Making waves: The power of concentration gradients - Sasha Wright

翻译人员: sherry lee 校对人员: Yolanda Zhang

If you've ever floated on an ocean swell,

如果你曾经在海洋上漂浮，

you'll know that the sea moves constantly.

你就会知道海水是持续运动的。

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

放眼整个地球， 你就会了解更完整的运动状况：

our Earth, covered by 71 percent water,

我们地球71%的表面被水覆盖，

moving in one enormous current around the planet.

形成一个巨大的洋流， 绕着地球流动。

This intimidating global conveyor belt

这个全球传送带令人叹为观止，

has many complicated drivers,

其形成因素很多很复杂，

but behind it all is a simple pump

但我们可以用一个使海水绕地球流动的

that moves water all over the earth.

简单的水泵来概括。

The process is called thermohaline circulation,

这个过程叫做热盐环流，

and it's driven by a basic concept:

形成它的基础概念是

the concentration gradient.

浓度梯度。

Let's leave the ocean for one moment

让我们先把海洋环境放到一边，

and imagine we're in an empty room

想象我们身处一个空房间里，

with lots of Roombas sardined together

里面有很多扫地机器人吸尘器成堆地

in one corner.

挤在一个角落中。

Turn them all on at once

把它们全部启动的话，

and the machines glide outwards

这些机器就会划向四周，

bumping into and away from each other

互相撞来撞去，

until the room is filled with an evenly spaced distribution.

直到整个房间都均匀地 布满了这些吸尘器。

The machines have moved randomly

这些机器的运动方向是随机的，

towards equilibrium,

并最终达到平衡，

a place where the concentration of a substance

也就是在房间各个角落的分布

is equally spread out.

是均匀的。

That's what happens along a concentration gradient,

这就是浓度梯度的原理，

as substances shift passively from a high,

物质会被动地从

or squashed, concentration,

高密度的地方

to a lower, more comfortable one.

向低密度，更“舒适”的地方移动。

How does this relate to ocean currents and thermohaline circulation?

而这又与洋流和热盐循环有什么关系呢？

Thermo means temperature,

“thermo”意思就是温度，

and haline means salt

而“haline”是盐的意思，

because in the real world scenario of the sea,

因为在现实的海洋中，

temperature and salinity drive the shift

分布不均的温度和盐分促使

from high to low concentrations.

洋流从高浓度流到到低浓度。

Let's put you back in the ocean

让我们再回到海洋，

to see how this works.

看看现实情况是怎样的。

Snap!

啪！

You're transformed into a molecule of surface water,

你变成海面上的一个分子，

off the temperate coast of New York

身处纽约沿岸温和的海面上，

surrounded by a zillion rowdy others.

周围都是大量闹哄哄的其他分子。

Here, the sun's rays act as an energizer

在这里，太阳的光照提供了能量，

that set you and the other water molecules

使你和其他水分子

jostling about, bouncing off each other

相互推挤，撞来撞去，

like the Roombas did.

像机器人吸尘器一样。

The more you spread out,

你们分布得越广，

the less concentrated the water molecules

海面水分子的

at the surface become.

密度就越低。

Through this passive motion,

在这个被动过程中，

you move from a high to a lower concentration.

你从高密度区域移动到了低密度的区域。

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

让我们先暂时忘掉物理定律，

and pretend that your molecular self

假设作为分子的你

can plunge deep down into the water column.

可以一直潜入到海底深处。

In these colder depths,

在寒冷的海底，

the comparative lack of solar warmth

阳光照射相对较少，

makes water molecules sluggish,

水分子活性较低，

meaning they can sit quite still at high concentrations.

也就是说它们在高浓度时也依旧静止不动。

No jostling here.

不会发生碰撞。

But seeking relief

但它们也想

from the cramped conditions they're in,

从所在的拥挤环境挣脱出来，

they soon start moving upwards

于是它们开始向上游动

towards the roomier situation at the surface.

游向海面更宽敞的地方。

This is how temperature

这就是温度

drives a shift of water molecules

推动水分子流动的方式，

from high to low concentrations,

它们从高密度流向低密度，

towards equilibrium.

最终达到平衡。

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

但组成海水的不光有水分子。

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

还有大量的盐离子。

And like you, these guys have a similar desire

而像你一样，它们也想要

for spacious real estate.

在宽敞的环境中居住。

As the sun warms the sea,

当太阳光加热海水时，

some of your fellow water molecules

你们中有些水分子

evaporate from the surface,

从海面蒸发。

increasing the ration of salt to H2O.

增加了水中含盐量的比例。

The crowded salt ions left behind

拥挤的盐离子仍然留在水面，

notice that lower down,

并注意到海水深处的

salt molecules seem to be enjoying more space.

盐离子似乎能享受到更多的空间。

And so an invasion begins,

所以它们开始入侵了，

as they too move downwards in the water column.

它们也向下游到海水深处。

In the polar regions,

在极地地区，

we see how this small local process

我们可以看到这些微观的过程

effects global movement.

是如何影响全球环流的。

In the arctic and antarctic,

在南北极，

where ice slabs decorate the water's surface,

海面布满了浮冰，

there's little temperature difference

海面与海水深处产生了

between surface and deeper waters.

细微的温差。

It's all pretty cold.

其实两边都很冷。

But salinity differs,

但盐分分布不一样，

and in this scenario,

在这种情况下，

that's what triggers the action.

这种差距促使了反应的发生。

Here, the sun's rays melt surface ice,

这时，太阳光使部分表面浮冰融化，

depositing a new load of water molecules

使一些新的水分子

into the sea.

进入海水中。

That not only increases the proximity

这不仅使

between you and other water molecules,

水分子之间距离更近，

leaving you vying for space again,

让你再次想要寻找新的空间，

but it also conversely dilutes

还同时反过来稀释了

the concentration of salt ions.

盐离子的浓度。

So, down you go,

所以你会向下移动，

riding along the concentration gradient

沿着浓度梯度一路往下，

towards more comfortable conditions.

向更舒适的环境游去。

For salt ions, however,

而对盐离子来说，

their lower concentration at the surface,

它们在海面的低浓度

acts like an advertisement

就像宣传广告一样

to the clamoring masses of salt molecules below

吸引着底下大批的盐离子，

who begin their assent.

它们开始蠢蠢欲动。

In both temperate and polar regions,

无论是在温带还是在极地，

this passive motion along a concentration gradient,

这种沿着浓度梯度的被动过程

can get a current going.

都促成了洋流活动。

And that is the starting point

这就开始了

of the global conveyor

名为热盐环流的

called thermohaline circulation.

全球传送带。

This is how a simple concept

这就是一个简单的理论

becomes the mechanism underlying

支撑起了

one of the largest

我们地球规模最大

and most important systems on our planet.

以及最重要的系统之一。

And if you look around,

而如果你看看周围，

you'll see it happening everywhere.

你会发现这种现象无处不在。

Turn on a light, and it's there.

开灯也是这个原理。

Concentration gradients govern

浓度梯度支配着

the flow of electricity,

电流的产生，

allowing electrons squashed together in one space

使挤在一块儿的电子

to travel to an area of lower concentration

向电子密度更低的地方移动，

when a channel is opened,

当你打开开关，

which you do by flipping a switch.

电流通道也就打开了。

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

事实上，现在也有浓度梯度现象发生在

inside you as you breath air into your lungs

你体内，随着你把氧气吸入肺部，

letting the concentrated oxygen in that air

肺部堆积的氧气

move passively out of your lungs

就会被动地排出，

and into your blood stream.

进入到血液中。

We know that the world is filled

我们都知道，世界充满了

with complex physical problems,

复杂的物理问题，

but sometimes the first step

但是有时候，理解它们的第一步

towards understanding them can be simple.

是很简单的。

So when you confront the magnitude

所以当你遇到像

of the ocean's currents,

洋流这样宏大的问题，

or have to figure out how electricity works,

或想要了解电力如何运作时，

remember not to panic.

记住不要慌张。

Understanding can be as simple as flipping a switch.

认识的过程就像打开开关一样简单。