71% of the earth is covered in water, but only 2% of that water is pure.

地球表面有 71% 都被水覆蓋，但可飲用的淡水卻只占了 2%

As clean drinking water becomes more scarce,

當乾淨的飲用水變得越來越少

you may be wondering what happens if I drink seawater.

你可能會開始思考如果喝海水的話會發生什麼事？

Let's first examine how our bodies absorb water.

就先讓我們來了解一下我們的身體是如何吸收水分的吧！

You may remember the process of osmosis where water moves from

你大概還記得滲透作用，這個機制可以

a less concentrated solution to a more concentrated solution through a semipermeable membrane.

讓水透過半透膜從低濃度的地方流到高濃度的地方

The cell's membrane allows water to pass through, but not the particles dissolved in water like salt.

細胞膜可以讓水分子通過，但溶在水中的粒子像是鹽卻會被阻擋在外

Normally the saltiness of water inside ourselves is the same as the saltiness outside ourselves.

正常來說細胞膜內外的鹽度應該會是相同的

When you drink water, a concentration difference takes place.

但當你喝水時，濃度就會產生變化

Water from the outside of your cell moves inside to maintain balance.

細胞外的水會流到細胞內以維持濃度的平衡

This is called an isotonic state.

我們稱之為等滲壓的狀態

When you drink too much seawater, the saltiness outside your cells will increase rapidly

當你喝下過多的海水，細胞外的鹽度就會急遽上升

and the cells force water molecules out in order to restore balance.

此時細胞就會強迫讓水分子流到細胞外以恢復平衡

So, even if you are already dehydrated, drinking seawater will cause your cells to release more water

所以即使你已經脫水了，喝海水也只會讓更多水分從細胞流出

and you will end up peeing out more liquid than you take in.

最後你藉由尿液所排出的水分也只會比你喝進去的多

Conversely, if you chug a massive amount of pure water, the exact opposite will happen.

反之如果你突然喝下大量的純水，情況就會完全相反

The saltiness outside your cells will decrease rapidly and water will be forced into your cells.

細胞外的鹽度會馬上下降，水分子也會被迫進入細胞內

This can cause cells to swell and burst which in extreme cases leads to seizures, coma, and sometimes death.

這可能會造成細胞腫脹並破裂，再嚴重一點甚至會引發癲癇、昏迷、甚至是死亡

So what can you do if you are stranded on a deserted island with absolutely no fresh water around?

那如果你被困在一座四周沒有淡水的荒蕪之島該怎麼辦呢？

The simplest way to extract fresh clean water from the ocean

想要從海水裡得到可飲用的水，最簡單的方式

is through distillation which separates the salt from the water.

就是運用蒸餾來將海水裡的鹽跟水分離

In order to distill water, you must heat the seawater so it evaporates.

為了要把水蒸餾出來，你必須先加熱使海水蒸發

Then trap the evaporated water vapor until it cools and condenses back into liquid water.

再將這些蒸發後的水氣收集起來，並等到他冷卻凝結變回液態水

Kind of like the moisture on your bathroom mirror after a hot shower.

有點像是你在浴室洗完熱水澡後鏡子上的水氣

This condense water will be free of all salt and be 100% safe to drink.

這種冷凝水就完全沒有鹽，也可以百分之百安心飲用

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