this time of year the sun never sets. It was crazy. Why is it so hard to sleep when it's light out?

現在正是北極的永晝，日照時間長得很誇張。為什麼外面有光線時，我們會難以入睡呢？

Hey light sleepers, Trace here. This is DNews. Everything sleeps or has some kind of active

嘿，淺眠的人們，看過來吧。這是 DNews 頻道。生物都會睡覺，不睡覺的，腦部也會有活躍

and inactive cycle, but not everything sleeps at night, like we do.

與不活躍的週期。但是，不是每種生物都跟人類一樣在晚上睡覺。DNews的固定觀眾

Regular DNews watchers will know about the circadian rhythm, the pattern of sleep and wakefulness connected to the amount of light entering the eye.

想必有聽過生理時鐘這個模式。睡眠跟失眠與

When we perceive daylight, our brains lessen the release of melatonin,

進入眼睛的光線多寡有關。當我們接受到日光，我們的腦袋會減少褪黑激素的釋放

making us more wakeful. And at night, more melatonin, more sleepy.

使得我們更難以入睡。而到了晚上呢？腦中會釋放褪黑激素，讓我們也更想睡覺

But, it's not just about sleepiness.

然而，這不只跟睡眠相關而已

Even self-proclaimed night owls need darkness to sleep.

甚至自詡為夜貓族的人也需要在黑暗的環境中睡覺

We evolved to sleep in the dark, and we know this because when it's dark our hormone levels fluctuate causing widespread changes in our physiology.

人類已經演化成在黑暗的環境中睡覺的生物。因為在黑暗的環境中，我們的賀爾蒙會產生變動，造成人體生理的改變

It's built-in. Melatonin lowers blood pressure, sugar levels, and body temperature.

這是內建的。褪黑激素降低了血壓、血糖以及體溫

Leptin makes us less hungry.

瘦蛋白會減低我們的飢餓感

(Both of these) prepping us for rest.

賀爾蒙與瘦體素會讓身體準備進入休息狀態

When we're sleeping, the levels of cortisol, a stress hormone, drop, and our immune function improves.

。當我們在睡覺時，皮質醇 (壓力賀爾蒙) 的濃度會下降，而且我們的免疫功能也會變強

Even though this explains why we sleep at night, it doesn't tell us why we evolved this way.

即使這樣解釋了我們在晚上睡覺的原因，但是我們還是不知道，為什麼人類會演化成在夜晚睡覺的生物

Sleeping at night is actually kinda weird. Only 20 percent of mammals sleep at night.

在夜裡睡覺其實有點詭異。僅有百分之二十的哺乳類動物會在夜裡睡覺

Most mammals are nocturnal, spending their days tucked away for sleepy time.

大多的哺乳類是夜行性的動物，他們在白天睡覺

A study of fossils from the last 100 million years found nocturnal species evolved way before mammals even appeared.

人們針對一億年前的化石進行研究，發現夜行性動物在哺乳類出現之前就已經演化了

Primates don't have a specific pattern of day-night cycling.

靈長類並沒有特定日夜循環的型態

In fact, a study in the American Journal of Physical Anthropology looked at fossils of primates

事實上，美國體格人類學雜誌研究靈長類的化石

and found species can be either diurnal (day active) or nocturnal (night active).

發現有些靈長類是日行性 (日間活躍)，有些則是夜行性 (夜間活躍)

But because we sleep at night, modern humans must have evolved from a diurnal group of ancient primates.

但因為我們在晚上睡覺，所以現代人類一定是從日行性的靈長類祖先演化而來的

And this is supported by scientists who study pre-industrial societies before the electric light.

研究尚未工業化時期社會的科學家也支持這樣論點

They've found humans went to sleep just after sunset for a while, woke up, were active in the middle of the night (in the dark),

。在工業化之前，電燈並不存在於人類社會他們發現人們會在太陽下山後去睡一陣子，接著起床，在半夜做點事情 (黑暗中)

and then slept again -- that's our second sleep, by the way. That's awesome. That's our natural order,

然後再去睡 -- 這是我們的第二段睡眠。非常好！這是人類睡眠的自然規律 --

sleeping twice, of course, in the dark.

進行兩次睡眠，當然是在天黑後

But now, even a little light can mess up our sleep schedules because we have electricity. Because our brain is just watching,

但是現在，因為我們有電的緣故，所以即使是一點點光線也會打亂你的睡覺時間表。因為我們的大腦一直在觀察

always watching. and it gets confused when any light is present…

一直觀察。一旦晚上有燈光，我們的大腦會十分困惑......

because it didn't evolve to have light at night. Even when your eyes are closed your brain sees light through your eyelids,

因為大腦還沒進化成能適應夜晚有光線的出現，即使你閉上眼，你的大腦也能透過眼皮感受到光線

and lowers melatonin release, making you more awake. You're affected by glowing electronics,

進而降低褪黑激素的分泌，所以你會更清醒。你會被發光的電子產品

digital clocks, and lights from other rooms or the street that shine onto you. A study with rats

數位時鐘，還有從其他房間或是街道上照到你的光線所影響。有個研究老鼠的實驗

found they slept in different positions and had different sleep behaviors when exposed only to dim twilight sleep,

發現老鼠只接觸到一點微光時，他們會有不同的睡姿，睡覺時也會有不同的行為

and a study with hamsters found signs of depression when they slept with a light at the equivalent of a glowing TV screen in their room.

在另一個研究倉鼠的實驗中，當倉鼠睡在一間房間，其亮度等同於開啟中的電視所散發出的亮光時，科學家發現倉鼠變得沮喪

Studies have correlated

研究指出

excess light at night with breast cancer, and darkness at night with better performance of a breast cancer drug,

夜晚過量的光線與胸腔癌有所關連，而醫治胸腔癌的藥物，如果配上沒有光線干擾的夜晚，藥效會更好

and even connected lessened tumor growth with more sleep.

而更多的睡眠甚至可以減緩腫瘤的生長

Not to mention all the normal immune, obesity, depressive and other health effects associated with having too much or too little sleep.

其他更不用說了！我們免疫力、肥胖、憂鬱症等都跟睡眠有關，不管睡太多或睡太少都會對健康造成影響

So, while we don't know exactly why we evolved to sleep in the dark, we know our eyes and

雖然我們不知道，人類為何演化成在夜裡睡覺的動物，但我們的眼睛

our brains have adapted to work better during the daytime and put us to sleep at night.

還有大腦在白天的工作效率比晚上好，而晚上就是睡覺休息

Thus, we should sleep in a dark room, regardless of the actual time of day.

因此，不管我們一天實際的睡眠時間多長，都應該在全黑的房間裡睡覺

And this is supported by research in, of course, National Sleep Foundation, so... *yawn* maybe… I should… (have a nap). Give me that pillow.

美國國家睡眠基金會支持這個做法。或許......我現在應該要去睡個午覺，把那個枕頭給我

Have a nap!

來睡一會吧！

*yawn again* Why is it that yawning makes you want to yawn? Why do we even YAWN!?

(再次打哈欠) 為什麼打哈欠會傳染？我們究竟為什麼會打哈欠呢？

Check out this old video, opens it wide, and checks in on this weird universal behavior.

看看之前的影片：張大嘴巴。一起看看這個全世界都有的怪異行為

The act itself is usually associated with being tired.

打哈欠的行為通常和疲勞有關

Of course a symbol of boredom in humans

當然這也是人類覺得無聊的訊號

But in animals, yawning could be associated with sexual arousal, fear, uncertainty,

但對於動物而言，打哈欠可能表達的是性興奮、恐懼、不確定感、

mating rituals, and even as a warning sign on other animals .

求偶的儀式，或警告其他動物的訊息

Perhaps a it's a way to passively show large teeth to the enemy.

也許，打哈欠是動物自然而然對敵人秀出尖牙的方法

Do you sleep in PURE DARKNESS? Or you are more of a...... "I'll sleep anywhere" person

你在全黑的環境中睡覺嗎？還是你是那種「我在哪裡都可以睡」的人呢？

Subscribe so you get more DNews.Thanks for watching and let us know down on the comments.

訂閱我們的頻道，你可以看到更多 DNews 的影片。謝謝你的觀賞，有什麼想法，請留在下面評論區讓我們知道喔！