Faraday was particularly interested in candles, because inside their delicate flames, they hold some amazing lessons on how fire really works.

法拉第對燭火特別感興趣，因為在那雅致的火光中，潛藏著能夠讓我們理解火焰運作原理的寶貴機會。

Now, you might have seen fire described like this in chemistry class, but a chemical formula doesn’t explain what fire is anymore than a recipe explains what chocolate chip cookies taste like.

你可能有在上化學課的時候看過火焰被以這樣的形式描述，但就像食譜沒辦法完整表達一片巧克力碎片餅乾嘗起來的滋味一樣，單純一個化學式並沒有辦法解釋清楚火焰究竟是什麼。

The first thing we notice about a candle flame is all those colors.

我們在看著燭火時首先注意到的就是它不同的色澤。

Hot things glow because of black body radiation, which we talked about in our video about the color of the universe.

炎熱的物體會因為黑體輻射而散發出光芒，我們有在另一個討論宇宙中不同顏色的影片中解釋過。

And down at the bottom of the flame, it’s hotter, so it glows blue, and in the middle, it’s cooler, so it glows yellowish-orangish.

而火焰的最底部是最熱的部分，因此會發出藍色光芒，而中間沒那麼熱，所以會發出黃橘色的光。

Inside of that flame, there can be hundreds of chemical reactions taking place.

在火焰裡面，可能同時有著數百個化學反應正在進行。

The oxygen in the air and the carbon and hydrogen in the candle don’t do anything on their own.

若單純只有空氣中的氧氣以及蠟燭裡的碳與氫元素並不會產生什麼反應。

It takes a little outside heat to get things started.

我們需要一點點來自外部的熱能才能讓反應開始進行。

Solid fuel is vaporized by the heat and ripped into smaller chunks.

固態燃料因為熱能而被蒸發，然後碎裂成小塊小塊的碎片。

This is called pyrolysis, and you can’t have a flame without it.

這個過程被稱為熱裂解，而少了它便無法產生火焰。

You can sometimes see a dark cone around the wick where there’s no fire.

你有時能在燭芯的周圍看到一圈黑色且沒有火焰的椎狀區域。

That's where vaporized wax is coming off the candle, but hasn’t started to burn yet.

那裡就是蠟開始從蠟燭蒸發，但還沒開始燃燒的地方。

And the hydrocarbons and oxygen in the air slam into each other, and their atoms begin to rearrange.

在空氣中的碳水化合物與氧氣互相撞擊，讓它們的原子開始重新排列。

Sometimes electrons in those atoms get into an excited state, and when they come back down again they give off light.

有時這些原子中的電子會進入激發態，而當它們回復正常後便會散發出光芒。

That’s why the bottom of the flame glows blue.

這就是為什麼火焰的底部會是藍色的原因。

Not all the carbon in the candle gets converted to CO2, so leftover carbon atoms come together and form tiny particles of soot,

不是所有蠟燭中的碳元素都會被轉化為二氧化碳，因此剩下的碳原子就會堆積在一起並形成小分子的煤灰，

which heat up and glow orange and yellow like the hot coals under a grill.

接著在被加熱後發出橘色與黃色的光芒，就好像烤爐中的木炭一樣。

This glowing soot is where most of a candle’s light comes from.

這些發光的煤灰是燭光的主要來源。

Eventually, at the tip of the flame, all the soot has burned away, and we’re left with only carbon dioxide and water floating off into the air.

最後所有的煤灰會在火焰的頂端被燒盡，只在空氣中留下二氧化碳和水蒸汽。

You can investigate all the different parts of a flame for yourself with just a cold piece of metal.

你可以用上一片冰涼的金屬片來自己試著查看火焰中的各個部分。

Up here, we find water vapor.

在最上面我們能發現水蒸氣。

In the yellow part of the flame, soot.

在火焰黃色的部份我們能找到煤灰。

And down just next to the wick, we can even recover unburned wax.

而在底部燭芯旁邊的部分，我們甚至能獲取到尚未燃燒的蠟。

Flames look really cool, too. They’re almost hypnotic…

火焰看起來也非常令人著迷。它們甚至有種催眠的效果...

Wait, what was I talking about? Oh, oh right, shape.

等等，我剛才說到哪了？噢，噢，對，形狀。

Gravity pulls cool, denser air down, makes hot air rise, and this buoyancy is what gives flames their familiar shape.

重力會將密度較大的冷空氣向下拉，使得熱空氣因此上升，而這樣的浮力給了火焰特殊的形狀。

But if you light a flame in zero-g, say, on the space station, it will look very different.

但如果你在例如太空站這樣的無重力環境下點燃火焰，它的形狀看起來會非常不同。

All the chemical and quantum reactions that make a flame glow can only happen where it meets the air,

讓火焰發光的所有化學與量子反應只會在火焰與空氣接觸時發生，

so even though they look like solid cones, candle flames are actually hollow.

所以雖然燭火看起來是個結實的椎體，它的內部其實是中空的。

As long as there’s fuel and oxygen, a flame will burn and burn. Why?

只要有燃料與氧氣，火焰便能一直燃燒下去。為什麼？

It’s not the molecular ripping apart that makes a flame hot.

讓火焰發熱的並不是分子被扯散的過程。

It's the formation of new molecules and new bonds is what creates heat, and that heat drives the chain reaction forward,

形成新的分子與鍵結的過程才是產生出熱能的原因，而這樣的熱能會促使整個連鎖反應繼續進行下去，

vaporizing more fuel, slamming more molecules into one another, and making the fire burn on.

蒸發更多燃料，把分子互相撞擊在一起，讓火焰繼續燃燒下去。

Our species has been gathering around fire for thousands of years, telling stories and asking questions over a flickering flame.

人類作為一個物種已經圍繞著火焰生活了數千年，圍坐在搖曳的火堆旁述說故事並提出疑問。

And that's part of what helped make us human in the first place.

而這正是使我們人類之所以為人類的其中一個因素吧。

Stay curious.

保持好奇。