General relativity is just a fancy 20th-century name for gravity – the force that pulls

廣義相對論只是20世紀引力的一個花哨的名字--拉扯的力量。

stuff to the ground and keeps the planets in orbit around the sun .

並使行星保持在圍繞太陽的軌道上。

General relativity is the idea that gravity happens because space is curved – like how

廣義相對論認為，引力的發生是因為空間是彎曲的--就像... ...

when you walk along the surface of a ball, you end up curving downwards.

當你沿著球的表面行走時，你最終會向下彎曲。

Actually general relativity is the idea that space and time aren't separate – time

其實廣義相對論就是認為空間和時間不是分開的--時間

is a physical dimension, and together they form a single geometry called spacetime – and

是一個物理維度，它們共同構成了一個叫做時空的幾何體--而

gravity is caused by curvature in spacetime.

重力是由時空的曲率引起的。

Except, curvature in spacetime on its own doesn't explain gravity – I mean, just

只是，時空的曲率本身並不能解釋引力--我的意思是，只是。

because you're on a curved ball that doesn't mean you follow a specific path on the ball.

因為你在一個彎曲的球上，並不意味著你遵循球的特定路徑。

General relativity is the combination of the ideas that spacetime is curved AND that stuff

廣義相對論是結合了時空是彎曲的，以及那些東西的想法。

in spacetime obeys laws of motion : an object in motion stays in motion along a “straight”

在時空中遵循運動規律：運動中的物體沿著 "直線 "做運動。

path in curved spacetime . Like following a straight line along the surface of a ball.

在彎曲的時空中的路徑 。就像沿著球的表面走直線一樣。

But spacetime can't be curved any which way.

但時空不可能以任何方式彎曲。

Just like how a ball looks flat when you're close enough, curved spacetime is locally

就像一個球在足夠近的時候看起來是平的一樣，彎曲的時空是局部的。

flat (rather than crumpled, or something).

平坦的（而不是皺巴巴的，或者別的什麼）。

Of course, flat space makes sense, but what does it mean for spacetime to be flat?

當然，平坦的空間是有意義的，但時空平坦是什麼意思呢？

That it obeys the rules of special relativity!

它遵守狹義相對論的規則!

Finite speed of light, time dilation and length contraction, relative addition of velocities,

光速有限，時間膨脹和長度收縮，速度的相對加法。

and all that.

和所有這些。

Basically, if general relativity is like a globe, special relativity is being on the

基本上，如果說廣義相對論就像一個地球儀，那麼狹義相對論則是被在

surface of the globe (and mathematicians call the globe a pseudo-Riemannian manifold with

的表面（數學家稱地球儀為偽裡曼歧面，並有

Lorentzian signature).

Lorentzian簽名）。)

Except we still haven't said anything about what determines the curviness, or shape, of

除了我們仍然沒有說過任何關於什麼決定了曲線，或者說形狀的東西。

spacetime in the first place!

時空在第一時間!

Or why objects tend to follow straight paths in that spacetime.

或者說，為什麼在那個時空裡，物體往往會沿著直線行駛。

General Relativity is actually the idea that all the stuff in spacetime – matter, radiation,

廣義相對論其實就是認為時空中所有的東西--物質、輻射。

pressure, energy, momentum, particles, and so on – all that, together with spacetime

壓力、能量、動量、粒子等等--所有這些，加上時空

itself, obeys a set of equations called the Einstein Field Equations.

本身，服從一組方程，稱為愛因斯坦場方程。

These equations look simple if you write them in a clever way, but they're actually a

這些方程如果寫得巧妙的話，看起來很簡單，但實際上是一個

very complicated set of ten nonlinear differential equations [2nd order] that you have to solve

十個非常複雜的非線性微分方程組[二階]，你必須要解。

in order to make predictions about how spacetime will curve and how the stuff in it will move,

以便對時空如何彎曲和其中的東西如何運動進行預測。

depending on how spacetime is curving and how the stuff is moving .

取決於時空是如何彎曲的，東西是如何移動的 。

The solutions to the Einstein Field Equations of General Relativity describe gravity around

廣義相對論的愛因斯坦場方程的解描述了周圍的引力。

solitary objects like black holes or the sun or the earth, and they facilitate very accurate

像黑洞、太陽或地球這樣的單獨物體，它們有助於非常精確地測量出

predictions of orbits around these objects . But these equations aren't limited to

圍繞這些物體的軌道的預測 。但這些方程並不限於

describing just energy and matter and spacetime around the earth or sun – they can be used

圍繞地球或太陽的能量、物質和時空的描述--它們可以被用於

on the universe as a whole to describe and understand the past and present and future

宇宙的整體，以描述和理解過去、現在和未來。

of the cosmos.

的宇宙。

So.

所以，

General relativity is the idea that the universe can be described by a pseudo-Riemannian manifold

廣義相對論是指宇宙可以用一個偽黎曼歧量來描述的觀點。

representing spacetime and an energy-momentum tensor representing all matter and energy,

代表時空，代表所有物質和能量的能量-動量張量。

which together obey the Einstein Field Equations.

它們共同服從愛因斯坦場方程。

For our 3+1 dimensional universe, the predictions generated by this idea have been experimentally

對於我們3+1維的宇宙來說，這個想法所產生的預言已經被實驗證明

verified by many many incredibly precise observations, ranging from the precession of the orbit of

很多很多精確的觀測結果都證實了這一點，從天體軌道的前傾到天體的後傾，再到天體的後傾。

Mercury, to the slight drift of the moon's orbit away from the earth, to the gravitational

水星，到月球軌道稍稍偏離地球，到引力

lensing and redshift of starlight, to time dilation of atomic clocks and precession of

從星光的透鏡和紅移，到原子鐘的時間膨脹，再到星光的前傾，再到星光的後退。

gyroscopes orbiting the earth, to observations of the polarization of the cosmic microwave

繞地球運行的陀螺儀，對宇宙微波的偏振進行觀測。

background radiation, to gravitational wave detections of black hole mergers, to direct

背景輻射，到引力波探測黑洞合併，再到直達黑洞。

imaging of the black hole at the center of the Milky Way.

銀河系中心黑洞的成像。

Wait but how does general relativity explain the everyday “force” of gravity we experience

等等，但是廣義相對論是如何解釋我們日常體驗到的重力 "力 "的呢？

on earth?

世上

Well, you know how when a vehicle turns but your body's inertia makes you want to go

你知道當車輛轉彎時，你的身體的慣性會讓你想轉彎

straight and it feels like you're being pulled sideways because you're being accelerated

感覺就像你被橫向拉動 因為你被加速了

away from your straight-line path?

偏離你的直線路徑？

In general relativity an object's straight-line inertial path is actually to fall towards

在廣義相對論中，一個物體的直線慣性路徑實際上是要落向

the center of the earth, and since the surface the earth accelerates us away from that straight-line

而由於地球表面加速了我們的速度，使我們遠離了那條直線

path, we feel that acceleration as a weight or force that we call gravity [equivalence

路徑，我們感覺到加速度是一種重量或力，我們稱之為重力[等價物]。

principle].

原則]。

If you're in free fall (or in orbit), then you are following a “straight path through

如果你在自由落體（或在軌道上），那麼你遵循的是一條 "直通的道路"。

curved spacetime”, that is, you're not accelerating in spacetime, so you feel like

彎曲的時空"，也就是說，你在時空中沒有加速，所以你感覺到像

you're floating or experiencing “0 g”.

你正在漂浮或經歷 "0克"。

And that explains gravity!

這就解釋了重力！

Oops.

糟了

General relativity doesn't explain quantum mechanical phenomena, and has problems jiving

廣義相對論不能解釋量子力學現象，而且有問題，無法與量子力學相提並論

with the theory of quantum mechanics in certain extreme situations.

與量子力學理論在某些極端情況下。

Physicists have been working for over 90 years to reconcile general relativity and quantum

90多年來，物理學家一直在努力調和廣義相對論和量子

mechanics in those situations, and while we've learned a lot, we still haven't come close

雖然我們學到了很多東西，但我們仍然沒有接近。

to solving everything!

以解決一切問題!

It's hard.

這是很難的。

General Relativity works so well in most cases where we can test it, and quantum mechanics

廣義相對論在大多數我們可以測試的情況下都能很好的運行，而量子力學呢？

works so well in most cases where we can test it, and they're both so mathematically sophisticated

在我們可以測試的大多數情況下都能很好地工作，而且它們在數學上都很複雜。

and constrained and distinct from each other, that imagining a different mathematical model

互相制約和區別，想象一個不同的數學模型。

that encompasses both while being just as accurate where they're already accurate

涵蓋了這兩個方面，同時在已經準確的地方也同樣準確。

and better where they're in conflict is… very high level stuff.

而更好的是，他們在衝突中是... 非常高級的東西。

If you want even more levels of General Relativity, I have an extended version of this video on

如果你想要更多層次的廣義相對論，我有一個擴展版本的這個視頻上的

Nebula, the Streamy-award-nominated independent streaming service that's the co-sponsor

Nebula，獲得Streamy獎提名的獨立流媒體服務，是聯合主辦方。

of this video.

的這個視頻。

[short teaser of the extended video] Nebula was created by and for a collection of educational

[延長視頻的簡短預告]星雲是由併為收集教育而創建的。

video creators including Real Engineering, Mike Boyd, Up and Atom, Jordan Harrod - and

包括Real Engineering、Mike Boyd、Up and Atom、Jordan Harrod在內的視頻創作者--以及。

me - and Nebula has partnered with CuriosityStream, which offers thousands of documentaries and

我--而星雲則與CuriosityStream合作，它提供了數千部紀錄片和。

nonfiction titles to give you access to both in one go!

非小說類書籍，讓您一次性獲得這兩方面的資訊!

I recommend Vitamania, about the history and science (or lack thereof, in some cases) of

我推薦Vitamania，關於Vitamania的歷史和科學（或在某些情況下缺乏）。

vitamins and supplements.

維生素和補充劑；

Sign up for CuriosityStream using the link in the description and you'll also get access

使用描述中的鏈接註冊CuriosityStream，您還可以訪問

to Nebula, including the extended version of this video as well as an ad-free viewing

到星雲，包括該視頻的擴展版以及免廣告觀看。

experience across the site.

整個網站的體驗。

Oh yeah, and you'll also get 26% off an annual subscription to CuriosityStream.

哦，對了，你還可以享受到26%的優惠，每年訂閱《好奇心流》。