What is the rarest color in nature? - Victoria Hwang

譯者: Camila Lin 審譯者: Bruce Sung

Every color you see in front of you can be found in nature.

你眼前的所有顏色， 都能在大自然中找到。

Some plant, animal, or mineral bears almost every hue imaginable.

有些植物、動物、礦物， 含有你能想像到的幾乎所有顏色。

But which of these colors are you least likely to see in the natural world?

但在這些顏色之中， 哪一種顏色最難在自然中發現？

There are two factors that drive the rarity of color in nature:

自然顏色的稀有度， 主要由兩個因素決定：

physics and evolution.

物理和演化。

Let’s start with physics.

讓我們先來看看物理學。

Colors are generated when wavelengths of light interact with objects,

顏色是光的波長 和物體表面互動的結果。

and most of the colors you’ve seen outside a screen

你在螢幕外看見的大多數顏色，

were produced in one of two ways.

由兩種方式產生。

In absorption-based colors,

就基於吸收而產生的顏色來說，

certain wavelengths are absorbed by an object, while others are not.

物體會吸收特定波長的光波， 而反射其他波長的光波。

The result is a matte final color generated by these leftover light waves.

這些被反射的光波彼此混合， 產生最終顯示的顏色。

Most naturally occurring colors fall into this category,

大多數的自然顏色都是這樣產生，

including those of many fruits and flowers.

包括許多水果和花卉的顏色。

Plants are full of compounds called pigments that absorb light waves

植物飽含名為「光合色素」的化合物，

用來吸收光線，作為光合作用的一環。

as part of photosynthesis,

the process by which they convert sunlight into energy.

光合作用能將陽光轉化為能量。

While different plants have evolved different pigments

由於不同植物演化出不同的色素，

that result in different colors,

所以它們呈現的顏色也不同，

higher energy wavelengths are more easily absorbed than lower energy ones.

較高能量的波長， 比較低能量的光更容易被吸收。

And blue light has some of the highest energy wavelengths

而在可見光中，

藍光是能量最高的光波之一。

in the visible spectrum.

Numerous pigments have evolved to absorb blue light,

許多光合色素演化出吸收藍光的功能，

including chlorophyll, which absorbs blue and red wavelengths

例如能吸收紅光和藍光的葉綠素，

to produce nature’s trademark green.

製造出大自然的標誌性綠色。

However, green light is still fairly energetic,

但是，綠光的能量也不低，

and the most common class of pigments evolved to absorb these wavelengths

因此最常見的光合色素也都演化出

吸收綠光的功能。

as well.

There are over 1,100 types of carotenoids,

有超過 1100 種類胡蘿蔔素，

pigments which absorb high energy blue and green light,

這是一種能吸收高能量的藍光與綠光，

while leaving behind the lower energy red and yellow light.

同時反射低能量的 紅光與黃光的光合色素。

While carotenoids are present in most green plants,

雖然幾乎每種植物都含有類胡蘿蔔素，

they only become visible each fall when chlorophyll gets broken down

但要到每年秋天，植物為了 儲備過冬能量而分解葉綠素時，

to save energy for the winter.

我們才能看見它們的顏色。

But whether they’re working alone or side by side,

但無論這些光合色素 是分工合作，或是單打獨鬥，

these pigments absorb blue light in virtually all plants.

幾乎所有植物都會吸收藍光。

Even fruits and flowers that appear blue

就算是看似藍色的水果或花朵，

actually have pigments that are red or purple,

其實也含有紅色或紫色的色素，

and only truly turn blue under specific chemical conditions.

並只在特定化學條件下才會變成藍色。

So, is blue the rarest color in nature?

所以藍色是自然中最稀有的顏色嗎？

Not quite.

還不能下定論。

Absorption is just one of the two main ways light generates color.

吸收只是光產生顏色的其中一種方法。

In the second method, some wavelengths are scattered and amplified—

第二種方法中， 某些光波被散射、放大，

overpowering the others to determine an object's final color.

凌駕於其他光波之上， 決定了物體最終的顏色。

These structural colors occur

這些結構色之所以產生，

because some objects around us are made of microscopic particles

是因為我們周遭的 某些東西由微粒組成，

which can form nanostructures that interfere with visible light.

能產生奈米結構，和可見光相互作用。

For example, this feather has no blue pigments in it.

例如，這根羽毛並不含藍色的色素。

But when light strikes it, the electrons within its nanostructure

但光照射在羽毛上時， 羽毛奈米結構中的電子

vibrate at the same frequency as the weight.

會用和光波相同的頻率震動。

This makes the particles send out a new wave with the same frequency,

因此，粒子也會發射相同頻率的新波，

starting a chain reaction that amplifies and scatters blue light.

開始一段能放大、 折射藍光的連鎖反應。

Nanostructures of various shapes and sizes scatter different wavelengths,

不同形狀和尺寸的奈米結構， 會折射出不同波長，

but they typically scatter high-energy wavelengths most easily—

但它們通常最容易折射高能量的光波，

making blue the most common structural color.

讓藍光成了最常見的「構造色」。

Meanwhile, low-energy wavelengths like red are only weakly scattered.

而紅色這種低能量的光波， 折射力道通常很弱。

Even when something evolves specific nanostructures

就算有東西演化出特別的奈米結構，

that strongly scatter red light

能折射出強烈的紅光，

they still resonate with other wavelengths,

這些結構仍會和其他波長的光共振，

only appearing red at some angles of illumination and observation.

只能以某些角度照明、觀察， 才能看見紅色。

This gives us two contenders for nature’s rarest color:

這讓我們看見自然界 最稀有顏色的兩個競爭者：

absorption-based matte blues and structural iridescent reds.

因吸收混合出的藍色， 以及結構色中的紅色。

Between these two, structural reds are much rarer.

以這兩者來說，結構色的紅色更稀有。

Only a handful of animals and rocks scatter red light

只有少數動物和石頭能折射出紅光，

and none of them scatter red light exclusively.

但沒有一種物體能只折射出紅光。

But since red and blue are rare in one way and common in another,

在兩種形成顏色的方式中，紅色 和藍色各是一種稀缺另一種普遍，

we actually end up seeing both colors quite often.

因此我們仍能時常看見紅色與藍色。

So what color is least likely to be generated

所以，究竟是哪種顏色最難製造，

in structural and absorption-based forms?

不管是以結構色還是吸收色而言？

The answer is violet.

答案是藍紫色。

Not to be confused with purple, which is just a combination of red and blue light,

可別把它誤認成 紅光和藍光混合出的紫色。

violet occupies a small portion of the visible light spectrum.

藍紫光也是可見光譜裏的小小一員。

There are only a few nanostructures precise enough

只有少數夠精確的納米結構，

to exclusively scatter violet light.

才能特別散射出藍紫光。

And violet wavelengths are even more energetic than blue ones,

藍紫光的能量比藍光更強，

making them likely to be absorbed by pigment.

因此更容易被光合色素吸收。

So if you ever stumble onto the iridescent violet wings

所以如果你碰巧看到

紫帝王蝶的藍紫色雙翅，

of a purple emperor butterfly,

take a second to appreciate one of nature’s rarest spectacles.

就花點時間，欣賞 大自然中最獨特的奇觀吧。