to the distance squared”, Schrodinger’s equation, and so on – don’t say anything

距離的平方成反比“，薛定諤 方程，等等 - 都沒有討論到

about the direction of time.

任何關於時間的方向的問題。

Sure, they relate what’s going on now to what happens next, and to what happened previously,

當然，它們與現在到未來發生甚麼事有關，到以前發生哪些事情，

but there’s no distinction between forwards and backwards in time.

但有這與時間往前或往後並沒有關係。

The past and future are on an equal footing, as far as the microscopic laws of physics

過去和將來都是平起平坐， 這些都是根據物理的微觀規律。

are concerned.

不過在宏觀世界，是有 一個關於時間規則的

In the macroscopic world, however, there is one rule that does have time going in one

唯一的方向：熱力學第二定律。

direction only: the second law of thermodynamics.

在這個定律裡任何孤立系統會往增加熵的方向前進， 或成為混亂的狀態。

That says that any isolated system will tend towards increasing entropy, or disorder.

如將牛奶和熱咖啡混合在一起 變成微溫的咖啡牛奶，但絕沒有辦法

Like how cold milk and hot coffee mix together into luke-warm coffee-milk, but will never

“分開”。

“unmix”.

一旦系統到達其完全無序 狀態 - 也就是平衡 - 就再也沒有

Once a system gets to its fully-disordered state -- its equilibrium -- there’s no more

能夠決定時間方向的熵產生。

direction of increasing entropy to determine the arrow of time.

因此，事實上，我們所經歷的 時間流逝，意味著我們並沒有達到平衡。

So the fact that we experience the flow of time right now means that we’re not in equilibrium.

基本上有兩種可能發生的方式。

There are basically two ways that could happen.

其一是宇宙恰好現在正在這個特殊的、低熵狀態，而在這個架構

Either the universe just happens to be, right now, in this particular, low-entropy, configuration

在熵增加的同時隨著時間的兩個方向向前 與向後流出熵；

with two directions of time flowing out forward and backward from it with increasing entropy

其二是或在遙遠到宇宙開始的那個過去的某個點

in both directions; or at some point in the far distant past the universe started with

那時有更低的熵，而混亂則不停地產生。

even lower entropy, and disorder has been increasing ever since.

[劇透：第二個才是對的。]

[Spoiler alert: it’s option number two.]

這種低熵的結構被稱為大爆炸。

That low-entropy configuration was the Big Bang.

138億年前，宇宙是炙熱、 緻密且光滑，並迅速擴大。

13.8 billion years ago, the universe was hot, dense, smooth, and rapidly expanding.

這些顆粒狀的光滑稠密等離子體 似乎沒有組織及低熵，但當時的

A smooth dense plasma of particles might not seem organized & low-entropy, but when the

物質密度極高， 粒子間的引力極大。

density of matter is extremely high, the gravitational force between particles is enormous.

在這種情況下的表面並不穩定，但它確實處於一個非常

Smoothness, in the face of such tendencies, is not equilibrium, but is actually a very

微妙的平衡、低熵狀態。

delicately-balanced, low entropy state.

事物被引力匯聚成稠密的結構

Things want to be gravitationally clumped together into concentrated configurations

像是原恆星、原星系，或甚至 黑洞。

like proto-stars, proto-galaxies, or even black holes.

一個高熵、平衡的宇宙 會是甚麼樣子？

What would a high-entropy, equilibrium universe look like?

那裏將甚麼也沒有。

It would be empty space.

事實上，那正是我們將面臨的狀況： 宇宙正在膨脹和稀釋，以及

And indeed, that’s where we’re headed: the universe is expanding and diluting, and

最終所有的星星會燒光、 黑洞會蒸發，我們將

eventually all the stars will burn out and black holes will evaporate and we’ll be

一無所有，只剩下一望無際的虛無。

left with nothing but emptiness in every direction.

屆時，時間的箭頭會消失， 而生命與意志則不可能存在。

At that point, time’s arrow will have disappeared, and nothing like life or consciousness will

事實上那些點綴著我們星空的千億顆星星與銀河，與我們生意昂然

be possible.

的生態系，反映著我們正是 低熵的開端。

The fact that our sky is decorated with billions of stars and galaxies, and our biosphere is

我們不知道為什麼宇宙的開始 會是這種有序的狀態，但我們應該

teeming with life, is a reflection of our low-entropy beginnings.

感到高興：它給我們讓時間流動的 非平衡狀態，

We don’t know why the universe started in such an orderly initial state, but we should

就如我們所知的時間得以存在。

be glad it did: it gave us the non-equilibrium starting point that’s necessary for the

隨後的一切 - 從 恆星和星系的排列到生命的起源

flow of time, as we know it, to exist.

- 就是一直在增加熵的故事。

Everything that followed -- from the formation of stars and galaxies to the origin of life

時間的方向並不是大多數基本物理定律的核心；

-- has been a story of increasing entropy.

它缺少存在於我們的宇宙中的具體初始條件。

Time’s arrow isn’t a deep feature of the most fundamental laws of physics; it owes

嘿，這裡是亨利，感謝收看。

its existence to the specific initial conditions of our universe.

這是第一[第二，第三等] 在一系列關於時間和熵的影片製作

Hey, Henry here, thanks for watching.

與物理學家肖恩·卡羅爾的合作。

This is the first [second, third, etc] video in a series about time and entropy made in

該系列影片的支持與資助是由 Google’s Making和Science initiative提供，

collaboration with physicist Sean Carroll.

其目的是鼓勵更多的年輕人 （和所有年齡的人），以了解和

The series is supported with funding from Google’s Making and Science initiative,

愛上科學以及他們身處的世界，影片都基於肖恩的

which seeks to encourage more young people (and people of all ages) to learn about and

新書“大視野：論生命的起源、意義與宇宙本身，“

fall in love with science and the world around them, and the videos are based off of Sean’s

你可以在網路上或世界各地的書店找到。

book “The Big Picture: On the Origins of Life, Meaning, and the Universe Itself,”

which you can find online or in bookstores around the world.