Sean Carroll: Distant time and the hint of a multiverse

208,802 views ・ 2011-05-06

TED


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翻译人员: Lily Yichen Shi 校对人员: Jenny Yang
00:15
The universe
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宇宙
00:17
is really big.
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非常大
00:19
We live in a galaxy, the Milky Way Galaxy.
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我们生活在一个名为银河的星系
00:22
There are about a hundred billion stars in the Milky Way Galaxy.
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银河系中有约一千亿颗恒星
00:25
And if you take a camera
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如果你拿起相机
00:27
and you point it at a random part of the sky,
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并把它指向空中的任何一处
00:29
and you just keep the shutter open,
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打开快门并让它开在那里
00:31
as long as your camera is attached to the Hubble Space Telescope,
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只要你的相机接通着哈勃天文望远镜
00:34
it will see something like this.
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这就是它会看到的
00:36
Every one of these little blobs
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这里的每一小点
00:39
is a galaxy roughly the size of our Milky Way --
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都是与我们的银河系大小相当的星系
00:41
a hundred billion stars in each of those blobs.
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每一小点中都有一千亿颗恒星
00:44
There are approximately a hundred billion galaxies
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而在整个可见宇宙中
00:47
in the observable universe.
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约有一千亿个星系
00:49
100 billion is the only number you need to know.
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所以你记住一千亿这个数字就行了
00:51
The age of the universe, between now and the Big Bang,
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宇宙的年龄 自大爆炸以来
00:54
is a hundred billion in dog years.
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在狗看来已过了一千亿年
00:56
(Laughter)
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(笑)
00:58
Which tells you something about our place in the universe.
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这就告诉了你 我们在这宇宙中的位置
01:01
One thing you can do with a picture like this is simply admire it.
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面对这样的画面 你可以做的一件事便是欣赏
01:03
It's extremely beautiful.
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它极其美丽
01:05
I've often wondered, what is the evolutionary pressure
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我常想 在星系的照片还不存在的时候
01:08
that made our ancestors in the Veldt adapt and evolve
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究竟是什么推动了我们远在非洲大草原的祖先
01:11
to really enjoy pictures of galaxies
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让他们适应 进化
01:13
when they didn't have any.
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并欣赏这些星系的呢?
01:15
But we would also like to understand it.
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但除了欣赏 我们也想要了解它们
01:17
As a cosmologist, I want to ask, why is the universe like this?
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作为一个宇宙学家 我想问问 宇宙为什么是这样的呢?
01:21
One big clue we have is that the universe is changing with time.
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宇宙随着时间流逝的演变 是一条重要的线索
01:24
If you looked at one of these galaxies and measured its velocity,
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如果你选中一个星系并测量它的速度
01:27
it would be moving away from you.
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你会发现它正离你远去
01:29
And if you look at a galaxy even farther away,
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而如果你选中的是一个更远的星系
01:31
it would be moving away faster.
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你会发现它正以更快的速度离你远去
01:33
So we say the universe is expanding.
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所以说 宇宙正在膨胀
01:35
What that means, of course, is that, in the past,
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当然 这就意味着过去所有的一切
01:37
things were closer together.
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彼此之间都比较接近
01:39
In the past, the universe was more dense,
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曾经的宇宙密度比现在高
01:41
and it was also hotter.
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它也比现在热
01:43
If you squeeze things together, the temperature goes up.
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如果你把东西紧捏在一切 温度便会上升
01:45
That kind of makes sense to us.
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听起来有道理吧
01:47
The thing that doesn't make sense to us as much
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而让我们觉得没道理的
01:49
is that the universe, at early times, near the Big Bang,
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是宇宙初期 大爆炸之后那个
01:52
was also very, very smooth.
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极度光滑的宇宙
01:54
You might think that that's not a surprise.
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你或许觉得这并不值得惊讶
01:56
The air in this room is very smooth.
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这房间里的空气便十分光滑
01:58
You might say, "Well, maybe things just smoothed themselves out."
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你也许会说 “大概这些东西就是会自己慢慢平滑掉的”
02:01
But the conditions near the Big Bang are very, very different
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但大爆炸不久之后的环境 与这房间里的空气相比
02:04
than the conditions of the air in this room.
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十分 十分的不同
02:06
In particular, things were a lot denser.
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特别是一切的密度
02:08
The gravitational pull of things
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当时的地心引力
02:10
was a lot stronger near the Big Bang.
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比现在强很多
02:12
What you have to think about
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我们不得不想想
02:14
is we have a universe with a hundred billion galaxies,
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这个宇宙里有一千亿个星系
02:16
a hundred billion stars each.
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而每个星系里都有一千亿颗恒星
02:18
At early times, those hundred billion galaxies
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在宇宙初期 那一千亿个星系
02:21
were squeezed into a region about this big --
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被挤压到这么小的空间
02:24
literally -- at early times.
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毫不夸张 当初就这么小
02:26
And you have to imagine doing that squeezing
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我们得想象一下这个挤压过程
02:28
without any imperfections,
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这个完美的过程
02:30
without any little spots
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毫无瑕疵
02:32
where there were a few more atoms than somewhere else.
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这里比那里多一两个原子也不行
02:34
Because if there had been, they would have collapsed under the gravitational pull
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如果真有任何瑕疵 地心引力也会把它们
02:37
into a huge black hole.
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压成一个巨大的黑洞
02:39
Keeping the universe very, very smooth at early times
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让初期的宇宙保持在极度光滑的状态并非易事
02:42
is not easy; it's a delicate arrangement.
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这是个极为精细的布置
02:44
It's a clue
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这条线索意味着初期宇宙
02:46
that the early universe is not chosen randomly.
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并非任意选择的产物
02:48
There is something that made it that way.
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是某些东西把它造就成那样的
02:50
We would like to know what.
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而我们想知道那是什么
02:52
So part of our understanding of this was given to us by Ludwig Boltzmann,
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19世纪的奥地利物理学家路德维希·玻尔兹曼
02:55
an Austrian physicist in the 19th century.
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给予了我们不少对此的了解
02:58
And Boltzmann's contribution was that he helped us understand entropy.
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玻尔兹曼的贡献在于他帮助我们理解了熵
03:01
You've heard of entropy.
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你们听见过熵
03:03
It's the randomness, the disorder, the chaoticness of some systems.
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在某些系统中 它是随意性 是不规则 是混乱
03:06
Boltzmann gave us a formula --
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玻尔兹曼给了我们一条
03:08
engraved on his tombstone now --
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被刻在了他墓碑上的公式
03:10
that really quantifies what entropy is.
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让我们得以在数量上解释熵
03:12
And it's basically just saying
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这条公式所说的 不过是
03:14
that entropy is the number of ways
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我们可以重新组合
03:16
we can rearrange the constituents of a system so that you don't notice,
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构成一个系统的各个要素 而在宏观上
03:19
so that macroscopically it looks the same.
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你看不出任何变化
03:21
If you have the air in this room,
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在感受这房间里的空气时
03:23
you don't notice each individual atom.
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你不可能注意每一个原子吧
03:26
A low entropy configuration
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如果能够组合出某个布局的方式屈指可数
03:28
is one in which there's only a few arrangements that look that way.
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那这个布局的熵值就会很小
03:30
A high entropy arrangement
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反之 若能组合出某个布局的方式很多
03:32
is one that there are many arrangements that look that way.
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这个布局的熵值就会很大
03:34
This is a crucially important insight
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对这一点的领悟极其关键
03:36
because it helps us explain
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因为它帮助我们解释
03:38
the second law of thermodynamics --
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热力学第二定律——
03:40
the law that says that entropy increases in the universe,
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在整个宇宙 或是被隔离开的部分宇宙中
03:43
or in some isolated bit of the universe.
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熵值只可增大
03:45
The reason why entropy increases
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熵值增大的原因很简单
03:47
is simply because there are many more ways
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只因呈现出对应于大熵值的布局
03:50
to be high entropy than to be low entropy.
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比呈现出对应于小熵值的布局的方式多得多
03:52
That's a wonderful insight,
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虽说领会到这些很奇妙
03:54
but it leaves something out.
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但还有被遗漏的部分
03:56
This insight that entropy increases, by the way,
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值得提及的是 正是熵值的增大
03:58
is what's behind what we call the arrow of time,
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推动着我们的时间之箭
04:01
the difference between the past and the future.
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造就着过去与未来的不同
04:03
Every difference that there is
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过去与未来
04:05
between the past and the future
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它们之间的所有区别
04:07
is because entropy is increasing --
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都呈现于熵值的增大
04:09
the fact that you can remember the past, but not the future.
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正如你能记得往事 却无法去记住将来所要发生的
04:12
The fact that you are born, and then you live, and then you die,
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又如你出生 成长 死亡的过程
04:15
always in that order,
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这些不变的顺序
04:17
that's because entropy is increasing.
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都源于熵值的增大
04:19
Boltzmann explained that if you start with low entropy,
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玻尔兹曼解释道 如果你从小熵值出发
04:21
it's very natural for it to increase
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它会很自然的增大
04:23
because there's more ways to be high entropy.
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因为处于大熵值状态的途径更多
04:26
What he didn't explain
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但他并没有解释
04:28
was why the entropy was ever low in the first place.
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为什么最初的熵值那么小
04:31
The fact that the entropy of the universe was low
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宇宙初期的小熵值
04:33
was a reflection of the fact
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意味着的莫过于
04:35
that the early universe was very, very smooth.
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初期的宇宙非常非常的光滑
04:37
We'd like to understand that.
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而我们想要理解它的原由
04:39
That's our job as cosmologists.
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那便是作为宇宙学家的我们的任务
04:41
Unfortunately, it's actually not a problem
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遗憾的是 我们并没有
04:43
that we've been giving enough attention to.
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给予这个问题多大的关注
04:45
It's not one of the first things people would say,
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如果你问一个现代宇宙学家
04:47
if you asked a modern cosmologist,
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“我们正研究着的问题有哪些?”
04:49
"What are the problems we're trying to address?"
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这不会是回答中你最先听到的问题之一
04:51
One of the people who did understand that this was a problem
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认识到这个问题的重要性的其中一人
04:53
was Richard Feynman.
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便是理查德·费曼
04:55
50 years ago, he gave a series of a bunch of different lectures.
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50年前 他给了一系列的演讲
04:57
He gave the popular lectures
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他面向大众的讲座
04:59
that became "The Character of Physical Law."
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成了《物理之美》
05:01
He gave lectures to Caltech undergrads
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他面向加州理工学院本科生的讲课
05:03
that became "The Feynman Lectures on Physics."
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成了《费曼物理学讲义》
05:05
He gave lectures to Caltech graduate students
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他面向加州理工学院研究生的讲课
05:07
that became "The Feynman Lectures on Gravitation."
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成了《费曼引力学讲义》
05:09
In every one of these books, every one of these sets of lectures,
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在上述的每本书 费曼的每个讲座中
05:12
he emphasized this puzzle:
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他都强调了这个难题
05:14
Why did the early universe have such a small entropy?
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为什么初期的宇宙有着那么小的熵值?
05:17
So he says -- I'm not going to do the accent --
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我就不模仿他的口音了
05:19
he says, "For some reason, the universe, at one time,
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他说:“虽说宇宙中包含着的能量巨大
05:22
had a very low entropy for its energy content,
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某些原因使它曾一度拥有小熵值
05:25
and since then the entropy has increased.
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而从那以后 熵值不断增大
05:27
The arrow of time cannot be completely understood
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直至我们能够真正理解 而非单单推测
05:30
until the mystery of the beginnings of the history of the universe
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整个宇宙历史的 开端的秘密
05:33
are reduced still further
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时间之箭
05:35
from speculation to understanding."
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便无法被完全理解”
05:37
So that's our job.
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这就是我们的使命
05:39
We want to know -- this is 50 years ago, "Surely," you're thinking,
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这是费曼50年前说的 你也许在想:“那么久了
05:41
"we've figured it out by now."
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我们现在弄清了吧”
05:43
It's not true that we've figured it out by now.
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错了 我们到现在也没弄清
05:45
The reason the problem has gotten worse,
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非但没把问题弄清
05:47
rather than better,
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它还变得更糟糕了
05:49
is because in 1998
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因为在1998年
05:51
we learned something crucial about the universe that we didn't know before.
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一个关于宇宙的新发型展现在了我们面前
05:54
We learned that it's accelerating.
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宇宙不仅在膨胀
05:56
The universe is not only expanding.
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而且在加速膨胀
05:58
If you look at the galaxy, it's moving away.
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如果你看见一个星系正离你远去
06:00
If you come back a billion years later and look at it again,
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十亿年后再回来看它时
06:02
it will be moving away faster.
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你会发现它远去的速度加快了
06:05
Individual galaxies are speeding away from us faster and faster
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各个星系离我们远去的速度都在不断加快着
06:08
so we say the universe is accelerating.
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所以我们说这个宇宙正在加速膨胀
06:10
Unlike the low entropy of the early universe,
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与宇宙初期的小熵值不同
06:12
even though we don't know the answer for this,
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虽然我们没有答案 但要解释这现象
06:14
we at least have a good theory that can explain it,
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我们至少还有一套不错的理论
06:16
if that theory is right,
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如果那理论是正确的
06:18
and that's the theory of dark energy.
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我是在说暗能量理论
06:20
It's just the idea that empty space itself has energy.
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它说 真空区自身便有能量
06:23
In every little cubic centimeter of space,
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这空间中的任何一立方厘米中
06:26
whether or not there's stuff,
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无论那里有没有东西
06:28
whether or not there's particles, matter, radiation or whatever,
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无论那里有没有粒子 物质 辐射 或任何别的什么
06:30
there's still energy, even in the space itself.
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那里仍有能量 就这空间中便有
06:33
And this energy, according to Einstein,
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在爱因斯坦看来
06:35
exerts a push on the universe.
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这能量推动着宇宙
06:38
It is a perpetual impulse
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这是一股永恒的冲量
06:40
that pushes galaxies apart from each other.
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使各星系之间的距离越来越大
06:42
Because dark energy, unlike matter or radiation,
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因为暗能量 与物质和辐射不同
06:45
does not dilute away as the universe expands.
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它不会因为宇宙的膨胀而被稀释
06:48
The amount of energy in each cubic centimeter
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即便宇宙越来越大
06:50
remains the same,
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每立方厘米中的能量
06:52
even as the universe gets bigger and bigger.
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都将保持不变
06:54
This has crucial implications
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这对宇宙未来的发展
06:57
for what the universe is going to do in the future.
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有着关键的影响
07:00
For one thing, the universe will expand forever.
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其中之一 便是宇宙会永远膨胀下去
07:02
Back when I was your age,
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当我像你们那么小的时候
07:04
we didn't know what the universe was going to do.
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我们并不知道宇宙是否会膨胀下去
07:06
Some people thought that the universe would recollapse in the future.
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某些人认为 宇宙将会再坍缩
07:09
Einstein was fond of this idea.
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爱因斯坦就很喜欢这想法
07:11
But if there's dark energy, and the dark energy does not go away,
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但如果有暗能量 而暗能量又会永远留在那里
07:14
the universe is just going to keep expanding forever and ever and ever.
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宇宙便会永不停息的 这样膨胀下去
07:17
14 billion years in the past,
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从140亿年前
07:19
100 billion dog years,
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狗的一千亿年前
07:21
but an infinite number of years into the future.
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直至无数年以后 直至永恒的未来
07:24
Meanwhile, for all intents and purposes,
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在此期间 不论我们有什么意图或目的
07:27
space looks finite to us.
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宇宙空间在我们看来都是有限的
07:29
Space may be finite or infinite,
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宇宙或许有限 或许无限
07:31
but because the universe is accelerating,
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但因为它正在膨胀
07:33
there are parts of it we cannot see
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我们看不到它的某些部分
07:35
and never will see.
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也将永远无法看到
07:37
There's a finite region of space that we have access to,
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能让我们获取信息的宇宙空间非常有限
07:39
surrounded by a horizon.
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它被边界包围着
07:41
So even though time goes on forever,
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所以即便时间不停下它的脚步
07:43
space is limited to us.
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宇宙空间对我们来说还是有限的
07:45
Finally, empty space has a temperature.
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最后 真空区有它的温度
07:48
In the 1970s, Stephen Hawking told us
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在70年代 斯蒂芬·霍金告诉我们
07:50
that a black hole, even though you think it's black,
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虽然你认为黑洞是黑的
07:52
it actually emits radiation
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它其实会辐射
07:54
when you take into account quantum mechanics.
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如果把量子力学考虑进去的话
07:56
The curvature of space-time around the black hole
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黑洞周围的空间曲率
07:59
brings to life the quantum mechanical fluctuation,
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是会导致真空量子涨落的
08:02
and the black hole radiates.
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黑洞也就会辐射
08:04
A precisely similar calculation by Hawking and Gary Gibbons
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根据霍金与加利·基本斯的 一个类似的精确计算
08:07
showed that if you have dark energy in empty space,
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如果真空区里有暗能量
08:10
then the whole universe radiates.
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整个宇宙便会辐射
08:13
The energy of empty space
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真空区的能量
08:15
brings to life quantum fluctuations.
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带来量子涨落
08:17
And so even though the universe will last forever,
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所以虽然宇宙是永恒的
08:19
and ordinary matter and radiation will dilute away,
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而且一般的物质和辐射会被稀释
08:22
there will always be some radiation,
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但某些辐射会永远留下
08:24
some thermal fluctuations,
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某些热涨落
08:26
even in empty space.
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即便那是真空区
08:28
So what this means
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这也就是说
08:30
is that the universe is like a box of gas
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宇宙好比一盒气体
08:32
that lasts forever.
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永恒的气体
08:34
Well what is the implication of that?
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这又意味着什么呢?
08:36
That implication was studied by Boltzmann back in the 19th century.
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玻尔兹曼在19世纪对此进行了研究
08:39
He said, well, entropy increases
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他说 熵值只会增大
08:42
because there are many, many more ways
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因为让宇宙处于大熵值状态的方式
08:44
for the universe to be high entropy, rather than low entropy.
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比让它处于小熵值状态的方式 多得多
08:47
But that's a probabilistic statement.
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但那是一个概率性的称述
08:50
It will probably increase,
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它可能会增大
08:52
and the probability is enormously huge.
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而且这可能性奇大无比
08:54
It's not something you have to worry about --
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我们不需要担心
08:56
the air in this room all gathering over one part of the room and suffocating us.
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这房间里的空气不会挤到一处 并让我们窒息
09:00
It's very, very unlikely.
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这可能性极小极小
09:02
Except if they locked the doors
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但如果门被锁上
09:04
and kept us here literally forever,
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我们被关在这里直至永远
09:06
that would happen.
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这便会发生
09:08
Everything that is allowed,
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所有被允许的
09:10
every configuration that is allowed to be obtained by the molecules in this room,
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这房间里的分子的布局
09:13
would eventually be obtained.
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都终究会出现
09:15
So Boltzmann says, look, you could start with a universe
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所以玻尔兹曼说 你可以从一个
09:18
that was in thermal equilibrium.
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处于热平衡状态的宇宙出发
09:20
He didn't know about the Big Bang. He didn't know about the expansion of the universe.
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他没听说过大爆炸 也没听过宇宙膨胀
09:23
He thought that space and time were explained by Isaac Newton --
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他以为牛顿对时空做出了充分的解释
09:26
they were absolute; they just stuck there forever.
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时空是绝对的 它被永恒的固定在那里
09:28
So his idea of a natural universe
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所以他在眼中的自然宇宙里
09:30
was one in which the air molecules were just spread out evenly everywhere --
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空气中的分子都平均的分散在各处
09:33
the everything molecules.
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所有的分子
09:35
But if you're Boltzmann, you know that if you wait long enough,
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但如果你是玻尔兹曼的话 你知道 如果你等的够久
09:38
the random fluctuations of those molecules
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那些分子无规则的涨落
09:41
will occasionally bring them
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会偶尔使它们
09:43
into lower entropy configurations.
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处于小熵值的布局
09:45
And then, of course, in the natural course of things,
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但肯定的是 在那之后 随着自然规律
09:47
they will expand back.
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它们会涨回到分散的状态
09:49
So it's not that entropy must always increase --
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所以说 并非是熵值必须要增大
09:51
you can get fluctuations into lower entropy,
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涨落会带来小熵值
09:54
more organized situations.
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带来更规则的状态
09:56
Well if that's true,
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就这样
09:58
Boltzmann then goes onto invent
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玻尔兹曼接着发明了
10:00
two very modern-sounding ideas --
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两个听上去很现代化的概念
10:02
the multiverse and the anthropic principle.
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多元宇宙与人择原理
10:05
He says, the problem with thermal equilibrium
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他说 热平衡的问题在于
10:07
is that we can't live there.
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我们无法生活在这样的状态下
10:09
Remember, life itself depends on the arrow of time.
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记得吗 生命本身便依赖于时间之箭
10:12
We would not be able to process information,
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如果我们生活在热平衡的状态下
10:14
metabolize, walk and talk,
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我们将无法处理信息
10:16
if we lived in thermal equilibrium.
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没法新陈代谢 没法走路 没法说话
10:18
So if you imagine a very, very big universe,
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如果你想象一个很大很大的宇宙
10:20
an infinitely big universe,
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一个无限大的宇宙
10:22
with randomly bumping into each other particles,
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粒子间无规律的碰撞
10:24
there will occasionally be small fluctuations in the lower entropy states,
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会偶尔带来小熵值下的小涨落
10:27
and then they relax back.
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然后它们会复原
10:29
But there will also be large fluctuations.
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但也会存在大涨落
10:31
Occasionally, you will make a planet
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偶然造出个行星
10:33
or a star or a galaxy
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恒星 星系
10:35
or a hundred billion galaxies.
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或是一千亿个星系
10:37
So Boltzmann says,
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所以玻尔兹曼说
10:39
we will only live in the part of the multiverse,
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我们只可能生活在多元宇宙里
10:42
in the part of this infinitely big set of fluctuating particles,
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这无限大的涨落中的粒子群里
10:45
where life is possible.
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允许生命的那部分
10:47
That's the region where entropy is low.
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也就是有着小熵值的区域
10:49
Maybe our universe is just one of those things
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也许我们宇宙的诞生不过就是
10:52
that happens from time to time.
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那些时而发生的事之一
10:54
Now your homework assignment
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你们的回家作业
10:56
is to really think about this, to contemplate what it means.
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是去好好想想这些 这到底意味着什么
10:58
Carl Sagan once famously said
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引用卡尔·萨根的名言
11:00
that "in order to make an apple pie,
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“要做个苹果派
11:02
you must first invent the universe."
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你必须先造出个宇宙”
11:05
But he was not right.
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但他说错了
11:07
In Boltzmann's scenario, if you want to make an apple pie,
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根据玻尔兹曼 如果你想要做个苹果派
11:10
you just wait for the random motion of atoms
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你只需等着 让原子不规则的运动
11:13
to make you an apple pie.
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帮你做个苹果派
11:15
That will happen much more frequently
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这比等着原子不规则的运动
11:17
than the random motions of atoms
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造出个苹果园
11:19
making you an apple orchard
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造出些糖和烤箱
11:21
and some sugar and an oven,
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然后再帮你做个苹果派
11:23
and then making you an apple pie.
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可能性大得多
11:25
So this scenario makes predictions.
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这论点包含着某些预测
11:28
And the predictions are
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这些预测包括
11:30
that the fluctuations that make us are minimal.
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造出我们的是最小限度的涨落
11:33
Even if you imagine that this room we are in now
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即便你想象我们现在的这个房间
11:36
exists and is real and here we are,
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真实的存在着 而我们也就在这里
11:38
and we have, not only our memories,
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我们不仅有着我们的回忆
11:40
but our impression that outside there's something
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也坚信着这房间外面还有东西
11:42
called Caltech and the United States and the Milky Way Galaxy,
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有加州理工学院 有美国 有银河系
11:46
it's much easier for all those impressions to randomly fluctuate into your brain
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让这些想法通过不规则的涨落进入你的大脑
11:49
than for them actually to randomly fluctuate
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比起让这些涨落真正造出加州理工学院
11:51
into Caltech, the United States and the galaxy.
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造出美国 造出银河系 要容易得多
11:54
The good news is that,
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好消息是
11:56
therefore, this scenario does not work; it is not right.
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这论点行不通 是错误的
11:59
This scenario predicts that we should be a minimal fluctuation.
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它预测我们应该是个小涨落
12:02
Even if you left our galaxy out,
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即便你忽略我们的星系
12:04
you would not get a hundred billion other galaxies.
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你也没法弄到一千亿个其他星系
12:06
And Feynman also understood this.
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费曼也明白这一点
12:08
Feynman says, "From the hypothesis that the world is a fluctuation,
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他说:“假设这世界便是涨落
12:12
all the predictions are that
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那这也就意味着 如果我们
12:14
if we look at a part of the world we've never seen before,
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对从未观测过的那部分世界进行观测
12:16
we will find it mixed up, and not like the piece we've just looked at --
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我们会发现它很混乱 与我们之前观测的
12:18
high entropy.
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大熵值的部分不同
12:20
If our order were due to a fluctuation,
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如果我们的秩序来自于涨落
12:22
we would not expect order anywhere but where we have just noticed it.
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我们便不会认为除了刚注意到的秩序 另外还有秩序
12:24
We therefore conclude the universe is not a fluctuation."
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所以我们断定 宇宙并非涨落
12:28
So that's good. The question is then what is the right answer?
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这算是好了 但正确的答案又是什么呢?
12:31
If the universe is not a fluctuation,
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如果宇宙不是涨落
12:33
why did the early universe have a low entropy?
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初期宇宙的熵值为什么那么小?
12:36
And I would love to tell you the answer, but I'm running out of time.
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我很乐意回答你 但我没时间了
12:39
(Laughter)
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(笑)
12:41
Here is the universe that we tell you about,
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我们告诉你的宇宙 对应着
12:43
versus the universe that really exists.
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真正存在着的宇宙
12:45
I just showed you this picture.
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我刚刚给你们看过这画面
12:47
The universe is expanding for the last 10 billion years or so.
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一百多亿年来 宇宙不断膨胀着
12:49
It's cooling off.
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它也冷却着
12:51
But we now know enough about the future of the universe
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但我们现在对宇宙的了解
12:53
to say a lot more.
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足够让我们说出更多的
12:55
If the dark energy remains around,
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如果暗能量留在周围不动
12:57
the stars around us will use up their nuclear fuel, they will stop burning.
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我们周围的恒星将用尽他们的核子燃料 它们将停止燃烧
13:00
They will fall into black holes.
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它们会变成黑洞
13:02
We will live in a universe
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我们将生活在一个 除了黑洞
13:04
with nothing in it but black holes.
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空空如也的宇宙
13:06
That universe will last 10 to the 100 years --
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那宇宙将会存在10的100次方年
13:10
a lot longer than our little universe has lived.
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比我们的小宇宙长寿多了
13:12
The future is much longer than the past.
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为了比过去长得多
13:14
But even black holes don't last forever.
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但就连黑洞也不是永恒的
13:16
They will evaporate,
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它们会蒸发
13:18
and we will be left with nothing but empty space.
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除了一个真空宇宙我们将一无所有
13:20
That empty space lasts essentially forever.
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这真空宇宙将会是永远的
13:24
However, you notice, since empty space gives off radiation,
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但你意识到 因为真空区也会有辐射
13:27
there's actually thermal fluctuations,
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所以热涨落其实存在着
13:29
and it cycles around
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它以存在于真空区中的
13:31
all the different possible combinations
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有着各种不同组合的
13:33
of the degrees of freedom that exist in empty space.
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自由度之间 不断的循环着
13:36
So even though the universe lasts forever,
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所以即便宇宙将永远的存在下去
13:38
there's only a finite number of things
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能够在宇宙中发生的事
13:40
that can possibly happen in the universe.
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却是有限的
13:42
They all happen over a period of time
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它们都在10到10的120次方年
13:44
equal to 10 to the 10 to the 120 years.
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这段时间内发生
13:47
So here's two questions for you.
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我想问你们两个问题
13:49
Number one: If the universe lasts for 10 to the 10 to the 120 years,
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第一:如果宇宙会存在10到10的120次方年
13:52
why are we born
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我们为什么出生于
13:54
in the first 14 billion years of it,
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最初的140亿年间
13:57
in the warm, comfortable afterglow of the Big Bang?
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出生于这大爆炸带来的温暖 舒适的环境中?
14:00
Why aren't we in empty space?
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我们为什么不在真空区?
14:02
You might say, "Well there's nothing there to be living,"
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你也许会说:“那里根本没有活着的东西”
14:04
but that's not right.
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但这不对
14:06
You could be a random fluctuation out of the nothingness.
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你可以来自空无一物中无规则的涨落
14:08
Why aren't you?
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而你为什么不是呢?
14:10
More homework assignment for you.
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还有些回家作业要布置给你们
14:13
So like I said, I don't actually know the answer.
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如我所说 我并不知道答案
14:15
I'm going to give you my favorite scenario.
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就让我来谈谈我最喜欢的情形吧
14:17
Either it's just like that. There is no explanation.
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也许它本该如此 根本没有解释
14:20
This is a brute fact about the universe
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这就是个不容争议的关于宇宙的事实
14:22
that you should learn to accept and stop asking questions.
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你必须接受它 并不再询问任何问题
14:26
Or maybe the Big Bang
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或者说 大爆炸
14:28
is not the beginning of the universe.
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并非宇宙的开端
14:30
An egg, an unbroken egg, is a low entropy configuration,
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一只完整的鸡蛋 处于小熵值的状态
14:33
and yet, when we open our refrigerator,
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但当我们打开冰箱时
14:35
we do not go, "Hah, how surprising to find
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我们不会想:“哇 能在冰箱里看到这样一个
14:37
this low entropy configuration in our refrigerator."
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小熵值状态实在太惊人了“
14:39
That's because an egg is not a closed system;
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那是因为一只鸡蛋并非一个封闭系统
14:42
it comes out of a chicken.
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它是某只鸡生出来的
14:44
Maybe the universe comes out of a universal chicken.
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也许整个宇宙都是一只宇宙鸡生出来的
14:48
Maybe there is something that naturally,
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也许通过物理定律的发展
14:50
through the growth of the laws of physics,
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某些东西会自然的导致
14:53
gives rise to universe like ours
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这个宇宙
14:55
in low entropy configurations.
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以小熵值的形式诞生
14:57
If that's true, it would happen more than once;
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如果那是正确的话 它不会只发生一次
14:59
we would be part of a much bigger multiverse.
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我们会是巨大的多元宇宙的一部分
15:02
That's my favorite scenario.
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这便是我最中意的情形
15:04
So the organizers asked me to end with a bold speculation.
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组织者们让我以一个大胆的推测结束我的演讲
15:07
My bold speculation
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我大胆的推测
15:09
is that I will be absolutely vindicated by history.
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便是我将会绝对的被历史维护
15:12
And 50 years from now,
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今后的50年间
15:14
all of my current wild ideas will be accepted as truths
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我现在所有疯狂的想法都会
15:17
by the scientific and external communities.
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被科学界以及整个社会 接受为现实
15:20
We will all believe that our little universe
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我们将全都相信 我们的小宇宙
15:22
is just a small part of a much larger multiverse.
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不过是更大的多元宇宙中的一部分
15:25
And even better, we will understand what happened at the Big Bang
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不仅如此 我们将理解大爆炸时发生的一切
15:28
in terms of a theory
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将有一套能够
15:30
that we will be able to compare to observations.
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被观察支持的理论
15:32
This is a prediction. I might be wrong.
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这只是预测 我也许错了
15:34
But we've been thinking as a human race
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那么多年来 作为人类
15:36
about what the universe was like,
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我们不断思考着 曾经的宇宙
15:38
why it came to be in the way it did for many, many years.
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是怎样的 而它又是怎么变成它当时的样子的
15:41
It's exciting to think we may finally know the answer someday.
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令人兴奋的是 或许终有一天我们会找到答案
15:44
Thank you.
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谢谢
15:46
(Applause)
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(掌声)
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