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遥远的时间和多元宇宙的启示

发布者: 五毒 | 发布时间: 2022-10-6 21:30| 查看数: 55| 评论数: 0|



Back when I was your age, we didn't know what the universe was going to do.

当我像你们那么大的时候,我们不知道宇宙会发生什么。

Some people thought that the universe would recollapse in the future.

某些人认为宇宙将会再坍缩。

Einstein was fond of this idea.

爱因斯坦就很喜欢这想法。

But if there's dark energy, and the dark energy does not go away,

但如果有暗能量,而暗能量又会永远留在那里,

the universe is just going to keep expanding forever and ever and ever.

宇宙便会永不停息的这样膨胀下去。

14 billion years in the past, 100 billion dog years, but an infinite number of years into the future.

从140亿年前狗的一千亿年前,直至无数年以后,直至永恒的未来。

Meanwhile, for all intents and purposes, space looks finite to us.

在此期间,无论出于何种意图和目的,空间对我们来说都是有限的。

Space may be finite or infinite, but because the universe is accelerating, there are parts of it we cannot see and never will see.

空间可能是有限的,也可能是无限的,但因为宇宙正在膨胀,所以它的某些部分我们看不见,也将永远不会看到。

There's a finite region of space that we have access to, surrounded by a horizon.

能让我们获取信息的宇宙空间非常有限,它被边界包围着。

So even though time goes on forever, space is limited to us.

所以即便时间不停下它的脚步,宇宙空间对我们来说还是有限的。

Finally, empty space has a temperature.

最后,真空区有它的温度。

In the 1970s, Stephen Hawking told us that a black hole, even though you think it's black,

在20世纪70年代,史蒂芬·霍金告诉我们,虽然你认为黑洞是黑的,

it actually emits radiation when you take into account quantum mechanics.

如果把量子力学考虑进去的话,它实际上会发出辐射。

The curvature of space-time around the black hole brings to life the quantum mechanical fluctuation, and the black hole radiates.

黑洞周围的空间曲率是会导致真空量子涨落,黑洞也就会辐射。

A precisely similar calculation by Hawking and Gary Gibbons showed that if you have dark energy in empty space, then the whole universe radiates.

根据霍金与加利·基本斯的一个类似的精确计算,如果真空区里有暗能量,整个宇宙便会辐射。

The energy of empty space brings to life quantum fluctuations.

真空区的能量带来量子涨落。

And so even though the universe will last forever, and ordinary matter and radiation will dilute away, there will always be some radiation,

所以虽然宇宙是永恒的,而且一般的物质和辐射会被稀释,

some thermal fluctuations, even in empty space.

但某些辐射会永远留下某些热涨落,即便那是真空区。

So what this means is that the universe is like a box of gas that lasts forever.

这也就是说宇宙好比一盒气体,永恒的气体。

Well what is the implication of that?

那么这意味着什么呢?

That implication was studied by Boltzmann back in the 19th century.

玻尔兹曼在19世纪对此进行了研究。

He said, well, entropy increases because there are many, many more ways for the universe to be high entropy, rather than low entropy.

他说熵值只会增大,因为让宇宙处于大熵值状态的方式比让它处于小熵值状态的方式多得多。

But that's a probabilistic statement.

但那是一个概率性的陈述。

It will probably increase, and the probability is enormously huge.

它可能会增大,而且这可能性奇大无比。

It's not something you have to worry about -- the air in this room all gathering over one part of the room and suffocating us.

我们不需要担心这房间里的空气不会挤到一处并让我们窒息。

It's very, very unlikely.

这可能性极小极小。

Except if they locked the doors and kept us here literally forever, that would happen.

但如果门被锁上,我们被关在这里直至永远这,这种情况就会发生。

Everything that is allowed, every configuration that is allowed to be obtained by the molecules in this room, would eventually be obtained.

这个房间里的分子所允许的一切,每一种布局,都终究会出现。

So Boltzmann says, look, you could start with a universe that was in thermal equilibrium.

所以玻尔兹曼说,你可以从一个处于热平衡状态的宇宙出发。

He didn't know about the Big Bang.

他没听说过大爆炸。

He didn't know about the expansion of the universe.

也没听过宇宙膨胀。

He thought that space and time were explained by Isaac Newton -- they were absolute.

他以为牛顿对时空做出了充分的解释,时空是绝对的。

They just stuck there forever.

它被永恒的固定在那里。

So his idea of a natural universe was one in which the air molecules were just spread out evenly everywhere -- the everything molecules.

所以他对自然宇宙的想法是,空气分子均匀地散布在各处,所有的分子。

But if you're Boltzmann, you know that if you wait long enough,

但如果你是玻尔兹曼,如果你等待的时间足够长,你就会知道,

the random fluctuations of those molecules will occasionally bring them into lower entropy configurations.

那些分子无规则的涨落会偶尔使它们处于小熵值的布局。

And then, of course, in the natural course of things, they will expand back.

但肯定的是在那之后随着自然规律它们会涨回到分散的状态。

So it's not that entropy must always increase -- you can get fluctuations into lower entropy, more organized situations.

因此,并不是说熵必须总是增加,涨落会带来小熵值,带来更规则的状态。

Well if that's true, Boltzmann then goes onto invent two very modern-sounding ideas -- the multiverse and the anthropic principle.

就这样玻尔兹曼接着发明了两个听上去很现代化的概念,多元宇宙与人择原理。

He says, the problem with thermal equilibrium is that we can't live there.

他说热平衡的问题在于我们无法生活在这样的状态下。

Remember, life itself depends on the arrow of time.

记得吗,生命本身便依赖于时间之箭。

We would not be able to process information, metabolize, walk and talk, if we lived in thermal equilibrium.

如果我们生活在热平衡的状态下,我们将无法处理信息,没法新陈代谢,没法走路没,法说话。

So if you imagine a very, very big universe, an infinitely big universe, with randomly bumping into each other particles,

如果你想象一个很大很大的宇宙一个无限大的宇宙,粒子间无规律的碰撞,

there will occasionally be small fluctuations in the lower entropy states, and then they relax back.

会偶尔带来小熵值下的小涨落,然后它们会复原。

But there will also be large fluctuations.

但也会存在大涨落。

Occasionally, you will make a planet or a star or a galaxy or a hundred billion galaxies.

偶然造出个行星、恒星、星系或是一千亿个星系。

So Boltzmann says, we will only live in the part of the multiverse, in the part of this infinitely big set of fluctuating particles,

所以玻尔兹曼说我们只可能生活在多元宇宙里,这无限大的涨落中的粒子群里,

where life is possible.

允许生命存在的那部分。

That's the region where entropy is low.

这也就是有着小熵值的区域。

Maybe our universe is just one of those things that happens from time to time.

也许我们宇宙的诞生不过就是那些时而发生的事之一。

Now your homework assignment is to really think about this, to contemplate what it means.

你们的回家作业是去好好想想这些这到底意味着什么。

Carl Sagan once famously said that "in order to make an apple pie, you must first invent the universe."

引用卡尔·萨根的名言“要做个苹果派你必须先造出个宇宙”。

But he was not right.

但他说错了。

In Boltzmann's scenario, if you want to make an apple pie, you just wait for the random motion of atoms to make you an apple pie.

在玻尔兹曼的设想中,如果你想做一个苹果派,你只需等着让原子不规则的运动帮你做个苹果派。

That will happen much more frequently than the random motions of atoms making you an apple orchard and some sugar and an oven.

这比等着原子不规则的运动造出个苹果园,造出些糖和烤箱,

and then making you an apple pie.

然后再帮你做个苹果派可能性大得多。

So this scenario makes predictions.

这论点包含着某些预测。

And the predictions are that the fluctuations that make us are minimal.

这些预测包括造出我们的是最小限度的涨落。

Even if you imagine that this room we are in now exists and is real and here we are, and we have, not only our memories,

即便你想象我们现在的这个房间真实的存在着,而我们也就在这里,我们不仅有着我们的回忆,

but our impression that outside there's something called Caltech and the United States and the Milky Way Galaxy,

也坚信着这房间外面还有东西,有加州理工学院,有美国,有银河系,

it's much easier for all those impressions to randomly fluctuate into your brain than for them actually to randomly fluctuate into Caltech,

让这些想法通过不规则的涨落进入你的大脑,比起让这些涨落真正造出加州理工学院,

the United States and the galaxy.

造出美国和银河系要容易得多。

The good news is that, therefore, this scenario does not work; it is not right.

好消息是,这论点行不通,它是错误的。

This scenario predicts that we should be a minimal fluctuation.

它预测我们应该是个小涨落。

Even if you left our galaxy out, you would not get a hundred billion other galaxies.

即便你忽略我们的星系,你也没法弄到一千亿个其他星系。

And Feynman also understood this.

费曼也明白这一点。

Feynman says, "From the hypothesis that the world is a fluctuation.

他说:“假设这世界便是涨落,

all the predictions are that if we look at a part of the world we've never seen before,

那这也就意味着如果我们对从未观测过的那部分世界进行观测,

we will find it mixed up, and not like the piece we've just looked at -- high entropy.

我们会发现它很混乱,与我们之前观测的大熵值的部分不同。

If our order were due to a fluctuation, we would not expect order anywhere but where we have just noticed it.

如果我们的秩序来自于涨落,我们便不会认为除了刚注意到的秩序另外还有秩序。

We therefore conclude the universe is not a fluctuation."

所以我们断定宇宙并非涨落。”

So that's good. The question is then what is the right answer?

这算是好了 但正确的答案又是什么呢?

If the universe is not a fluctuation, why did the early universe have a low entropy?

如果宇宙不是涨落的,为什么初期宇宙的熵值那么小?

And I would love to tell you the answer, but I'm running out of time.

我很乐意回答你,但我没时间了。

Here is the universe that we tell you about, versus the universe that really exists.

我们告诉你的宇宙对应着真正存在着的宇宙。

I just showed you this picture.

我刚刚给你们看过这画面。

The universe is expanding for the last 10 billion years or so.

一百多亿年来宇宙不断膨胀着。

It's cooling off.

它也冷却着。

But we now know enough about the future of the universe to say a lot more.

但我们现在对宇宙的了解足够让我们说出更多。

If the dark energy remains around, the stars around us will use up their nuclear fuel, they will stop burning.

如果暗能量留在周围不动,我们周围的恒星将用尽他们的核子燃料,它们将停止燃烧。

They will fall into black holes.

它们会变成黑洞。

We will live in a universe with nothing in it but black holes.

们将生活在一个除了黑洞空空如也的宇宙。

That universe will last 10 to the 100 years -- a lot longer than our little universe has lived.

那宇宙将会存在10的100次方年,比我们的小宇宙长寿多了。

The future is much longer than the past.

未来比过去长得多。

But even black holes don't last forever.

但即使是黑洞也不会永远存在。

They will evaporate, and we will be left with nothing but empty space.

它们会蒸发,除了一个真空宇宙我们将一无所有。

That empty space lasts essentially forever.

这真空宇宙将会是永远的。

However, you notice, since empty space gives off radiation, there's actually thermal fluctuations,

但你意识到,因为真空区也会有辐射,所以热涨落其实存在着,

and it cycles around all the different possible combinations of the degrees of freedom that exist in empty space.

它以存在于真空区中的有着各种不同组合的自由度之间不断的循环着。

So even though the universe lasts forever, there's only a finite number of things that can possibly happen in the universe.

因此,即使宇宙是永恒的,能够在宇宙中发生的事却是有限的。

They all happen over a period of time equal to 10 to the 10 to the 120 years.

它们都在10到10的120次方年这段时间内发生。

So here's two questions for you.

我有两个问题要问你。

Number one: If the universe lasts for 10 to the 10 to the 120 years,

第一:如果宇宙会存在10到10的120次方年,

why are we born in the first 14 billion years of it, in the warm, comfortable afterglow of the Big Bang?

我们为什么出生于最初的140亿年间,出生于这大爆炸带来的温暖舒适的环境中?

Why aren't we in empty space?

我们为什么不在真空区?

You might say, "Well there's nothing there to be living," but that's not right.

你也许会说:“那里根本没有活着的东西,”但这不对。

You could be a random fluctuation out of the nothingness.

你可以来自空无一物中无规则的涨落。

Why aren't you?

而你为什么不是呢?

More homework assignment for you.

还有些回家作业要布置给你们。

So like I said, I don't actually know the answer.

如我所说,我并不知道答案。

I'm going to give you my favorite scenario.

就让我来谈谈我最喜欢的情形吧。

Either it's just like that.

也许它本该如此。

There is no explanation.

根本没有解释。

This is a brute fact about the universe that you should learn to accept and stop asking questions.

这就是个不容争议的关于宇宙的事实,你必须接受它,并不再询问任何问题。

Or maybe the Big Bang is not the beginning of the universe.

或许大爆炸并不是宇宙的开始。

An egg, an unbroken egg, is a low entropy configuration, and yet, when we open our refrigerator, we do not go,

一只完整的鸡蛋处于小熵值的状态,然而,当我们打开冰箱时,我们不会想:

"Hah, how surprising to find this low entropy configuration in our refrigerator."

“哇,能在冰箱里看到这样一个小熵值状态实在太惊人了。”

That's because an egg is not a closed system; it comes out of a chicken.

那是因为一只鸡蛋并非一个封闭系统,它是某只鸡生出来的。

Maybe the universe comes out of a universal chicken.

也许整个宇宙都是一只宇宙鸡生出来的。

Maybe there is something that naturally, through the growth of the laws of physics, gives rise to universe like ours in low entropy configurations.

也许通过物理定律的发展,某些东西会自然的导致这个宇宙以小熵值的形式诞生。

If that's true, it would happen more than once; we would be part of a much bigger multiverse.

如果这是真的,它将不止一次发生;我们会是巨大的多元宇宙的一部分。

That's my favorite scenario.

这便是我最中意的情形。

So the organizers asked me to end with a bold speculation.

组织者们,让我以一个大胆的推测结束我的演讲。

My bold speculation is that I will be absolutely vindicated by history.

我的大胆猜测是,我将会绝对的被历史维护。

And 50 years from now, all of my current wild ideas will be accepted as truths by the scientific and external communities.

今后的50年间我现在所有疯狂的想法都会被科学界以及整个社会接受为现实。

We will all believe that our little universe is just a small part of a much larger multiverse.

我们将全都相信我们的小宇宙不过是更大的多元宇宙中的一部分。

And even better, we will understand what happened at the Big Bang in terms of a theory that we will be able to compare to observations.

不仅如此,我们将理解大爆炸时发生的一切将有一套能够被观察支持的理论。

This is a prediction.

这只是一个预测。

I might be wrong.

我可能错了。

But we've been thinking as a human race about what the universe was like, why it came to be in the way it did for many, many years.

那么多年来,作为人类我们不断思考着曾经的宇宙是怎样的,而它又是怎么变成它当时的样子的。

It's exciting to think we may finally know the answer someday.

令人兴奋的是,或许终有一天我们会找到答案。

Thank you.

谢谢。


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