Not little green humanoids arriving in shiny UFOs,

我所說不是長得像人的綠色小個子 乘坐發光飛碟抵達地球，

although that would be nice.

儘管那個主題也很好。

But it's the search for planets orbiting stars far away.

我們在找尋的是 繞行恆星的遠方行星。

Every star in our sky is a sun.

天空中每一顆恆星都是一個太陽。

And if our sun has planets --

如果我們的太陽有行星

Mercury, Venus, Earth, Mars, etc.,

如水星、金星、地球、火星等等，

surely those other stars should have planets also,

當然那些其他恆星也應該有行星，

and they do.

它們確實有行星。

And in the last two decades,

在過去的二十年，

astronomers have found thousands of exoplanets.

天文學家已發現數千顆系外行星。

Our night sky is literally teeming with exoplanets.

夜晚的天空幾乎佈滿系外行星。

We know, statistically speaking,

依據統計，我們知道，

that every star has at least one planet.

每顆恆星至少有一顆行星。

And in the search for planets,

在探尋行星中，

and in the future, planets that might be like Earth,

未來，行星或許像地球一樣，

we're able to help address

我們能夠提出

some of the most amazing and mysterious questions

一些令人訝異且神秘的問題

that have faced humankind for centuries.

這問題已經圍繞人類數百年之久。

Why are we here?

我們為什麼在這裡？

Why does our universe exist?

我們的宇宙為什麼存在？

How did Earth form and evolve?

地球是如何形成與演變而來的？

How and why did life originate and populate our planet?

生命的起源是什麼 我們為何生活在這顆星球上？

The second question that we often think about is:

我們經常思考的第二個問題是：

Are we alone?

我們獨立存在宇宙中嗎？

Is there life out there?

有其他的生物存在嗎？

Who is out there?

他們是誰？

You know, this question has been around for thousands of years,

你知道， 這個問題已經圍繞人類數千年了，

since at least the time of the Greek philosophers.

至少從古希臘哲學家那時候起 就已經有這個問題。

But I'm here to tell you just how close we're getting

但此時我要告訴你 我們有多接近

to finding out the answer to this question.

取得這個問題的答案。

It's the first time in human history that this really is within reach for us.

這是人類史上的第一次

Now when I think about the possibilities for life out there,

當我思索其他生物存在的可能性，

I think of the fact that our sun is but one of many stars.

事實上太陽是眾多恆星之一。

This is a photograph of a real galaxy,

這是一張真實銀河星系的照片，

we think our Milky Way looks like this galaxy.

我們認為銀河就像這張照片。

It's a collection of bound stars.

是由眾多恆星組成。

But our [sun] is one of hundreds of billions of stars

太陽是千億恆星中的一員

and our galaxy is one of upwards of hundreds of billions of galaxies.

我們的銀河是千億銀河中的一員。

Knowing that small planets are very common,

我們知道小行星是非常普遍的，

you can just do the math.

可以算得出來。

And there are just so many stars and so many planets out there,

那裡有好多的恆星行星，

that surely, there must be life somewhere out there.

必然一定有生物存在。

Well, the biologists get furious with me for saying that,

生物學家 對我這樣的說法會非常生氣，

because we have absolutely no evidence for life beyond Earth yet.

因為我們的確無法證明 地球之外有生物存在。

Well, if we were able to look at our galaxy from the outside

如果我們能夠從外部觀察銀河系

and zoom in to where our sun is,

將太陽的位置放大觀察，

we see a real map of the stars.

我們看到一張真實的恆星地圖。

And the highlighted stars are those with known exoplanets.

高亮度的恆星 是那些為大家所知的系外行星。

This is really just the tip of the iceberg.

這只是冰山的一角。

Here, this animation is zooming in onto our solar system.

這個動畫放大太陽系的位置。

And you'll see here the planets

你會看到這些行星

as well as some spacecraft that are also orbiting our sun.

和一些太空船一樣繞著太陽轉。

Now if we can imagine going to the West Coast of North America,

想像我們到北美的西岸，

and looking out at the night sky,

看著那裡的夜空，

here's what we'd see on a spring night.

這就是當地春天的夜晚。

And you can see the constellations overlaid

你可以看到佈滿星群

and again, so many stars with planets.

同樣的，很多的恆星和行星。

There's a special patch of the sky where we have thousands of planets.

天空有一特殊區塊 那裡有數千顆行星。

This is where the Kepler Space Telescope focused for many years.

這是克卜勒太空望遠鏡 多年來關注的地方。

Let's zoom in and look at one of the favorite exoplanets.

我們放大畫面 觀察其中一顆我們喜愛的系外行星。

This star is called Kepler-186f.

這恆星被稱為克卜勒-186f。

It's a system of about five planets.

是一個由五個行星組成的系統。

And by the way, most of these exoplanets, we don't know too much about.

順道一提，大部分的系外行星 我們並不太了解。

We know their size, and their orbit and things like that.

我們知道它們的大小， 運行軌道之類的。

But there's a very special planet here called Kepler-186f.

有一個非常特別的行星 被稱為克卜勒-186f。

This planet is in a zone that is not too far from the star,

這顆行星所在區域 距離恆星不遠，

so that the temperature may be just right for life.

其溫度可能適合生物生存。

Here, the artist's conception is just zooming in

這是藝術家的觀念，將畫面放大

and showing you what that planet might be like.

向你們展示那顆行星的樣子。

So, many people have this romantic notion of astronomers

因此， 很多人對天文學家有浪漫的想法

going to the telescope on a lonely mountaintop

在一個孤寂的山頂 對著望遠鏡

and looking at the spectacular night sky through a big telescope.

透過大的望遠鏡 觀察壯觀的夜空。

But actually, we just work on our computers like everyone else,

但事實上，我們只是 和其他人一樣在電腦前忙碌，

and we get our data by email or downloading from a database.

透過郵件或從資料庫下載 以取得資料。

So instead of coming here to tell you

我不是跑到這裡來告訴你

about the somewhat tedious nature of the data and data analysis

有點冗長乏味的資料和資料分析

and the complex computer models we make,

以及我們做的複雜電腦程式，

I have a different way to try to explain to you

我要以不同的方式向你們解說

some of the things that we're thinking about exoplanets.

我們對系外行星的一些想法。

Here's a travel poster:

這是一張旅行海報：

"Kepler-186f:

「克卜勒-186f：

Where the grass is always redder on the other side."

這草的顏色 總是比另一邊的草還要紅。」

That's because Kepler-186f orbits a red star,

那是因為克卜勒-186f 繞著紅恆星運轉，

and we're just speculating that perhaps the plants there,

我們只是推測那裡的行星，

if there is vegetation that does photosynthesis,

如果有進行光合作用的植物，

it has different pigments and looks red.

會有不同的色素 看起來是紅色。

"Enjoy the gravity on HD 40307g,

「盡情享受 HD 40307g 的重力，

a Super-Earth."

一顆超級地球。」

This planet is more massive than Earth

這顆行星遠大於地球

and has a higher surface gravity.

而且有較大地表引力。

"Relax on Kepler-16b,

「在克卜勒-16b上放輕鬆

where your shadow always has company."

影子在那裡成雙成對。」

(Laughter)

(笑聲）

We know of a dozen planets that orbit two stars,

我們知道繞著二顆恆星 運轉的十二顆行星，

and there's likely many more out there.

那裡可能有更多的行星。

If we could visit one of those planets,

如果我們能夠參觀其中一顆行星，

you literally would see two sunsets

你幾乎可以看到二個日落

and have two shadows.

和二個自己的影子。

So actually, science fiction got some things right.

事實上， 科幻小說的故事有些是正確的。

Tatooine from Star Wars.

星際大戰裡的塔圖因星

And I have a couple of other favorite exoplanets

我還有我喜歡的外行星

to tell you about.

要告訴你。

This one is Kepler-10b,

這顆是克卜勒-10b，

it's a hot, hot planet.

是一顆很熱的行星，

It orbits over 50 times closer to its star

繞行就近的恆星超過五十次

than our Earth does to our sun.

超過地球繞太陽的次數。

And actually, it's so hot,

事實上，它的溫度很高

we can't visit any of these planets, but if we could,

我們無法參觀任何這類的行星 如果可以的話，

we would melt long before we got there.

在我們到達之前就已經融化。

We think the surface is hot enough to melt rock

我們認為其表面溫度很高 足以融化岩石

and has liquid lava lakes.

有液體熔岩湖。

Gliese 1214b.

格利澤 1214b。

This planet, we know the mass and the size

這顆行星，我們知道它的質量和體積

and it has a fairly low density.

其密度極低。

It's somewhat warm.

有溫暖的氣候。

We actually don't know really anything about this planet,

事實上我們對這星球一無所知，

but one possibility is that it's a water world,

但有一個可能性是 這顆行星是個水世界，

like a scaled-up version of one of Jupiter's icy moons

像一顆放大版的木星冰冷衛星之一

that might be 50 percent water by mass.

或許水就佔了質量的一半。

And in this case, it would have a thick steam atmosphere

在這種情況下， 它有厚厚的大氣流，

overlaying an ocean,

覆蓋著一片海洋，

not of liquid water,

但不是液體形態的水，

but of an exotic form of water, a superfluid --

而是異質形態的水，一種超級液體，

not quite a gas, not quite a liquid.

不完全是氣態，不完全是液態。

And under that wouldn't be rock,

在海洋下面並非岩石，

but a form of high-pressure ice,

而是一種高壓冰的形態，

like ice IX.

如同冰 IX。

So out of all these planets out there,

在那些行星範圍之外的地方，

and the variety is just simply astonishing,

其多樣性也令人驚訝，

we mostly want to find the planets that are Goldilocks planets, we call them.

我們大部分想找的行星 是金髮星球行星。

Not too big, not too small,

體積不太大，也不太小，

not too hot, not too cold --

溫度不太熱，也不太冷，

but just right for life.

剛好適合生物生存。

But to do that, we'd have to be able to look

不過要做到這一點， 我們必須能夠

at the planet's atmosphere,

觀察到這顆行星的大氣，

because the atmosphere acts like a blanket trapping heat --

因為大氣就像一塊保溫地毯

the greenhouse effect.

溫室效應。

We have to be able to assess the greenhouse gases

我們必須能夠偵測到其他行星的

on other planets.

溫室氣體。

Well, science fiction got some things wrong.

這方面，科幻小說的描述有誤。

The Star Trek Enterprise

「星艦迷航－企業號」

had to travel vast distances at incredible speeds

必須以高速繞行其他行星

to orbit other planets

做長距離旅行

so that First Officer Spock could analyze the atmosphere

因此副艦長斯波克才能分析大氣

to see if the planet was habitable

以看出該行星是否適合生物定居

or if there were lifeforms there.

或者是否有生物存在。

Well, we don't need to travel at warp speeds

我們不需要以極高速度行駛

to see other planet atmospheres,

以取得其他其他行星的大氣資料，

although I don't want to dissuade any budding engineers

雖然我不想去勸阻 新進工程師

from figuring out how to do that.

去找到實踐這項工作的方法。

We actually can and do study planet atmospheres

實際上我們可以 由地球軌道

from here, from Earth orbit.

去研究那些行星的大氣。

This is a picture, a photograph of the Hubble Space Telescope

這是哈柏望遠鏡的照片

taken by the shuttle Atlantis as it was departing

由太空梭亞特蘭蒂斯號 返航時所拍攝的照片

after the last human space flight to Hubble.

最後一次載人太空船到哈柏之後。

They installed a new camera, actually,

他們在太空船上安裝新的照相機，

that we use for exoplanet atmospheres.

可以用來收集外行星大氣資料。

And so far, we've been able to study dozens of exoplanet atmospheres,

目前，我們已經能夠 研究數十個外行星大氣資料，

about six of them in great detail.

其中六個有非常詳細的資料。

But those are not small planets like Earth.

這些行星不像地球是個小行星。

They're big, hot planets that are easy to see.

它們體積大且溫度高， 是容易觀察到的行星。

We're not ready,

我們還沒準備好，

we don't have the right technology yet to study small exoplanets.

我們沒有相當的技術 以研究小行星。

But nevertheless,

儘管如此，

I wanted to try to explain to you how we study exoplanet atmospheres.

我仍然想要向大家解釋 我們是如何研究外行星大氣。

I want you to imagine, for a moment, a rainbow.

大家可以想像一下彩虹。

And if we could look at this rainbow closely,

如果我們可近距離觀察彩虹，

we would see that some dark lines are missing.

可以看到一些暗色線消失了。

And here's our sun,

這是我們的太陽。

the white light of our sun split up,

白色光分解了。

not by raindrops, but by a spectrograph.

不是被雨滴，而是被光譜儀分解了。

And you can see all these dark, vertical lines.

你可以看到這暗色垂直的線。

Some are very narrow, some are wide,

有些非常窄，有些寬，

some are shaded at the edges.

有些邊緣被遮住了。

And this is actually how astronomers have studied objects in the heavens,

這就是天文學家 如何研究太空物質的方式，

literally, for over a century.

這是過去一百年的研究方式。

So here, each different atom and molecule

這張圖，每一原子和分子

has a special set of lines,

各有特殊的頻譜線，

a fingerprint, if you will.

你可以把它當作指紋，

And that's how we study exoplanet atmospheres.

那就是我們利用這訊息 來研究外行星的大氣成份

And I'll just never forget when I started working

我永遠忘不了 二十年前

on exoplanet atmospheres 20 years ago,

剛開起研究外行星大氣的時候，

how many people told me,

多少人告訴我，

"This will never happen.

「這行不通。

We'll never be able to study them. Why are you bothering?"

我們永遠無法做到。 為何費心在這種事上？」

And that's why I'm pleased to tell you about all the atmospheres studied now,

那就是為什麼我很高興要告訴你們 目前所有有關的大氣研究，

and this is really a field of its own.

它已成形了。

So when it comes to other planets, other Earths,

當談及到其他行星， 其他類似地球行星，

in the future when we can observe them,

將來我們可以觀察到，

what kind of gases would we be looking for?

什麼是我們要尋找的氣體？

Well, you know, our own Earth has oxygen in the atmosphere

你知道，地球的大氣

to 20 percent by volume.

含有百分之二十的氧氣。

That's a lot of oxygen.

含量很高。

But without plants and photosynthetic life,

但若沒有植物及其光合作用。

there would be no oxygen,

大氣中不會有氧氣。

virtually no oxygen in our atmosphere.

事實上我們的大氣中沒有氧氣。

So oxygen is here because of life.

因為生物的存在才有氧氣。

And our goal then is to look for gases in other planet atmospheres,

我們目標就是尋找 其他行星大氣中的氣體，

gases that don't belong,

氣體原本不存在，

that we might be able to attribute to life.

或許我們可以歸功於生物。

But which molecules should we search for?

我們在尋找哪些分子呢？

I actually told you how diverse exoplanets are.

我告訴過各位外行星的種類很多。

We expect that to continue in the future

未來會陸續發現更多

when we find other Earths.

當我們發現其他類似地球的行星。

And that's one of the main things I'm working on now,

這是我目前正在從事的最主要工作，

I have a theory about this.

我有個自己的理論。

It reminds me that nearly every day,

它幾乎每天提醒我，

I receive an email or emails

我收到一封或多封郵件

from someone with a crazy theory about physics of gravity

是對重力物理學理論

or cosmology or some such.

或是宇宙論 提出瘋狂想法的人所寄來的。

So, please don't email me one of your crazy theories.

所以請不要再給我發這種郵件了。

(Laughter)

（笑聲）

Well, I had my own crazy theory.

我有自己瘋狂的理論。

But, who does the MIT professor go to?

麻省理工學院的教授要跟誰探討呢？

Well, I emailed a Nobel Laureate in Physiology or Medicine

我向諾貝爾生理及醫學獎得主發信

and he said, "Sure, come and talk to me."

他說，「好，我們討論一下。」

So I brought my two biochemistry friends

我帶了二個 我的生物化學領域的朋友

and we went to talk to him about our crazy theory.

要和他討論我們的瘋狂理論。

And that theory was that life produces all small molecules,

那理論是，生命製造了所有小分子，

so many molecules.

許許多多的分子。

Like, everything I could think of, but not being a chemist.

所有我可以想得到的事情， 雖然我不是個化學領域專家。

Think about it:

想想看：

carbon dioxide, carbon monoxide,

二氧化碳，一氧化碳，

molecular hydrogen, molecular nitrogen,

氫分子，氮分子,

methane, methyl chloride --

甲烷，氯甲烷，

so many gases.

等諸多氣體。

They also exist for other reasons,

它們的存在也有其原因，

but just life even produces ozone.

生物即可產生臭氧。

So we go to talk to him about this,

所以我們和他談論這個主題，

and immediately, he shot down the theory.

結果立刻被他否決。

He found an example that didn't exist.

他找到一個不存在的氣體的例子。

So, we went back to the drawing board

所以我們回去從頭做起

and we think we have found something very interesting in another field.

我們發現在其他領域 非常有趣的東西。

But back to exoplanets,

回到外行星這個話題，

the point is that life produces so many different types of gases,

重點是生物製造各種不同的氣體，

literally thousands of gases.