TEDxBoulder
Dave Brain: What a planet needs to sustain life
戴維．布萊因: 行星維持生命存在的要素
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Readability: 4.1
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「金星太熱，火星太冷，地球剛剛好。」行星科學家戴維．布萊因如是說。但是為什麼？布萊因在這場風趣幽默的演講中，探索行星要維持生命存在所需的幾項有趣科學，並且談到在行星維持生命的時間軸上，為什麼人類可能只是恰好在天時、地利、人和的情況下在地球上生活。
Dave Brain - Planetary scientist
Dave Brain studies the plasma environments and atmospheres of unmagnetized planets. Full bio
Dave Brain studies the plasma environments and atmospheres of unmagnetized planets. Full bio
Double-click the English transcript below to play the video.
00:12
I'm really glad to be here.
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我真的很高興能來這裡。
00:15
I'm glad you're here,
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我也很高興你們能來這裡，
00:16
because that would be a little weird.
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要不然會有點奇怪。
00:19
I'm glad we're all here.
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我很高興我們都在這裡。
00:22
And by "here," I don't mean here.
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我說的「這裡」，不是現場這裡。
00:26
Or here.
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或這裡。
00:28
But here.
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卻是這裡。
00:29
I mean Earth.
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我指的是地球。
00:31
And by "we," I don't mean
those of us in this auditorium,
those of us in this auditorium,
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而且我說的「我們」，
不是這座大禮堂裡的各位，
不是這座大禮堂裡的各位，
00:35
but life,
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而是生命，
00:37
all life on Earth --
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地球上所有的生命──
00:38
(Laughter)
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（笑聲）
00:44
from complex to single-celled,
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從複合體到單細胞，
00:46
from mold to mushrooms
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從黴菌到蘑菇，
00:48
to flying bears.
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到飛天熊都是。
00:50
(Laughter)
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（笑聲）
00:53
The interesting thing is,
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有趣的是，
00:55
Earth is the only place
we know of that has life --
we know of that has life --
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地球是我們知道
唯一有生命的地方──
唯一有生命的地方──
00:58
8.7 million species.
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八百七十萬種生物。
01:00
We've looked other places,
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我們找過其它地方，
01:01
maybe not as hard
as we should or we could,
as we should or we could,
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可能找得還不夠勤快，
01:04
but we've looked and haven't found any;
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但是我們找過，
沒有發現任何生物。
沒有發現任何生物。
01:06
Earth is the only place
we know of with life.
we know of with life.
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地球是我們所知唯一有生命的地方。
01:09
Is Earth special?
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地球得天獨厚嗎？
01:11
This is a question I've wanted
to know the answer to
to know the answer to
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這個問題的答案
我從小時候就想知道，
01:14
since I was a small child,
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01:15
and I suspect 80 percent
of this auditorium
of this auditorium
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而且我猜禮堂裡八成的人
01:17
has thought the same thing
and also wanted to know the answer.
and also wanted to know the answer.
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都想過同樣的事，也想知道答案。
01:20
To understand whether
there are any planets --
there are any planets --
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要知道是否有別的行星──
01:23
out there in our solar system or beyond --
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無論是在我們的太陽系
還是其它地方──
還是其它地方──
01:25
that can support life,
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能支持生命，
01:26
the first step is to understand
what life here requires.
what life here requires.
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第一步要了解在這裡
生命的要素是什麼。
生命的要素是什麼。
01:30
It turns out, of all of those
8.7 million species,
8.7 million species,
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事實證明，
這八百七十萬種物種
這八百七十萬種物種
01:34
life only needs three things.
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只需要三件事就能維持生命。
01:37
On one side, all life
on Earth needs energy.
on Earth needs energy.
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那邊那張照片，
地球上所有的生命都要能量，
地球上所有的生命都要能量，
01:39
Complex life like us derives
our energy from the sun,
our energy from the sun,
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像我們這樣的複合生物體
要從太陽取得能量，
要從太陽取得能量，
01:43
but life deep underground
can get its energy
can get its energy
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地下深處的生物
則從化學反應取得能量。
01:45
from things like chemical reactions.
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01:47
There are a number
of different energy sources
of different energy sources
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地球上有很多種能量來源
01:49
available on all planets.
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可供大家使用。
01:51
On the other side,
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另外那一邊照片，
01:52
all life needs food or nourishment.
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所有的生命都需要食物或營養。
01:55
And this seems like a tall order,
especially if you want a succulent tomato.
especially if you want a succulent tomato.
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這聽起來像是無理的要求，
尤其在你想要一顆多汁的番茄時。
尤其在你想要一顆多汁的番茄時。
02:00
(Laughter)
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（笑聲）
（譯註：一般超市的番茄都很乾）
（譯註：一般超市的番茄都很乾）
02:01
However, all life on Earth
derives its nourishment
derives its nourishment
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然而，地球上所有的生命
02:05
from only six chemical elements,
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只要六種化學元素就能取得營養，
02:07
and these elements can be found
on any planetary body
on any planetary body
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而這些元素可在
我們的太陽系中
每一個行星體上找到。
每一個行星體上找到。
02:10
in our solar system.
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02:12
So that leaves the thing
in the middle as the tall pole,
in the middle as the tall pole,
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所以這讓中間這項成了高不可及、
02:15
the thing that's hardest to achieve.
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很難拿到的東西。
02:17
Not moose, but water.
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不是麋鹿，是水。
02:19
(Laughter)
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（笑聲）
02:23
Although moose would be pretty cool.
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雖然麋鹿也滿酷的。
02:25
(Laughter)
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（笑聲）
02:26
And not frozen water, and not water
in a gaseous state, but liquid water.
in a gaseous state, but liquid water.
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不是冰凍的水，也不是氣狀的水，
而是液態水。
而是液態水。
02:32
This is what life needs
to survive, all life.
to survive, all life.
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這是生命要生存都需要的東西。
所有的生命。
所有的生命。
02:35
And many solar system bodies
don't have liquid water,
don't have liquid water,
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許多太陽系沒有液態水，
02:39
and so we don't look there.
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所以我們不去那裡找。
02:40
Other solar system bodies
might have abundant liquid water,
might have abundant liquid water,
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有些太陽系可能有大量液態水，
02:43
even more than Earth,
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甚至可能多過地球，
02:45
but it's trapped beneath an icy shell,
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但是都困在冰層底下，
02:47
and so it's hard to access,
it's hard to get to,
it's hard to get to,
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所以很難拿到，很難接近，
02:49
it's hard to even find out
if there's any life there.
if there's any life there.
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甚至很難發現那裡到底有沒有生命。
02:53
So that leaves a few bodies
that we should think about.
that we should think about.
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這樣只剩下幾座星體我們應該考慮。
02:56
So let's make the problem
simpler for ourselves.
simpler for ourselves.
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所以我們來為自己簡化一下問題。
02:58
Let's think only about liquid water
on the surface of a planet.
on the surface of a planet.
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我們只要想想
在星球表面的液態水就好。
在星球表面的液態水就好。
03:02
There are only three bodies
to think about in our solar system,
to think about in our solar system,
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這樣我們的太陽系裡
只剩三座星體可想，
只剩三座星體可想，
03:05
with regard to liquid water
on the surface of a planet,
on the surface of a planet,
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考慮行星表面是否有液態水，
03:07
and in order of distance from the sun,
it's: Venus, Earth and Mars.
it's: Venus, Earth and Mars.
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與太陽的距離依次是
金星、地球及火星。
金星、地球及火星。
03:13
You want to have an atmosphere
for water to be liquid.
for water to be liquid.
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你要有大氣層使水能維持液態。
03:16
You have to be very careful
with that atmosphere.
with that atmosphere.
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你必須非常小心考慮大氣層。
03:19
You can't have too much atmosphere,
too thick or too warm an atmosphere,
too thick or too warm an atmosphere,
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你不能有太大的大氣層，
太厚或太溫暖都不行，
太厚或太溫暖都不行，
03:22
because then you end up
too hot like Venus,
too hot like Venus,
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因為這樣會像金星一樣太熱，
03:25
and you can't have liquid water.
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而且沒有液態水。
03:27
But if you have too little atmosphere
and it's too thin and too cold,
and it's too thin and too cold,
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但是如果你的大氣層太少，
而且太薄太冷，
而且太薄太冷，
03:31
you end up like Mars, too cold.
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結果就會像火星一樣太冷。
03:33
So Venus is too hot, Mars is too cold,
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所以金星太熱，火星太冷，
03:36
and Earth is just right.
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地球則是剛剛好。
03:37
You can look at these images behind me
and you can see automatically
and you can see automatically
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看看我後面的照片，你自然會看到
03:41
where life can survive
in our solar system.
in our solar system.
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我們的太陽系
哪裡有生命可以存活。
哪裡有生命可以存活。
03:44
It's a Goldilocks-type problem,
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這是典型的
《金髮女孩與三隻熊》問題，
《金髮女孩與三隻熊》問題，
03:45
and it's so simple
that a child could understand it.
that a child could understand it.
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而且這太簡單了，小孩都能理解。
03:49
However,
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然而，
03:51
I'd like to remind you of two things
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我要提醒各位兩件事，
03:54
from the Goldilocks story
that we may not think about so often
that we may not think about so often
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是《金髮女孩與三隻熊》故事中，
常常被我們忽略
常常被我們忽略
03:57
but that I think are really relevant here.
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但我認為非常切題的事。
04:00
Number one:
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第一：
04:02
if Mama Bear's bowl is too cold
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金髮女孩走進屋時，
如果熊媽媽碗裡的粥太冷，
如果熊媽媽碗裡的粥太冷，
04:05
when Goldilocks walks into the room,
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04:08
does that mean it's always been too cold?
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那是指粥早就冷了？
04:11
Or could it have been just right
at some other time?
at some other time?
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還是曾有剛剛好的時間？
04:15
When Goldilocks walks into the room
determines the answer
determines the answer
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金髮女孩走進屋的時間決定了
04:19
that we get in the story.
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故事的答案。
04:21
And the same is true with planets.
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行星也一樣。
04:22
They're not static things. They change.
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行星不是靜態的東西。
它們一直在改變。
它們一直在改變。
04:24
They vary. They evolve.
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它們變化，它們演化。
04:26
And atmospheres do the same.
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大氣層也一樣。
04:28
So let me give you an example.
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我舉一個例子。
04:30
Here's one of my favorite
pictures of Mars.
pictures of Mars.
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這是我很愛的一張火星照片。
04:32
It's not the highest resolution image,
it's not the sexiest image,
it's not the sexiest image,
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這既非最高解析度，也並非最美，
04:35
it's not the most recent image,
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更不是最新的照片，
04:37
but it's an image that shows riverbeds
cut into the surface of the planet;
cut into the surface of the planet;
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但這張照片顯示河床切過行星表面；
04:41
riverbeds carved by flowing, liquid water;
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被流動、液態水切割出的河床；
04:45
riverbeds that take hundreds or thousands
or tens of thousands of years to form.
or tens of thousands of years to form.
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河床要上百、上千
甚至上萬年才能形成。
甚至上萬年才能形成。
04:50
This can't happen on Mars today.
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現在的火星不可能發生這件事。
04:52
The atmosphere of Mars today
is too thin and too cold
is too thin and too cold
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現在的火星大氣層太薄太冷，
水因而不能維持液態。
04:54
for water to be stable as a liquid.
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04:56
This one image tells you
that the atmosphere of Mars changed,
that the atmosphere of Mars changed,
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這一張照片告訴我們
火星的大氣改變了，
火星的大氣改變了，
05:01
and it changed in big ways.
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而且改變很大。
05:03
And it changed from a state
that we would define as habitable,
that we would define as habitable,
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它從我們定義的適居狀態
變成現在的樣子，
變成現在的樣子，
05:08
because the three requirements
for life were present long ago.
for life were present long ago.
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因為生命三大要素
在很久以前曾經出現過。
在很久以前曾經出現過。
05:13
Where did that atmosphere go
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本來能讓水在地表
維持液態的大氣去了哪裡？
維持液態的大氣去了哪裡？
05:15
that allowed water
to be liquid at the surface?
to be liquid at the surface?
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05:17
Well, one idea is it escaped
away to space.
away to space.
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嗯，有人說它逃逸到宇宙。
05:21
Atmospheric particles
got enough energy to break free
got enough energy to break free
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大氣粒子有足夠的能量
05:24
from the gravity of the planet,
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逃脫此行星的重力，
05:25
escaping away to space, never to return.
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散逸到太空，一去不返。
05:28
And this happens with all bodies
with atmospheres.
with atmospheres.
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這種現象在有大氣的
星體上都會發生。
星體上都會發生。
05:31
Comets have tails
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彗星的尾巴
05:32
that are incredibly visible reminders
of atmospheric escape.
of atmospheric escape.
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正是大氣逃逸絕佳的視覺提醒。
05:35
But Venus also has an atmosphere
that escapes with time,
that escapes with time,
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但是金星的大氣也會隨時間逃逸，
05:39
and Mars and Earth as well.
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火星及地球也一樣。
05:40
It's just a matter of degree
and a matter of scale.
and a matter of scale.
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這只是程度及規模的問題。
05:44
So we'd like to figure out
how much escaped over time
how much escaped over time
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所以我們要找出逃逸的速率，
05:46
so we can explain this transition.
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才能解釋這種轉變。
05:48
How do atmospheres
get their energy for escape?
get their energy for escape?
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大氣怎麼得到逃逸所需的能量？
05:51
How do particles get
enough energy to escape?
enough energy to escape?
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粒子怎麼得到足以逃逸的能量？
05:53
There are two ways, if we're going
to reduce things a little bit.
to reduce things a little bit.
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如果我們簡化一下來看，
有兩種方式。
有兩種方式。
05:56
Number one, sunlight.
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第一，陽光。
05:58
Light emitted from the sun can be absorbed
by atmospheric particles
by atmospheric particles
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從太陽射出的光被大氣粒子吸收，
06:01
and warm the particles.
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使粒子增溫。
06:03
Yes, I'm dancing, but they --
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是，我是在跳舞，不過它們──
06:05
(Laughter)
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（笑聲）
06:07
Oh my God, not even at my wedding.
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天啊，我在自己的婚禮上都沒跳。
06:09
(Laughter)
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（笑聲）
06:11
They get enough energy
to escape and break free
to escape and break free
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它們得到足夠的能量逃逸
06:14
from the gravity of the planet
just by warming.
just by warming.
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並掙脫重力，
這一切只要增溫就夠了。
這一切只要增溫就夠了。
06:16
A second way they can get energy
is from the solar wind.
is from the solar wind.
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得到能量的第二種方法是太陽風。
06:19
These are particles, mass, material,
spit out from the surface of the sun,
spit out from the surface of the sun,
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這些是從太陽表面噴出的
粒子、團塊及物質，
粒子、團塊及物質，
06:24
and they go screaming
through the solar system
through the solar system
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而且它們在太陽系裡
06:27
at 400 kilometers per second,
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以每秒 400 公里的速率呼嘯而過，
06:29
sometimes faster during solar storms,
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在太陽風暴期間有時候還更快，
06:31
and they go hurtling
through interplanetary space
through interplanetary space
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而且它們飛馳通過行星際空間，
06:34
towards planets and their atmospheres,
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朝著行星及其大氣飛去，
06:37
and they may provide energy
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因而它們也可以提供能量
06:38
for atmospheric particles
to escape as well.
to escape as well.
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讓大氣粒子逃逸。
06:41
This is something that I'm interested in,
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這就是我感興趣的東西，
06:43
because it relates to habitability.
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因為這跟適居性有關。
06:45
I mentioned that there were two things
about the Goldilocks story
about the Goldilocks story
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我曾說過金髮女孩的故事中有兩件事
06:48
that I wanted to bring to your attention
and remind you about,
and remind you about,
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我要你們注意並提醒你們一下，
06:51
and the second one
is a little bit more subtle.
is a little bit more subtle.
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第二件事更微妙一點。
06:53
If Papa Bear's bowl is too hot,
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如果熊爸爸碗裡的粥太燙了，
06:58
and Mama Bear's bowl is too cold,
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而熊媽媽的粥太冷了，
07:03
shouldn't Baby Bear's bowl be even colder
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那熊寶寶的粥不就應該更冷了，
07:07
if we're following the trend?
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如果我們順著趨勢想？
07:10
This thing that you've accepted
your entire life,
your entire life,
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你一輩子都沒懷疑過的這件事，
07:12
when you think about it a little bit more,
may not be so simple.
may not be so simple.
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仔細一想後可能沒那麼簡單。
07:16
And of course, distance of a planet
from the sun determines its temperature.
from the sun determines its temperature.
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當然，行星的溫度取決於
它與太陽的距離。
它與太陽的距離。
07:20
This has to play into habitability.
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這就與適居性有關。
07:22
But maybe there are other things
we should be thinking about.
we should be thinking about.
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但是我們可能還必須考慮其它事。
07:25
Maybe it's the bowls themselves
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可能碗本身
07:27
that are also helping to determine
the outcome in the story,
the outcome in the story,
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也會決定這個故事的結局，
07:30
what is just right.
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也就是「剛剛好」的問題。
07:32
I could talk to you about a lot
of different characteristics
of different characteristics
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我可以跟大家講很多
這三個行星不同的特性，
07:35
of these three planets
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07:36
that may influence habitability,
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這些特性可能也會影響適居性，
07:38
but for selfish reasons related
to my own research
to my own research
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但是我有私心，
因為那跟我的研究有關係，
因為那跟我的研究有關係，
07:41
and the fact that I'm standing up here
holding the clicker and you're not --
holding the clicker and you're not --
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而且站在這裡拿著遙控器的是我，
不是你們──
不是你們──
07:44
(Laughter)
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（笑聲）
07:45
I would like to talk
for just a minute or two
for just a minute or two
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所以我只跟你們講一兩分鐘就好，
07:47
about magnetic fields.
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來談一下磁場。
07:49
Earth has one; Venus and Mars do not.
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地球有磁場；金星及火星沒有。
07:52
Magnetic fields are generated
in the deep interior of a planet
in the deep interior of a planet
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磁場在行星內部深處產生，
07:55
by electrically conducting
churning fluid material
churning fluid material
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由導電的液態物質環繞流動
07:59
that creates this big old magnetic field
that surrounds Earth.
that surrounds Earth.
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而產生這個環繞地球的
巨大古老磁場。
巨大古老磁場。
08:02
If you have a compass,
you know which way north is.
you know which way north is.
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如果你有羅盤，
你會知道哪邊是北邊。
你會知道哪邊是北邊。
08:05
Venus and Mars don't have that.
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金星與火星沒有這個。
08:06
If you have a compass on Venus and Mars,
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如果你在金星及火星上用羅盤，
08:08
congratulations, you're lost.
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恭喜喔！你迷路了。
08:09
(Laughter)
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（笑聲）
08:11
Does this influence habitability?
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這會影響適居性嗎？
08:15
Well, how might it?
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又怎麼影響？
08:17
Many scientists think
that a magnetic field of a planet
that a magnetic field of a planet
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許多科學家認為行星的磁場
08:19
serves as a shield for the atmosphere,
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就像大氣層的防護罩，
08:22
deflecting solar wind particles
around the planet
around the planet
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使在行星四周的太陽風粒子偏轉，
08:25
in a bit of a force field-type effect
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有點像（星際爭霸戰）
力場防護罩效應，
力場防護罩效應，
08:27
having to do with electric charge
of those particles.
of those particles.
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因為跟這些粒子的電荷有關。
08:30
I like to think of it instead
as a salad bar sneeze guard for planets.
as a salad bar sneeze guard for planets.
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我喜歡把它比喻為沙拉吧上面
擋噴嚏的防護罩。
擋噴嚏的防護罩。
08:34
(Laughter)
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（笑聲）
08:36
And yes, my colleagues
who watch this later will realize
who watch this later will realize
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是的，以後看這片的同僚會發現，
08:40
this is the first time in the history
of our community
of our community
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這是史上頭一遭有人在我們這行
08:42
that the solar wind has been
equated with mucus.
equated with mucus.
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2279
把太陽風等同為黏液。
08:45
(Laughter)
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（笑聲）
08:48
OK, so the effect, then, is that Earth
may have been protected
may have been protected
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好吧，所以這個效應，
就是地球可以受到保護
就是地球可以受到保護
08:52
for billions of years,
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幾十億年，
08:53
because we've had a magnetic field.
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因為我們有磁場。
08:55
Atmosphere hasn't been able to escape.
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2179
大氣至今無法逃脫。
08:57
Mars, on the other hand,
has been unprotected
has been unprotected
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2107
另一方面，火星沒有受到保護，
08:59
because of its lack of magnetic field,
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因為它沒有磁場，
09:01
and over billions of years,
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1952
所以幾十億年來，
09:03
maybe enough atmosphere
has been stripped away
has been stripped away
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2180
可能已經揭掉了夠多的大氣，
09:05
to account for a transition
from a habitable planet
from a habitable planet
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使這個原本適居的行星轉變為
09:08
to the planet that we see today.
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今天我們看到的樣子。
09:11
Other scientists think
that magnetic fields
that magnetic fields
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其他科學家認為磁場的
09:14
may act more like the sails on a ship,
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作用可能更像船上的帆，
09:16
enabling the planet to interact
with more energy from the solar wind
with more energy from the solar wind
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讓行星能與太陽風的能量
產生更多交互作用，
產生更多交互作用，
09:22
than the planet would have been able
to interact with by itself.
to interact with by itself.
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3272
比自身的交互作用還要更多。
09:25
The sails may gather energy
from the solar wind.
from the solar wind.
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2491
帆可以聚集風的能量。
09:27
The magnetic field may gather
energy from the solar wind
energy from the solar wind
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2666
磁場可以聚集太陽風的能量，
09:30
that allows even more
atmospheric escape to happen.
atmospheric escape to happen.
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3244
讓更多大氣逃逸。
09:33
It's an idea that has to be tested,
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2254
這個理論還需要證明，
09:36
but the effect and how it works
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1885
但是其影響及作用方式
09:37
seems apparent.
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看起來很明顯。
09:39
That's because we know
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1151
那是因為我們知道
09:40
energy from the solar wind
is being deposited into our atmosphere
is being deposited into our atmosphere
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3075
太陽風的能量會注入
地球上的大氣層。
09:43
here on Earth.
215
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1151
09:44
That energy is conducted
along magnetic field lines
along magnetic field lines
216
572599
2405
那股能量順著磁力線傳導，
09:47
down into the polar regions,
217
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1348
向下導入兩極，
09:48
resulting in incredibly beautiful aurora.
218
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2136
產生炫麗無比的極光。
09:50
If you've ever experienced them,
it's magnificent.
it's magnificent.
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如果你曾看過極光，那真是壯麗！
09:53
We know the energy is getting in.
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2006
我們知道能量進來了。
09:55
We're trying to measure
how many particles are getting out
how many particles are getting out
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我們試著測量有多少粒子跑出去，
09:58
and if the magnetic field
is influencing this in any way.
is influencing this in any way.
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還有磁場是否
以任何方式影響這一點。
以任何方式影響這一點。
10:02
So I've posed a problem for you here,
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所以我丟了一個問題給各位，
10:05
but I don't have a solution yet.
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但是我還沒有答案。
10:06
We don't have a solution.
225
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1276
我們沒有解答。
10:08
But we're working on it.
How are we working on it?
How are we working on it?
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2357
但是我們正在找。
怎麼找呢？
怎麼找呢？
10:11
Well, we've sent spacecraft
to all three planets.
to all three planets.
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2298
嗯，我們送了幾艘太空船
到這三個行星上。
到這三個行星上。
10:13
Some of them are orbiting now,
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1476
有些已經在軌道上環繞了，
10:14
including the MAVEN spacecraft
which is currently orbiting Mars,
which is currently orbiting Mars,
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3072
包括目前正在環繞火星的 MAVEN
（火星大氣與揮發物演化任務）太空船，
（火星大氣與揮發物演化任務）太空船，
10:18
which I'm involved with
and which is led here,
and which is led here,
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我有參與這項計畫，
而且由此地的科羅拉多大學領導。
10:21
out of the University of Colorado.
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1809
10:23
It's designed to measure
atmospheric escape.
atmospheric escape.
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611390
2282
我們用它測量大氣逃逸。
10:26
We have similar measurements
from Venus and Earth.
from Venus and Earth.
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2474
我們對金星及地球也做了
類似的測量。
類似的測量。
10:28
Once we have all our measurements,
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1665
一旦我們收及到所有的測量數據，
10:30
we can combine all these together,
and we can understand
and we can understand
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我們就能把這些綜合起來，
我們就能了解
我們就能了解
10:33
how all three planets interact
with their space environment,
with their space environment,
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3417
這三個行星如何與太空環境，
10:36
with the surroundings.
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與它們周邊的環境交互作用，
10:38
And we can decide whether magnetic fields
are important for habitability
are important for habitability
238
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3522
我們就能決定磁場
對適居性的重要與否。
對適居性的重要與否。
10:41
or not.
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1158
10:42
Once we have that answer,
why should you care?
why should you care?
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2265
一旦我們有了答案，
我們為什麼要在意？
我們為什麼要在意？
10:45
I mean, I care deeply ...
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1300
我是說，我很在意──
10:48
And financially as well, but deeply.
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2006
財務上我也很在意啦！
不過真的很在意。
不過真的很在意。
10:50
(Laughter)
243
638158
1842
（笑聲）
10:52
First of all, an answer to this question
244
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1918
首先，這個問題的答案
10:54
will teach us more
about these three planets,
about these three planets,
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2103
會教我們更多這三個行星的事，
10:56
Venus, Earth and Mars,
246
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1160
金星、地球及火星，
10:58
not only about how they interact
with their environment today,
with their environment today,
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2911
不只是它們如何
與現今的環境交互作用，
與現今的環境交互作用，
11:00
but how they were billions of years ago,
248
648951
1927
還有幾十億以前的交互作用，
11:02
whether they were habitable
long ago or not.
long ago or not.
249
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2062
很久以前的適居性如何。
11:04
It will teach us about atmospheres
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1644
它會教我們很多
11:06
that surround us and that are close.
251
654656
1995
環繞及靠近我們的大氣層的事。
11:09
But moreover, what we learn
from these planets
from these planets
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2184
此外，我們從這幾個行星學到的，
11:11
can be applied to atmospheres everywhere,
253
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2021
可以應用到別處的大氣層，
11:14
including planets that we're now
observing around other stars.
observing around other stars.
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2913
包括我們正在觀察的幾個行星，
它們環繞著其它恆星。
它們環繞著其它恆星。
11:17
For example, the Kepler spacecraft,
255
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1755
舉個例子，克卜勒太空望遠鏡，
11:19
which is built and controlled
here in Boulder,
here in Boulder,
256
667201
3208
就在波德這裡建造並控制，
11:22
has been observing
a postage stamp-sized region of the sky
a postage stamp-sized region of the sky
257
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3285
已經觀察了郵票大小的天空
11:25
for a couple years now,
258
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1247
好幾年了，
11:27
and it's found thousands of planets --
259
675013
2228
它發現了數千個行星──
11:29
in one postage stamp-sized
region of the sky
region of the sky
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2913
就在郵票大小的一小片天空中，
11:32
that we don't think is any different
from any other part of the sky.
from any other part of the sky.
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4089
這片天跟其它部分的天空
沒什麼不同。
沒什麼不同。
11:36
We've gone, in 20 years,
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1810
在 20 年內，我們從以為
11:38
from knowing of zero planets
outside of our solar system,
outside of our solar system,
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4037
太陽系以外沒有行星，
11:42
to now having so many,
264
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1753
到現在我們知道有這麼多，
11:44
that we don't know
which ones to investigate first.
which ones to investigate first.
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3139
甚至不知道該從哪一個
開始調查起。
開始調查起。
11:49
Any lever will help.
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1460
任何方法都有幫助。
11:52
In fact, based on observations
that Kepler's taken
that Kepler's taken
267
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3584
其實，從克卜勒太空望遠鏡
11:56
and other similar observations,
268
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2129
及其它類似的觀測所發現的來看，
11:58
we now believe that,
269
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1169
我們現在相信
11:59
of the 200 billion stars
in the Milky Way galaxy alone,
in the Milky Way galaxy alone,
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4699
光是在我們銀河系的
二千億顆星星裡，
二千億顆星星裡，
12:04
on average, every star
has at least one planet.
has at least one planet.
271
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4604
每顆星平均都至少有一個行星。
12:10
In addition to that,
272
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1503
除此之外，
12:12
estimates suggest there are somewhere
between 40 billion and 100 billion
between 40 billion and 100 billion
273
720346
5701
估計這些行星中
還有約四百億到一千億顆，
還有約四百億到一千億顆，
12:18
of those planets
that we would define as habitable
that we would define as habitable
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3332
我們可以定義為適居，
12:23
in just our galaxy.
275
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1412
僅僅在我們的銀河！
12:26
We have the observations of those planets,
276
734590
2037
我們有這些行星的觀測，
12:28
but we just don't know
which ones are habitable yet.
which ones are habitable yet.
277
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2484
但是我們還不知道
哪一個是適合居住的。
哪一個是適合居住的。
12:31
It's a little bit like
being trapped on a red spot --
being trapped on a red spot --
278
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3606
這就跟困在 TED
這塊紅地毯上一樣，
這塊紅地毯上一樣，
12:34
(Laughter)
279
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1171
（笑聲）
12:35
on a stage
280
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1232
在舞台上，
12:38
and knowing that there are
other worlds out there
other worlds out there
281
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3562
你知道還有其它的世界存在，
12:43
and desperately wanting to know
more about them,
more about them,
282
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2776
極度想要更了解他們，
12:47
wanting to interrogate them and find out
if maybe just one or two of them
if maybe just one or two of them
283
755174
3934
想調查並找出是不是有一兩個
12:51
are a little bit like you.
284
759132
1610
和自己有點像。
12:54
You can't do that.
You can't go there, not yet.
You can't go there, not yet.
285
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2559
你做不了這件事，
你去不了那裡，還不行。
你去不了那裡，還不行。
12:56
And so you have to use the tools
that you've developed around you
that you've developed around you
286
764827
3993
所以你必須使用你手邊
為了金星、地球及火星
而發展的工具，
而發展的工具，
13:00
for Venus, Earth and Mars,
287
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1295
13:02
and you have to apply them
to these other situations,
to these other situations,
288
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2813
還必須將它們應用在
這些不同的狀況下，
這些不同的狀況下，
13:05
and hope that you're making
reasonable inferences from the data,
reasonable inferences from the data,
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希望自己能從數據做出合理的推斷，
13:09
and that you're going to be able
to determine the best candidates
to determine the best candidates
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希望自己能選出最好的
13:12
for habitable planets,
and those that are not.
and those that are not.
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適居行星，還要找出不合適的。
13:16
In the end, and for now, at least,
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最終，至少目前，
13:18
this is our red spot, right here.
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這是我們的紅地毯，就在這裡。
13:22
This is the only planet
that we know of that's habitable,
that we know of that's habitable,
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這是目前我們所知唯一適居的行星，
13:25
although very soon we may
come to know of more.
come to know of more.
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雖然我們可能很快就會發現
還有其它的。
還有其它的。
13:28
But for now, this is
the only habitable planet,
the only habitable planet,
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但是目前，這是唯一適居的行星，
13:31
and this is our red spot.
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這就是我們的紅地毯。
13:33
I'm really glad we're here.
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我真的很高興我們都在這裡。
13:36
Thanks.
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謝謝。
13:37
(Applause)
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（掌聲）
ABOUT THE SPEAKER
Dave Brain - Planetary scientistDave Brain studies the plasma environments and atmospheres of unmagnetized planets.
Why you should listen
Dave Brain is an Assistant Professor of Astrophysics and Planetary Science at the University of Colorado at Boulder. He's interested in the evolution of the atmospheres of planets such as Mars, Venus and Earth, and in particular how planets lose (and gain) atmosphere over time. He uses spacecraft data and computer models to help figure out how light and particles from our sun strip away atmospheric particles, possibly changing them from habitable worlds.
More profile about the speakerDave Brain | Speaker | TED.com