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  • Why is the sky dark at night?

    夜晚的天空為什麼是黑暗的?

  • You might think the answer is obvious - the sun isn't up! But the only reason the sky

    你可能認為答案很明顯--太陽沒有升起!但天空的唯一原因是

  • looks blue during the day is that sunlight scatters off of the atmosphere - if we didn’t

    白天看起來是藍色的,是因為陽光從大氣層中散射出來--如果我們不這樣做的話

  • have an atmosphere (like on the moon), the sky would always be dark, even when the sun

    有大氣層的時候,即使在太陽底下,天空也是一片漆黑

  • is shining. So let’s rephrase the question - why is space dark?

    是發光的。所以,我們換個問題--為什麼空間是黑暗的?

  • I mean, space is full of stars - countless stars which are all about as bright as the

    我的意思是,太空中到處都是星星--無數的星星,它們的亮度都和

  • sun, and in an infinite eternal universe, no matter what direction you picked, if you

    太陽,在無限的永恆宇宙中,無論你選擇什麼方向,如果你

  • looked far enough in that direction, you would see a star or galaxy. So the whole sky should

    從這個方向看去,你會看到一顆恆星或星系。所以整個天空應該

  • be as bright as the sun, night and day!

    燦若驕陽,夜以繼日!

  • And since it's not, does the darkness of the night sky mean that there's some distance

    既然不是,那麼夜空的黑暗是否意味著有一些距離呢?

  • away from us when stars and galaxies juststop? A boundary between something and nothing?

    當恆星和星系... 停下來的時候,我們就離開了?在什麼和什麼之間的界限?

  • An "edge" to the universe?

    一個"邊緣"對宇宙的?

  • Not exactly - all of our evidence seems to indicate that space has no edge. But the universe

    不完全是--我們所有的證據似乎都表明,空間沒有邊緣。但宇宙

  • itself doesnot a spatial edge, but a temporal oneas far as we know, the universe had

    本身也是如此--不是空間邊緣,而是時間邊緣:據我們所知,宇宙有

  • a beginning. Or at least, a time about 13.7 billion years ago when the universe was so

    一個開始或者至少是在137億年前 宇宙是如此的脆弱不堪

  • small and crumpled-up with itself that our standard notion of space and time breaks down.

    渺小而又皺巴巴的自己,我們的標準空間和時間概念被打破了。

  • And since only a finite amount of time has passed since this so-called beginning, that

    由於這個所謂的開始只過去了有限的時間,所以,這

  • means that some of the stars necessary to fill up the "brightness in every direction"

    意味著一些恆星必要充實"各個方向的亮度&quot。

  • are so far away that light from them plain hasn't had time to reach us yetit's as

    是如此之遠,從他們平原的光還沒有來得及到達我們... ... 它是作為作為

  • if the universe were a big thunderstorm and we're still waiting to hear the thunder from

    如果宇宙是一個大雷雨,我們'仍然等待聽到雷聲從

  • the really distant stars.

    真正遙遠的星星。

  • But wait, it’s better than that - since light takes time to travel across the universe,

    但是,等等,比這更好的是--因為光在宇宙中旅行需要時間。

  • when we point our telescopes at something really far away, we're actually seeing that

    當我們把望遠鏡對準遠處的東西時,我們實際上看到的是...

  • part of universe as it was when the light was emitted. So when we look at 13.5 billion-year-old

    宇宙的一部分,因為它是 當光被髮射。所以當我們看135億年前的宇宙時

  • light, it's not that we don't see stars just because light from them hasn't gotten to us

    光,它'不是我們不'看不到星星只是因為從他們的光沒有得到我們。

  • yet - we don't see any stars because were getting a peek at the universe before any

    然而 - 我們不'看到任何恆星,因為我們得到一個窺視宇宙之前任何

  • stars had formed! A star-less universe! Now that sounds to me like a pretty good reason

    恆星已經形成!一個沒有恆星的宇宙!現在,這聽起來像是一個很好的理由

  • why we look up and see a dark night sky.

    為什麼我們抬頭看到的是一片漆黑的夜空。

  • Butit’s not. I mean, it is true that we can find points in the sky where there

    但是... 不是這樣的我的意思是,這是真的,我們可以找到點 在天空中,那裡有...

  • aren’t any stars by looking past the earliest stars and thus farther back in time. But even

    沒有任何恆星,通過看過去最早的恆星,從而更遠的時間。但即使是

  • when we point our telescopes past the earliest stars, we still see light. Not starlight,

    當我們把望遠鏡對準最早的恆星時,我們仍然能看到光。不是星光

  • but the light left over from the big bang. And we detect thiscosmic background radiation

    但大爆炸後留下的光。而我們檢測到的這種 "宇宙背景輻射"

  • coming more or less evenly from all directions, forming a background beyond the stars. So,

    從四面八方或多或少地均勻湧來,形成了恆星之外的背景。所以

  • I guess the night sky ISN’T actually dark to begin with.

    我想,夜空其實並不是一開始就黑暗的。

  • Right... so if our telescopes tell us that the night sky isn’t dark, then why does

    好吧... 所以如果我們的望遠鏡告訴我們夜空並不黑暗,那麼為什麼... ...

  • it look dark?

    它看起來很黑?

  • Here’s a clue to the real answer: when the Hubble telescope photographed the distant

    這裡有一個真正答案的線索:當哈勃望遠鏡拍攝到遙遠的。

  • stars of the astoundingly beautiful Hubble extreme deep field, it took the picture using

    恆星的驚人美麗的哈勃極深場,它拍攝的照片使用的是

  • an infrared camera. Why? Well, distant stars and galaxies are moving away from us because

    紅外線攝影機。為什麼呢? Why? 遙遠的恆星和星系正在遠離我們 Well, distant stars and galaxies are moving away from us because.遙遠的恆星和星系正在遠離我們,因為...

  • the universe is expanding. So the same way a record slowing down lowers the pitch of

    宇宙正在膨脹是以,同樣的方式,一個記錄慢下來降低了音調的

  • my voice, the doppler effect causes stars moving away from us to become redder, and

    我的聲音,多普勒效應會使遠離我們的恆星變得更紅,並且...

  • the farther away they are, the faster they move away from us and the redder they become,

    它們離我們越遠,它們離我們越快,它們變得越紅。

  • until they becomeinfrared. And then we can't see them any more. At least not with

    直到它們變成... 紅外線然後我們就看不到它們了 And then we can't see them any more.至少不是用...

  • our human eyes - and that’s why the night sky appears dark!

    我們人類的眼睛--這就是為什麼夜空看起來很黑的原因!

  • In summary: If we lived in an infinite, unchanging universe, the entire sky would be as bright

    總結:如果我們生活在一個無限的、不變的宇宙中,那麼整個天空就會像

  • as the sun. But the sky is dark at night, both because the universe had a beginning

    作為太陽。但夜晚的天空是黑暗的,這既是由於宇宙有一個起點

  • so there aren't stars in every direction and more importantly because the light from super

    所以並不是每個方向都有恆星,更重要的是,因為光從超級

  • distant stars (and the even-more-distant cosmic background radiation) gets red-shifted away

    遙遠的恆星(以及更遙遠的宇宙背景輻射)會被紅移開來

  • from the visible spectrum by the expansion of the universe, so we just plain can't see

    從可見光光譜由宇宙的擴張, 所以我們只是普通的可以不看

  • it.

    它。

  • Finally! Weve shed some light on why the night sky is dark. And why it isn’t.

    終於!我們終於明白了為什麼夜空是黑暗的。還有為什麼它不是。

Why is the sky dark at night?

夜晚的天空為什麼是黑暗的?

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B1 中級 中文 恆星 宇宙 夜空 黑暗 天空 遙遠

為何夜晚總是黑暗 Why is it Dark at Night?

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    Why Why 發佈於 2013 年 03 月 27 日
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