a huge role in human life.

在人類的生活中有著重要的地位

We constantly desire to know “why” things happen, in science, love, sports, philosophy,

我們持續不斷地渴望知道"為什麼"事情會發生: 在科學領域、愛情、運動、哲學

and so on.

以及其他許多領域都是如此

But because the underlying laws of physics don’t care about the direction of time,

但是因為物理的基本定律不在乎時間的方向

cause and effect don’t have the same meaning at a fundamental level.

因與果在根本上沒有同等的意義

It’s not that anything goes.

它並不是萬物運行的法則

The basic constituents of the universe -- the particles and forces of modern physics -- behave

宇宙的基本組成--現代物理的粒子和交互作用

in predictable ways according to the laws of nature.

以按照自然法則的方式運作

In principle, you can just as easily know their past paths as their future ones.

原則上 要知道它們過去和未來的軌跡一樣容易

The current momentum and position of a particle determine its movement forward in the next

一個粒子此刻的動量和位置決定了它 下一秒鐘要怎麼運動

second, but they also determine how it was moving in the previous second.

但也決定了它前一秒鐘是怎麼運動的

Neither is really a “cause” preceding an “effect”, there’s just a pattern

兩者其實都不是"因"接著"果" 只是個

that particles follow.

粒子遵守的規律

Kind of like how the integer after 42 is 43, and the integer before it is 41, but 42 doesn’t

有點像是接著42的正整數是43 而在它之前的是41 但42並不是

“cause” 41 or 43 – there’s just a pattern traced out by those numbers.

41或43的"因"--只不過是在這些正整數中有一套規律罷了

At a fundamental, microscopic level, all we can say is that there are patterns between

從基本、微觀的角度而言 我們能說的只是在事件之間有套規律

events.

從基本、微觀的角度而言 我們能說的只是在事件之間有套規律

The macroscopic, human-scale concepts of cause and effect only emerge when you have larger

因與果這種巨觀、人類尺度的概念 只在有一大群粒子的時候

collections of particles, like humans!

才會出現 像是人!

As we know, time does have a direction for larger-scale systems, and we can indeed talk

如同我們所知 時間在大尺度系統中 的確有方向 而我們當然也可以說

about a spark causing oxygen and hydrogen to turn into water and an explosion.

一個火花導致氧氣和氫氣變成水和爆炸

“Spark plus oxygen plus hydrogen” and then “water plus explosion” is a sequence

"火花+氧氣+氫氣" 接著是"水+爆炸" 是個

the universe follows, and it only happens in one direction.

宇宙遵守的順序 而且只能是這個方向

You never see a reverse explosion where water spontaneously splits into oxygen and hydrogen

你永遠不會看到反過來的爆炸 水自發地分解成氧氣和氫氣

gas and then at the very end emits a little spark.

並在最後發出一點火花

One way of thinking about causes is that the tiny spark has great “leverage” over the

一種思考因果的方式是 小火花對推論未來

future.

發生了什麼事很重要

If you hadn’t lit the spark, we wouldn’t have seen a giant explosion.

如果你沒有點起火花 我們也不會看到大爆炸

It doesn’t work the other way: removing or changing a tiny part of the giant explosion

但反過來卻不是這樣: 稍微改變或移除大爆炸的一小部分

doesn’t imply that there wasn’t a preceding spark.

並不代表先前就沒有火花

When a small change to the present implies a big change to the future, the small thing

當現在的一個小改變會導致未來的大改變時 那個小改變

we’re changing is generally thought of as a “cause”.

通常就會被我們當作"因"

Leverage can also go the other way.

反過來也說得通

Take this new pencil: the wood it’s made of contains trace amounts of radioactive carbon-14,

以這支新的鉛筆為例: 製造它所用的木頭裡含有微量由核彈試爆

created by nuclear bomb testing.

所產生的碳14

If the pencil didn’t contain that carbon-14, that would imply that no nuclear bombs had

如果這支鉛筆並不含有碳14 那就代表在過去80年裡沒有

been detonated in the last 80 years; while if you removed a pencil-sized amount of one

核彈被引爆 然而如果你讓核彈裡相當於鉛筆大小

of the atomic bombs, this pencil would still be basically the same.

的一部分消失 這支鉛筆仍然會長得差不多

In this case, the fact that the pencil has lots of carbon 14 means that it has a lot

在這個例子中 鉛筆含有很多碳14代表著它

of “leverage” over the past.

對於推論過去發生了什麼事很重要

Instead of calling the carbon 14 in this pencil a “cause” of the earlier detonation of

我們不把這支鉛筆稱作先前引爆的

hundreds of nuclear bombs, we call it a “record” of the bombs.

數百顆核彈的"因" 我們稱它為"紀錄"

In general, when a small change to the present would imply a big change to the past, the

原則上 如果現在的一個小改變 會對過去造成很大的改變

small thing we’re changing is thought of as a “record” or a “memory”.

這個我們改變的小東西就被稱為"紀錄"或者"記憶"

So the distinctions between “cause” and “effect”, “records” and “predictions”,

所以"因"與"果"、"紀錄"和"預言"之間的差異

aren’t fundamental to underlying physics – they only really make sense on the large

並不在於基礎的物理原理上-- 他們只在巨觀尺度上

scale, because of the direction of time.

因為時間的流向才說得通