The science of snowflakes - Maruša Bradač

譯者: Shang-Yung Sun 審譯者: Max Chern

If you ever find yourself gazing at falling snow,

如果你曾經凝視過飄落的雪

why not catch a few snowflakes on your glove and examine their shapes?

何不試試用手套接幾片雪花， 仔細觀察它們的形狀？

You might notice that they look symmetrical,

你可能會注意到 它們看起來很對稱

and if you look closely,

但如果你更靠近一點看

you'll see they have six sides.

你會發現它們都有六個邊

You could say a snowflake is simply frozen water,

你可以說雪花就是結凍的水

but compare one with an ice cube from the freezer,

但把它和冷凍庫裡面的冰塊比較一下

and you'll realize they're very different things.

你就會了解其實它們差異很大

Unlike ice cubes, formed when liquid freezes into a solid,

它不像冰塊， 冰塊是由液體結凍成固體

snowflakes form when water vapor turns straight into ice.

而雪花是由水蒸氣直接結凍成冰

But that still doesn't explain why snowflakes have six sides.

但這仍然沒有解釋 為什麼雪花會是六邊形

To understand that,

為了瞭解原因

we need to delve deeper into the physics of water.

我們需要更深入探索水的物理特性

Water is made out of two hydrogen atoms and one oxygen atom.

水分子是由兩個氫原子 與一個氧原子所構成

A single water molecule thus has ten protons and ten electrons,

因此，一個水分子中 會有十個質子和十個電子

eight from oxygen and one from each hydrogen atom.

八個來自於氧， 而兩個氫原子各提供一個

The two electrons from oxygen's outer shell

氧原子最外殼層的兩個電子

are shared with two electrons from both hydrogens as they bond together,

和兩個氫原子的電子互相分享 鍵結在一起

and the remaining four outer shell electrons from oxygen

氧原子剩下的四個外層電子

form two pairs.

則形成兩個電子對

We call the bonds between these atoms covalent bonds.

這些原子之間的鍵結， 稱為「共價鍵」

The pairs of electrons are all negatively charged.

電子對全都是帶負電

Similar charges repel,

同性相斥

so they tend to stay as far away from each other as possible.

所以它們盡可能的遠離彼此

The pairs form four electron clouds,

這些 電子對 會形成四個「電子雲」

two of which are where the hydrogen and oxygen share electrons.

其中兩個是由氫和氧共價產生

The repulsion between the unbonded pairs

沒有共價的電子對

is even stronger than repulsion between the shared pairs,

斥力比共價的電子對還要強

so the two hydrogens get pushed a little further

所以兩個氫原子被推遠離些

to an angle of 104.5 degrees.

形成一個 104.5 度角

The water molecule as a whole is electrically neutral,

水分子整體而言是電中性

but oxygen gets a larger share of electrons,

但共價的電子會比較傾向靠近氧

making it slightly negative and the hydrogens slightly positive.

致使氧微帶負電荷， 而氫微帶正電荷

Due to its negative charge,

因為氧微帶負電荷

the oxygen in one molecule

所以水分子中的氧

is attracted to the positive charge of the hydrogen in another molecule.

會被另一個水分子中 帶正電荷的氫所吸引

And so a weak bond between the two molecules,

因此，兩個分子之間 形成一個較弱的鍵

called a hydrogen bond, is formed.

稱為「氫鍵」

When water freezes, this bonding occurs on repeat,

當水結冰時，這種結合持續產生

ultimately forming a hexagonal structure

最後形成六角形結構

due to the angle between hydrogens and oxygen within each molecule.

那是因每個分子中 氫、氧之間的角度所致

This is the seed of a snowflake,

這即是雪花的晶粒

and it retains a hexagonal shape as it grows.

當它增大時， 仍繼續維持六角形的形狀

As the snowflake moves through the air,

當雪花在空氣中飛舞時

water vapor molecules stick to the six sharp edges

水蒸氣會附著在其六個銳利邊緣

and expand the snowflake outwards, bit by bit.

雪花因此漸漸往外擴大

A snowflake's developing shape depends on atmospheric conditions,

雪花的形狀則依大氣的狀態而定

like humidity and temperature.

例如濕度及溫度

As a snowflake falls,

當雪花落下時

changes in weather conditions can affect how it grows,

天氣的條件也會影響其形成

and even small differences in the paths two snowflakes take

甚至兩片雪花飄落路徑中， 條件有些不同

will differentiate their shapes.

形狀就會不一樣

However, since conditions at the six sharp edges of one snowflake are similar,

既然每片雪花的六個銳邊 其條件都相似

a symmetric snowflake can grow.

雪花便形成對稱形狀

Weather conditions affect snow on the ground, as well.

天氣條件也會影響地上的雪

Warmer ground temperatures produce a wetter snow that is easier to pack

較高的地面溫度 會產生較濕且易黏聚的雪

because liquid water molecules help snowflakes stick to each other.

因為液態水分子 促使雪花互相黏合一起

Melted snow also plays a critical role in another wintry activity, skiing.

融雪也是冬季運動的重要角色 ── 滑雪

Completely dry snow is very difficult to ski on

完全乾的雪是很難滑行的

because there's too much friction between the jagged snowflakes and the ski surface.

因為凹凸不平的雪花和滑雪板之間， 有極大的摩擦力

So what's happening is that as skis move,

當滑雪板移動時

they rub the surface of the snow and warm it up,

它們摩擦雪地的表面，使它增溫

creating a thin layer of water, which helps them slide along.

產生一層薄薄的水，幫助滑雪板滑動

So technically, it's not really snow skiing,

所以嚴格說，我們並非真正在滑雪

but water skiing.

而是在滑水

But it is true that no matter how hard you look,

但是的確，不管你多認真找

you're almost definitely not going to find two identical snowflakes,

你幾乎絕對不可能找到 兩片一模一樣的雪花

and that's a mystery that scientists are still trying to solve,

這也是個科學家們正極力解答的謎團

though we know that it has to do

我們知道的是

with the many possible branching points in snowflake formation,

它與雪花形成中眾多的分支點

and the differences in temperature and humidity,

及不同溫度、溼度有所關聯

and while we wait for the answer,

而當我們仍在等待答案時

we can enjoy watching these tiny fractals falling from the sky.

請好好觀賞這些從天而降的小碎片們吧

翻譯：Shang-Yung Sun