But looking up at the night sky is different.

但抬頭看夜空就不一樣了。

When we look at the stars we're actually looking at the past, we aren't seeing the stars, or

當我們看星星的時候，我們其實是在看過去，我們不是在看星星，也不是在看

really anything in the universe as they currently are.

真正的宇宙中的任何東西，因為他們目前。

We're seeing them as they were.

我們看到的是他們原來的樣子。

This all comes down to the way that light travels through space.

這一切都歸結於光在空間中的傳播方式。

Understanding space-time and why light moves the way it does means that one day we could

理解時空和為什麼光的運動方式意味著有一天我們可以做到以下幾點

look so far into the cosmos, we could be able to see the very first light at the birth of

遙望宇宙，我們可以看到宇宙誕生時的第一道光。

the universe, nearly 13.8 billion years ago.

宇宙，近138億年前。

And, in fact, there are astronomers and cosmologists working on this right now.

而事實上，現在就有天文學家和宇宙學家在研究這個問題。

The most important point you need to remember is that light travels at a constant speed,

你需要記住的最重要的一點是，光的傳播速度是恆定的。

which means that it takes time to get anywhere.

這意味著，它需要時間才能到達任何地方。

So if you look up the Big Dipper.

所以如果你查北斗星。

The stars are anywhere from 79 to 125 light years away.

恆星距離79到125光年不等。

That means that what you're seeing is really the light that left the star 79 or more years

這意味著你所看到的是離開恆星79年或更久的光芒

ago, when you look up and see the moon, that's what it looked like 1.3 seconds ago.

前，當你抬頭看到月亮時，那是1.3秒前的樣子。

Same idea with planets, and it works in reverse too, if you looked at Earth through a super

行星也是一樣的想法，反過來說也是一樣的，如果你通過一個超強的地球來觀察地球的話

powerful telescope, from a galaxy 65 million light years away, you would see the earth

在六千五百萬光年外的星系中，你會看到地球。

as it was 65 million years ago, or around the time that T rex went extinct.

和6500萬年前一樣，也就是霸王龍滅絕前後。

Thinking about the speed of light isn't a new concept, there's some evidence that scholars in 14th

思考光速並不是一個新的概念，有一些證據表明，在14世紀的學者們

century India were exploring the speed of sunlight.

世紀的印度在探索太陽光的速度。

They thought of light as a sort of wind, and though they couldn't prove anything concretely,

他們認為光是一種風，雖然他們無法具體證明什麼。

when converted into modern units, ancient calculations came surprisingly close to the

當換算成現代組織、部門時，古人的計算結果竟然接近於......。

actual speed of light.

實際光速。

Today, we've calculated that speed down to the nanosecond. Light speed applies here on

今天，我們已經把這個速度計算到了納秒。光速在這裡適用

earth too just in much smaller distances.

地球也只是距離小得多。

If you look at an object one meter away from you, you're not seeing it as it was

如果你看著離你一米遠的物體，你就不會看到它的本來面目。

three billionths of a second ago.

十億分之三秒前。

This might seem too small to even matter.

這可能看起來太小，甚至不重要。

After all, it's impossible for us to discern three billionths of a second.

畢竟，我們不可能分辨出三十億分之一秒的時間。

But when we talk about space, those distances are so immense that the speed of light creates

但當我們談論空間時，這些距離是如此巨大，以至於光速產生了... ...

huge gaps in observational time.

觀測時間上的巨大差距。

So what does this mean for astronomers making observations of the stars?

那麼，這對於對恆星進行觀測的天文學家意味著什麼呢？

Well, it makes things a lot more complicated, especially since the universe is expanding

這讓事情變得更復雜了 尤其是宇宙正在膨脹的時候

the stretching of the fabric of the universe ever outward affects the light traveling through

宇宙的結構不斷向外延伸，影響了光的穿行

it.

它。

Another way I like to say this is that the light sticks to the fabric of space-time as

我喜歡說的另一種方式是，光粘在時空結構上，作為

the fabric of the universe expands, so to the waves of light.

宇宙的結構擴大了，光波也擴大了。

This is what's known as the Doppler effect.

這就是所謂的多普勒效應。

It's the same reason why ambulance sirens seem to get higher and pitch, as it passes

這也是為什麼救護車的警笛聲會越來越高，音調越來越高的原因。

you. The waves are getting shortened, and then stretched out again.

你。的波浪越來越短，然後又被拉長。

With light, it's the color of each wavelength changes as the object gets farther away, and the light waves

對於光來說，就是隨著物體的距離越來越遠，每個波長的顏色都會發生變化，而光波

are more stretched out.

是比較捉襟見肘的。

This is what's known as redshift. Red because the longer the wavelength, the more red the

這就是所謂的紅移。紅色是因為波長越長，越是紅色的

light appears.

光出現。

At some point the waves get so long, they no longer appear as visible light, and slip

在某些時候，波浪變得如此之長，它們不再以可見光的形式出現，並滑落到

into infrared. Redshift isn't something you can see with the naked eye, as it only applies

成紅外線。紅移不是肉眼能看到的東西，因為它只適用於

for objects that are really far away, and the change in hue is very slight.

對於真正距離很遠的物體，而且色調變化非常輕微。

So, if you want to look at anything, really, really far away into the universe, you would

所以，如果你想看任何東西， 真的，真的很遠的宇宙，你會

need to account for the redshift.

需要考慮到紅移的問題。

This is why the Hubble Space Telescope, was built to see a small portion of the infrared

這就是為什麼哈勃太空望遠鏡，是為了看到一小部分的紅外線而建造的

spectrum.

譜。

In 2016, Hubble observed a galaxy 32 billion light years away, but since this galaxy is

2016年，哈勃觀測到一個320億光年外的星系，但由於這個星系是

so far away and the universe has been stretching since the light first left it,

如此遙遠，而宇宙從光第一次離開它開始就一直在延伸。

we're really looking at the galaxy as it was 13.4 billion years ago, I know.

我們看到的是134億年前的銀河系，我知道。

Leave it to the universe to make things more complicated.

讓宇宙把事情變得更復雜。

This is the closest we've come to observing the birth of the universe, this galaxy GNZ-11

這是我們最接近觀測宇宙誕生的地方，這個星系GNZ-11。

is located near Ursa Major, but even if you squint as hard as you can, you still won't

位於大熊座附近，但即使你儘可能地眯著眼睛，你也不會發現。

be able to see it, unless of course you have some seriously impressive infrared super vision.

能夠看到它，當然，除非你有一些嚴重令人印象深刻的紅外超視力。

Oh, and you'd have to be floating above Earth, because our atmosphere blocks some of the

哦，你必須要漂浮在地球上空，因為我們的大氣層會阻擋一些... ...

infrared.

紅外線。

Now, telescopes are getting even better, so much so that they may one day, even be able

現在，望遠鏡的性能越來越好了，以至於有一天，它們甚至可以做到

to see the beginning of the universe.

以見宇宙之初。

Thinking about the beginning of the universe as we know it.

思考我們所知道的宇宙的開始。

We're thinking of stars and galaxies, and that's a little bit later in the universe.

我們考慮的是恆星和星系，那是宇宙中稍後的事情。

Not very much though.

不過不是很喜歡。

And so, to see that, we actually might have a chance with these future telescopes

所以，看到這一點，我們其實可能有機會用這些未來的望遠鏡。

and we might be able to see the supernovae of the first stars, we might be

我們可能會看到第一顆恆星的超新星，我們可能會... ...

able to find the first galaxies ever.

能夠找到有史以來第一個星系。

Astrophysicist Taylor Hutchison studies distant galaxies, close to the time of the Big Bang.

天體物理學家泰勒-哈奇森研究遙遠的星系，接近大爆炸的時間。

The galaxies I look at are some of the most distant galaxies we've ever

我所看到的星系是我們所見過的最遙遠的星系之一

found so far, and the galaxies we're seeing existed about a billion years after

我們所看到的星系在我們發現的10億年後就已經存在了。

the Big Bang.

大爆炸。

So to kind of translate that that's about 13 billion years ago from our present day.

所以說，從我們今天開始，大約是130億年前的事了。

And in order to observe these galaxies, accounting for redshift is super important.

而為了觀測這些星系，核算紅移是超級重要的。

Light is all getting stretched and shifted to longer and longer wavelengths.

光線都在被拉伸，轉移到越來越長的波長。

So, because that's such a vast distance the light we see from these galaxies from the ultraviolet

所以，因為距離太遠 我們從這些星系看到的光是從紫外線來的

is actually in the near infrared, which is hard to see, That means that you need telescopes,

其實是在近紅外，這是難以看到的， 這意味著，你需要望遠鏡。

and instruments that are sensitive to that and working from the ground is really hard

以及對這一點很敏感的儀器，在地面上工作真的很困難

in the near-infrared, then you need a space telescope.

在近紅外，那麼你需要一個空間望遠鏡。

So we're really always pushing the limitations of what the current technology can give us.

所以我們真的一直在挑戰當前技術所能給予我們的限制。

The James Webb Space Telescope is going to be a serious game changer for these kinds

詹姆斯-韋伯太空望遠鏡將嚴重改變這類遊戲。

of observations, because it will observe from outside Earth's atmosphere and specialize

觀測，因為它將從地球大氣層外進行觀測，並專

partly in the infrared.

部分在紅外。

While we wait for these findings about the early universe, remember that every time you

當我們在等待這些關於早期宇宙的發現時，請記住，每當你

look at the stars, you're seeing back in time, and looking up at Ursa Major you can imagine

仰望星空，你看到的是時光倒流 抬頭看大熊座，你可以想象到

how the Earth would look in reverse.. Pretty incredible right?

地球會是怎樣的反轉樣子...很不可思議吧？

Thank you so much for watching this video.

非常感謝你觀看這個視頻。

I know that the more I learned about astronomy, the more questions I have, so please let us

我知道，我對天文知識瞭解得越多，問題就越多，請讓我們的

know what else you'd like us to cover down in the comments.

知道你還想讓我們在評論中報道什麼。