Light waves, visible and invisible

譯者: 復鈞(Frederic) 謝 審譯者: Shelley Krishna Tsang

What if you could only see one color?

如果你只能看見 一種顏色那會怎麼樣?

Imagine, for instance,

想像一下，比如說

that you could only see things that were red

你只能看見紅色的東西

and that everything else

而其他所有東西

was completely invisible to you.

對你來說都是隱形的

As it turns out,

實際上， 我們一直都是這樣生活的

that's how you live your life all the time

because your eyes can only see

因為我們的眼睛只能看到

a minuscule part of the full spectrum of light.

全光譜中微不足道的一小部分

Different kinds of light are all around you everyday

我們每天被不同的光波所包圍

but are invisible to the human eye,

但它們對人眼來說都是看不見的

from the radio waves that carry your favorite songs,

從你最愛歌曲的無線電波

to the x-rays doctors use to see inside of you,

到醫生用來觀察人身體內部的X光線

to the microwaves that heat up your food.

還有可用來加熱食物的微波

In order to understand

為了能夠理解

how these can all be light,

它們是如何被叫做光

we'll need to know a thing or two

我們需要一些

about what light is.

關於什麼是光的問題

Light is electromagnetic radiation

光就是電磁輻射

that acts like both a wave and a particle.

它間兼具有波與粒子的性質

Light waves are kind of like waves on the ocean.

光波和海浪有些許類似

There are big waves and small waves,

波浪本身有大小之分

waves that crash on the shore

波浪就是

one right after the other,

一波一波沖上岸

and waves that only roll in every so often.

而且波浪不會常常翻滾

The size of a wave is called its wavelength,

波浪的大小稱為波長

and how often it comes by

波浪重複的快慢

is called its frequency.

叫做波的頻率

Imagine being a boat in that ocean,

想像你坐在海上的一艘船裡

bobbing up and down as the waves go by.

船隨著波浪上下起伏

If the waves that day have long wavelengths,

如果那天的波浪有著較長的波長

they'll make you bob only so often,

那麼海浪只會偶爾讓船上下起伏

or at a low frequency.

或者說以較低的頻率

If the waves, instead, have short wavelengths,

相反的，如果波長很短的波浪

they'll be close together,

波浪彼此之間的距離很短

and you'll bob up and down much more often,

然後你就會感覺船在明顯的上下浮動

at a high frequency.

這就是較高的頻率

Different kinds of light are all waves,

不同種類的光就是光波

they just have different wavelengths and frequencies.

只不過他們有不同的波長和頻率的區別

If you know the wavelength or frequency

如果你知道一種光波的波長或頻率

of a wave of light,

you can also figure out its energy.

你就可以知道這個光波的能量

Long wavelengths have low energies,

波長長的光波有較低的能量

while short wavelengths have high energies.

而波長短的光波有較高的能量

It's easy to remember

記住這個並不難

if you think about being in that boat.

假設你在船上

If you were out sailing on a day

如果你航行的某一天

with short, choppy waves,

那天有波濤洶湧的短浪

you'd probably be pretty high energy yourself,

為避免被東西砸到而四處閃躲的過程中

running around to keep things from falling over.

你可能會消耗很多能量

But on a long wavelength sea,

但在有長波的海上

you'd be rolling along, relaxed,

你只會稍微搖晃，感覺非常放鬆

low energy.

不太消耗能量

The energy of light tells us

光的能量告訴我們

how it will interact with matter,

它是如何跟物體交互作用

for example, the cells of our eyes.

舉例來說，我們眼中的細胞

When we see, it's because the energy of light

當我們能看見東西 是因為光的能量

stimulates a receptor in our eye

刺激眼球的受器

called the retina.

稱為視網膜

Our retina are only sensitive to light

我們的視網膜只對小範圍的光

with a very small range in energy,

比較敏感

and so we call that range of light visible light.

我們稱那範圍的光為可見光

Inside our retina are special receptors

我們視網膜內有特殊的感應器

called rods and cones.

稱為視桿及視錐細胞

The rods measure brightness,

視桿細胞會偵測亮度

so we know how much light there is.

所以我們感受到亮度

The cones are in charge of what color of light we see

視錐細胞則負責解讀光的顏色

because different cones are sensitive

因為不同的視錐細胞

to different energies of light.

對特定光的能量、波長很敏感

Some cones are more excited by light

有些視錐細胞對於

that is long wavelength and low energy,

波長較長、能量較低的光較敏感

and other cones are more excited

而有些視錐細胞

by short wavelength, high-energy light.

對由短波長、高能量的光比較敏感

When light hits our eye,

當光線照到你的眼球

the relative amount of energy each cone measures

每個視錐細胞衡量光能量的相對值

signals our brain to perceive colors.

讓我們的大腦感知顏色

The rainbow we perceive

我們看到彩虹

is actually visible light in order of its energy.

實際上是能量使光有不同顏色

At one side of the rainbow

在彩虹的一側是低能量的光

is low-energy light we see as red,

是我們看到的紅色

and at the other side is high-energy light

而在另一側是高能量的光

we see as blue.

是我們看到的藍色

If light shines on us

如果光照耀我們

that has an energy our retina can't measure,

有一些我們的視網膜無法測量的能量

we won't be able to see it.

我們就無法看到它

Light that is too short wavelength or high energy

波長過短或高能量

gets absorbed by the eye's surface

都會被眼球表面吸收

before it can even get to the retina,

無法到達視網膜

and light that is too long wavelength

而波長太長的光

不具有足夠的能量

doesn't have enough energy

to stimulate our retina at all.

去刺激我們的視網膜

The only thing that makes one kind of light

每一種光波長都不一樣

different from another is its wavelength.

Radio waves have long wavelengths,

無線電有長的波長

while x-rays have short wavelengths.

而X光有短的波長

And visible light, the kind you can actually see,

而我們所說的可見光

is somewhere in between.

則介於兩者之間

Even though our eyes can't detect light

即使眼睛不能檢測出的光

outside of the visible range,

因為這些光不在可見光的範圍

we can build special detectors

我們還是可以使用特殊的儀器

that are stimulated

去探查這些其他波長的光

by these other wavelengths of light,

kind of like digital eyes.

例如數位化眼睛

With these devices,

用這個設備

we can measure the light that is there,

即使我們看不見的光

even though we can't see it ourselves.

仍能測量得到

So, take a step back and think about

因此，回來想想

all of this for a moment.

所有的光

Even though they seem different,

即使似乎都不同

the warmth you feel from a crackling fire

你由火堆得到的溫暖

is the same as the sun shining on you

跟風和日麗的日子

on a beautiful day,

照耀著你的陽光，紫外線一樣

the same as ultraviolet light

you put on sunscreen to protect yourself from,

像你的電視

你的收音機

the same thing as your TV,

和你的微波爐

your radio,

and your microwave.

而你用防曬乳來保護自己 不被這些波長的光照射

Now, those examples are all things here on Earth,

在地球上，在你日常生活裡

things you experience in your everyday life,

有很多這樣的例子

but here's something even more amazing.

但是有些東西更令人稱奇

Our universe gives off the full spectrum of light, too.

我們的宇宙也散發出光的全光譜

When you think of the night sky,

當你想到的夜空

you probably think of being able

你可能認為是能夠

to see the stars shining with your own eyes,

用自己的眼睛去看閃爍的星星

but that's just visible light,

但你看到的只有可見光

which you now know is only a tiny part

但你看到的

of the full spectrum.

只有全光譜中的一小部分

If we had to draw the universe

如果我們繪製宇宙

and could only use visible light,

並且只能使用可見光

it would be like having only one crayon --

它會像只有一個蠟筆

pretty sad.

看起來很傷心

To see the universe in its full spectrum,

如果要看到的宇宙的全光譜

we need to have the right eyes,

我們需要有個正確的眼睛

and that means using special telescopes

這意味著我們要使用特殊望遠鏡

that can help us see beyond visible light.

他可以幫助我們看到超越可見光的範圍

You've probably heard of the Hubble Space Telescope

你可能聽說過哈伯太空望遠鏡

and seen its beautiful pictures

並看到了它美麗的圖畫

taken in visible and ultraviolet light.

他可以看到可見光和紫外線

But you might not know

但你可能不知道

that there are 20 space telescopes in orbit,

這個太空望遠鏡的

missions that can each see part

任務是看到每個

of the full spectrum of light.

光的全光譜

With telescopes acting as our virtual eyes,

隨著望遠鏡充當我們的虛擬眼睛

both in space and here on Earth,

無論是在外太空還是在地球上

we can see some amazing things.

我們可以看到一些令人驚訝的事情

And the coolest thing of all,

而所有的最酷的事情

no matter the wavelength or energy,

不管波長或能量

the light that we see out in the distant universe

我們在遙遠宇宙中看到的光

is the same thing as the light

跟我們在地球上可以感受和學習的光

that we can experience and study here on Earth.

是同一樣東西

So, since we know the physics

所以，當我們知道物理學

of how x-ray,

在X光

ultraviolet light,

紫外線

or microwaves work here,

或是微波爐的運作原理，

we can study the light of a distant star or galaxy

我們也可以研究遙遠恆星或星系的光

and know what kinds of things

並了解

are happening there too.

那裡正在發生什麼事

So, as you go about your daily life,

因此，當你回到你的日常生活

think beyond what your eyes can and can't see.

想像你的眼睛能看到和不能看到的光

Knowing just a little bit about the natural world

了解自然世界的一點點

can help you perceive the full spectrum

可以幫助你隨時隨地感知你身邊的全光譜

around you all the time.