The fundamentals of space-time: Part 3 - Andrew Pontzen and Tom Whyntie

時空基礎理論 3 - Andrew Pontzen 與 Tom Whyntie

譯者: Neoh Yi Yuan 審譯者: 瑞文Eleven 林Lim

重力(萬有引力或引力)，它控制整個宇宙，

Gravity. It controls the universe.

Everything attracts everything else.

令萬物相互吸引。

Ouch!

哎喲！

Including you.

包括你，

Ow!

啊！

In this final lesson,

在這個系列的最後一課，

we'll explore what gravity means for space-time,

我們將探索重力對時空的影響，

or rather what space-time means for gravity.

應該說：時空對重力的影響。

Until now, we've been dealing with things moving

我們之前講的都與等速運動有關，

at constant speeds,

with straight world lines in space-time.

在時空中等速直線運動。

But once you add gravity,

但是，當我們考慮到重力時，

if you measure a speed at one moment,

如果你現在測量物體的速度，

then again a bit later,

然後在別的時間再測量一次，

the speed may have changed.

物體的速度可能就會不同了。

In other words, as I discovered,

換句話說，我們發現

gravity causes acceleration,

重力會產生“加速”

so we need the world line to look different

所以我們的世界線看起來一直在變。

from one moment to the next.

As we saw in the last lesson,

我們上節課學到，

the correct way to tilt an object's world line

如果要正確地扭曲一個物體的世界線，

is using a Lorentz transformation:

我們需要用Lorentz洛倫茲轉換理論：

Einstein's stretch and squash trick.

愛因斯坦的扭曲小把戲。

讓我們看看重力如何影響Tom的運動，

So, to map out what gravity is doing to Tom's motion,

we need to create a whole load of little patches of space-time,

首先我們要想像有很多很多時空碎片，

each transformed by different amounts.

每一個都或多或少被扭曲。

So that my world line is at a different angle in each one.

這樣我的世界線和其他的都會是不同角度，

And then, we're ready to stitch everything together.

然後我們把這些時空碎片全部拼接起來。

We assemble a cozy quilt of space-time

我們拼成了一幅被套般的時空，

where world lines look curved.

這個時空的世界線是彎曲的。

Where the world lines join, the objects collide.

世界線的交點，就是物體碰撞的地方。

By making these connections between the patches,

當我們把這些碎片連起來時，

a curvature gets built into space-time itself.

時空本身就形成了它獨有的曲率。

But Einstein's true genius

愛因斯坦實在是太天才了，

was to describe precisely how each patch

他由物體四周物質的質量與能量， 精確地算出每個碎片扭曲了多少。

is stretched and squashed

according to nearby mass and energy.

物體的存在就會使時空扭曲，

The mere presence of stuff curves the space-time,

and curving space-time moves the stuff around.

扭曲的時空可以讓物體移動。

This is gravity, according to Einstein.

這就是愛因斯坦對重力的詮釋。

Previously, Isaac Newton had explained gravity

之前，牛頓以力與加速度

using the ideas of force and acceleration,

來解釋力的概念，

without any wibbily wobbly space-time,

沒有用到這些扭來扭去的時空，

and that did pretty well.

那個理論是相當不錯。

But Einstein's theory does just slightly better

但是愛因斯坦的理論有更寬廣的適用範圍，

at predicting, for example,

比如，在預測水星繞太陽的軌道，

the orbit of Mercury around the Sun,

or the way that light rays are deflected by massive objects.

或者巨大質量(如恆星)影響光的行進方向。

More importantly, Einstein's theory predicts things

更重要的是，愛因斯坦的理論推測出

that simply don't exist in older theories

舊理論（認為空間、時間、重力毫不相關） 沒有想到的新發現。

where space, time and gravity were separate.

The stitching can leave wrinkles in the space-time material.

時空碎片的拼接會讓時空出現“皺褶”

These are called gravitational waves,

我們稱其為“重力波”

which should be detectable as tiny, repetitive,

藉由偵測空間中細微、重複的起伏，

subtle squashes and stretches in space.

來探測重力波。

So we're building experiments to check if they are there.

我們正在開發可以探測到它們的實驗。

In the meantime, indirect evidence,

與此同時，從間接的證據上看，

most recently in the polarization patterns of light

如宇宙大爆炸留下的光波極化現象，

left over from the Big Bang,

strongly suggest that they are.

即是重力波存在的有力證據。

But despite Einstein's successes,

雖然愛因斯坦的理論蠻管用的，

when too much stuff gets concentrated

可是當太多物質聚集

in too small a space,

在極小的空間中，

like in a black hole,

比如 黑洞

the curvature of space-time becomes so large,

時空的曲率變得太大，

that his equations collapse.

愛因斯坦的公式本身也崩塌(不適用)了！

We need a new picture of space-time

所以我們需要新的時空圖像來解釋

that incorporates quantum mechanics

當導入量子力學後

to unlock the secret at the heart of black holes.

這樣我們就可以解開黑洞的秘密，

Which means there's plenty more to be discovered

就是說我們要發現的東西還有很多，

about space, time, and space-time in the future.

時間、空間、時空，來日方長！