Does time exist? - Andrew Zimmerman Jones

譯者: Lilian Chiu 審譯者: Helen Chang

時間是什麼？

The earliest time measurements were

最早出現的時間測量

observations of cycles of the natural world,

是觀察自然世界的循環，

using patterns of changes from day to night

用白天到黑夜、一季到下一季的

and season to season to build calendars.

改變模式，來建立出日曆。

More precise time-keeping, like sundials

更精確的時間記錄，比如日晷

and mechanical clocks, eventually came along

以及機械時鐘，最終都出現了，

to put time in more convenient boxes.

把時間放在更方便的盒子中。

But what exactly is it that we’re measuring?

但，我們在測量的到底是什麼？

Is time something that physically exists,

時間有實體的存在嗎？

or is it just in our heads?

還是它只是我們腦中的想像？

At first the answer seems obvious—

一開始，答案似乎很明顯——

of course time exists;

時間當然存在；

it constantly unfolds all around us,

它經常會出現在我們的周邊，

and it’s hard to imagine the universe without it.

很難想像沒有時間的宇宙。

But our understanding of time started

但，要歸功於愛因斯坦，

getting complicated thanks to Einstein.

我們對於時間的了解開始變複雜。

His theory of relativity tells us that time

他的相對論告訴我們，

passes for everyone, but doesn’t always pass

對每個人，時間都會過去，

但過去的速度就會因情況而異了，

at the same rate for people in different situations,

like those travelling close to the speed of light

比如在接近光速旅行的情況，

or orbiting a supermassive black hole.

或是在超大質量的黑洞 旁邊運行的情況。

Einstein resolved the malleability of time

愛因斯坦解決了時間的 可塑性（延展性），

by combining it with space to define space-time,

將時間與空間結合， 來定義「空間—時間」，

which can bend, but behaves in consistent, predictable ways.

它可以被彎曲，

但行為仍然是一致、可預測的。

Einstein’s theory seemed to confirm that time

愛因斯坦的理論似乎確認了

時間是被織入到宇宙織物中的。

is woven into the very fabric of the universe.

But there’s a big question it didn’t fully resolve:

但還有一個大問題， 是這個理論沒有完全解決的：

why is it we can move through space in any direction,

為什麼在空間中我們 能朝任何方向移動，

but through time in only one?

但在時間中的方向只有一個？

No matter what we do, the past is always,

不論我們怎麼做，過去始終都

stubbornly, behind us.

很固執地留在我們身後。

This is called the arrow of time.

這就是所謂的時間箭頭。

When a drop of food coloring is

當一滴食物色素被滴入一杯水中，

dropped into a glass of water,

we instinctively know that the coloring

我們直覺上就知道，

該色素會從水滴中擴散出來，

will drift out from the drop,

eventually filling the glass.

最終充滿整個杯子。

Imagine watching the opposite happen.

想像一下相反的狀況。

Here, we’d recognize time as unfolding backwards.

在這裡，我們認為 時間是反向呈現的。

We live in a universe where the food coloring

我們所住的宇宙中，

spreads out in the water,

食用色素散佈在水中各處，

not a universe where it collects together.

而不是集合起來成一滴的。

In physics, this is described by

在物理上，

可以用熱力學第二定律來描述它，

the Second Law of Thermodynamics,

which says that systems will gain disorder,

該定律說的是，系統會

隨著時間得到混亂或是熵。

or entropy, over time.

Systems in our universe move from order to disorder,

在我們宇宙中的系統， 會從有秩序變成混亂，

and it is that property of the universe

正是宇宙的這項特性

that defines the direction of time’s arrow.

定義了時間箭頭的方向。

So if time is such a fundamental property,

所以，如果時間 是這種根本的特性，

it should be in our most fundamental equations

它就應該要出現在 我們用來描述宇宙的

describing the universe, right?

最根本的方程式當中，對吧？

We currently have two sets of

目前，我們有兩組 支配物理的方程式。

equations that govern physics.

General relativity describes the

廣義相對論描述

behavior of very large things,

大型物體的行為，

while quantum physics explains the very small.

而量子物理解釋非常小的物體。

One of the biggest goals in theoretical physics

在過去半個世紀， 理論物理最大的目標之一，

over the last half century has been reconciling

就是將兩者調解整合

the two into one fundamental “theory of everything."

成為單一的「萬物之理」。

There have been many attempts

許多人嘗試過，卻沒一個被證明——

—none yet proven—

and they treat time in different ways.

它們都以不同的方式來看待時間。

Oddly enough, one contender called the Wheeler-DeWitt

很怪的是，其中一個角逐者是 惠勒—德威特方程式，

equation, doesn’t include time at all.

它完全沒有納入時間。

Like all current theories of everything,

和目前所有的萬物之理一樣，

that equation is speculative.

該方程式純屬理論推測。

But as a thought experiment,

但就思想實驗來說，

if it or a similarly time-starved equation

如果它或同樣缺乏時間的方程式，

turned out to be true, would that mean

最後證明是真的，

那是否意味著時間不存在於 最根本的層級上？

that time doesn’t exist, at the most fundamental level?

Could time just be some sort of illusion generated

時間是否可能只是一種幻覺，

by the limitations of the way

因我們受限於對宇宙的感知方式

we perceive the universe?

而產生出來的幻覺？

We don’t yet know, but maybe that’s

我們還不知道答案，

但也許那是錯誤的時間思考方式。

the wrong way of thinking about it.

Instead of asking if time exists as a fundamental property,

不問時間是否真的是 一種根本特性的存在，

maybe it could exist as an emergent one.

而是問它是否是 一種突顯特性的存在。

Emergent properties are things that don’t exist

突顯的特性不存在於

in individual pieces of a system,

系統中的個別部分，

but do exist for the system as a whole.

而是存在於整個系統當中。

Each individual water molecule doesn’t have a tide,

個別的水分子沒有潮汐，

but the whole ocean does.

但整體的海洋卻有。

A movie creates change through time by using

電影透過時間創造出改變，

a series of still images that appear to have a fluid,

使用一系列靜態影像，

各影像間有著流暢、連續的改變。

continuous change between them.

Flipping through the images fast enough,

只要非常快速翻動這些影像，

our brains perceive the passage of time

我們的大腦就認為靜態影像序列

from the sequence of still images.

是有的時間經過的。

No individual frame of the movie changes

電影中沒有任何一個畫格會改變，

or contains the passage of time,

單一畫格也不包含時間經過，

but it’s a property that comes out of how

但當各部分被串接在一起時，

the pieces are strung together.

就會產生出時間這種特性。

The movement is real, yet also an illusion.

動作是真實的，同時也是種幻覺。

Could the physics of time somehow be a similar illusion?

時間的物理有沒有可能 在某種層面上也是類似的幻覺？

Physicists are still exploring these and other questions,

物理學家仍然在探究 這些及其他問題，

so we’re far from a complete explanation.

我們離完整的解釋還很遙遠。

At least for the moment.

至少目前是如此。