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为什么引力如此特别呢

Why is gravity different?

Gravity seems very familiar.
引力好像在生活中很常见
After all, it’s what makes stuff fall,
毕竟它能使物体下落
it’s what keeps the planets in their orbits,
引力也能使行星不脱离自身轨道
but thinking about the fundamental physics of gravity
但是思考引力物理学基础
has led scientists to question the very existence of space and time.
让科学家们开始怀疑空间和时间是否存在
This is because gravity is very different
这是因为与其他的力相比
from the other forces.
引力是非常不同的
So why is gravity so unique?
那么为什么引力如此特别呢
I’m Jared Kaplan and this is “Why is Gravity Different?”
我是Jared Kaplan 欢迎收看“为什么引力如此独特呢”
You may know that there are four fundamental forces –
你应该知道有四种基本力
electromagnetism, the weak force, the strong force,
电磁力 弱核力 强核力
and also, of course, gravity.
当然还有引力
The electromagnetic force is responsible for
电磁力的存在
the interactions of charged particles,
使带电粒子能相互作用
for magnetism, and holding electrons in their atoms.
也能引发磁力 同时也让电子束缚在原子中
The weak and strong nuclear forces
弱核力和强核力
are responsible for subatomic processes,
能支配亚原子粒子的行为
and for holding protons and neutrons together.
能把质子和中子束缚在一起
To understand these three fundamental forces,
为了理解这三种基本力
we take a reductionist approach.
我们采取了约化性方法
We take matter apart into its most fundamental constituents
我们把最重要的分解成最基本的成分
and then watch those constituents interact.
然后看看这些成分之间会发生什么反应
The enormous particle accelerators
物理学家使用的巨型粒子加速器
that physicists use are really like giant microscopes.
真的很像一个巨大的显微镜
So why do we build big particle accelerators
那么我们为什么要建造
that use high energies?
高能耗的大型粒子加速器呢
It’s because of Heisenberg’s uncertainty principle.
这源于海森堡不确定原理
To see small stuff we need big energies.
我们需要很大的能量才能看见很小的物体
It might seem like gravity is very similar to the other forces–
所有行星围绕太阳公转的事实
after all the orbits of the planets around the sun
启发了电子围绕原子核运动的猜想
were an inspiration for the idea that electrons orbit atomic nuclei–
由此可见 引力好像与其他的力相似
but in fact gravity is very different
但事实上引力
from the other forces.
和其他力十分不同
Gravity gets stronger and stronger and stronger
随着加速器的能量的增大
as you increase the energy of your accelerator,
引力会越来越强
so that if you were to try to probe gravity at a fundamental level
所以如果你试着从基本的角度来研究重力
all you’d do is make a black hole.
你只需要创造一个黑洞
And that black hole would destroy your microscope.
不过这个黑洞可能会摧毁你的粒子加速器
So we have to study gravity a bit differently.
所以我们必须用有点不一样的方式来研究重力
Our best theory of gravity
我们最先进的引力学的理论
is Einstein’s theory of general relativity.
是爱因斯坦的广义相对论
Which famously says that
最著名的说法是
the gravitational force is due to the curvature of spacetime.
时空曲率产生了引力
Fortunately, the very existence of black holes
幸运的是 黑洞的存在
points to a new way of thinking about quantum gravity.
把对量子引力的思考指向了一个新的方向
We had the first hint of a major revolution
我们首次迎来了一个重大发现
when in 1972,Jacob Bekenstein argued that
在1972年 雅各布·贝肯斯坦声称
the total information inside a black hole
黑洞的总体信息
is actually proportional to the surface area of the black hole
是与黑洞的表面积成正比
and not to its volume.
而不是与它的体积成正比
But why is this such a surprising and revolutionary insight?
但为什么这个观点如此令人惊讶且具有革命性呢
So if information is stored on areas rather than in volumes,
因为如果信息是存储在面积上而不是存储在体积上
perhaps the laws of physics should be formulated
也许物理学的定律应该
in fewer spacetime dimensions.
用更少的时空维度中的公式来表述
Why would we think something so surprising and crazy?
为什么我们会想到这么令人惊讶和疯狂的事情呢
Well, let’s take a step back and think about information.
好的 让我们退一步 想一想信息
Fundamentally, information is a description of
从根本上说 信息是
the state or the configuration of the universe.
对宇宙状态和结构的描述
On a practical level, we can think of it
在现实条件下 我们可以把它想象成
in terms of a hard drive.
硬盘驱动器
Hard drives store information with tiny little magnets,
磁盘驱动器靠小小的磁性材料储存信息
and the more magnets you have, the more information you have.
磁性材料越多的话 你能存储的信息也就越多
But that means that information should
但这意味着信息
scale with the volume of our hard drive.
需要与硬盘驱动器的容量成正比
But What happens if our hard drive falls into a black hole?
但是如果我们的硬盘驱动器掉进黑洞里会发生什么
The information on the hard drive won’t be lost,
硬盘驱动器的信息不会丢失
instead it will be encoded in the state of the black hole.
相反它会在黑洞状态下被编码
Yet, if the total amount of information a black hole can hold
然而如果一个黑洞能容纳的信息总量
is proportional to its surface area,
与表面积成比例
it means,actually
这意味着 实际上
that intuitive volume scaling law of our hard drive was wrong.
硬盘上直观的体积缩放定律是错误的
This says that volume, which is essentially space itself,
这说明本质上就是空间的体积
isn’t fundamental.
其实不是最基本的
In other words, the fundamental theory of gravity
换句话说 重力基本定律
should have fewer dimensions.
需要基于更小的纬度
The area law challenges many very basic principles.
面积定律挑战了很多基本原理
It calls into question
它引发了一个问题
whether stuff can interact with nearby stuff via forces.
物质是否可以通过力与附近的物质相互作用
This leads to a new way of thinking about physics,
这引发了一种新的思考物理学的方式
where the Universe is a hologram.
把宇宙是看作一个全息图
Just as a hologram provides a three-dimensional image
正如全息图可以从二维影像中
from a two-dimensional plate,
提供三维影像一样
the fundamental description of our Universe
当我们身处一个虚幻的三维世界中
could be lower dimensional,
我们对宇宙的基本描述
while we experience an illusory three-dimensional world.
可以是更低维度的
Applying this idea to black holes,
把这个想法运用到黑洞里
we can look at the information in the lower dimensional theory of physics
我们可以在物理的低维理论中研究这些信息
to unpack the information in the black hole.
来解开黑洞中的信息
So because black holes would break our microscope,
因为黑洞可以破坏我们的粒子加速器
we can’t study quantum gravity in the same way
我们不能像研究其它基本力那样
that we studied the other fundamental forces.
以同样的方式去研究量子引力
But fortunately black holes have provided us
但幸运的是 黑洞给我们提供了
with a way to think about gravity on a quantum level.
一个能在量子能级上研究引力的方法
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视频来源

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