Name: 肖恩-卡羅爾解釋為什麼物理學既簡單又不可能 | 完整訪談 (Sean Carroll explains why physics is both simple and impossible | Full Interview)
Uploaded: 2025-08-22T18:24:44.000Z
Duration: 1 h 26 min 40 s

轉承詞

I like to say that physics is hard because physics is easy.

我喜歡說物理很難，因為物理很簡單。

程度副詞

By which I mean, we actually think about physics as students, you know, we took classes, we read books, and it was hard because there's all this new stuff, all these ideas, all these equations that we don't come across in our everyday lives. But the reason those ideas are hard and those equations are there, is because physicists have a technique that has been amazingly successful, which is to take all the messy world around us with all its peculiarities and specificities, and to boil it down to really, really simple systems. I'm Sean Carroll,

我的意思是，作為學生，我們實際上在思考物理學，你知道，我們上課，我們看書，這很難，因為有所有這些新的東西，所有這些想法，所有這些方程，我們在日常生活中不會遇到。但這些想法和方程之所以難，是因為物理學家有一種非常成功的技術，那就是把我們周圍紛亂的世界，以及所有的特殊性和具體性，歸結為非常非常簡單的系統。我是肖恩-卡羅爾

I'm a physicist and philosopher at Johns Hopkins University, host of the

我是約翰霍普金斯大學的物理學家和哲學家，也是

Mindscape podcast, and also author of a bunch of books, most recently

Mindscape 播客，同時也是多部書籍的作者，最近的作品是

The Biggest Ideas in the Universe series, including

宇宙中最偉大的思想》系列，包括

Spacetime in Motion and Quanta in Fields.

The Biggest Ideas in Physics, with Sean Carroll.

物理學中最偉大的思想》，與肖恩-卡羅爾合著。

You might imagine or remember when you were taking physics courses, there were frictionless surfaces, there were pendula that rocked back and forth perfectly. We're always idealizing, we're always imagining there are no complications, and then we're putting them back in.

你可能會想象或記得，在你學習物理課程的時候，有一些無摩擦的表面，有一些可以完美地前後搖擺的擺錘。我們總是在理想化，總是在想象沒有任何複雜因素，然後又把它們放回去。

That's a strategy that would completely fail if you tried to do it for psychology or biology or political science, but for physics it turns out to work incredibly well. There's a joke that physicists like to tell each other, they don't like to tell it to others because it's not very funny, but the idea is that a dairy farmer wants to improve his yield, more milk out of the cows, and for some reason he approaches a physicist and says, could you look at my farm and tell me how to get more milk out of the cows? And the physicist thinks about it, and he comes back with a sheet of calculations and he says, okay, first, imagine a spherical cow.

這種策略如果用在心理學、生物學或政治學上會完全失敗，但用在物理學上卻非常有效。有一個笑話，物理學家們喜歡互相講，他們不喜歡講給別人聽，因為這並不好笑，但這個笑話的意思是，一個奶農想提高產量，讓奶牛產更多的奶，出於某種原因，他找到一個物理學家說，你能不能看看我的農場，告訴我如何讓奶牛產更多的奶？物理學家想了想，拿著一張計算表回來說，好的，首先，想象一頭球形奶牛。

The idea, I know it's not that funny, but the idea is that the first thing the physicist is going to do is try to imagine a simpler situation.

我知道這並不有趣，但我的想法是，物理學家要做的第一件事就是試著想象一種更簡單的情況。

Real cows are not spherical, it would be a very different dairy farm if the cows were spherical, but you can calculate the volume of the cow and the metabolic rate of the cow much more easily if it were spherical.

真實的奶牛不是球形的，如果奶牛是球形的，奶牛場的情況就會大不一樣，但如果奶牛是球形的，你就可以更容易地計算出奶牛的體積和新陳代謝率。

And the joke, of course, is that that doesn't work in dairy farming, but it works really well when you're considering a spherical universe or a spherical solar system or a spherical atom. The first really huge revolution in physics was the existence of classical mechanics, handed down by Isaac Newton and others. It took a while, Newton was building on the shoulders of giants, but before Newton there was Aristotle, and Aristotle says that things have natural places they want to be, natural ways they want to move. And Newton says something completely different. He says, if something is not acted on by a force, it's going to continue in a straight line at a constant velocity forever.

當然，有一個笑話是，這在奶牛養殖業中行不通，但當你考慮球形宇宙、球形太陽系或球形原子時，它卻非常有效。物理學中第一次真正意義上的巨大變革是由艾薩克-牛頓和其他人傳承下來的經典力學的存在。牛頓是站在巨人的肩膀上成長起來的，但在牛頓之前有亞里士多德，亞里士多德說事物有其自然的位置，自然的運動方式。牛頓說的則完全不同。他說，如果一個物體沒有外力作用 它就會以恆定的速度永遠保持在一條直線上

And if it is acted on by a force, I can tell you how it will move, I have an equation to do that. Physicists like to simplify things a great deal, but billiards, the pool game, is pretty close to being simple. It's not exactly because when you hear those balls click against each other, that sound is giving off energy and it's kind of wasteful, but in principle, if you had no friction, no sound, no air resistance, the balls bouncing around the pool table, let's also imagine there's no pockets so the balls can just bounce off the edges of the table forever, they would go forever, they wouldn't stop. The energy contained in the system remains constant, and the laws of physics, as Laplace points out, suffice it to predict exactly what the balls are going to do at every moment, given what they're doing right now.

如果它受到一個力的作用，我可以告訴你它將如何移動，我有一個方程式可以做到這一點。物理學家喜歡把事情簡化得很簡單，但撞球，也就是撞球遊戲，卻非常接近於簡單。但從原理上講，如果沒有摩擦、沒有聲音、沒有空氣阻力，球在臺球桌上彈來彈去，我們也可以想象沒有球袋，所以球可以永遠在臺球桌邊緣彈來彈去，它們會永遠彈下去，不會停下來。系統中包含的能量保持不變，正如拉普拉斯指出的那樣，物理定律足以準確預測球在每一時刻會做什麼，因為它們現在正在做什麼。

So to the extent that it's okay to ignore friction and noise and things like that, not only is it true that if you imagine hitting the balls and watching them move, you could predict exactly what's going to happen on the basis of the laws of physics, if somehow you could take a snapshot later in their motion, so you know both where they are and how fast they're moving, so maybe a little clip of a movie, then the laws of physics would let you go backwards and reverse-engineer what exact configuration the balls were in.

是以，在忽略摩擦和噪音等因素的情況下，如果你想象一下擊球並觀察球的運動，你不僅可以根據物理定律準確預測將要發生的事情，而且如果你能在球運動的過程中拍攝一張快照，這樣你就能知道球在哪裡，運動的速度有多快，所以也許是電影的一個小片段，那麼物理定律就能讓你倒退回去，逆向設計出球的具體構造。

We don't perceive that in our everyday world because the world is full of noise and dissipation and air resistance and things like that, but in the pristine perfect world of imagined classical mechanics, the past and future work equally well, you can go from any one moment to any other moment.

在我們的日常生活中，我們感覺不到這一點，因為這個世界充滿了噪音、耗散、空氣阻力等諸如此類的東西，但在想象中的經典力學的原始完美世界裡，過去和未來同樣有效，你可以從任何一個時刻去到任何其他時刻。

It's interesting that Newton came up with the framework of classical mechanics in the 1600s, and people were very excited, physicists, mathematicians, philosophers, they didn't really have physicists at the time, they were all considered to be natural philosophers, but they worked on it, they thought about the motions of the planets and things like that, and the implications of this idea are profound for how we think about what physics is, what physics tells us, because it wasn't realized until

有趣的是，牛頓在 1600 年代提出了經典力學的框架，當時人們、物理學家、數學家、哲學家都非常興奮，當時還沒有真正意義上的物理學家，他們都被認為是自然哲學家，但他們研究了這一框架，思考了行星的運動等問題，這一想法對我們思考物理學是什麼、物理學告訴我們什麼意義深遠，因為它直到 19 世紀才被意識到。

Pierre-Simone Laplace over a hundred years after Newton, but the structure of classical mechanics implies that if you knew the position and velocity, not just of one particle, but of every particle in the universe, and you knew the laws of physics, and you had infinite calculational abilities, none of these are at all plausible, but we're imagining right now, then the laws of physics would determine what happens next, at the next moment, and the next moment, and infinitely far into the future, and for that matter, indefinitely far into the past.

皮埃爾-西蒙-拉普拉斯（Pierre-Simone Laplace）比牛頓晚了一百多年，但經典力學的結構意味著，如果你知道位置和速度，不只是一個粒子的位置和速度，而是宇宙中每一個粒子的位置和速度，你知道物理定律，你有無限的計算能力，這些都完全不靠譜，但我們現在就在想象，那麼物理定律就會決定下一刻、下下一刻、無限遠的未來，以及無限遠的過去會發生什麼。

So you can take any one moment in the history of the universe, according to classical mechanics, and the information contained in what is going on at that moment is sufficient to fix what will happen at every other moment in history, and Laplace, who was quite imaginative about these things, put it in terms of a metaphor, he says, imagine a vast intelligence, later commentators dubbed it Laplace's demon, he didn't call it that, he was famously an atheist, he didn't like to talk about demons, but the demon, the vast intelligence, who could know everything about the universe at any one moment, Laplace says, to that vast intelligence, the past and future are an open book. You would know everything because what happens now fixes the entirety of space and time. The idea that the laws of physics fix what's going to happen, in principle, precisely and exactly, if you know what's happening right now. So this became known as the clockwork universe paradigm. The universe clicks along in perfect accord with the laws of physics forever.

是以，根據經典力學，你可以從宇宙歷史中的任何一個時刻出發，而那個時刻所發生的事情所包含的資訊足以決定歷史上其他時刻將會發生的事情，拉普拉斯對這些事情頗有想象力，他用一個比喻來說明這一點，他說："想象一個巨大的智慧，後來的評論家把它稱為拉普拉斯的惡魔、拉普拉斯說："想象一個巨大的智慧，後來的評論家稱之為拉普拉斯的惡魔，但他並沒有這麼稱呼它，他是著名的無神論者，他不喜歡談論惡魔，但這個惡魔，這個巨大的智慧，可以在任何時刻知道宇宙的一切，對這個巨大的智慧來說，過去和未來都是一本打開的書。你會知道一切，因為現在發

Now, this might bother you a little bit if you want to think, well, wait a minute,

現在，如果你想 "好吧，等一下"，這可能會讓你有點困擾、

I'm a person, I'm a human being, I have the ability to make choices,

我是一個人，我是一個人，我有能力做出選擇、

I'm not determined by the laws of physics, and both scientists and philosophers thought about that. They still don't agree on what the right way to think about it is, but the favorite way to think about it is the following.

我不是由物理定律決定的，科學家和哲學家都思考過這個問題。他們仍然沒有就正確的思考方式達成一致，但最喜歡的思考方式如下。

In principle, if you knew exactly everything that was going on in the universe, you could predict the future. Now, classical mechanics isn't quite right, eventually we're going to talk about quantum mechanics, so that's another thing you have to keep in mind, but to the approximation that classical mechanics is good, you are determined in what is going to happen. But guess what? You don't know all the positions of all the atoms and all the molecules that make up you. Indeed, you literally cannot know them because the memory storage capacity to know all that would be at least as big as your brain, if not bigger. If you made your brain bigger, now you just have more molecules to keep track of. It is impossible to actually have a real apostle's demon in the universe.

原則上，如果你對宇宙中發生的一切瞭如指掌，你就可以預測未來。現在，經典力學並不完全正確，最終我們將討論量子力學，所以這是你必須牢記的另一件事，但在經典力學良好的近似條件下，你可以確定將要發生什麼。但你猜怎麼著？你並不知道構成你的所有原子和分子的所有位置。事實上，你根本無法知道它們的位置，因為要知道所有這些，記憶存儲容量至少要和你的大腦一樣大，甚至更大。如果你把大腦變大了，現在你只需要記住更多的分子。宇宙中不可能真的有使徒的惡魔。

It's just a thought experiment to make vivid the implications of determinism. So philosophers have settled on what they decided to call compatibilism, in the sense that on the one hand, the deep down microscopic laws of physics are perfectly deterministic, or they're not if you're in quantum mechanics, but they're pretty deterministic anyway. But since you don't know it, you should be asking yourself, what is the best I can do? What is the best way that I can try to understand human beings given the vastly incomplete information I have? I know about my friend's personality and their predilections and their traits, but I don't know every neuron in their brain. And under those circumstances, you will model, you will think about a fellow human being or about yourself as an agent capable of making choices. Everyone does that, and that's the right thing to do because you are not Laplace's demon.

這只是一個思想實驗，旨在生動地說明決定論的含義。是以，哲學家們決定將其稱為兼容自由主義，即一方面，物理學深層次的微觀法則是完全決定論的，或者說，如果你是在量子力學中，它們就不是，但無論如何，它們都是相當決定論的。但既然你不知道，你就應該問自己，我能做的最好的是什麼？在我所掌握的資訊極不完整的情況下，我能嘗試理解人類的最好方法是什麼？我知道我朋友的性格、偏好和特徵，但我不知道他們大腦中的每一個神經元。在這種情況下，你就會建立模型，你就會把一個人類同伴或你自己當成一個能夠做出選擇的人。每個人都會這樣做，這樣做

Isaac Newton, you may have heard, was a smart fellow and one of the interesting things when you invent a whole new way of doing physics if you're right and it becomes successful, then later on people kind of take it for granted. They're like, yeah, this is how the world works or whatever. But at the time, you're still very careful, and Newton was himself super duper careful about all the assumptions that went into his theory and what their implications were and so on.

艾薩克-牛頓，你可能聽說過，是個聰明的傢伙，當你發明了一種全新的物理學方法時，如果你是對的，並且取得了成功，那麼有趣的事情之一就是，後來人們會認為這是理所當然的。他們會想，是啊，世界就是這樣運轉的，或者別的什麼。但在當時，你仍然非常小心謹慎 牛頓本人也超級小心謹慎地對待他理論中的所有假設 以及這些假設的含義等等。

One part of classical mechanics is the idea of space and time both separately existing and being absolute. There is a meaningfulness to that. There is no preferred position in the universe.

經典力學的一個部分就是空間和時間都是單獨存在的，而且是絕對的。這是有意義的。宇宙中沒有首選位置。

You can be anywhere you want. The laws of physics work the same. There's not even a preferred velocity to the universe. This was figured out by Galileo, and Newton kind of took it on board. If you started everything moving at one mile per hour to the left, the world will look exactly the same. There's no actual frame of rest that you can measure. But there is space and there is time, and everyone agrees on what those two things mean. When I say I am one mile away from a certain other point, everyone in the universe agrees. You are one mile away. Yes, that is correct. When I snap my fingers and say at the moment I snap my fingers, a certain thing is happening in Los

你可以去任何你想去的地方。物理定律也是一樣的宇宙甚至沒有優先速度。伽利略發現了這一點 牛頓也接受了這一點如果你讓所有物體以每小時一英里的速度向左移動，世界看起來都是一樣的。你無法測量實際的靜止框架。但空間和時間是存在的，每個人都同意這兩樣東西的含義。當我說我離某一點有一英里遠時，宇宙中的每個人都會同意。你在一英里之外。是的，這是正確的。當我打響指，並說在我打響指的那一刻，洛斯的某件事情正在發生。

Angeles, everyone agrees that indeed at that moment it's a well-defined concept to say what is happening at some point far away. Not just Los

在洛杉磯，每個人都同意，在那一刻，說在遙遠的某一點正在發生什麼，確實是一個定義明確的概念。不僅僅是洛杉磯

Angeles, but Alpha Centauri or the Andromeda Galaxy.

洛杉磯，而是半人馬座阿爾法星或仙女座星系。

Turns out those assumptions are not quite right.

事實證明，這些假設並不完全正確。

It was a journey to get there, as it often is. It started in the 1800s with the invention of electromagnetism.

要達到這一目標，往往需要經歷一段旅程。它始於 19 世紀電磁學的發明。

All these new phenomena that people were thinking about since Ben Franklin flew his kite and studied lightning coming down.

自從本-富蘭克林放飛風箏、研究閃電落下後，人們就開始思考所有這些新現象。

It was James Clark Maxwell who put the whole story together after work by people like

是詹姆斯-克拉克-麥克斯韋（James Clark Maxwell）等人的研究成果將整個故事串聯起來的。

Faraday and Ampere and so forth. And what he realized is there's two fields pervading the universe, an electric field and a magnetic field. And he wrote down some equations that these fields obey and they sort of play with each other and push around and charge particles and things like that.

法拉第和安培等等。他意識到宇宙中存在著兩種場 電場和磁場他寫下了一些方程式 這些磁場會互相作用 互相推動 給粒子充電等等

People were very happy at the existence of electromagnetism.

人們對電磁學的存在感到非常高興。

They started thinking about what it all meant and what they realized is that the sort of way that space and time are treated in Maxwell's theory of electromagnetism is different than the way they are apparently treated in Newton's theory. In particular,

他們開始思考這一切意味著什麼，他們意識到麥克斯韋電磁學理論處理空間和時間的方式與牛頓理論處理空間和時間的方式顯然不同。特別是

Maxwell's equations predicted a special velocity. There's no special velocity in Newtonian mechanics. Every velocity is created the same. Maxwell says there's something called the speed of light. It is the speed at which waves in the electromagnetic fields move. And naively you look at the equations and everyone measures the same value for the speed of light. It's a constant of nature. How can it possibly be the case that everyone measures the same speed for light even if they're moving with respect to each other? So for a long time, for decades, people, physicists bashed their heads against this problem. They came up with very elaborate schemes to get rid of it. And it was Einstein, Albert Einstein in his great paper in 1905 who first said you should get rid of the idea of these waves traveling through a medium. You should think of the electromagnetic waves as really being the thing that exists and when the equations tell you everyone measures the speed of light the same, that's because they do.

麥克斯韋方程預言了一種特殊速度。牛頓力學中沒有特殊速度。每個速度的產生都是一樣的麥克斯韋說有一種速度叫做光速它是電磁場中波移動的速度天真地看方程式 每個人測量的光速值都是一樣的這是一個自然常數。怎麼可能每個人測量出的光速都是一樣的，即使他們是相互移動的呢？所以在很長一段時間裡，幾十年來，人們，物理學家們都在為這個問題絞盡腦汁。他們想出了很多辦法來解決這個問題是愛因斯坦，阿爾伯特-愛因斯坦在他1905年的偉大論文中首次提出 你應該擺脫這些波在介質中傳播的想法。你應該把電磁波看作真正存在的東西 當方程告訴你每

Take that seriously. All you have to do is entirely rejigger your thoughts about what space and time are.

請認真對待。你所要做的，就是完全重新調整你對空間和時間的理解。

And in fact it wasn't until two years later when Herman Minkowski who was a mathematician who had been one of Einstein's professors said, you know, the right way to think about Einstein's theory is to say that space and time aren't separate anymore.

事實上，直到兩年後，曾是愛因斯坦教授之一的數學家赫爾曼-閔科夫斯基（Herman Minkowski）才說："你知道，思考愛因斯坦理論的正確方法是說，空間和時間不再是分開的。

To imagine there's one thing called space time and different people, different observers moving in different ways through the universe will divide it up into space and time differently. There's no objective true fact about when I snap my fingers now, what's happening light years away. That's going to depend on who's doing the observing and who's doing the measuring. It can all be explained very beautifully by imagining a single four dimensional space time instead of separate space and time. Einstein himself was not impressed by this move. Einstein was a hilarious character because he was a physicist's physicist. He was very mathematically adept.

想象一下，有一種東西叫做時空，而不同的人、不同的觀察者以不同的方式在宇宙中移動時，會以不同的方式將其劃分為不同的時空。當我現在打響指時，光年之外發生了什麼，這並不是一個客觀真實的事實。這取決於誰在觀測，誰在測量。通過想象一個單一的四維時空，而不是獨立的空間和時間，可以很好地解釋這一切。愛因斯坦本人對這一舉動並不以為然。愛因斯坦是個有趣的人物，因為他是物理學家中的物理學家。他精通數學。

Don't believe the stories that Einstein wasn't good at math in school. He was very good at it.

不要相信愛因斯坦在學校數學不好的說法。他非常擅長數學。

But he wasn't in it for the math. He was in it for the physics. So he learned as much math as he needed. And when Minkowski says I have some new math that unifies space and time based on Einstein's theories, Einstein himself is like

但他不是為數學而學的他是為了物理所以他需要多少數學就學多少當明考斯基說我有一些新的數學方法 可以在愛因斯坦理論的基礎上統一時空時 愛因斯坦自己就會說

I don't need that. That's like extra mathematical nonsense. He soon changed his mind because it turns out that that move from space and time being separate to being combined is super useful going forward, including 10 years later, he would invent his general theory of relativity that include gravity into the space time story.

我不需要那個。那就像是額外的數學廢話。他很快就改變了主意，因為事實證明，從空間和時間分離到結合的這一轉變對未來超級有用，包括10年後，他發明了廣義相對論，將萬有引力納入了時空故事。

When Einstein put together what we now call the special theory of relativity, the idea that there's no preferred standard of rest in the universe, but also everyone thinks the speed of light is the same. All you have to do is imagine ultimately that space and time are glued together.

當愛因斯坦提出我們現在所說的 狹義相對論時 他認為宇宙中不存在靜止的標準 但每個人都認為光速是相同的你所要做的就是想象 最終空間和時間是粘在一起的

That was a radical reworking of the framework of physics.

這是對物理學框架的徹底改造。

Newton's idea of separate space and separate time absolute and agreed upon by everyone had been there for hundreds of years. And when you do that, when you say, OK, I'm going to completely invent space and time in part because I want to match this wonderful theory we have, Maxwell's theory of electricity and magnetism, you have to go back to everything that was a success in your previous way of doing things and say, does it still work?

牛頓關於獨立空間和獨立時間的觀點已經存在了數百年之久。當你這樣做的時候，當你說，好吧，我要完全發明空間和時間，部分原因是我想與我們擁有的這個美妙的理論--麥克斯韋的電學和磁學理論--相匹配的時候，你就必須回到你以前做事方式的一切成功之處，然後說，它還行得通嗎？

The biggest success of Newtonian classical mechanics was gravity.

牛頓經典力學的最大成功是萬有引力。

The famous inverse square law of gravity. Newton posited that if you have two objects with two different masses, they have a gravitational force that will pull them together that diminishes as one over the square of the distance between them.

著名的萬有引力平方反比定律。牛頓假設，如果有兩個品質不同的物體，它們之間會產生一種引力，這種引力會把它們拉到一起，而這種引力會隨著它們之間距離的平方而減小。

And that simple rule, plus the framework of Newtonian mechanics is enough to match exactly what you see in the sky in terms of the planets moving around. It's enough to launch a rocket and get it to the moon.

這個簡單的規則，再加上牛頓力學的框架，就足以與你在天空中看到的行星運動完全吻合。這足以發射火箭，讓它飛向月球。

So Einstein comes along and says, well, OK, can I make a version of Newton's theory of gravity that is compatible with my new theory of special relativity? And after trying he said, no, I can't. You have to do something much more dramatic. And what he realized is that gravity is a special force of nature. You know, Maxwell talks about electricity and magnetism.

於是愛因斯坦來了，他說，好吧，我能做出一個牛頓萬有引力理論的版本，與我的狹義相對論相兼容嗎？在嘗試之後，他說，不，我做不到。你必須做一些更戲劇性的事情。他意識到萬有引力是一種特殊的自然力麥克斯韋談到了電和磁

If I want to know what the electric field is at one point in space, it's very easy to do. I put a positively charged particle, a negatively charged particle, they get pushed in opposite directions by the electric field. But Einstein realized that every particle reacts the same way to gravity. If I have a very heavy particle and a very light particle and I drop them, Galileo showed that they drop at exactly the same rate. They're not pushed around in a different way.

如果我想知道空間中某一點的電場是多少，這很容易做到。我放一個帶正電的粒子和一個帶負電的粒子 它們會被電場推向相反的方向但愛因斯坦意識到，每個粒子對重力的反應都是一樣的。如果我有一個很重的粒子和一個很輕的粒子，我把它們扔下去，伽利略發現它們的下落速度是完全一樣的。它們並沒有被以不同的方式推著走。

So because of that, gravity seems to disappear if you only look at it in a tiny region of the universe. If you were in a sealed box and you were dropping things and going, oh, I have gravity here, you don't know that for sure. Maybe you're in a rocket ship and the rocket is accelerating and you're being tricked into thinking you have gravity. So

正因為如此，如果你只觀察宇宙中的一小塊區域，引力似乎就會消失。如果你在一個密封的盒子裡，你掉下東西，然後說，哦，我這裡有引力，你並不能確定。也許你在火箭飛船裡，火箭在加速，你被欺騙了，以為自己有引力。所以

Einstein, because he's Einstein, he's very smart, you or I would go, huh, that's interesting. But he says, I think what that means is that gravity is not a force on top of space-time.

愛因斯坦，因為他是愛因斯坦，他非常聰明，你或我會說，嗯，這很有趣。但他說，我認為這意味著 重力並不是時空之上的一種力。

It's a feature of space-time itself. What feature could it be? Well, my ex-professor Minkowski says that space-time has a geometry. It's one combined thing and there are equations telling me how particles move in it. Maybe that geometry is curved. Maybe it's not like a flat tabletop like Euclidean geometry. Maybe it's warped and bent and dynamical and changes in response to the existence of mass and energy and things like that. It's a good idea to have.

這是時空本身的一個特徵。會是什麼特徵呢？我的前教授閔科夫斯基說 時空有一個幾何圖形它是一個組合體 有方程式告訴我粒子如何在其中運動也許這個幾何形狀是彎曲的也許它不像歐幾里得幾何那樣是平的桌面。也許它是扭曲的、彎曲的、動態的，並隨著品質和能量的存在而變化。這是個不錯的想法

It takes you a lot of effort and a lot of mathematical work to figure it out.

你需要花費大量的精力和數學運算才能弄明白。

So ten years later, in 1915, Einstein finally completes what we call the General Theory of Relativity. And the General Theory of Relativity says space-time is a four-dimensional thing. That four-dimensional thing has a geometry. It's pushed around by matter and energy and we experience the curvature of space-time as the force of gravity. When Einstein and Minkowski figured out that space and time are both two different ways of slicing up space-time, what does that mean?

十年後的1915年 愛因斯坦終於完成了我們所說的《廣義相對論》廣義相對論認為時空是一個四維空間四維空間有一個幾何形狀它被物質和能量推來推去 我們體驗到的時空曲率就是萬有引力當愛因斯坦和閔科夫斯基發現空間和時間 是分割時空的兩種不同方式時，這意味著什麼？

What does that mean in our guts? What does it visually or measurably imply? In space, there's something called the distance between two points. If you say

這在我們的內心深處意味著什麼？它在視覺上或測量上意味著什麼？在空間中，有一種東西叫做兩點之間的距離。如果你說

I'm here in Washington, D.C. and a friend of mine is in Los Angeles, there's a distance between those two cities. And we all agree on what that distance is because implicitly, we're imagining the shortest distance path, the straight line that connects these two points. But of course if you actually travel between these two cities, you won't exactly necessarily take that much distance because you're going to go right and left.

我在華盛頓特區，我的一個朋友在洛杉磯，這兩個城市之間有一段距離。我們都同意這個距離是多少，因為隱含地，我們在想象最短的距離路徑，即連接這兩點的直線。但當然，如果你真的在這兩個城市之間旅行，你並不一定會走那麼長的距離，因為你要左拐右拐。

You're not going to go exactly on a straight line. So in space, we're all very, very used to the idea that different paths have different lengths even if they start and end at the same point. In special relativity, now that space and time are unified, what that means is that time is like that.

你不可能完全沿著一條直線前進。所以在空間中，我們都非常非常習慣於這樣的觀點：不同的路徑有不同的長度，即使它們的起點和終點都是相同的。在狹義相對論中，空間和時間是統一的，這意味著時間也是如此。

The time you personally measure on your wristwatch is very analogous to the distance that you travel moving on some path. What that means is that rather than being a universal thing that everyone agrees on, time depends on the trajectory you take through the universe. The most famous example of this is the twin paradox. You imagine two twins. They don't have to be twins, but it's more vivid if they are because you think of twins as being the same age.

你個人用手錶測量的時間，與你在某條路徑上移動的距離非常相似。這意味著，時間並不是一個人人都同意的普遍現象，而是取決於你在宇宙中行走的軌跡。最有名的例子就是雙胞胎悖論。你可以想象兩個雙胞胎。他們不一定是雙胞胎，但如果是就會更生動，因為你認為雙胞胎的年齡是一樣的。

One twin just doesn't move, just stays home. This is the lazy twin.

有一對雙胞胎就是不動，只是呆在家裡。這就是懶惰的雙胞胎。

And they get older like the rest of us all do.

The other twin hops in a rocket ship that moves out very close to the speed of light.

另一對孿生兄弟則乘坐火箭飛船，以非常接近光速的速度飛行。

You need to move close to the speed of light to feel the effects of relativity.

你需要接近光速運動，才能感受到相對論的影響。

And then comes back. And so they left at the same time.

然後又回來了。所以他們是同時離開的。

They were the same age. They come back to the same point in space and the same point in time. But the twin who traveled is now younger.

他們是同齡人。他們回到了同一空間點和同一時間點。但穿越時空的雙胞胎現在更年輕了。

The twin who traveled has experienced less time than the twin who stayed home. And the reason why is because they took different paths through space-time. Space and time are similar to each other, but not exactly the same. That's why in space the shortest distance path is a straight line.

旅行的雙胞胎經歷的時間比留在家裡的雙胞胎少。原因就在於他們穿越時空的路徑不同。空間和時間彼此相似，但並不完全相同。這就是為什麼在空間中，距離最短的路徑是一條直線。

But in time, the longest time path is the straight line.

但在時間上，最長的時間路徑是直線。

The twin who stays stationary and doesn't move that's moving in a straight line through space-time. That's the one that feels more time pass before the other twin comes back.

靜止不動的雙胞胎在時空中做直線運動。在另一對雙胞胎回來之前，這對雙胞胎會感覺到更多的時間流逝。

When people hear this stuff about relativity and moving through space and things, what they want to say is, oh, so you're saying that time moves more slowly when you're traveling near the speed of light. No, I do not want to say that. I very much do not want to say that. What is the rate at which time moves? It is one second per second. You're being tricked by your use of the English language.

當人們聽到相對論和空間移動之類的東西時，他們想說的是，哦，你是說當你以接近光速的速度旅行時，時間會走得更慢。不，我不想這麼說。我非常不想這麼說。時間移動的速度是多少？是每秒一秒你被你的英語語言騙了

Because you move through space and it makes perfect sense to say

I'm moving at one meter per second or two meters per second or whatever.

我正在以每秒一米或每秒兩米的速度移動。

The rate at which you move is the number of distance you travel per unit time. But the amount of time you travel per unit time is always one. Now, the accumulated time along two different trajectories can be different.

移動速度是指組織、部門時間內移動的距離。但是，組織、部門時間內你所走過的時間總是一。現在，沿著兩條不同的軌跡累積的時間可能不同。

That's the origin of something like the twin paradox. Or when gravity comes into the game, the amount of total time you experience will be less if you're deep in a gravitational field than if you're out there in interstellar space where gravity is not that important.

這就是類似孿生悖論的起源。或者說，當引力進入遊戲時，如果你身處引力場深處，你所經歷的總時間就會少於你身處星際空間的時間，因為在星際空間裡，引力並不那麼重要。

In general relativity, being a strong gravitational field is much like moving out there close to the speed of light.

在廣義相對論中，處於強引力場中就像以接近光速的速度運動。

If you had someone stay back here on Earth, someone else go near a black hole, for example. A black hole is the strongest kind of gravitational field you can have. Don't go in to the black hole because then you can't come back out.

例如，如果你讓一個人留在地球上，另一個人去黑洞附近。黑洞是最強的引力場。不要進入黑洞，因為那樣你就出不來了。

But if you go near it and then you come back, you will be younger than the person who just stayed behind. You will have experienced less time.

但如果你走近它，然後再回來，你就會比剛剛留下來的人年輕。你經歷的時間會更少。

Your wristwatch is still clicking at one second per second, but the accumulated amount of time is different because you have taken a different path through curved spacetime. In Interstellar, the Christopher

你的手錶仍在以每秒一秒的速度轉動，但累積的時間卻不同了，因為你在彎曲的時空中走過了不同的路徑。在《星際穿越》中，克里斯托弗

Nolan movie, this is wonderfully illustrated. Kip Thorne, who is a Nobel Prize winning physicist, was the executive producer and one of the instigators of that movie. He put all of his physics knowledge in there about wormholes and black holes and gravity and time travel.

諾蘭的電影，對此進行了精彩的詮釋。基普-索恩是諾貝爾物理學獎得主，他是這部電影的執行製片人和發起人之一。他把自己所有關於蟲洞、黑洞、引力和時空旅行的物理學知識都放了進去。

Up until the very last scenes when they're in the library and everything goes haywire, all the physics in that movie is completely respectable.

直到他們在圖書館裡的最後一幕，一切都亂套了，那部電影裡的所有物理學都是完全值得尊敬的。

One thing that is true even in Newtonian ways of thinking about space and time or in Einsteinian ways of thinking about space and time is that these fundamental laws, as Laplace's demon shows us, work forward and backward in time. Knowing everything about the universe at one moment predicts the past as well as the future. That's because what we think of as the fundamental laws of physics do not have a directionality to time. They treat the past and future the same. But there's clearly a direction to time in the world. I remember what I was doing yesterday. I might guess what I'm going to do tomorrow, but I don't remember it in the same way. I have no photographs or memory books of the future. I was younger.

即使按照牛頓的時空思維方式或愛因斯坦的時空思維方式，有一點也是正確的，那就是這些基本定律，正如拉普拉斯定律向我們展示的那樣，在時間上向前和向後都起作用。在某一時刻了解宇宙的一切，就能預測過去和未來。這是因為我們所認為的基本物理定律並不具有時間方向性。它們對過去和未來一視同仁。但在這個世界上，時間顯然是有方向的。我記得我昨天在做什麼。我可能會猜測我明天要做什麼，但我不會以同樣的方式記住它。我沒有關於未來的照片或回憶錄。我年輕的時候

I will always be older in the future. What is going on with that?

我將來總會變老。這是怎麼回事？

And the answer is it's not the fundamental laws of physics.

答案是，這與基本物理定律無關。

It's the collective behavior of many, many things in the universe that start out in a special state. It goes back to the idea of entropy from the 1800s, the idea of the disorderliness of a system, the randomness, the disorganization. And entropy increases with time. That's the famous second law of thermodynamics.

它是宇宙中許許多多事物的集體行為，這些事物一開始都處於一種特殊的狀態。這可以追溯到 19 世紀的熵的概念，即系統的無序性、隨機性和無組織性。熵隨時間增加。這就是著名的熱力學第二定律。

Why does entropy increase with time? Because there are more ways for a system to be arranged in a high-entropy configuration than a low-entropy one, by definition. And the universe started in a very special low-entropy state. Nobody knows why that is true. This is a mystery to cosmology. But the entropy of the universe was very, very low to start, and it's been increasing ever since.

為什麼熵會隨時間增加？因為根據定義，一個系統的高熵構型比低熵構型有更多的排列方式。而宇宙是以一種非常特殊的低熵狀態開始的。沒人知道為什麼會這樣。這是宇宙學的一個謎。但宇宙的熵一開始就非常非常低，而且一直在增加。

And us having memories of the past but not the future, the ability to have records, the fact that we age in the same direction, this is all because entropy is increasing in one direction rather than the other.

我們有過去的記憶卻沒有未來的記憶，我們有記錄的能力，我們的衰老方向是一致的，這些都是因為熵在朝一個方向而不是另一個方向增加。

I like to think if you were a physicist circa 1895, the very end of the 19th century, you would have been forgiven for thinking that we were almost there. We were almost having a complete theory of nature in our grasp. Because they had the idea of particles. The idea of an atom was a little bit sketchy to a lot of physicists in the 1800s, but they eventually caught on and they were beginning to realize that atoms were made of other particles, protons, neutrons, electrons, and so forth. And then the particles, which make up matter, are pushed around by fields, by the electric field, by the magnetic field, by the gravitational field, and so forth. So you have this sort of two-part harmony. Matter is made of particles, forces come from fields, and all the effort in the future of physics would be figuring out what are all the particles, what are all the fields, and then you'd be done. There were a couple of clouds on the horizon. One of them ended up being relativity.

我想，如果你是一位物理學家，大約在 1895 年，也就是 19 世紀末，你一定會認為我們就快成功了。我們幾乎掌握了完整的自然理論因為他們有了粒子的概念在19世紀，原子的概念對很多物理學家來說還有點模糊，但他們最終明白了原子是由其他粒子組成的，如質子、中子、電子等等。這些構成物質的粒子受到電場、磁場、引力場等場的推動。於是就有了這種兩部分的和諧。物質是由粒子構成的，力來自於場，未來物理學的所有努力都是為了弄清粒子和場的區別，然後就大功告成了。地平線上有幾朵烏雲。其中之一就是相對論

The fact that the symmetries of Maxwell's theory of electromagnetism were different than the symmetries of Newton's theory of classical mechanics.

麥克斯韋電磁學理論的對稱性與牛頓經典力學理論的對稱性不同。

But the others were that there were certain properties of matter and materials that didn't quite seem to make sense. And I'm going to be ahistorical now. Let's pop forward to like 1911. They were putting together the picture of the atom that is the cartoon you've always seen, right? There's a little nucleus at the center of the atom and electrons are circling around it like planets orbiting a star. This is called the Rutherford atom model after Ernest Rutherford, who was a brilliant experimental and theoretical physicist.

但其他的則是，物質和材料的某些特性似乎並不合理。我現在要講講歷史了。讓我們回到1911年他們正在繪製一幅原子圖畫 這幅圖畫就是你經常看到的漫畫，對嗎？原子中心有一個小原子核 電子圍繞著它轉 就像行星圍繞著恆星轉一樣這就是歐內斯特-盧瑟福原子模型，他是一位傑出的實驗和理論物理學家。

And this was entertained and people liked the idea that electrons were kind of like little planets, but they instantly figured out it can't possibly be right. Because that electron orbiting the nucleus would give off electromagnetic waves.

人們很喜歡這個想法，認為電子就像小行星，但他們馬上發現這不可能是對的。因為圍繞原子核運轉的電子 會發出電磁波

It's a moving particle. Moving charged particles give off light.

這是一個移動的粒子。運動的帶電粒子會發光。

All of the light you're looking at right now came from some electron in motion moving around. So you can calculate. You can say if the electron is moving around in orbit around the atomic nucleus if it gives off light it will lose energy and spiral into the nucleus.

你現在看到的所有光線，都來自於某個正在運動的電子。所以你可以計算一下。你可以說，如果電子在原子核周圍的軌道上運動，如果它發出光，它就會失去能量並螺旋形地進入原子核。

How long should that take? And the answer is every atom in the universe, including the ones in the chair you're sitting on or even in your own body, should collapse to a point in a hundredth of a billionth of a second. So that clearly does not happen.

這需要多長時間？答案是宇宙中的每一個原子，包括你所坐的椅子上的原子，甚至你自己身體裡的原子，都應該在千億分之一秒內坍縮到一個點上。所以這顯然是不可能發生的。

The idea that electrons are like little planets in the solar system is just wrong. And this and other things, blackbody radiation and other experimental results convinced people that there wasn't this clean division between particles and forces. They said there's aspects of light, which is supposed to be a wave, which are particle-like. Einstein said that. There are aspects of particles, like electrons, that are wavelength. Louis de Broglie following work by Niels Bohr and others said that. And this whole thing coalesces almost exactly a hundred years ago in 1925 in the theory of quantum mechanics.

認為電子就像太陽系中的小行星是錯誤的。黑體輻射和其他實驗結果讓人們相信 粒子和力之間並沒有明確的界限他們說光的某些方面本應是波 但卻像粒子一樣愛因斯坦是這麼說的。粒子也有波長的一面，比如電子。路易斯-德-布羅格利在尼爾斯-玻爾等人的研究之後提出了這一觀點。而這一切，幾乎就在一百年前的1925年，在量子力學理論中凝聚起來。

And almost right at the same time two different versions of it came out.

而幾乎就在同一時間，又有兩個不同的版本問世。

Werner Heisenberg had his version called matrix mechanics.

維爾納-海森堡（Werner Heisenberg）將其版本稱為矩陣力學。

Erwin Schrodinger had his version called wave mechanics. They showed that they were actually mathematically equivalent. But quantum mechanics,

埃爾溫-薛定諤的版本稱為波動力學。他們證明了它們在數學上是等價的。但是量子力學

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