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  • To human eyes, the world at night is a formless canvas of grey.

    在人類的眼中,夜晚的世界籠罩在一層灰色無形的布幕之下

  • Many nocturnal animals, on the other hand,

    另一方面許多夜行性動物

  • experience a rich and varied world bursting with details, shapes, and colors.

    能感受到一個充滿細節、形狀及色彩等豐富多樣的世界

  • What is it, then, that separates moths from men?

    那麼到底是什麼區隔了蛾與人?

  • Moths and many other nocturnal animals see at night

    蛾與其他許多夜行性動物有夜視力

  • because their eyes are adapted to compensate for the lack of light.

    是因為牠們的眼睛可以去彌補光線不足的情形

  • All eyes, whether nocturnal or not,

    所有眼睛,不管是不是夜行性動物的,

  • depend on photoreceptors in the retina to detect light particles,

    依賴視網膜上的感光細胞去偵測光粒子

  • known as photons.

    也就是光子

  • Photoreceptors then report information about these photons to other cells

    感光細胞接著會將這些光子的資訊傳給其他

  • in the retina and brain.

    在視網膜或是腦中的細胞

  • The brain sifts through that information and uses it to build up an image

    腦會篩選資訊並利用它來形成一個

  • of the environment the eye perceives.

    眼睛所接收到的環境的影像

  • The brighter the light is, the more photons hit the eye.

    光線越亮,越多光子打進眼睛裡

  • On a sunny day,

    在晴朗的一天

  • upwards of 100 million times more photons are available to the eye

    眼睛可接收到多一億倍的光子

  • than on a cloudy, moonless night.

    比起一個陰天、沒有月亮的夜晚

  • Photons aren't just less numerous in darkness,

    光子在黑暗中不只是數量比較少

  • but they also hit the eye in a less reliable way.

    且它們以較不準確的方式打進眼睛中

  • This means the information that photoreceptors collect

    意思就是感光細胞所收集的資訊

  • will vary over time,

    每次都不同

  • as will the quality of the image.

    而影像的品質也是一樣

  • In darkness, trying to detect the sparse scattering of randomly arriving photons

    在黑暗中,試著去偵測稀疏散落且隨機分布的光子

  • is too difficult for the eyes of most daytime animals.

    對許多日行性動物來說太困難了

  • But for night creatures, it's just a matter of adaptation.

    但是對夜間動物來說,這只是適應上的問題

  • One of these adaptations is size.

    其中一項是尺寸的適應

  • Take the tarsier, whose eyeballs are each as big as its brain,

    舉每顆眼球都和腦袋一樣大的跗猴為例,

  • giving it the biggest eyes compared to head size of all mammals.

    和頭相比牠可說是所有哺乳類中擁有最大的眼睛

  • If humans had the same brain to eye ratio, our eyes would be the size of grapefruits.

    如果人類也擁有相同的腦-眼比例,我們的眼睛會和柚子一樣大

  • The tarsier's enlarged orbs haven't evolved to make it cuter, however,

    然而,跗猴的大眼球並沒有讓牠看起來比較可愛

  • but to gather as much light as possible.

    但可以盡量聚集光線

  • Bigger eyes can have larger openings, called pupils,

    比較大的眼睛就會有比較大的開口,也就是瞳孔

  • and larger lenses,

    以及比較大的晶狀體

  • allowing for more light to be focused on the receptors.

    可以讓更多的光線聚集在感覺器官上

  • While tarsiers scan the nocturnal scene with their enormous peepers,

    當跗猴用牠們巨大的眼睛掃過夜景

  • cats use gleaming eyes to do the same.

    貓用閃閃發光的眼來做同樣的事情

  • Cats' eyes get their shine from a structure called the tapetum lucidum

    貓的眼睛從一個稱為脈絡膜層的構造來發亮

  • that sits behind the photoreceptors.

    脈絡膜層在感光細胞的後面

  • This structure is made from layers of mirror-like cells containing crystals

    這構造是由層層包含水晶的鏡狀細胞所組成

  • that send incoming light bouncing back towards the photoreceptors

    水晶會反彈進去的光線回到感光細胞

  • and out of the eye.

    並到眼睛外面

  • This results in an eerie glow,

    這導致了奇異的光線

  • and it also gives the photoreceptors a second chance to detect photons.

    且這讓感光細胞有第二次偵測光子的機會

  • In fact, this system has inspired the artificial cats' eyes we use on our roads.

    事實上,這系統給我們製造出在路上所用的人工貓眼的靈感

  • Toads, on the other hand, have adapted to take it slow.

    蟾蜍,另一方面,適應去慢慢來

  • They can form an image

    牠們可以製造影像

  • even when just a single photon hits each photoreceptor per second.

    甚至在每秒每個感光細胞只能收到一個光子的情況下

  • They accomplish this with photoreceptors

    牠們利用感光細胞來完成

  • that are more than 25 times slower than human ones.

    接收比人類還要慢25倍

  • This means toads can collect photons for up to four seconds,

    這代表蟾蜍可以收集四秒鐘的光子

  • allowing them to gather many more than our eyes do

    讓牠們能夠聚集到比我們眼睛能夠做到的更多的光子

  • at each visual time interval.

    在每個視覺時間間隔

  • The downside is that this causes toads to react very slowly

    缺點是這讓蟾蜍反應非常遲緩

  • because they're only receiving an updated image every four seconds.

    因為牠們只能每四秒接收到一個更新的影像

  • Fortunately, they're accustomed to targeting sluggish prey.

    幸虧牠們習慣獵捕行為緩慢的獵物

  • Meanwhile, the night is also buzzing with insects,

    同時,夜晚也充滿著嗡嗡的昆蟲

  • such as hawk moths,

    像是鷹蛾

  • which can see their favorite flowers in color, even on a starlit night.

    鷹蛾可以看見牠們最愛的花的顏色,甚至在星光燦爛的夜晚

  • They achieve this by a surprising move -

    牠們利用一個令人驚訝的行為來做到這事:

  • getting rid of details in their visual perception.

    牠們的視覺擺脫了細節

  • Information from neighboring photoreceptors is grouped in their brains,

    在鄰近的感光細胞收到的資訊會在腦中成群

  • so the photon catch of each group is higher

    所以每群接收到的光子比較多

  • compared to individual receptors.

    跟單一的受器比起來

  • However, grouping photoreceptors loses details in the image,

    然而,群聚的感光細胞的影像會失去些細節

  • as fine details require a fine grid of photoreceptors,

    因為完整的細節需要良好的感光細胞

  • each detecting photons from one small point in space.

    每個細胞都能從一個小點的空間偵測到光子

  • The trick is to balance the need for photons with the loss of detail

    這手段是以失去影像細節來平衡對光子的需求

  • to still find their flowers.

    但仍能找到牠們想要的花

  • Whether eyes are slow, enormous, shiny, or coarse,

    不管是接收慢的、巨大的、亮晶晶的、或是粗糙的眼睛

  • it's the combination of these biological adaptations

    那都是生物的適應

  • that gives nocturnal animals their unique visual powers.

    讓夜行性動物擁有牠們獨特的視覺力量

  • Imagine what it might be like to witness through their eyes

    想像一下從牠們的眼睛來觀看是什麼感覺

  • the world that wakes up when the sun goes down.

    看這個當太陽下山才醒來的世界

To human eyes, the world at night is a formless canvas of grey.

在人類的眼中,夜晚的世界籠罩在一層灰色無形的布幕之下

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B2 中高級 中文 美國腔 TED-Ed 光子 細胞 眼睛 光線 影像

【TED-Ed】為什麼動物可以在黑暗中看得一清二楚?? (How do animals see in the dark? - Anna Stöckl)

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    吳D 發佈於 2016 年 09 月 22 日
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