ABOUT THE SPEAKER
Dave Brain - Planetary scientist
Dave 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 speaker
Dave Brain | Speaker | TED.com
TEDxBoulder

Dave Brain: What a planet needs to sustain life

Dave Brain: 行星維持生命嘅條件

Filmed:
1,867,290 views

行星科學家 Dave Brain 話「金星太熱，火星太冷，地球啱啱好」。但係點解？Dave Brain 喺呢場開心幽默嘅演講，講解咗行星維持生命所需要嘅幾項有趣科學條件，同埋點解人類喺地球上生活只係因為天時同埋地利。
- Planetary scientist
Dave Brain studies the plasma environments and atmospheres of unmagnetized planets. Full bio

Double-click the English transcript below to play the video.

我好高興可以喺度
00:12
I'm really glad開心 to be here.
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00:15
I'm glad開心 you're here,
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我都好高興你哋可以喺度
00:16
because that would be a little weird奇怪.
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因爲冇你哋嘅話，會些少奇怪
我好高興我哋都喺度
00:19
I'm glad開心 we're all here.
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我講嘅「呢度」 唔係指 TED 呢度
00:22
And by "here," I don't mean here.
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或者呢度
00:26
Or here.
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00:28
But here.
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係呢度
我指嘅係地球
00:29
I mean Earth地球.
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00:31
And by "we," I don't mean
those of us in this auditorium禮堂,
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而我所講嘅「我哋」唔係指
呢度演講廳嘅咁多位
而係生命
00:35
but life,
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00:37
all life on Earth地球 --
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地球上所有嘅生命
（笑聲）
00:38
(Laughter笑聲)
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由複雜細胞到單細胞
00:44
from complex複雜 to single-celled單細胞,
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00:46
from mold模具 to mushrooms蘑菇
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由黴菌到蘑菇
到飛天熊都係
00:48
to flying飛行 bears熊.
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00:50
(Laughter笑聲)
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（笑聲）
00:53
The interesting有趣 thing is,
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有趣嘅係
00:55
Earth地球 is the only place地方
we know of that has life --
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地球係我哋知道唯一有生命嘅地方
00:58
8.7 million万 species物種.
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八百七十萬種生物
我哋人類其實有睇過其他地方
01:00
We've我哋都 looked看 other places地方,
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01:01
maybe not as hard努力
as we should or we could,
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不過可能冇畀心機搵喇
但係我哋搵咗之後都冇發現有生物
01:04
but we've我哋都 looked看 and haven't冇 found發現 any;
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01:06
Earth地球 is the only place地方
we know of with life.
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地球係我哋知道唯一有生命嘅地方
01:09
Is Earth地球 special特殊?
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地球特殊嗎？
01:11
This is a question個問題 I've wanted
to know the answer回答 to
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呢個問題由我細時就已經想知
01:14
since因為 I was a small小 child孩子,
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01:15
and I suspect懷疑 80 percent百分比
of this auditorium禮堂
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而我估呢座禮堂八成嘅人
都諗過同樣嘅事
01:17
has thought the same相同 thing
and also也 wanted to know the answer回答.
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亦都想知道答案
01:20
To understand理解 whether係唔係
there are any planets行星 --
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要知道有冇其他行星
01:23
out there in our solar太陽 system系統 or beyond超越 --
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喺我哋太陽系或者其他地方
能夠支持生命
01:25
that can support支持 life,
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01:26
the first step步 is to understand理解
what life here requires需要.
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第一步需要了解地球嘅生命需要啲乜
01:30
It turns輪流 out, of all of those
8.7 million万 species物種,
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事實證明，喺呢八百七十萬個物種之中
01:34
life only needs需要 three三 things.
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生命只需要三件事
01:37
On one side一邊, all life
on Earth地球 needs需要 energy能源.
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三張相嘅一邊
地球上所有生命都需要能量
01:39
Complex複雜 life like us derives派生
our energy能源 from the sun太陽,
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好似我哋咁嘅複合生物體
需要從太陽取得能量
01:43
but life deep深 underground地下
can get its energy能源
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但係地下深處嘅生物
可以由化學反應取得能量
01:45
from things like chemical化學 reactions反應.
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01:47
There are a number數量
of different不同 energy能源 sources來源
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能量嘅來源喺每個星球都有好多種
01:49
available可用 on all planets行星.
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01:51
On the other side一邊,
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相片另一邊
01:52
all life needs需要 food食品 or nourishment營養.
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所有生命都需要食物或者營養
01:55
And this seems好似 like a tall高 order以,
especially尤其係 if you want a succulent肉質 tomato番茄.
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咁聽起嚟係過分要求
尤其當你想要一隻多汁嘅番茄時
02:00
(Laughter笑聲)
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（笑聲）
但係地球上所有嘅生命
只需由六種化學元素取得營養
02:01
However然而, all life on Earth地球
derives派生 its nourishment營養
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02:05
from only six六 chemical化學 elements元素,
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02:07
and these elements元素 can be found發現
on any planetary行星 body身體
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呢啲元素都可以喺我哋嘅太陽系
任何一個行星上面發現
02:10
in our solar太陽 system系統.
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02:12
So that leaves葉 the thing
in the middle中間 as the tall高 pole極,
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所以剩低中間嘅嘢最難達到
02:15
the thing that's hardest難 to achieve實現.
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02:17
Not moose駝鹿, but water水.
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唔係麋鹿，係水
（笑聲）
02:19
(Laughter笑聲)
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02:23
Although雖然 moose駝鹿 would be pretty好 cool酷.
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雖然如果係麋鹿都幾型
02:25
(Laughter笑聲)
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（笑聲）
唔係冰結嘅水，亦唔係氣態嘅水
02:26
And not frozen冷凍 water水, and not water水
in a gaseous氣體 state狀態, but liquid液 water水.
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而係液態水
水係所有生命生存都需要嘅嘢
02:32
This is what life needs需要
to survive生存, all life.
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太陽系好多星球都冇液態水
02:35
And many好多 solar太陽 system系統 bodies機構
don't have liquid液 water水,
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所以我哋唔去呢啲星球度搵
02:39
and so we don't look there.
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02:40
Other solar太陽 system系統 bodies機構
might可能 have abundant豐富 liquid液 water水,
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但有啲太陽系嘅星球可能有大量液態水
02:43
even more than Earth地球,
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甚至多過地球
02:45
but it's trapped被困 beneath下 an icy冰冷 shell殼,
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但啲水都係困喺冰層底下
02:47
and so it's hard努力 to access訪問,
it's hard努力 to get to,
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所以好難接近，好難用到
02:49
it's hard努力 to even find out
if there's any life there.
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亦都令到我哋好難探測
冰層下面有冇生命
咁只剩低幾個星球值得考慮
02:53
So that leaves葉 a few幾個 bodies機構
that we should think about.
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所以等我哋簡化一下問題
02:56
So let's make the problem個問題
simpler簡單 for ourselves自己.
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02:58
Let's think only about liquid液 water水
on the surface表面 of a planet星球.
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我哋只要諗喺星球表面搵到液態水就好
03:02
There are only three三 bodies機構
to think about in our solar太陽 system系統,
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咁我哋嘅太陽系裡邊
只有三個星球可以諗
03:05
with regard方面 to liquid液 water水
on the surface表面 of a planet星球,
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03:07
and in order以 of distance距離 from the sun太陽,
it's: Venus金星, Earth地球 and Mars火星.
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按太陽嘅距離依次序為：
金星、地球、火星
03:13
You want to have an atmosphere氣氛
for water水 to be liquid液.
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因為你想大氣層畀到水係液體狀態
03:16
You have to be very careful小心
with that atmosphere氣氛.
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所以要對大氣層非常講究
大氣層唔可以太厚或者太暖
03:19
You can't have too much atmosphere氣氛,
too thick厚 or too warm溫暖 an atmosphere氣氛,
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因為咁樣嘅話會好似金星一樣咁熱
03:22
because then you end結束 up
too hot熱 like Venus金星,
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03:25
and you can't have liquid液 water水.
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而且冇可能有液態水
03:27
But if you have too little atmosphere氣氛
and it's too thin薄 and too cold冷,
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但係如果你嘅大氣層太薄太凍
結果就會好似火星一樣咁凍
03:31
you end結束 up like Mars火星, too cold冷.
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所以金星太熱，火星太凍
03:33
So Venus金星 is too hot熱, Mars火星 is too cold冷,
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地球就啱啱好
03:36
and Earth地球 is just right.
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03:37
You can look at these images圖像 behind背後 me
and you can see automatically自動
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睇下我後邊嘅相，你自然會睇到
03:41
where life can survive生存
in our solar太陽 system系統.
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我哋嘅太陽系邊度可以有生命
呢個係「金髮女孩
與三隻熊故事」嘅問題
03:44
It's a Goldilocks-type金鳳型 problem個問題,
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03:45
and it's so simple簡單
that a child孩子 could understand理解 it.
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簡單到兒童都可以理解
03:49
However然而,
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不過，我想提醒各位兩件事
03:51
I'd like to remind點 you of two things
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03:54
from the Goldilocks金髮姑娘 story故事
that we may可能 not think about so often經常
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喺金髮女孩與三隻熊個故事裡面
03:57
but that I think are really relevant相關 here.
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我哋經常忽略、但我認為非常切題嘅事
04:00
Number數量 one:
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第一
04:02
if Mama亞媽 Bear's熊的 bowl碗 is too cold冷
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當金髮女孩行入屋時
如果熊媽媽碗粥太凍
04:05
when Goldilocks金髮姑娘 walks走 into the room間房,
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咁碗粥係咪一路都係凍嘅呢？
04:08
does that mean it's always been too cold冷?
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04:11
Or could it have been just right
at some other time?
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定係喺之前係暖嘅呢？
金髮女孩行入屋時就一口咬定咗個答案
04:15
When Goldilocks金髮姑娘 walks走 into the room間房
determines決定 the answer回答
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04:19
that we get in the story故事.
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04:21
And the same相同 is true真係 with planets行星.
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行星都一樣
行星唔係靜態嘅嘢，佢哋一直改變緊
04:22
They're not static靜態 things. They change變.
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04:24
They vary不同. They evolve進化.
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佢哋會變化、會演化
04:26
And atmospheres大氣 do the same相同.
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大氣層都一樣
我舉一個例子
04:28
So let me give you an example例子.
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呢個係我最鍾意嘅火星圖片
04:30
Here's呢度有 one of my favorite中意
pictures圖片 of Mars火星.
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佢唔係最高解析度，亦唔係最靚
04:32
It's not the highest最高 resolution分辨率 image圖像,
it's not the sexiest性感 image圖像,
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都唔係最新嘅相
04:35
it's not the most最 recent最近 image圖像,
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但係佢顯示行星表面嘅河床
04:37
but it's an image圖像 that shows顯示 riverbeds河床
cutcut into the surface表面 of the planet星球;
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液態水流動而形成嘅河床
04:41
riverbeds河床 carved雕刻 by flowing流動, liquid液 water水;
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04:45
riverbeds河床 that take hundreds數以百計 or thousands數以千計
or tens成千上萬 of thousands數以千計 of years年 to form形式.
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河床要上百上千甚至上萬年先能形成
依家嘅火星冇可能發生呢件事
04:50
This can't happen發生 on Mars火星 today今日.
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04:52
The atmosphere氣氛 of Mars火星 today今日
is too thin薄 and too cold冷
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依家嘅火星大氣層太薄太冷
導致水唔可以維持液態
04:54
for water水 to be stable穩定 as a liquid液.
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呢張相話我哋知火星嘅大氣層改變咗
04:56
This one image圖像 tells話畀 you
that the atmosphere氣氛 of Mars火星 changed變,
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05:01
and it changed變 in big大 ways方式.
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而且改變好大
05:03
And it changed變 from a state狀態
that we would define定義 as habitable居住,
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佢由可居住嘅狀態變成依家咁
以前之所以可居住係因為
生命三大要素曾經喺嗰度出現過
05:08
because the three三 requirements要求
for life were present目前 long ago前.
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以前大氣層可以令地表維持液態水
05:13
Where did that atmosphere氣氛 go
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05:15
that allowed允許 water水
to be liquid液 at the surface表面?
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但依家火星嘅大氣層去咗邊度？
05:17
Well, one idea想法 is it escaped逃脫
away to space空間.
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一種理論係佢逃逸去到太空
05:21
Atmospheric大氣 particles粒子
got enough夠 energy能源 to break打破 free自由
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話大氣粒子有足夠嘅能量
走出行星嘅引力
05:24
from the gravity重力 of the planet星球,
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05:25
escaping逃避 away to space空間, never to return返回.
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散逸到太空，一去不返
05:28
And this happens發生 with all bodies機構
with atmospheres大氣.
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呢種現象喺有大氣層嘅星球上面
都會發生
05:31
Comets彗星 have tails條尾
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彗星嘅尾就係大氣逃逸嘅最佳例子
05:32
that are incredibly令人難以置信 visible可見 reminders點
of atmospheric大氣 escape逃脫.
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05:35
But Venus金星 also也 has an atmosphere氣氛
that escapes逃脫 with time,
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但係金星嘅大氣都會隨著時間逃逸
火星與地球都會
05:39
and Mars火星 and Earth地球 as well.
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05:40
It's just a matter個問題 of degree程度
and a matter個問題 of scale規模.
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只不過係程度同規模嘅問題
所以我哋要搵出逃逸嘅速率
先能夠解釋大氣層消失嘅現象
05:44
So we'd我哋會 like to figure圖 out
how much escaped逃脫 over time
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05:46
so we can explain解釋 this transition過渡.
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05:48
How do atmospheres大氣
get their佢哋 energy能源 for escape逃脫?
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大氣點得到逃逸所需嘅能量？
05:51
How do particles粒子 get
enough夠 energy能源 to escape逃脫?
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粒子點得到足以逃逸嘅能量？
05:53
There are two ways方式, if we're going
to reduce減少 things a little bit位.
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如果我哋簡單嚟睇，有兩種方法
第一，陽光
05:56
Number數量 one, sunlight陽光.
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大氣粒子吸收太陽發出嘅光
05:58
Light光 emitted排放 from the sun太陽 can be absorbed吸收
by atmospheric大氣 particles粒子
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06:01
and warm溫暖 the particles粒子.
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令到粒子增溫
06:03
Yes, I'm dancing跳舞, but they --
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係，我跳緊舞，不過粒子佢哋…
06:05
(Laughter笑聲)
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（笑聲）
該煨，我喺自己嘅婚禮都冇跳過…
06:07
Oh my God, not even at my wedding婚禮.
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06:09
(Laughter笑聲)
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（笑聲）
佢哋增溫就已經得到足夠嘅能量
去逃離引力
06:11
They get enough夠 energy能源
to escape逃脫 and break打破 free自由
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06:14
from the gravity重力 of the planet星球
just by warming變暖.
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06:16
A second第二 way they can get energy能源
is from the solar太陽 wind風.
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第二種方法係靠太陽風
由太陽表面噴出嘅粒子、物質
06:19
These are particles粒子, mass質素, material材料,
spit嘔 out from the surface表面 of the sun太陽,
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06:24
and they go screaming尖叫
through透過 the solar太陽 system系統
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會喺太陽系裡邊
以每秒 400 公里嘅速度呼嘯而過
06:27
at 400 kilometers公里 per每 second第二,
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06:29
sometimes有時 faster更快 during在 solar太陽 storms風暴,
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太陽風暴嚟嗰陣有時仲會快啲添
06:31
and they go hurtling飛馳
through透過 interplanetary星際 space空間
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佢哋穿梭行星之間
向著行星同行星嘅大氣飛去
06:34
towards啱 planets行星 and their佢哋 atmospheres大氣,
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06:37
and they may可能 provide提供 energy能源
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佢哋可能畀到大氣粒子能量去逃逸
06:38
for atmospheric大氣 particles粒子
to escape逃脫 as well.
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06:41
This is something that I'm interested興趣 in,
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呢個就係我覺得有興趣嘅嘢
因為呢個同適居性有關
06:43
because it relates涉及 to habitability居住.
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06:45
I mentioned提到 that there were two things
about the Goldilocks金髮姑娘 story故事
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我講過金髮女孩嘅故事
有兩樣嘢你哋要留意一下
06:48
that I wanted to bring帶 to your attention注意
and remind點 you about,
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而第二件事更加微妙︰
06:51
and the second第二 one
is a little bit位 more subtle微妙.
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如果熊爸爸碗粥太熱
06:53
If Papa老竇 Bear's熊的 bowl碗 is too hot熱,
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而熊媽媽碗粥太凍
06:58
and Mama亞媽 Bear's熊的 bowl碗 is too cold冷,
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07:03
shouldn't唔该 Baby寶貝 Bear's熊的 bowl碗 be even colder冷
153
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咁熊寶寶碗粥咪應該更加凍？
如果我哋跟著個趨勢諗
07:07
if we're following以下 the trend趨勢?
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07:10
This thing that you've accepted接受
your entire整個 life,
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呢件你成世人都以為嘅事
如果仔細諗下，可能冇咁簡單
07:12
when you think about it a little bit位 more,
may可能 not be so simple簡單.
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當然，行星溫度取決於佢同太陽嘅距離
07:16
And of course課程, distance距離 of a planet星球
from the sun太陽 determines決定 its temperature溫度.
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07:20
This has to play玩 into habitability居住.
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就同適居性有關
但係我哋可能需要考慮其他事情
07:22
But maybe there are other things
we should be thinking思維 about.
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可能碗本身都會決定個故事嘅結局︰
07:25
Maybe it's the bowls碗 themselves自己
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07:27
that are also也 helping幫手 to determine確定
the outcome結果 in the story故事,
161
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07:30
what is just right.
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亦即係乜為之啱啱好
我可以同大家講好多
關於呢三個行星唔同嘅特性
07:32
I could talk to you about a lot
of different不同 characteristics特徵
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07:35
of these three三 planets行星
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07:36
that may可能 influence影響 habitability居住,
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點樣影響適居性
07:38
but for selfish自私 reasons原因 related相關
to my own自己 research研究
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但係因為我研究嘅關係
同埋因為我係講者
07:41
and the fact事實 that I'm standing站 up here
holding舉行 the clicker遙控器 and you're not --
167
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（笑聲）
07:44
(Laughter笑聲)
168
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07:45
I would like to talk
for just a minute分鐘 or two
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所以我想花一兩分鐘同你哋講下磁場
07:47
about magnetic磁 fields領域.
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07:49
Earth地球 has one; Venus金星 and Mars火星 do not.
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地球有磁場；金星同火星就冇
地球內部深處有一啲電導液體物質
07:52
Magnetic磁 fields領域 are generated生成
in the deep深 interior內部 of a planet星球
172
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07:55
by electrically電 conducting進行
churning攪動 fluid流體 material材料
173
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呢啲電導液體物質流動嗰陣
會形成地球嘅磁場
07:59
that creates創建 this big大 old老 magnetic磁 field領域
that surrounds圍繞 Earth地球.
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如果你有指南針，你就會知道邊邊係北
08:02
If you have a compass羅經,
you know which的 way north北 is.
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但金星同火星都冇磁場
08:05
Venus金星 and Mars火星 don't have that.
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08:06
If you have a compass羅經 on Venus金星 and Mars火星,
177
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如果你喺金星同火星上面用指南針
恭喜！你盪失路
08:08
congratulations祝福, you're lost失去.
178
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08:09
(Laughter笑聲)
179
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（笑聲）
磁場會影響適居性嗎？
08:11
Does this influence影響 habitability居住?
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2040
08:15
Well, how might可能 it?
181
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會點影響？
08:17
Many好多 scientists科學家 think
that a magnetic磁 field領域 of a planet星球
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好多科學家認為行星嘅磁場
就好似大氣層嘅防護罩
08:19
serves服務 as a shield屏蔽 for the atmosphere氣氛,
183
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08:22
deflecting偏轉 solar太陽 wind風 particles粒子
around the planet星球
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令行星四周嘅太陽粒子改變方向
屬於力場效應嘅一種
08:25
in a bit位 of a force力 field-type字段類型 effect影響
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08:27
having有 to do with electric電 charge負責
of those particles粒子.
186
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亦都同粒子嘅電荷有關
我鐘意將佢比喻為
麫包鋪廚窗揭得開嘅玻璃蓋
08:30
I like to think of it instead相反
as a salad沙律 bar酒吧 sneeze打噴嚏 guard警衛 for planets行星.
187
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08:34
(Laughter笑聲)
188
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（笑聲）
08:36
And yes, my colleagues同事
who watch this later之後 will realize實現
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係嘅，之後睇呢段片嘅同事會發覺
08:40
this is the first time in the history歷史
of our community社區
190
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呢個係我哋第一次
將太陽風等同為口水唾沫
08:42
that the solar太陽 wind風 has been
equated等同 with mucus粘液.
191
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2279
08:45
(Laughter笑聲)
192
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（笑聲）
08:48
OK, so the effect影響, then, is that Earth地球
may可能 have been protected保護
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好，所以地球之所以
幾十億年嚟都受到保護
08:52
for billions数十亿 of years年,
194
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08:53
because we've我哋都 had a magnetic磁 field領域.
195
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1850
全因我哋有磁場
以至大氣冇辦法逃脫
08:55
Atmosphere氣氛 hasn't冇 been able能 to escape逃脫.
196
523544
2179
另一方面因為火星冇磁場
08:57
Mars火星, on the other hand手,
has been unprotected保護
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2107
08:59
because of its lack缺乏 of magnetic磁 field領域,
198
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1842
火星嘅大氣冇保護
09:01
and over billions数十亿 of years年,
199
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以致可能幾十億年嚟火星失去嘅大氣
09:03
maybe enough夠 atmosphere氣氛
has been stripped剝奪 away
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足以令到呢個原本可以居住嘅行星
09:05
to account帳戶 for a transition過渡
from a habitable居住 planet星球
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09:08
to the planet星球 that we see today今日.
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變成今日我哋睇到嘅樣
其他科學家認為磁場可能更似船嘅帆
09:11
Other scientists科學家 think
that magnetic磁 fields領域
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09:14
may可能 act行為 more like the sails帆 on a ship船,
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09:16
enabling使 the planet星球 to interact互動
with more energy能源 from the solar太陽 wind風
205
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令行星可以同太陽風交換更多嘅能量
09:22
than the planet星球 would have been able能
to interact互動 with by itself本身.
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09:25
The sails帆 may可能 gather收集 energy能源
from the solar太陽 wind風.
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磁場可以收集太陽風嘅能量
畀更加多嘅大氣脫逃到
09:27
The magnetic磁 field領域 may可能 gather收集
energy能源 from the solar太陽 wind風
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09:30
that allows允許 even more
atmospheric大氣 escape逃脫 to happen發生.
209
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09:33
It's an idea想法 that has to be tested測試,
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呢個理論仲需要去證實
09:36
but the effect影響 and how it works工程
211
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但係佢嘅效應同運作方式睇起來好明顯
09:37
seems好似 apparent明顯.
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1151
09:39
That's because we know
213
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咁係因為我哋知道
09:40
energy能源 from the solar太陽 wind風
is being被 deposited沉積 into our atmosphere氣氛
214
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太陽風嘅能量已經注入緊
我哋地球嘅大氣層度
09:43
here on Earth地球.
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嗰股能量順著磁力線傳導
09:44
That energy能源 is conducted進行
along沿 magnetic磁 field領域 lines線
216
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向下導入兩極
09:47
down into the polar極 regions一區,
217
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09:48
resulting導致 in incredibly令人難以置信 beautiful靚 aurora極光.
218
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2136
化成無比璀璨嘅極光
09:50
If you've ever experienced經歷 them,
it's magnificent宏偉.
219
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如果你有睇過極光，你就知佢有幾壯麗
09:53
We know the energy能源 is getting得到 in.
220
581240
2006
我哋知道能量入緊嚟
09:55
We're trying試圖 to measure措施
how many好多 particles粒子 are getting得到 out
221
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我哋想計下有幾多粒子逃逸
同埋睇下磁場係咪真係有影響
09:58
and if the magnetic磁 field領域
is influencing影響 this in any way.
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我有一個問題畀大家
10:02
So I've posed提出 a problem個問題 for you here,
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但係我未有答案，我們冇答案
10:05
but I don't have a solution解決方案 yet尚未.
224
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10:06
We don't have a solution解決方案.
225
594696
1276
但係我哋努力緊。我哋係點努力呢？
10:08
But we're working工作 on it.
How are we working工作 on it?
226
596702
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我哋送咗太空船去呢三個行星度
10:11
Well, we've我哋都 sent送 spacecraft航天器
to all three三 planets行星.
227
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2298
10:13
Some of them are orbiting軌道 now,
228
601405
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有啲圍繞緊行星
10:14
including包括 the MAVENMaven spacecraft航天器
which的 is currently目前 orbiting軌道 Mars火星,
229
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包括 MAVEN 太空船
目前喺火星嘅軌道上面
10:18
which的 I'm involved涉及 with
and which的 is led here,
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呢項計劃我都有參與
而且係由呢度嘅科羅拉多大學帶領
10:21
out of the University大學 of Colorado科羅拉多州.
231
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1809
個計劃為咗測量大氣逃脫
10:23
It's designed設計 to measure措施
atmospheric大氣 escape逃脫.
232
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我哋喺金星同地球都有類似嘅量度
10:26
We have similar類似 measurements測量
from Venus金星 and Earth地球.
233
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當我哋集齊所有嘅量度數據
10:28
Once一旦 we have all our measurements測量,
234
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10:30
we can combine結合 all these together一起,
and we can understand理解
235
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2875
我哋就可以將佢哋併埋一齊
就可以了解呢三個行星
點樣同周圍嘅太空環境互動
10:33
how all three三 planets行星 interact互動
with their佢哋 space空間 environment環境,
236
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10:36
with the surroundings環境.
237
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10:38
And we can decide決定 whether係唔係 magnetic磁 fields領域
are important重要 for habitability居住
238
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3522
我哋就可以決定磁場係咪對適居性重要
10:41
or not.
239
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就算我哋有咗答案
但係點解你哋要咁在乎？
10:42
Once一旦 we have that answer回答,
why should you care護理?
240
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2265
10:45
I mean, I care護理 deeply深深 ...
241
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1300
我意思係，我好在乎
10:48
And financially經濟 as well, but deeply深深.
242
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我亦都在乎研究經費
10:50
(Laughter笑聲)
243
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（笑聲）
10:52
First of all, an answer回答 to this question個問題
244
640763
1918
首先，呢個問題嘅答案
會教我哋更多關於
金星、地球以及火星嘅事
10:54
will teach教 us more
about these three三 planets行星,
245
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2103
10:56
Venus金星, Earth地球 and Mars火星,
246
644832
1160
唔單止包括佢哋點樣同現今嘅環境互動
10:58
not only about how they interact互動
with their佢哋 environment環境 today今日,
247
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仲包括佢哋幾十億以前嘅狀態
11:00
but how they were billions数十亿 of years年 ago前,
248
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1927
同埋佢哋好耐以前係咪適合居住
11:02
whether係唔係 they were habitable居住
long ago前 or not.
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2062
11:04
It will teach教 us about atmospheres大氣
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答案會揭示大氣層嘅嘢
11:06
that surround環繞 us and that are close關閉.
251
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1995
11:09
But moreover此外, what we learn學習
from these planets行星
252
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2184
另外，我哋從呢幾個行星嘅
大氣層學到嘅知識
11:11
can be applied應用 to atmospheres大氣 everywhere周圍,
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2021
可以應用喺其他星球嘅大氣層度
包括我哋觀察緊嘅
幾個環繞著其他恆星嘅行星
11:14
including包括 planets行星 that we're now
observing觀察 around other stars星星.
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2913
舉個例子，喺波德呢度
建造同埋控制嘅哈勃太空望遠鏡
11:17
For example例子, the Kepler勒 spacecraft航天器,
255
665422
1755
11:19
which的 is built建立 and controlled控制
here in Boulder博尔德,
256
667201
3208
11:22
has been observing觀察
a postage郵資 stamp-sized郵票大小 region一區 of the sky天空
257
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3285
已經好幾年觀察緊
一塊郵票咁大嘅天空範圍
11:25
for a couple夫婦 years年 now,
258
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1247
11:27
and it's found發現 thousands數以千計 of planets行星 --
259
675013
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佢目前已經喺郵票咁大嘅天空裏面
發現咗幾千個行星
11:29
in one postage郵資 stamp-sized郵票大小
region一區 of the sky天空
260
677265
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而我哋唔覺呢塊天空
同其他天空有咩唔同
11:32
that we don't think is any different不同
from any other part部分 of the sky天空.
261
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4089
11:36
We've我哋都 gone走, in 20 years年,
262
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1810
廿年裏邊
我哋由一個太陽系以外嘅
行星都唔認識
11:38
from knowing知 of zero零 planets行星
outside外面 of our solar太陽 system系統,
263
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4037
到依家知道有咁多行星
11:42
to now having有 so many好多,
264
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11:44
that we don't know
which的 ones的 to investigate探討 first.
265
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我哋都唔知應該由邊度開始探索
11:49
Any lever槓桿 will help.
266
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任何幫手都歡迎
11:52
In fact事實, based基於 on observations觀察
that Kepler's開普勒的 taken採取
267
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3584
其實，跟據哈勃太空望遠鏡得到嘅觀察
11:56
and other similar類似 observations觀察,
268
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2129
加上其他類似嘅觀測，我哋宜家相信
11:58
we now believe that,
269
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1169
剩係我哋銀河系二千億個星裡邊
11:59
of the 200 billion億 stars星星
in the Milky乳白色 Way galaxy星系 alone一手一腳,
270
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4699
平均每個恆星至少有一個行星
12:04
on average平均, every每 star明星
has at least最小 one planet星球.
271
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4604
12:10
In addition除咗 to that,
272
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1503
除此之外，單單喺我哋嘅銀河
12:12
estimates估計 suggest建議 there are somewhere地方
between之間 40 billion億 and 100 billion億
273
720346
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我哋估計有大概四百億
到一千億個行星係適居嘅
12:18
of those planets行星
that we would define定義 as habitable居住
274
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3332
12:23
in just our galaxy星系.
275
731139
1412
12:26
We have the observations觀察 of those planets行星,
276
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2037
我哋得到呢啲行星嘅觀測資料
但係我哋仲未知邊一個係適合居住嘅
12:28
but we just don't know
which的 ones的 are habitable居住 yet尚未.
277
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2484
有點似被困喺台上嘅呢塊紅地氈一樣
12:31
It's a little bit位 like
being被 trapped被困 on a red紅 spotD --
278
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3606
（笑聲）
12:34
(Laughter笑聲)
279
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1171
12:35
on a stage階段
280
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1232
12:38
and knowing知 that there are
other worlds世界 out there
281
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3562
但係你又知道仲有其他世界存在
12:43
and desperately拼命 wanting希望 to know
more about them,
282
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2776
你又極想了解佢哋
12:47
wanting希望 to interrogate審問 them and find out
if maybe just one or two of them
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你又想調查睇下有冇一兩個星球
好似自己嘅星球
12:51
are a little bit位 like you.
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12:54
You can't do that.
You can't go there, not yet尚未.
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但係你就係做唔到，你去唔到
12:56
And so you have to use the tools工具
that you've developed開發 around you
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所以你要用上
為到金星、地球同火星開發嘅工具
13:00
for Venus金星, Earth地球 and Mars火星,
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1295
13:02
and you have to apply應用 them
to these other situations情況,
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你要將工具用喺其他情況度
並確保能夠從數據裏面作出合理嘅推斷
13:05
and hope希望 that you're making決策
reasonable合理 inferences推論 from the data數據,
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從而揀出最有可能適居嘅行星
13:09
and that you're going to be able能
to determine確定 the best最好 candidates候選人
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同埋搵出最冇可能適居嘅行星
13:12
for habitable居住 planets行星,
and those that are not.
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最終，同埋至少目前
13:16
In the end結束, and for now, at least最小,
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呢個就係我哋嘅紅地氈，就喺呢度
13:18
this is our red紅 spotD, right here.
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呢個係目前我哋所知唯一適居嘅行星
13:22
This is the only planet星球
that we know of that's habitable居住,
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雖然好快我哋可能會發現仲有其他嘅
13:25
although雖然 very soon好快 we may可能
come to know of more.
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但係目前，呢個係唯一適居嘅行星
13:28
But for now, this is
the only habitable居住 planet星球,
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呢個就係我哋嘅紅地氈
13:31
and this is our red紅 spotD.
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我真係好高興我哋都喺度
13:33
I'm really glad開心 we're here.
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多謝
13:36
Thanks多謝.
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（掌聲）
13:37
(Applause掌聲)
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Translated by Tammy Lee
Reviewed by Chak Lam Wan

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ABOUT THE SPEAKER
Dave Brain - Planetary scientist
Dave 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 speaker
Dave Brain | Speaker | TED.com
THE ORIGINAL VIDEO ON TED.COM