Making waves: The power of concentration gradients - Sasha Wright

譯者: Regina Chu 審譯者: Marssi Draw

If you've ever floated on an ocean swell,

如果你曾在海浪中沉浮

you'll know that the sea moves constantly.

你就知道海水不斷地在移動

Zoom out, and you'll see the larger picture:

拉遠點看比較清楚

our Earth, covered by 71 percent water,

我們的地球，71% 為水覆蓋

moving in one enormous current around the planet.

以巨大的水流移動著

This intimidating global conveyor belt

這個令人生畏的環球輸送帶

has many complicated drivers,

有很多複雜的驅動器

but behind it all is a simple pump

但背後其實是一個簡單的泵

that moves water all over the earth.

讓水在地球上移動

The process is called thermohaline circulation,

這個過程叫溫鹽環流

and it's driven by a basic concept:

使其流動的基本概念

the concentration gradient.

就叫做濃度梯度

Let's leave the ocean for one moment

先撇開海洋不談

and imagine we're in an empty room

想像我們在一個空房間

with lots of Roombas sardined together

裡頭有很多掃地機器人

像沙丁魚般擠在一個角落

in one corner.

Turn them all on at once

將它們同時啟動

and the machines glide outwards

掃地機器人就會向外滑行

bumping into and away from each other

撞來撞去越分越開

until the room is filled with an evenly spaced distribution.

最後掃地機器人 平均分散在整個房間

The machines have moved randomly

這些機器在隨機運動之下

towards equilibrium,

達到平衡

a place where the concentration of a substance

就是物質密度

is equally spread out.

平均分布的意思

That's what happens along a concentration gradient,

濃度梯度也是同樣的道理

as substances shift passively from a high,

就是物質會從高濃度

or squashed, concentration,

或從很擠的地方

to a lower, more comfortable one.

被動地移到低濃度，比較舒服的地方

How does this relate to ocean currents and thermohaline circulation?

這跟洋流及溫鹽環流又有何干呢？

Thermo means temperature,

「溫」就是溫度

and haline means salt

「鹽」就是鹽度

because in the real world scenario of the sea,

因為在海洋中，實際情況是

temperature and salinity drive the shift

溫度和鹽度驅動著

from high to low concentrations.

高濃度往低濃度的移動

Let's put you back in the ocean

讓我們回到海上

to see how this works.

看看這到底如何運作

Snap!

啪！

You're transformed into a molecule of surface water,

你變成水面的一個分子

off the temperate coast of New York

在紐約旁的溫帶海域中

surrounded by a zillion rowdy others.

數不清的喧鬧水分子包圍著你

Here, the sun's rays act as an energizer

在這裡，陽光就像勁量電池一樣

that set you and the other water molecules

讓你和其他水分子

jostling about, bouncing off each other

互相推擠、彈開

like the Roombas did.

就像掃地機器人一樣

The more you spread out,

水分子散得愈開

the less concentrated the water molecules

表面的密度

at the surface become.

就會愈小

Through this passive motion,

藉著這種被動運動

you move from a high to a lower concentration.

你從高密度移動到低密度的地方

Let's suspend the laws of physics for a moment,

先不管物理法則

and pretend that your molecular self

假裝你這個分子

can plunge deep down into the water column.

能潛到水層深部

In these colder depths,

在較冷的深層水中

the comparative lack of solar warmth

相對缺少陽光的熱能

makes water molecules sluggish,

水分子幾乎不太動

meaning they can sit quite still at high concentrations.

所以可以維持極高的密度

No jostling here.

不會撞來撞去

But seeking relief

但是為了要舒緩

from the cramped conditions they're in,

這種擁擠的情況

they soon start moving upwards

他們很快開始向上移動

towards the roomier situation at the surface.

至更寬敞的水面

This is how temperature

這就是溫度如何

drives a shift of water molecules

驅使水分子

from high to low concentrations,

從高密度往低密度移動

towards equilibrium.

達到平衡

But sea water is made up of more than just H2O.

但海水中不只有水分子

There are a great deal of salt ions in it as well.

還有許多的鹽離子

And like you, these guys have a similar desire

就像你一樣，這些傢伙也想要

for spacious real estate.

寬敞的豪宅

As the sun warms the sea,

太陽溫暖了海洋

some of your fellow water molecules

你的某些水分子同伴

evaporate from the surface,

隨之從水面蒸發

increasing the ration of salt to H2O.

鹽對水的比例相對增高

The crowded salt ions left behind

留下來的擁擠鹽離子

notice that lower down,

注意到在比較深的地方

salt molecules seem to be enjoying more space.

鹽分子似乎享受著更寬敞的空間

And so an invasion begins,

因此一場入侵戰爭開打

as they too move downwards in the water column.

他們也要向下移動到水層深部

In the polar regions,

在極地區

we see how this small local process

我們看到這種小區域的過程

effects global movement.

如何影響全球波動

In the arctic and antarctic,

在北極與南極

where ice slabs decorate the water's surface,

冰塊點綴在水面上

there's little temperature difference

表層與深層的水

between surface and deeper waters.

溫差極小

It's all pretty cold.

全部都很冷

But salinity differs,

但鹽度卻有差別

and in this scenario,

在這情節下

that's what triggers the action.

這就是觸發行動的原因

Here, the sun's rays melt surface ice,

這裡，陽光融化了表冰

depositing a new load of water molecules

為海洋注入一堆

into the sea.

新的水分子

That not only increases the proximity

這不但拉近了

between you and other water molecules,

你與其他水分子的距離

leaving you vying for space again,

致使你又開始爭奪空間

but it also conversely dilutes

另一方面還會稀釋

the concentration of salt ions.

鹽離子的濃度

So, down you go,

所以你往下走

riding along the concentration gradient

順著濃度梯度一路下滑

towards more comfortable conditions.

到更舒適的地方

For salt ions, however,

但對鹽離子而言

their lower concentration at the surface,

他們在水面的低濃度狀況

acts like an advertisement

就像廣告般吸引著

to the clamoring masses of salt molecules below

下面喧鬧不休的巨量鹽分子

who begin their assent.

於是他們向上攀升

In both temperate and polar regions,

在溫帶與極地氣候區

this passive motion along a concentration gradient,

這種順著濃度梯度的被動運動

can get a current going.

能產生水流

And that is the starting point

而這正是

of the global conveyor

一種全球輸送帶

called thermohaline circulation.

稱為溫鹽環流的起始點

This is how a simple concept

這就是一個簡單的概念如何

becomes the mechanism underlying

變成主要機制，潛藏在

one of the largest

地球上最大

and most important systems on our planet.

且最重要的系統下

And if you look around,

如果你環顧四周

you'll see it happening everywhere.

你會發現這隨處可見

Turn on a light, and it's there.

把燈打開也會看到此現象

Concentration gradients govern

濃度梯度掌控

the flow of electricity,

電力流動的方向

allowing electrons squashed together in one space

使擠在一處的電子

to travel to an area of lower concentration

移動到較低濃度的地方

when a channel is opened,

在電路通的時候

which you do by flipping a switch.

即你打開開關時

Right now, in fact, there's some gradient action going on

其實現在就有好幾個梯度作用

inside you as you breath air into your lungs

在你體內發生，例如你吸空氣進入肺

letting the concentrated oxygen in that air

使得在那團空氣中濃縮的氧氣

move passively out of your lungs

被動運動進入肺中

and into your blood stream.

及你的血液中

We know that the world is filled

我們知道這世界充滿了

with complex physical problems,

複雜的物理問題

but sometimes the first step

但常常了解它們的第一步

towards understanding them can be simple.

可能很簡單

So when you confront the magnitude

所以當你面臨巨大的洋流

of the ocean's currents,

or have to figure out how electricity works,

或必須搞清楚電力如何運作時

remember not to panic.

記得不要驚慌

Understanding can be as simple as flipping a switch.

要了解這些就如打開開關一樣簡單