when I look at the sky with other people,

當我和別人一起看著天空

they always ask me,

他們總會問我：

"What is your favorite place in the universe?

「你最喜歡宇宙的哪個地方？

What is your favorite galaxy?

最喜歡哪個星系？

What is your favorite planet?"

最喜歡哪個行星？」

My answer is

我的答案是：

Earth. That's right.

地球！沒錯

This is a very special place, even for an astronomer.

即使對天文學家，地球也很特別

We look at a lot of places,

我們看過許多地方

but there's only one that we know of in the whole universe

但這是我們所知，全宇宙

that we can live on.

唯一可住人的地方

It's an amazing planet,

在這驚人的行星上

there is an amazing number of things happening,

許多驚人的事正在發生

some of them, you are hearing about it today.

接著要介紹其中的一些

That's the only place in the universe

這是我們所知宇宙中

where we know that there is life,

唯一有生命的地方

so that makes it extremely special.

這讓它非常特殊

What I'm going to talk to you about

我想告訴你的是

is this great adventure in astronomy that is happening

天文學的偉大探險正在進行

where we are actually actively looking

我們正在積極尋找

for other places like this.

其他像這樣的行星

It's impossible to imagine the number of possibilities,

難以想像有哪些可能性

what happens on those other planets

其他可居住的行星

that can be habitable.

是什麼樣子

So that's what I'm going to tell you about.

接下來我要告訴你

So, the first thing we have to think of

我們思考的第一件事是：

is, well, what makes a planet habitable?

行星能住人，有什麼條件？

And, the easiest thing to do

最簡單的做法

is to look at our own solar system.

就是先看我們的太陽系

We have multiple examples.

有好幾個例子

The first thing we learn is that size matters.

首先我們了解，大小很重要

We can't have a planet that's too small or too big.

行星太大、太小都不行

If we look at a planet that is too small,

行星如果太小

it doesn't have an atmosphere.

就不會有大氣層

The moon, technically not a planet,

如月亮，雖然不是行星

but a good example for this,

但仍是個好例子

is too small,

它太小了

it doesn't hold an atmosphere.

沒辦法抓住大氣層

Jupiter - very, very big -

木星—非常、非常巨大

and it actually is mostly composed of gas,

實際上主要由氣體組成

it has no surface you can stand on.

所以連站的地方都沒有

The Earth is just right.

地球的大小則剛剛好

The second thing that we learned

第二個條件是

is that the planet has to be

這行星必須

at the right distance from its star.

和恆星保持適當距離

If the planet is too close to its star,

如果和恆星太接近

it's too hot.

就會太熱

That's the case for Venus.

金星就是這樣

Here I have a picture that was taken by a spacecraft

這是太空船登陸金星時

that landed on Venus,

所拍的照片

and the surface, although it's rocky and quite familiar to us

岩石地表，看來很熟悉

compared to Earth,

跟地球很像

it's really too hot.

但實在太熱了

At the opposite end, if a planet is too far from the star,

相反的，若行星和恆星離得太遠

it is too cold.

就會太寒冷

That's the case for Mars.

火星就是這樣

So, we need to look for planets

所以要找的行星

that are at the right distance from their star

不但和恆星距離適中

and also of the right size.

大小也要適中

So, one other thing,

另一件事

you know, you might think, "Oh, this is really hard

你可能會想：「這太難了吧！

because the planet has to be just right.

距離要剛剛好，

It only happened once in our solar system."

在我們的太陽系裡也只有一個。」

But when you look at the sky at night,

但你夜晚看著星空

and here's a video that I took actually from Hawaii,

這是我在夏威夷拍的影片

a dark place where you can see a lot of stars,

那裡沒光害，可看到很多星星

the first thing you notice is that there are a lot of stars.

首先注意的是，星星好多

So, the odds are in our favor,

機率並不低

even if a small fraction of the stars

即使很少恆星有

have habitable planets.

可居住的行星

There are a lot of stars.

但恆星很多

On a moonless night, in a dark site,

在沒月亮、沒光害時

if you count the stars in the sky

若數著天空的星星

and you count five stars per second,

每秒數五顆

it would take you 15 minutes to count

也要十五分鐘

all of the stars in the sky.

才能數完所有星星

That is a tiny fraction of the stars in our galaxy.

這只是我們星系中的極小部份

If you count all the stars in our galaxy,

如果要數我們星系裡的所有星星

and you also count at five stars per second,

一樣每秒數五顆

it would take you more than 1,000 years

要花一千年

to count all the stars in our galaxy.

才能數完我們星系裡的星星

And then, if you manage

接著，如果你打算

to count the galaxies in the universe,

數數宇宙中有幾個星系

if you count five galaxies per second,

每秒數五個星系

it would take you also more than 1,000 years

也要超過一千年

to count all of the galaxies in the universe.

才能數完宇宙中所有星系

So the numbers are just astronomical,

這真是「天文數字」

there's a lot of opportunities for exoplanets.

太陽系以外的「系外行星」 還有很多機會

There has to be a large number of exoplanets

一定有很多系外行星

along which there are,

其中的一些

on which there could be life.

可能會有生命

So this is very exciting.

這非常令人興奮

So let's imagine that maybe only 1 in 100 stars

我們可以想像 一百顆恆星中只有一顆

has the right kind of planet,

有條件相符的行星

and I think this is pessimistic.

我認為這算保守了

If you could visit one of those planets per second,

如果你可以每秒拜訪一顆 這樣的行星

it'll take you sixty years

要花你六十年時間

to actually visit all of them in our galaxy alone.

才能走完我們星系的這種行星

That's, I think, one second is not enough to study them.

我認為一秒不足以研究一顆行星

So, there's a few hundred of us in this room.

這裡有幾百人

If we divided the task and each of us basically took

如果我們分配任務

a couple of minutes to study each planet,

每人花幾分鐘研究一顆行星

it would take us a life time to do this.

也要花一輩子時間

Meet back again and tell those amazing stories

然後我們再見面，分享奇妙的故事

of what we would have seen

以及所見所聞

in maybe some TED senior event.

也許可辦個 TED 年長者會談

So, why is it hard?

那為什麼這麼困難？

Why don't we have pictures of exoplanets with aliens on them?

為什麼沒有系外行星上 外星人的照片？

Well, here's an example.

這裡有個例子

This is a picture that was taken

這是卡西尼號太空船

by the Cassinni spacecraft as it was orbiting Saturn.

繞行土星時拍的照片

It's actually behind Saturn,

實際上它在土星背面

so what you see is the sun

所以你可以看到太陽

that is blocked by Saturn.

被土星擋住了

And if you look very, in detail,

如果你很仔細看

if you have very sharp eyesight,

而且眼力很好

you will see all of us.

你會看到我們所有人

We're all on that picture.

我們都在這張照片上

Here is where we are.

我們的地球在這裡

Um, so that's what Earth starts to look like

這就是從很遠的地方

when we look at it from far away.

看地球的樣子

Now, we have to do the same thing around other stars,

我們要在其他恆星旁做一樣的事

and the planet is very close to the star.

行星很靠近恆星

So this is zooming in to us.

把影像放大後

All of us are on that little dot

在拍照片時

at the time the picture was taken.

我們所有人都在這小點上

So, what I work on is inventing optics, tricks to actually do this,

我的工作是發明光學和技巧

to take images of planets around those other stars.

拍下恆星附近的行星影像

This is my easiest coronagraph.

這是最簡單的「日冕觀測儀」

We call this optic tricks, "coronagraph".

這種光學技巧叫「日冕觀測法」

This is the easiest one I ever built.

這是最簡單的

I just put my thumb in front of the sun

用拇指擋住太陽

and then you can see things around it.

即可看到太陽附近的東西

That's what we're trying to do,

這就是我們想做的事

but we need to do it much better

不過我們做的

than what I did in this picture.

得要比照片裡的好很多

And, there are two things we need to do:

我們需要做兩樣事：

we need a much better eye,

視力更好的眼睛—

call them telescopes,

就是望遠鏡

and we need more fancy, clever ways to do it

比拇指更創新、更聰明

than putting a thumb.

的方法

So as an example, one of the projects I work on

舉例說，我參與的計畫之一

is for the Subaru Telescope,

是速霸陸望遠鏡

which you can see here in this picture.

你可以在照片中看到

It's a very large telescope,

這是非常大的望遠鏡

so I replace my eye by a large telescope.

我用大型望遠鏡取代眼睛

And, the other thing that we do

我們做的另一件事是

is the coronagraph is not just a stupid thumb,

日冕觀測儀不只是一根拇指

it's this very complicated thing

而是非常複雜的東西

that's shown in that picture

請看右下角

that I would love to have time to tell you about.

可惜沒時間詳細說明

Just to give you a sense for size,

接著讓你感覺一下大小

this arrow points to a door on the side of the telescope,

這箭頭指向望遠鏡的一扇側門

and if you have very sharp eyes,

如果你眼力很好

you can see that there is a railing going around the telescope,

可看到望遠鏡外圍有軌道

so it's a really big eye.

所以這眼睛真的很大

So, I think the most exciting thing for me

我認為，對我來說最興奮的事

is actually to look at the night sky,

就是看著星空、

to see all these stars and wonder,

看著所有的星星，然後想：

"Well, are there people on planets around those stars?"

「恆星旁的行星有沒有人？」

Because there must be amazing things happening

因為這些星星旁一定有許多

around those stars that we don't know yet.

驚人的事在發生

During your life time, we will start

在你有生之年，我們會開始

to actually figure out those things.

解開這些問題

And the most exciting thing for me

而對我來說，最興奮的

is to think about, maybe,

也許是想像

beings on those stars looking back at our star

那些星球的人可能看著我們的星球

and wondering the same thing.

思考著同一件事

So I think the future will be extremely exciting

所以我認為，未來將令人非常興奮

because we are starting to figure out those things

因為我們開始了解這些

and amazing range of possibilities

以及無數的可能

is, I think, even wider than our imagination.

我認為將遠遠超出想像

Thank you.

謝謝大家