The Boltzmann brain paradox - Fabio Pacucci

譯者: Camila Lin 審譯者: Helen Chang

How do you know you’re a person who has lived your life,

你怎麼知道，你是一個活生生的人，

rather than a just-formed brain full of artificial memories,

而不是一顆剛完成的大腦，

裡面還塞進了一堆虛假的記憶，

momentarily hallucinating a reality that doesn't actually exist?

讓你在瞬間經歷了一段 根本不存在的「現實」？

That may sound absurd,

也許這聽起來很荒唐，

but it’s kept several generations of top cosmologists up at night.

但好幾代的頂尖宇宙學家 因為這個問題而輾轉難眠。

They call it the Boltzmann brain paradox.

他們將這個假說稱為 「波茲曼大腦悖論」。

Its namesake, Ludwig Boltzmann, was a 19th century physicist

因為提出這個悖論的人，是十九世紀的 物理學家，路德維希・波茲曼。

operating in a period when scientists were passionately debating

在他活躍的年代， 科學家們熱烈地辯論這一問題：

whether the universe had existed for an infinite or finite time.

宇宙究竟是存在於無窮的時間中， 或是存在於有限的時間中。

Boltzmann’s main claim to fame was revolutionizing thermodynamics,

波茲曼的主張徹底推翻熱力學， 他也因此聲名大噪。

the branch of physics that studies energy.

熱力學是研究能量的物理學分支。

He put forward a new interpretation of entropy,

他以新的方式闡述熵，

which is a measure of the disorder of a system.

熵可被用來計算某系統的混亂程度。

A glass is an ordered system, whereas a shattered glass is disordered.

假設一片玻璃是有序的系統， 那麼碎玻璃就是混亂的系統。

The second law of thermodynamics states that closed systems tend towards disorder:

熱力學第二項定理指出， 封閉系統有變得無序的傾向，也就是說

you won’t see a shattered glass return to its pristine state.

碎玻璃永遠不會恢復成完好的玻璃。

Boltzmann’s insight was applying statistical reasoning to this behavior.

波茲曼以統計學的角度， 來看待這條定理。

He found that a system evolves to a more disordered state because it’s more likely.

他發現系統之所以會往無序前進， 是因為它本來就有無序的傾向。

However, the opposite direction isn’t impossible,

雖然也有系統反向運行， 變得更加有序的可能性，

just so unlikely that we’ll never witness things like scrambled eggs turning raw.

但機率非常低，就和我們看見 炒蛋變回生雞蛋的機率一樣低。

But if the universe exists over an infinitely long time,

不過，如果宇宙存在於無盡的時間中，

extremely unlikely events will happen,

機率極低的事件也終將發生，

including complex things forming out of random combinations of particles.

粒子隨機組合成某個複雜事物， 也並非不可能。

So what does that look like in a hypothetical infinitely old universe?

那麼，在這個非常古老的 假設宇宙中，會發生什麼事呢？

In this unremarkable stretch of near-nothingness,

在這近乎虛無、無趣延伸的宇宙中，

about eight octillion atoms randomly come together to form a replica

八十多億個原子隨機結合起來，

變成了一個義大利麵製的《沈思者》。

of the Thinker made of pasta.

It instantly dissolves.

但它卻很快地崩解了。

Over here, these particles suddenly form something like a brain.

但就在這裡，這些原子 突然又組成了一個類似大腦的東西，

It’s filled with false memories of a lifetime up to the present moment,

裡面充滿著虛假的記憶， 從以前紀錄到現在這一刻，

when it perceives a video saying these very words,

直到它察覺到這段影片的 這段話後，才腐敗消散。

before decaying.

And finally, by random fluctuations, all the particles in the cosmos

最後，隨機的波動讓宇宙中所有原子

concentrate in a single point,

集中在一個點上，

and an entire new universe spontaneously bursts into existence.

一個全新的宇宙突然生成了。

Of those last two, which is more likely?

你覺得上述的兩種情況， 哪一個更可能發生？

The brain, by far—

以目前的觀點，大腦更可能出現，

despite all its complexity, it’s a blip compared to an entire universe.

因為儘管大腦結構複雜， 但和宇宙相比，不過是一縷鴻毛。

Every one universe produced by random fluctuations has equivalent odds

每個因分子隨機組成而產生的宇宙，

to heaps upon heaps of insta-brains.

粒子拼湊出僅存在一瞬的大腦機率都相同。

So by this reasoning, it seems extremely more likely

所以，根據這個理論，

我們相信真實存在的事物， 更可能只是一種瞬間的幻覺，

that everything you believe to exist is actually a brief illusion,

soon to be extinguished.

即將立刻消失。

Boltzmann didn’t get quite that far in his thinking;

不過，波茲曼的理論沒有這麼極端。

the brains themselves were introduced by later cosmologists building on his work.

波茲曼大腦是後繼的宇宙學家， 根據他的理論提出的假說。

But they, like just about everyone else,

但他們就像其他人一樣，

were pretty sure that they themselves weren't just ephemeral brains.

相當肯定自己是活人， 而非轉眼即逝的一顆大腦。

So the paradox was: how could they be correct and the universe be eternal?

悖論因此誕生：該怎麼證明他們 是對的，而且宇宙是永恆存在的？

The resolution is something most take for granted today:

解答是我們現在 大多視為理所當然的常識：

that our universe has not existed forever,

我們的宇宙並非永恆的存在，

but rather time and space started with a Big Bang.

而是在大霹靂之後才產生的。

So that’s the paradox over and done with, right?

這樣悖論就解決了吧？

Well, maybe not.

嗯，可能還沒有。

In the last century, scientists have found evidence supporting the theory

上個世紀，科學家發現

of the Big Bang everywhere we look.

支持大霹靂學說的證據隨處可見。

Yet while we know that the Big Bang happened,

但就算我們知道大霹靂已經發生，

no one knows what, if anything, preceded and caused it.

也沒人知道大霹靂之前是否還發生過 其他事，或是大霹靂為何發生。

Why did the universe begin in such an extremely ordered, and unlikely, state?

為什麼宇宙剛誕生就這麼有秩序， 這不符合常理吧？

Is our universe in an unending cycle of creation and collapse?

我們的宇宙是處在 創生和毀滅的無限循環中嗎？

Or might we be in one of many universes expanding within a multiverse?

還是這只是多重宇宙中的一個宇宙？

In this context, Boltzmann’s paradox has found renewed interest

在這種情況下， 波茲曼的悖論再度獲得關注，

by contemporary cosmologists.

當代的宇宙學家們對其產生興趣。

Some argue that leading models for where the universe came from

有些宇宙學家認為， 現今風行的宇宙起源說，

still imply that Boltzmann brains are more likely than human brains,

仍然暗示波茲曼大腦 比人腦更容易產生，

suggesting something’s amiss.

而這就代表我們忽略了某些細節。

Others counter that slight modifications of the cosmological models

其他人則反駁， 只要稍微修正宇宙起源模型，

would avoid the problem,

就能解決這個問題，

or that Boltzmann’s brains can’t actually physically form.

也有人認為，以現實情況， 波茲曼大腦根本不可能產生。

Some researchers even attempted to calculate the probability

有些研究者甚至試圖計算出機率，

of a brain popping out of random quantum fluctuations

想知道隨機粒子組成一顆可存在夠久， 能夠思考的大腦的可能性。

long enough to think a single thought.

They got this incredible number

他們最後得出的機率小得驚人，

whose denominator is 10 to a number about a septillion times larger

分母竟約為 1 後面接著 10 的 50 次方個 0，

than the number of stars in the universe.

比宇宙中所有星星的數量加總都還大。

The Boltzmann brain paradox, despite its absurdity,

即使波茲曼大腦悖論看似荒唐，

is useful because it creates a bar that models have to rise to.

但仍相當實用，因為它為宇宙模型 設下一個必須跨越的障礙。

If, compared to numbers like this one,

如果拿像這個機率的數字來比較，

the current state of the universe is exceedingly unlikely,

宇宙幾乎不可能維持現在的狀態，

something in the model is almost certainly wrong.

那就代表模型有某個明顯的錯誤。

Unless you’re the one who is wrong...

除非，你才是那個錯誤的人。