Ask physicist Carlo Rovelli - black holes, white holes, and more
Summary
TLDR在这段视频脚本中,物理学家卡洛·罗韦利(Carlo Rovelli)分享了他对宇宙和物理学的深刻见解。他首先提出了一个有趣的问题,即如果有机会向一个外星超级智能生物或超级计算机提问,他会问什么。罗韦利选择了一个关于感受的问题,表达了他对探索未知的渴望。接着,他深入讨论了白洞的概念,解释了它们与黑洞的关系以及它们在宇宙中可能的存在形式。罗韦利还探讨了宇宙中零和无穷的概念,以及时间的单向性问题,他认为时间的方向性既不是大脑的感知,也不是时间本身的属性,而是宇宙特定历史的一种表现。最后,他提到了他的研究重点——白洞,并推荐了他的书籍,这本书不仅涵盖了他的研究成果,还分享了他在理论研究中的情感体验和思考过程。
Takeaways
- 🤔 卡洛·罗韦利认为,如果向一个全知的外星生物或超级计算机提问,他会选择询问它的感受和存在状态,而不是宇宙的秘密。
- ❓ 关于白洞是否存在的问题,罗韦利认为白洞是可能存在的,它们可能是黑洞的未来状态,物质从黑洞进入后出现在白洞中。
- 🔭 目前白洞的存在尚未在宇宙中得到证实,但理论上已经有很好的描述。它们可能是暗物质的候选者,尽管这需要复杂的理论工作来验证。
- 🚀 直接探测白洞是可能的,尽管当前技术还无法实现,但未来可能会发展出相应的探测技术。
- 🌌 宇宙是否真的存在零和无穷大?罗韦利认为,宇宙中确实有可以计数为零的事物,但无穷大是一个更微妙的概念,宇宙和空间不能无限分割。
- ⏳ 时间的单向性既不是大脑感知的结果,也不是时间本身的属性,而是由于宇宙的特定排列方式,导致了过去和未来的差异。
- 📚 罗韦利的书不仅讲述了关于白洞的研究,还涉及了理论研究的过程、情感和思考方式。
- 🧐 罗韦利提出,尽管物理定律本身不区分过去和未来,但宇宙的熵增方向性体现了时间的箭头。
- 📈 他的主要工作集中在量子引力领域,试图计算空间的最小单位,证明空间不能无限分割。
- 🌟 黑洞内部的奇点并不是位于中心的某一点,而是存在于未来,无论你在黑洞的哪个位置,最终都会被奇点挤压。
- 🕳️ 白洞和黑洞非常相似,它们通过时间反转相互关联,如果我们将黑洞的影像倒放,就会得到白洞。
- 🔬 罗韦利认为,尽管我们对黑洞内部和奇点有一定的了解,但对于穿过奇点后会发生什么,仍是基础物理学中的一个未解之谜。
Q & A
如果卡洛·罗韦利只能向来自另一个星球的超智能生物或超级计算机问一个问题,他会问什么?
-卡洛·罗韦利会问:'你感觉如何?在一个不同的星球上感觉如何?知道一切是什么感觉?它是否给你带来快乐?' 然后他会保留自己的乐趣,尝试发现宇宙中已知的事物。
白洞是黑洞的对立面吗?它们之间是否存在跨维度的相互作用?
-白洞是爱因斯坦广义相对论方程的一个特定解,描述了宇宙中可能发生的现象。白洞和黑洞非常相似,实际上它们通过时间反演相互关联。在黑洞内部,无论你在哪里,最终都会被奇点挤压,而奇点并不是在空间中的一个点,而是在未来。
白洞真的存在吗?如果存在,它们抛出的物质来自哪里?
-白洞确实可以存在。当你在黑洞内部,物质向你挤压时,接下来你会发现自己在白洞中。所有原本在黑洞内部的物质都会发现自己在白洞中。白洞抛出的物质来自之前进入黑洞的物质。
我们如何能够看到或检测到白洞?
-我们可以通过两种方式检测白洞:一是通过观察它们的影响并与自然界中观察到的现象进行比较,看是否可能是白洞;二是通过直接探测,比如构建一种机器等待白洞经过并检测到它。
暗物质可能是由许多小的白洞组成的吗?
-这是一种可能性,但需要复杂的理论工作来验证这个假设是否合理,包括考虑黑洞在过去是否可能形成、衰变成为白洞,以及这是否与宇宙学相一致。
宇宙中真的有零和无穷大吗?
-宇宙中确实有可以计数为零的事物。至于无穷大,它更微妙,因为我们经常使用无穷大来描述宇宙,比如空间中有无限多个点。但现实中,没有什么是真正的无限。宇宙不是无限的,空间不能无限分割。
时间本身是单向的,还是只是我们大脑感知的方式?
-时间的方向既不是依赖我们的大脑,也不是时间本身的属性。正确的答案是两者都不是。我们研究的现象,即使我们的大脑与之无关,也显示出时间的方向。另一方面,我们知道物理的基本定律并不区分过去和未来。时间的方向是由宇宙的特定历史决定的,我们用熵的概念来捕捉这种差异。
卡洛·罗韦利在量子引力领域的主要工作是什么?
-卡洛·罗韦利的主要工作是试图基于爱因斯坦的理论和量子力学来计算空间的最小单元大小,这表明空间不能无限分割。
白洞的研究对理解宇宙有什么重要意义?
-白洞的研究有助于我们理解黑洞和宇宙的演化过程。白洞可能存在于宇宙中,并且可能与暗物质有关,这为我们提供了探索宇宙奥秘的新途径。
卡洛·罗韦利的书《七堂极简物理课》主要讲述了哪些内容?
-这本书不仅讲述了白洞,还讲述了进行理论研究的过程,包括在已知知识的边缘进行猜测,尝试想象我们的知识片段如何组合在一起,以告诉我们更多超越当前知识的内容。书中还涉及了很多个人感受、情感、担忧以及进行理论研究的思考方式。
如何理解黑洞和白洞之间的关系?
-黑洞和白洞通过时间反演相互关联。在黑洞内部,物质只能向中心聚集,而在白洞中,物质只能向外抛出。黑洞内部的物质最终会在白洞中出现,这意味着两者之间存在一种转换关系。
为什么说时间的方向是由宇宙的特定历史决定的?
-时间的方向是由宇宙从过去到未来的特定排列方式决定的。宇宙在过去的低熵状态和未来的高熵状态之间的这种差异,定义了时间的一个特定方向,即从过去向未来的熵增方向。
卡洛·罗韦利如何看待理论物理学研究中的个人感受和情感?
-卡洛·罗韦利认为理论物理学研究不仅仅是理性的思考,还涉及到个人的感受、情感、担忧和恐惧。他在书中分享了他在进行理论研究时的个人体验,包括对未知的好奇、对错误的恐惧以及对新发现的兴奋。
Outlines
🌌 宇宙探索:与超智能生物的对话
Carlo Rovelli,一位物理学家,在视频中回答了观众的一些问题。他提出了一个假设性问题,如果他有机会向一个来自外星的超智能生物或一个知道宇宙一切的超级计算机提问,他会选择问:“你感觉如何?在另一个星球上的感觉如何?知道一切是什么感觉?这是否给你带来了快乐?”Rovelli表达了他对于探索宇宙未知事物的渴望,即使外星生物或超级计算机已经知晓答案。
🌟 白洞与黑洞:宇宙的另一端
Rovelli讨论了白洞和黑洞的概念,指出白洞是爱因斯坦广义相对论方程的一个解,描述了宇宙中可能发生的现象。他解释了白洞和黑洞之间的相似性,以及它们是如何通过时间反转相互关联的。Rovelli还探讨了黑洞内部和奇点的本质,以及物质如何从黑洞转移到白洞。他提到,尽管理论已经很好地描述了白洞,但我们仍不确定它们是否真实存在于宇宙中。他提出了两种可能的探测白洞的方法:通过观察它们对周围环境的影响,或通过直接探测。此外,他还提出了一个假设,即暗物质可能由许多小的白洞组成。
⚛️ 宇宙的数学语言:零与无限
Rovelli讨论了宇宙中零和无限的概念,指出这些数学概念被用来描述宇宙。他强调,宇宙中确实存在可以用零来描述的事物,例如五米长的iPad的数量。对于无限,他认为宇宙并不是无限的,空间不能无限分割,时间本身也可能不是无限的。他的工作主要集中在量子引力领域,旨在计算空间的最小单位,表明空间不能无限分割。Rovelli认为,尽管无限是一个有用的概念,但它并不精确地描述宇宙,而是一个用来表示“很多”的近似值。
⏳ 时间的方向:过去与未来
Rovelli探讨了时间的方向性问题,这是一个在物理学和神经科学中广泛讨论的话题。他认为,时间的方向性既不完全取决于我们的大脑,也不是时间本身的属性。他通过一个比喻说明了方向性是如何由环境的布局决定的,就像在山上北面是上坡,南面是下坡一样。对于宇宙,时间的方向性与宇宙的历史有关,我们通过熵的概念来捕捉过去和未来的不同。熵在宇宙的过去较低,在将来较高,这决定了过去和未来的方向性。Rovelli认为,我们对时间流逝的感觉、现在的固定性和未来的开放性是在我们的大脑中感觉到的,但时间方向性的根本差异是独立于我们的大脑的。
Mindmap
Keywords
💡白洞
💡黑洞
💡时间反转
💡奇点
💡暗物质
💡量子引力
💡熵
💡时间的方向性
💡零和无穷
💡理论物理研究
💡宇宙的结构
Highlights
卡洛·罗韦利(Carlo Rovelli)是物理学家,他将回答观众的问题,并探讨宇宙和物理学的奥秘。
罗韦利思考如果只能向一个外星超级智能生物或超级计算机提问,他会选择询问对方的感受和对知识的体验。
白洞是爱因斯坦广义相对论方程的一个解,与黑洞类似,但通过时间反转相关。
黑洞内部和奇点的描述,奇点并非位于中心,而是存在于未来。
罗韦利认为,穿过黑洞的奇点后,物质会继续存在于白洞中。
白洞的存在是理论上可能的,但尚未在宇宙中得到证实。
暗物质可能是由许多小的白洞组成的,这是白洞存在的一个潜在证据。
直接探测白洞的可能性,尽管技术上具有挑战性,但并非不可能。
宇宙是否真的存在零和无穷大的概念,罗韦利认为这些都是描述宇宙的工具,而非宇宙本身的属性。
时间和时间的单向性不是由大脑感知决定的,而是由宇宙的历史和熵的变化决定的。
罗韦利的主要研究领域包括白洞、量子引力,他写了一本关于这些研究的书。
书中不仅讨论了白洞,还涉及了理论研究的过程,包括情感、恐惧和思考方式。
罗韦利强调,时间的方向性是由宇宙的特定排列方式决定的,而非时间本身或大脑的感知。
空间不能无限分割,存在最小的空间单元,这与罗韦利在量子引力中的研究相符。
罗韦利认为,尽管我们可以使用零和无穷大来描述宇宙,但宇宙本身并不是无限的。
时间的感知与大脑有关,但时间的方向性是宇宙历史的一种表现,与大脑无关。
罗韦利提出,宇宙的过去和未来的差异,以及时间的定向性,可以用熵的概念来解释。
罗韦利的书是个人的,不仅讨论了他的研究,还分享了理论研究中的情感体验。
Transcripts
- Hi, I'm Carlo Rovelli.
I do physics and I'm going to answer some of your questions.
So welcome to "Ask Carlo."
(upbeat music)
@carloft, so it's my same name.
"If Carlo Rovelli could ask only one question
to a super intelligent creature from another planet
or a supercomputer
that knows pretty much everything about the universe
and the physics of it, what would he ask?"
This is a question that I have thought about.
I've considered, what would I do with the situation?
So I would ask the question, "How are you?
How you feel?
How does it feel to be in another planet?
And how does it feel to know everything?
Does it give you happiness or not?"
And then I will keep for myself
the pleasure of trying to discover
things about the universe that he does know already.
Question number two.
"It has been suggested that white holes
are the opposite of black holes,
as black holes supposedly have a singularity at the centre.
Could there be a possibility
of inter-dimensional interaction?"
Now, careful, a white hole is,
first of all and essentially,
a particular solution of the equations written by Einstein
back more than one century ago,
the equation of general relativity.
And this solution, describe a possible shape of space time,
describe a possible phenomenon
that can happen in the universe.
There is another similar solution, which is black hole.
The two are very similar, in fact,
because they're related by time inversion.
So if you could imagine filming one
and projecting the film backward,
you would get the other one.
The interior of black holes and the singularity,
we know pretty well how it is,
and the singularity is not at the centre.
Imagine you're in a black hole
and you go down to the centre.
You could imagine you could move
in a black hole a little bit.
Sometimes often we think that...
Here's an image of a black hole.
It's like a long tube,
and if you go down to the centre, you get here.
And often people think that the singularity is here,
but it's not true.
The singularity is not here.
The singularity is all over in the future.
So if you go in and wait,
whether you are here or here or here or here or here,
you get squeezed by the singularity.
So imagine this thing is actually shrinking
and squeezing you into a singularity.
So singularity is not at the same time.
It's in the future.
A black hole is like a room.
It's not somewhere in the room with singularity.
Wherever you are, you're gonna hit
or be hit by the singularity.
So what happened at the singularity
is the same question of what happened next
after everything squeezed.
And we are not sure of what happens,
but that's one open question in fundamental physics.
But what I think
is that there is no dimensional transmutation,
not anything like that.
You simply jump around the other side of the singularity.
You continue to exist into a white hole.
This takes us to the third question.
"Can a white hole exist?
If it can, where does the matter it throws out come from?"
And the answer to the question is yes.
I think that when you're inside a black hole
and things shrink around you,
what happened next is that you find yourself
in a white hole.
And so everything which was inside the black hole
finds itself in the white hole.
In the black hole, you could only go down.
In the white hole, you could only go up.
So where does it come from,
the matter that exit the white hole?
Well, it comes from the matter
that enters the black hole before.
The current situation about white holes
is that we know them well
because we have the theory,
mathematical theory that described them well,
like we knew black hole before seeing them.
But we don't know if they're realised in the universe.
Now, one possibility that they are realised in the universe
is that they come from the future of black holes,
or black holes becomes white holes later on.
How could we see them, detect them?
And there are two directions for that.
One is by seeing their effect,
their effect,
and by comparing with things we see in nature
and see whether what we see could be white holes.
And the other is by direct detection.
First possibility, a tempting possibility,
is that we have already seen them,
in what astronomers called dark matter,
this strange sort of powder halo,
which is around galaxies
of which we see the gravitational effects,
but we don't know what it is
because they're not things which interact with light.
So we don't see them, we see their effect.
It is possible that the dark matter could be made
by many small white holes.
To test whether this possibility is real,
it's a complicated story
because it requires asking whether it's possible
that black holes in the past could be formed,
decayed, become white hole.
So is this consistent with this of cosmology?
It's a complicated theoretical works
of seeing if this hypothesis
about dark matter is plausible.
Second possibility is by direct detection,
namely constructing a machine here
and waiting a white hole to pass by
and detecting it.
And there are theoretical papers out there
which make hypotheses about how this machine could be made.
It's not impossible.
It's not immediately possible with current technology.
But I would say 30 years ago,
it seemed totally impossible to see gravitational waves,
to build a machine that detect the gravitational waves.
Detecting a passing by white hole
should not be much more complicated than that.
The expected size of them is small.
White holes existing in the universe
are expected to be very small.
So they'd be teeny things that could fly by.
They interact only gravitationally,
so we cannot touch them, we cannot see them.
But we can see their gravitational pull.
So a machine would be sort of many little electronics
that feel the gravitational pool
of something that goes down.
One of the hypothesis of how to build such a machine
is a recent paper that I've just sent to journals
a few weeks ago.
So question number four,
"Does the universe really have zeros and infinities?"
This is a very good question.
It's not that universe has zeros
or number three or infinities.
It's that we use zero or infinity
or number three, number five, number seven,
for describing the universe.
So the right question is,
are there things in the universe
which can number zero of them?
Yeah, of course.
I mean, because I can define something
and then count how many of these things are.
The number of them can be zero.
Oh man, this is an iPad.
I mean, how many iPad long five metres exist?
Zero as far as I know.
Infiniti is much more subtle
because we often describe the universe using infinity.
We say that in space, an infinite number of points,
or we may think maybe the universe is infinite.
We can say we can go infinitely small.
I think that in reality, nothing is really infinite.
The universe is not infinite.
Space cannot be infinitely divided.
At some point, you get the minimal chunk of space.
And presumably time itself is not infinite.
In fact, my work, my main work in quantum gravity
has exactly been trying to compute
on the basis of Einstein's theory in quantum mechanics
the minimal size of a chunk of space,
which shows in fact that space cannot be infinitely divided.
So between my hands, the certain number of element of space,
huge number, but not an infinite number.
So I would say yes,
there are things which are zero in the universe.
Zero is useful.
It precisely describe the universe.
Infinite is useful,
but it does not precisely describe the universe.
It's just an approximation to say many.
Last question,
"Is time itself unidirectional
or it's just the way our brain perceive it?"
That's an important question, a beautiful question.
It's much debated.
Today, physics and neuroscience are cross-disciplines.
I think the correct answer of this question is neither.
Certainly in our perception of time,
a lot depend on our brain.
But I don't think that is correct to say
that the direction of time
is something that depend on our brain.
Because when we study phenomena
where our brain has nothing to do with it,
something that happens by itself,
this phenomena do show a direction of time.
On the other hand, it's not true either
that the direction of time is a property of time itself,
because we know, it has come as a surprise,
but we know from the basic laws of physics
that all of them don't distinguish the past from the future.
Suppose you live in a mountain, on a hill,
say Northern Italy,
and then one direction, if you go north, you go uphill,
and if you go south, you go downhill.
And then you can say, oh, to be uphill,
it's an intrinsic property of north.
No, because if you go the other side of the mountain,
you go uphill going south and downhill going north.
So what is uphill and downhill in a mountain?
It's just the arrangement of the mountains
and where you are with respect to the mountains.
So the universe in which we live
happened to be different in the past than in the future
because it's just on a particular history
that has this property.
And we capture this difference
between how the universe was arranged in the past
and how the universe happens to be arranged in the future
with this notion of entropy,
which is low in the past and high in the future.
That is, it changes in one particular direction.
And that's what makes the past different from the future.
So it's neither our brain by itself
nor time by itself.
It's just the way things are arranged
that in the past were arranged in a certain way
and the future gets arranged in another manner.
And this orients the time in the universe.
The universe's time would oriented by itself in a way.
This particular arrangement of the universe
is such that because of that,
the present happens to be full of traces of the past.
So we remember the past; we don't remember the future.
So this feeling of passage of time,
of fixity of the present, openness of the future,
that is what we feel.
It's in our brain.
But the root of the difference
between the two direction of time
is independent from our brain.
That's all.
White holes has been the main topic of my research
in physics and quantum gravity the last years
and this is the little book that I've written
telling about the research.
So if you want to know more about white holes, it's here.
But the book is not only about white holes.
It's also about what it is to do theoretical research,
what it is to be sort of the margin of what we know
and try to guess beyond it,
try to imagine how the pieces of our knowledge
could match together to tell us something more
beyond what we know.
So this is a book in which it is very personal book,
in which it's personal
not just because I talk about my own research,
but also because I talk a lot about the feeling,
the emotions, the fears, the worry,
the ways we think in doing theoretical research.
Thank you for all your questions.
Bye-Bye.
(upbeat music)
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