Why Black Holes Break The Universe

Summary

The script delves into the mysteries of black holes, exploring their role as the universe's abysses where even light cannot escape. It explains the concept of spacetime curvature and the escape velocity, leading to the theoretical prediction and eventual discovery of black holes. The paradox of information loss within black holes is highlighted, discussing the implications of Hawking radiation and the holographic principle. The video invites viewers to ponder the unresolved questions surrounding black holes and their significance in the quest for a unified theory of quantum gravity.

Takeaways

• 🌌 The script discusses the concept of black holes as regions of spacetime with such intense gravity that not even light can escape.
• 📚 It explains that black holes challenge our understanding of theoretical physics and the nature of reality, particularly concerning the concept of information loss.
• 🚀 The idea of escape velocity is introduced, which is the minimum speed needed for an object to escape the gravitational pull of a celestial body.
• 🔮 John Mitchell's prediction of 'dark stars' and Einstein's theory of general relativity are highlighted as foundational to the modern understanding of black holes.
• 🌌 The script touches on the historical discovery of Cygnus X-1, which provided the first evidence of the existence of black holes.
• 💥 It delves into the paradox of information loss in black holes, which contradicts the principle of unitarity in quantum theory, suggesting all processes are reversible.
• 🌐 The concept of singularity is explained as a point in time and space where the warping of spacetime is so severe that space and time effectively swap roles.
• 🌡️ Stephen Hawking's discovery of black hole evaporation through a process now known as Hawking radiation is discussed, challenging the idea of black holes as eternal.
• 🔒 The script presents the 'no-hair theorem', which states that black holes can be described by only three properties: mass, spin, and charge, with no other distinguishing features.
• 🔁 It explores the holographic principle, suggesting that all information contained within a 3D volume can be represented on its 2D surface, implying we are all 'holograms'.
• 🔍 The importance of studying black holes for gaining insights into a unified theory of quantum gravity, potentially the 'theory of everything', is emphasized.

Q & A

What is the main theme of the video script?

The main theme of the video script is the exploration of black holes, their properties, and the theoretical challenges they pose to our understanding of physics, particularly the information paradox and the principles of unitarity, equivalence, and locality.

What is a black hole and why is it considered a major problem for theoretical physics?

A black hole is a region of spacetime where gravity is so strong that nothing, not even light, can escape it. It poses a major problem for theoretical physics because it challenges the principle of unitarity, suggesting that information could be destroyed, which contradicts the idea that all processes are reversible in quantum theory.

How does the concept of spacetime curvature relate to the behavior of gravity?

In Einstein's theory of general relativity, gravity is not a force but a curvature of spacetime caused by mass. Objects like Earth curve spacetime, and other objects move along the shortest path, or geodesic, through this curved spacetime, which we perceive as the effect of gravity.

What is the escape velocity and how does it relate to black holes?

The escape velocity is the minimum speed needed for an object to break free from the gravitational pull of a celestial body. In the context of black holes, if the mass of an object is so great that the escape velocity equals the speed of light, it is considered a black hole because nothing can escape its gravity.

Who was the first to predict the existence of black holes and what did they call them?

John Mitchell was the first to predict the existence of black holes in 1783. He called them 'dark stars', theorizing that there should be a mass so great that its escape velocity equals the speed of light.

What evidence supports the existence of black holes?

Evidence supporting the existence of black holes includes x-ray binaries, tidal disruption events, gravitational wave astronomy, and direct imaging. The astronomical discovery of Cygnus X-1 in 1971 provided the first strong evidence of a black hole.

What is the principle of unitarity and why is it challenged by black holes?

The principle of unitarity states that all processes are reversible in quantum theory. It is challenged by black holes because anything that falls into a black hole seems to be lost forever, suggesting that information is not conserved, which contradicts unitarity.

What is the significance of the singularity in a black hole?

The singularity in a black hole is often thought of as the center of the black hole where spacetime curvature becomes infinite. However, it is better described as a future moment in time from which there is no escape, indicating a point of no return in the black hole's gravity well.

What is Hawking radiation and why is it significant for the information paradox?

Hawking radiation is the theoretical prediction that black holes are not completely black but emit small amounts of thermal radiation due to quantum effects near the event horizon. This is significant for the information paradox because it suggests that black holes can lose mass and eventually evaporate, raising questions about the fate of the information they have consumed.

What is the holographic principle and how does it relate to black holes?

The holographic principle suggests that all the information contained within a volume of space can be represented on the boundary to that space. In the context of black holes, it implies that the information about the 3D space inside the black hole can be encoded on its 2D event horizon, challenging our understanding of information capacity and conservation.

What is the firewall paradox and how does it challenge our understanding of black holes?

The firewall paradox arises from the idea that if Hawking radiation particles are entangled with particles inside the black hole, then there must be a high-energy 'firewall' at the event horizon that destroys information. This challenges the equivalence principle and our understanding of locality, suggesting that information cannot escape a black hole intact.

What are some of the proposed solutions to the black hole information paradox?

Proposed solutions to the information paradox include the idea that information is leaked through baby universes, black holes reversing into white holes, the existence of micro wormholes, or that information is encoded in the Hawking radiation in a way that preserves unitarity but is not yet understood.

Outlines

00:00

🌌 Journey into the Unknown: Black Holes

The script introduces the concept of black holes as regions of spacetime with such immense gravity that not even light can escape. It explains the historical development of the idea, from John Mitchell's prediction of 'dark stars' to Einstein's theory of general relativity and the discovery of Cygnus X-1. The video aims to explore the mysteries of black holes, their role in the universe, and the challenges they pose to our understanding of physics.

05:01

🔥 The Information Paradox: Black Holes and Quantum Theory

This paragraph delves into the conflict between black holes and the principle of unitarity in quantum theory, which states that all processes are reversible. It discusses the concept of information loss within black holes, the role of singularity, and the implications of Stephen Hawking's discovery of black hole evaporation through Hawking radiation. The script also touches on the no-hair theorem and the challenges of reconciling the loss of information with the expectation of reversibility in physical processes.

10:03

🌐 Entanglement and the Paradox of Black Hole Information

The script explores the role of quantum entanglement in the paradox of information loss in black holes. It explains how the entanglement of particles created near the event horizon leads to a dilemma for information escaping as Hawking radiation. The paragraph also introduces the concept of the holographic principle, suggesting that all 3D information can be encoded on a 2D surface, which has implications for understanding the nature of black holes and the conservation of information.

15:04

🔮 Theoretical Resolutions and the Firewall Controversy

This section discusses various theoretical approaches to resolving the black hole information paradox, including the possibility of information being ejected through baby universes, white holes, or wormholes. It also mentions the idea of micro wormholes and the concept of a multiverse for information conservation. The paragraph introduces the controversial idea of the firewall, a layer at the event horizon that could potentially destroy information, and the ongoing debate among physicists regarding these theories.

20:07

🚀 The Quest for Understanding: Black Holes and the Future of Physics

The final paragraph reflects on the importance of studying black holes for advancing our understanding of physics, particularly in the search for a unified theory of quantum gravity. It acknowledges the challenges of observing phenomena like Hawking radiation and the need for more data. The script concludes by emphasizing the value of continued research into black holes and encourages viewers to stay curious about the mysteries of the universe.

Keywords

💡Black Hole

A black hole is a region of spacetime exhibiting gravitational acceleration so strong that nothing, not even light, can escape it. In the video, black holes are central to the theme, illustrating the concept of spacetime curvature and the limits of our understanding of gravity and light. The script mentions black holes as 'abysses of the universe' and discusses their role in theoretical physics and their impact on the principle of unitarity.

💡Spacetime

Spacetime is a framework in which space and time are considered as a unified whole, as introduced by Einstein's theory of relativity. The script uses the concept of spacetime to explain how gravity is not a force but a curvature of spacetime caused by mass, and how this curvature affects the path of objects, including light, near a black hole.

💡Escape Velocity

Escape velocity is the minimum speed needed for an object to break free from the gravitational attraction of a celestial body without further propulsion. The script refers to escape velocity in the context of John Mitchell's prediction about a mass so great that its escape velocity equals the speed of light, which leads to the concept of dark stars or black holes.

💡General Relativity (GR)

General Relativity, formulated by Albert Einstein, is a theory of gravitation that describes gravity not as a force but as a curvature of spacetime caused by mass and energy. The script discusses GR in the context of Karl Schwarzschild's solution and its implications for the existence of black holes.

💡Event Horizon

The event horizon is the boundary around a black hole beyond which events cannot affect an outside observer. The script uses the term to describe the point of no return for anything falling into a black hole and to discuss the paradox of information loss and the concept of Hawking radiation.

💡Singularity

In the context of black holes, a singularity is the point at the core where density is theoretically infinite, and spacetime curvature becomes infinite. The script mentions the singularity as a point in our future from which we cannot avoid reaching, indicating the extreme warping of spacetime at this point.

💡Hawking Radiation

Hawking radiation is a theoretical process by which black holes can slowly lose energy and mass, as a result of quantum effects near the event horizon. The script explains this phenomenon as a process that leads to the eventual evaporation of black holes and raises questions about the conservation of information.

💡Unitarity

Unitarity in quantum mechanics is the principle that total probability must sum to one, implying that all processes are reversible. The script discusses the conflict between unitarity and the apparent information loss in black holes, which seems to violate this principle.

💡No-Hair Theorem

The no-hair theorem states that a black hole can be described by only three parameters: mass, charge, and angular momentum. The script refers to this theorem to explain why the Hawking radiation emitted by a black hole is purely thermal and does not carry information about the matter that fell into the black hole.

💡Quantum Entanglement

Quantum entanglement is a phenomenon where particles become interconnected and the state of one particle is dependent on the state of another, no matter the distance between them. The script discusses entanglement in the context of Hawking radiation and the information paradox, explaining how entanglement prevents information from being retrieved from a black hole.

💡Holographic Principle

The holographic principle suggests that all the information within a volume of space can be represented on the boundary to the region. The script mentions this principle in the context of black hole complementarity and the idea that the information content of a black hole can be described by its 2D event horizon, challenging our understanding of 3D space.

Highlights

The speaker embarks on a journey to explore black holes, a feat unparalleled in space exploration.

Black holes are described as regions of spacetime, not physical objects, where even light is trapped.

The concept of geodesics is introduced, explaining how objects follow the shortest path in curved spacetime due to gravity.

Einstein's theory of general relativity is highlighted, emphasizing the absence of force and the presence of curved spacetime.

The escape velocity concept is discussed, relating it to the speed needed to overcome Earth's gravity.

John Mitchell's prediction of dark stars, which are massive enough to have escape velocities equal to the speed of light, is mentioned.

Karl Schwarzschild's solution to general relativity and its implications for the existence of black holes are explored.

The discovery of Cygnus X-1 in 1971 is noted as the first evidence of black holes, supporting Einstein's theory.

Observational evidence for black holes is discussed, including x-ray binaries, tidal disruption events, and gravitational wave astronomy.

The role of black holes in the universe, particularly their presence in the center of galaxies, is highlighted.

The concept of unitarity in quantum theory is introduced, emphasizing the reversibility of processes and the conservation of information.

The problem of information loss in black holes is discussed, challenging the principle of unitarity.

Stephen Hawking's discovery that black holes can evaporate through Hawking radiation is mentioned, challenging the permanence of black holes.

The concept of the no-hair theorem is introduced, stating that black holes can be described by only three properties: mass, spin, and charge.

The holographic principle is discussed, suggesting that all 3D phenomena can be represented on a 2D surface.

The idea of black hole complementarity is presented, suggesting that information is conserved despite appearing to be lost.

The potential existence of firewalls at the event horizon of black holes is discussed, as a possible solution to the information paradox.

The need for more data and observational evidence to resolve the information paradox and understand black holes is emphasized.

The study of black holes is suggested as a key to developing a unified theory of quantum gravity.

Transcripts

- Tonight, my friends, we stand on the brink

of a feat unparalleled in space exploration.

I will travel where no man has dared to go.

- Into the black hole?

- Why, that's crazy!

(groaning) (soft dramatic music)

- Black holes are the abysses of the universe.

They're not really a thing,

but rather a region of spacetime

folded into an embrace so tight

that even light is forever ensnared.

And it's this nihilism that poses a major problem

for theoretical physics,

one which could unravel our very understanding

of the universe itself.

How does a black hole trap light?

If I throw a ball into the air, it falls back down

to Earth due to gravity following a curve,

or at least to me it looks like a curve.

But really the ball is following the shortest line,

also called a geodesic,

and it's spacetime that's truly curved.

It's the mass of the Earth that curves spacetime,

and if we made it heavier, then we'd increase that curvature

and thus the ball would appear to follow a tighter curve

back to the ground.

Curiously then, although we often speak of gravity

as a force, in this picture that Einstein painted for us,

there is no force, just curved spacetime.

Now, if I threw the ball hard enough, it would travel higher

and thus take longer to come back down.

And if I threw it really hard, I could give it enough speed

that it totally escaped Earth's gravity

and flew out into deep space.

The minimum speed needed to achieve this

is known as the escape velocity,

and classically it can be solved

by setting the kinetic energy of the ball

equal to its gravitational potential energy.

In 1783, John Mitchell did exactly that for a beam of light.

He predicted that there should exist a certain mass,

which is so great

that the escape velocity equals the speed of light.

Mitchell called these dark stars,

but nobody really took them very seriously

until GR came along.

That's Einstein's theory of general relativity.

While serving for Germany during the First World War,

Karl Schwarzschild found a solution to GR,

something that Einstein did not expect

to be achieved so easily,

but his solution researched the possibility

of these dark stars,

something considered implausible by Einstein,

and many others.

By 1971, the astronomical discovery of Cygnus X-1

provided the first evidence that this wasn't a trick

of the math, but a real phenomenon,

a black hole as physicist John Wheeler later dubbed them.

Of course, since then we've accumulated a wealth

of observational support for their existence,

from x-ray binaries to tidal disruption events,

from gravitational wave astronomy to direct imaging.

These enigmas that were so distasteful to Einstein

are now understood to be a critical component

to the universe, for example,

with a super massive black hole

appearing to be located in the center of every galaxy.

Before we explore further,

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Now back to the video.

Black holes are intoxicating

because of their finality, an absolute end.

Anything that falls in can never come out,

but that also raises a problem.

They seemingly destroy information for breakfast.

In quantum theory, a basic precept is so-called unitarity,

which essentially states

that all processes are, in principle, reversible.

For example, if I throw a book into a fire,

it will quickly smolder, burn, and dissipate away,=

into fine particles of smoke and ash.

In principle, unitarity dictates that we should be able

to collect up all of those particles,

piece them back together

and reconstruct every word on every page.

Of course, in practice you'd never be able to pull this off,

but in theory, it is possible.

This principle of unitarity

is often cast as a conservation law for information

akin to the conservation laws

that we have for energy and momentum.

But really, it's best to think of it

as a statement of reversibility.

Starting from some initial state,

we should be able to calculate the final state

and vice versa, from the final state,

we can go back and calculate the initial state,

hence reversible.

The black holes are the cosmic wrecking ball

to the principle of unitarity.

If I throw a book into the black hole,

then those words, that information

becomes trapped within a region of spacetime

from which nothing can escape.

It's true that the book's mass

will cause a slight ripple in spacetime

as it falls in, like the black hole merge events

observed by LIGO recently.

But it turns out that those gravitational waves

do not carry enough information away with them

to reconstruct the words on the page.

Now, as that book falls further into that dark abyss

far beyond the event horizon,

it will eventually reach the singularity.

We usually think of the singularity as a location in space,

the center of ablack hole.

But really, the warping of spacetime

is so severe here that space and time swap roles.

And really, the singularity is best described

as a future moment in time,

a point in our future from which we cannot avoid reaching

anymore than we can avoid tomorrow from happening.

What happens when you reach the singularity

is anyone's guess,

general relativity explodes to infinities at this point.

This uncertainty gave us this hope

that the apparent destruction of information was not real.

Maybe the information just gets trapped right down there

near the singularity or something.

At the end of the day, it didn't really matter

because black holes seemed to live forever,

and hence, we never actually have to deal

with this information loss.

This convenient excuse fell apart

when Stephen Hawking came along

and showed that black holes don't live forever

as initially assumed.

Quantum theory demands that they slowly evaporate.

The event horizon is just a region of empty space,

and like all empty space,

Heisenberg's Uncertainty Principle

allows for the spontaneous creation of particle pairs

fizzling in and out of existence.

Usually, these particles form

and merge within the briefest of intervals

popping in and out of existence,

so fast that the universe

doesn't have a chance to notice and complain.

But if this particle pair pops up either side

of the event horizon,

one can fall in and the other can escape.

From the outside,

the black hole seems to radiate energy away,

which means by e equals mc squared, it is losing mass.

This Hawking radiation means that black holes

are gradually, very, very gradually, losing mass,

and thus they will eventually die.

It's an unsettling thought.

Not only do stars eventually die,

but even black holes one day perish.

So the fact that black holes die

means that we cannot ignore the information

that they gobbled up.

By the principle of unitarity,

we expect reversibility,

so I should be able to collect up all that Hawking radiation

like the smoke and ash from the fire

and reconstruct the book.

But Hawking radiation doesn't comply,

which can be understood in two ways.

First, according to general relativity,

a black hole can be completely described

by just three numbers,

its mass, its spin, and its charge.

It has no surface features, no texture,

and we call this the no-hair theorem.

As a result, the Hawking radiation they emit

can be thought of as purely thermal radiation, heat,

and in fact, the temperature of that heat

is completely governed by the mass of the black hole.

So if we collected up all the Hawking radiation,

we could reconstruct the mass

of everything that fell into the black hole over time,

but we wouldn't be able to reconstruct the arrangement

of the particles that go into that mass.

We couldn't reconstruct the book.

The second way to understand this

is through quantum entanglement.

When a pair of particles pop up on the horizon,

they are always entangled.

This means that they are described by not two-way functions,

but by just one joint way function,

which describes the superposition of their states.

So for example, this wave function might say

that the sum of the spins of these two particles is zero,

but it doesn't tell us which one is up

nor which one is down.

When we measure one of these two particles,

the entanglement breaks

and this measured particle

is forced to choose one of those two states,

which instantaneously causes the other particle

to choose the opposite state.

In this way, the ledger remains a balance.

We don't accidentally end up with two up spins by mistake.

By the way, if you're wondering, no, you cannot use this

for faster than light communication,

see our earlier video as to why.

Now for Hawking radiation, this entanglement poses a barrier

to getting information out of the black hole.

Let's say that I threw into a black hole the information XY.

For this information to escape,

we can imagine one Hawking radiation particle escaping

at some later time and carrying away the X,

and then at an even later time,

one carrying away the information Y.

But the problem is how

does that second emitted particle know to carry Y

and not X?

That implies that it somehow knows

that X has already been emitted.

So to keep apprised of the full ledger

of emitted information,

we need these emitted particles

to be entangled to one another.

Fine, but there's the problem,

because remember that those Hawking radiation particles

are already entangled to their negative energy partner

that fell into the black hole.

And entanglement, like lobsters, are strictly monogamous.

There's no mistresses or swinger parties here.

They cannot be polygamously entangled.

So this means that we have a paradox.

Now, whenever we have a paradox,

we can typically resolve them

by removing one of the assumptions

upon which the paradox sits.

So for example, with the famous Fermi paradox,

which is where are all the aliens,

we can resolve that by trivially removing the assumption

that aliens exist.

Paradox resolved.

- No!

No!

(glass breaking)

- So what are the assumptions here?

Well, there are three basic ingredients,

the principle of unitarity, which we've already met,

and then on top of that,

we have the equivalence principle, and locality.

The equivalence principle is Einstein's happiest thought

that if someone fell from a roof,

they would not feel their own weight

as if there were no gravity.

A consequence of this

is that when someone passes the event horizon

of a black hole,

they wouldn't actually experience anything different.

They wouldn't notice any demarcation.

So that means that outside the black hole

we have just empty space.

And, similarly, on the horizon,

we also just have empty space,

hence why Hawking radiation can occur there.

The third preset is locality,

which is the trickiest to explain,

but essentially says that if you drop a stone in a pond,

the sound, the splash, and the resulting ripple

don't happen everywhere at once,

they are localized to a specific point.

It's pretty hard to imagine classical physics

without locality.

And so you can see that all three of these precepts

are foundational to modern physics,

and it would be painful to give up any of them.

So which is it?

Well, we don't know,

but certainly many physicists

have come up with many different ideas.

For example, in a famous wager by Hawking

and Kip Thorne against John Preskill,

they hedged that the information

that falls into the black hole

was irretrievably lost to the universe,

although it has to be said

that Hawking later changed his mind on this

and conceded the bet.

Roger Penrose is in this camp too.

And indeed, his conformal cyclic cosmology model,

which is a kind of cyclic universe scenario,

critically depends on the condition

that information is in fact lost inside black holes.

But today, most of the community believe

that unitarity is preserved

and somehow the information does get out of the black hole,

which means we have to update our theories

of how black holes work.

There are many ideas out there.

There are several variations

of the information simply being dumped somewhere else,

and this could be a baby universe inside the black hole,

episodes where the black hole reverses into a white hole

that spits out information

or that the black hole

is in fact a wormhole to somewhere else.

Recently, the idea of many micro wormholes existing

has been suggested.

Perhaps the particle that falls in

enters a tiny wormhole inside the event horizon

that carries it back out,

and that's why we see Hawking radiation.

Zooming out, it's also been suggested

that information is indeed lost in our universe,

but at the multiverse level, information is still conserved.

Personally, anything involving multiverses

feels like any media cop out,

it's kinda like saying aliens did it.

And anything involving wormholes risks violating causality,

which Hawking argued was sacred,

but Hawking did concede the bet, remember.

So what persuaded him that unitarity could be preserved?

As strange as it sounds,

a path towards resolution might come from holograms.

- What about the droid attack on the Wookiees?

- In 1993, Leonard Susskind suggested the notion

of black hole complementarity.

Someone who falls into the black hole

indeed seems to carry their information past the horizon

and eventually reach the singularity itself.

But someone watching from the outside

of the black hole wouldn't see this

because of the extreme time dilation down here,

they would see the astronaut

actually seem to slow down in time

as they approach the horizon

and eventually even seem to freeze there.

They wouldn't actually cross the threshold.

Yet more, their light is redshifted

and warped around the black hole.

From the outside, the in falling person appears

to be smeared across the horizon into a quantum thin layer.

Eventually, their information

reradiates from this thin layer

back out into space as Hawking radiation,

and thus information is conserved.

But this picture seems to violate

and contradict the astronaut's own experience.

Susskind suggested that both perspectives are right,

and although they contradict,

they can never actually come together

to note the discrepancy,

and thus the universe is actually okay with us.

This creates the strange idea

that the information is stuck there,

hovering in this incredibly thin layer

just above the surface of the event horizon.

But a surface is a 2D geometry,

and we usually think of black holes as 3D phenomena.

Surely, a 3D object contains far more information

than the 2D surface.

It turns out not.

In fact, this has now been proven mathematically

that the information content of a black hole

can always be completely described by just its 2D surface.

Indeed, this has now been generalized

to basically everything.

All 3D volumes must follow this rule.

They can never hold more information than that

which can be contained by their 2D surfaces.

Yet more, if you try to, you'd end up making a black hole,

which also of course adheres to this rule.

This is a holographic principle

that all 3D phenomena can in fact be reduced down

to a 2D representation.

We are all holograms, empty projections,

just ghostly shells, nothing more.

This equivalency, formally known

as the anti-de Sitter/conformal field theory correspondence

is a stunning result,

but it doesn't actually prove

that we are all truthfully holograms,

merely that this is an explanation

which is fully compatible

with everything we know about the universe.

Nevertheless, it was enough to persuade Hawking

to concede the bet.

The unitarity principle appears to survive.

But in its place we sacrificed

one of those other three key precepts, locality,

because now what originally seemed to be distinct 3D events

are all in fact collapsed onto a 2D surface.

But perhaps Hawking was premature to concede the bet,

as Kip Thorne thought, who refused to concede,

because despite the progress made, questions remain here.

Remember that Hawking radiation

stems from the particle pairs

produced in the vacuum near the horizon,

and thus they are monogamously entangled.

And also remember that information leakage

requires the Hawing radiation particles

to be entangled to each other at different times.

So we still have an apparent contradiction

that requires solving,

and as always, the best way to solve any paradox

is to let go of one of your assumptions.

What if the Hawking radiation particles

do not emerge from an empty vacuum,

but instead from a something?

In that case, the sum of two entangled states

need not be zero, like spin up, spin down.

Instead, they could sum to something

because they didn't come from nothing,

they came from something.

In this way, information can get out of the black hole

whilst preserving the rules of entanglement.

The implication is unsettling, though, at the event horizon,

there must exist a fiery thin layer known as the firewall,

which incinerates anything

that tries to fall into the black hole.

If this idea bothers you, it should.

Many physicists don't like it.

After all, this violates the equivalence principle,

being incinerated at the event horizon

is hardly Einstein's happiest thought,

and so many physicists

are still reaching for some other explanation.

Those baby universes

don't sound quite so unappealing now, do they?

A deeper issue in all of this is that yes,

we can come up with many possible explanations

to resolve the information paradox,

but how do we prove them?

Obviously, flying into a black hole would help,

but you'd discover the answer and never be able to share it.

You know, it would be incredibly cruel if the universe

insisted upon this as the only way which she would allow us

to unlock her secrets.

The ultimate deal with the devil.

- The equation couldn't reconcile relativity

with quantum mechanics, you need more, more.

- More what?

- More data, you need to see into a black hole.

- In principle, studying Hawking radiation would help

since we can measure its entropy, for example,

but Hawing radiation is so pitiful

that there's really no hope of observationally measuring it.

We'd have to build a micro black hole

in the laboratory for this,

and such energy scales are still far beyond our abilities,

and so it's quite possible that this puzzle will be with us

for a very long time,

a puzzle of which we can dream up

many allowed mathematical solutions to,

but frustratingly, we just can't prove any of them.

But working on this is still valuable in size,

like the holographic principle

are changing the way we approach fundamental physics

and providing new mathematical tools

to make further progress.

In truth, studying black holes may be our best hope

for a unified theory of quantum gravity,

the secret sauce to the ultimate theory of everything.

Who knew that studying something so dark

could reveal so much?

So until next time, stay thoughtful and stay curious.

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