了體積，因此有許多表面積，

Here's where the chain reaction starts.

所以溶解的二氧化碳更易進入氣泡中

Each one of these tiny bubbles has a lot of surface area for its volume,

當氣泡變大，就變得越輕，因此會向上移動，

so it's easy for the carbon dioxide dissolved in the beer to get into the bubble.

當氣泡往上升，他們經過許多二氧化碳，吸收更多氣體

The bubbles get bigger, getting lighter as they go,

反饋環就此啟動: 氣泡變得越大，上升的越快

which makes them rise towards the top.

二氧化碳吸收得越多，氣泡就變得越大

As they rise, they pass through new parts of the liquid,

這個過程就和核彈爆發後蕈狀雲有點類似，

with lots of spare carbon dioxide.

就是，在一個不受控制的連鎖犯應過後，猛烈的結果

A feedback loop starts:

這裡的話，只是結果比較不悲慘而已~~

the bigger the bubbles get, the faster they rise,

我是Michael Moyer，這是Scientific American's Instant Egghead

the more CO2 they absorb, which makes them get even bigger.

[音樂]

The process is not unlike the mushroom cloud of the nuclear bomb-

the violent result of an uncontrolled chain reaction,

and, depending on one's mood, only slightly less tragic.

For Scientific American's Instant Egghead, I'm Michael Moyer. [Music]

[English subtitles by moomoo & NagySandor.EU]