What Happens If You Jump Into A Black Hole?

PBS Space Time
1 May 202417:25

Summary

TLDRThe video script narrates a thought experiment involving Alice and Bob, two intrepid explorers, who embark on a journey to explore the enigmatic depths of a black hole. Alice, the more adventurous of the two, dives into Sagittarius A*, the supermassive black hole at the center of the Milky Way, while Bob observes from a safe distance. Alice carries a clock and a box containing a single electron, serving as a quantum bit of information. As she approaches the event horizon, Bob witnesses time dilation effects and the scrambling of information across the horizon. From Alice's perspective, she experiences no significant tidal forces and continues to fall towards the black hole's singularity. The crux of the narrative revolves around the paradox of quantum informationβ€”whether it is preserved within the black hole or emitted as Hawking radiation. Bob, in a monumental effort, constructs a detector to capture all future Hawking radiation, eventually recovering the quantum bit and Alice's information. The script delves into complex concepts such as the holographic principle, entanglement, and the conservation of quantum information, posing profound questions about the nature of spacetime and the fate of information within black holes.

Takeaways

  • πŸš€ **Alice and Bob's Mission**: The thought experiment involves Alice and Bob, famous explorers, jumping into a black hole to determine the fundamental structure of spacetime and its connection to quantum entanglement.
  • ⚫️ **Black Hole Exploration**: The script discusses the concept of black holes and their role in theoretical physics, including the holographic principle and the idea that spacetime may be 'knitted' from entanglement.
  • βŒ› **Time Dilation**: Bob observes Alice's time dilation as she approaches the event horizon, which slows her descent and eventually makes her appear to merge with the black hole's event horizon.
  • 🧲 **Gravitational Redshift**: As Alice falls, the photons emitted by her and the box are gravitationally redshifted, stretching to longer wavelengths and becoming fainter.
  • πŸ”¬ **Quantum Information**: Alice carries a box with a single electron, representing a quantum bit of information, to test the fate of quantum information inside a black hole.
  • πŸ” **Observer Perspectives**: The script contrasts the perspectives of Alice (falling into the black hole) and Bob (observing from a distance), highlighting the differences in their experiences.
  • 🌌 **Hawking Radiation**: Bob constructs a detector to collect Hawking radiation, hoping to find the quantum bit and thus prove that black holes do not destroy quantum information.
  • ⏳ **Time and Patience**: Bob waits for an incredibly long time (10^87 years), uploading his mind to a computer and building massive computers to analyze the data from the black hole.
  • πŸ”— **Entanglement's Role**: The script suggests that entanglement plays a crucial role in the structure of spacetime, possibly being the underlying fabric from which spacetime emerges.
  • πŸ’‘ **Unitarity and No-Cloning**: The script touches on the principles of quantum mechanics, including unitarity and the no-cloning theorem, which are challenged by the paradox of quantum information inside a black hole.
  • 🎁 **Merchandise**: The script ends with an announcement of limited edition merchandise available for sale, including a black hole enamel pin and a Star Wars-inspired t-shirt.

Q & A

  • Who are Alice and Bob in the context of the script?

    -Alice and Bob are famous explorers of the abstract landscapes of theoretical physics. They are heroes of the thought experiment whose life mission is to find contradictions in the deepest layers of scientific theories.

  • What is the significance of Alice and Bob jumping into a black hole?

    -Alice and Bob are jumping into a black hole to determine the fundamental structure of spacetime and its connection to quantum entanglement, which is a key aspect of understanding the fabric of the universe.

  • What is the holographic principle mentioned in the script?

    -The holographic principle is a concept in theoretical physics suggesting that all the information contained in a volume of space can be represented on the boundary to the same space.

  • How does quantum entanglement relate to the structure of space?

    -Quantum entanglement is thought to be a fundamental aspect of the structure of space. It is suggested that space may be 'knit together' from a network of mutual information of its contents, implying that entanglement plays a key role in the fabric of spacetime.

  • What is the ER=EPR conjecture?

    -The ER=EPR conjecture is a proposal in theoretical physics that connects entanglement (EPR) with wormholes (ER), suggesting a deep relationship between quantum entanglement and the structure of spacetime.

  • What is the black hole information paradox?

    -The black hole information paradox is a conflict between quantum mechanics and general relativity. It questions what happens to the information about physical states when it enters a black hole, as quantum mechanics states that information cannot be lost, while general relativity suggests that information is not retrievable from a black hole.

  • What is the concept of Hawking radiation?

    -Hawking radiation is a theoretical prediction by physicist Stephen Hawking that black holes emit radiation due to quantum effects near the event horizon. This radiation is faint and is named after Hawking for its theoretical discovery.

  • Why does Bob construct a detector to surround the black hole?

    -Bob constructs a detector to surround the black hole to collect all future Hawking radiation emitted by the black hole. This is in an attempt to not lose track of the experimental Cubit and potentially, signs of Alice.

  • What is the significance of the no-cloning theorem in quantum mechanics?

    -The no-cloning theorem states that it is impossible to create an identical copy of an arbitrary unknown quantum state. This is significant because it protects the integrity of quantum information and is a fundamental principle in quantum computing and quantum information theory.

  • What is the concept of unitarity in quantum mechanics?

    -Unitarity in quantum mechanics is the principle that the total probability of all possible outcomes of a quantum system must add up to one. It is a fundamental concept that ensures the conservation of probability in quantum processes.

  • What is the contradiction identified by the thought experiment involving Alice and Bob?

    -The contradiction identified is that two different observers, Alice and Bob, have irreconcilably different answers to the question of where the Cubit is. This challenges the principles of quantum mechanics, specifically unitarity and the equivalence principle, and is a key point of discussion in the script.

  • What is the significance of the limited edition merch mentioned at the end of the script?

    -The limited edition merch, including a black hole enamel pin and a Star Wars inspired SpaceTime t-shirt and sweatshirt, is a promotional item for the SpaceTime series. It serves to engage the audience and provide a tangible connection to the content they are consuming.

Outlines

00:00

πŸš€ Introduction to the Black Hole Experiment

The video introduces Alice and Bob, famous explorers of theoretical physics, who embark on a mission to explore the structure of spacetime and its connection to quantum entanglement. They plan to jump into a black hole to test these theories. Alice, the more adventurous, prepares to jump into Sagittarius A*, the supermassive black hole at the center of the Milky Way, while Bob watches from a safe distance. Alice carries a clock and a box containing a single electron to track time and quantum information. As Alice descends, Bob observes her through a gamma ray telescope, noticing gravitational time dilation and redshift. However, Alice appears to quickly merge with the event horizon, contrary to expectations of time dilation slowing her approach.

05:01

🌌 Bob's Observations of Alice's Descent

From Bob's perspective, Alice experiences gravitational time dilation, but as a free-falling observer, she moves quickly and doesn't experience the extreme dilation expected near the event horizon. Alice's body appears to flatten due to the gravitational forces, and Bob loses sight of her as her photons become indistinguishable from the black hole's Hawking radiation. Bob decides to construct a detector to collect all future Hawking radiation, hoping to find the quantum information carried by Alice. He also uploads his mind to the ship's computer to outlive the black hole and begins a long wait.

10:03

πŸ” Alice's Perspective Inside the Black Hole

Alice, in freefall, experiences no significant tidal forces or acceleration effects as she approaches the event horizon. She observes the black hole as a vast black surface that appears to move away from her. As she crosses the event horizon, she doesn't notice any unusual phenomena, which aligns with the equivalence principle of general relativity. Alice continues to fall, believing the experiment to be a success as she confirms that black holes can contain quantum bits. Meanwhile, Bob, outside the black hole, dedicates eons to collecting and analyzing Hawking radiation, eventually detecting a pattern that suggests the presence of the quantum bit, proving that black holes do not erase quantum information.

15:05

🧐 The Quantum Information Paradox

The video concludes with a paradox: Bob and Alice have different observations regarding the fate of the quantum bit, or 'Cubit'. Bob sees the Cubit freeze on the horizon and later recovers it from the Hawking radiation, while Alice sees it fall into the black hole. This contradiction challenges the principles of quantum mechanics, specifically unitarity, which states that quantum probabilities must sum to one, and the no-cloning theorem, which prohibits the duplication of quantum bits. The resolution to this paradox is promised in an upcoming video, which will explore concepts like black hole complementarity and the idea of a firewall at the event horizon.

πŸ›οΈ Merchandise Announcement

The video script concludes with an announcement about new limited edition merchandise available for sale. The items include a black hole enamel pin designed by the SpaceTime graphics team and a Star Wars-inspired SpaceTime t-shirt and sweatshirt designed by the director. The enamel pins are available for pre-sale with shipping expected in June, and the Star Wars-inspired items are available until May the 4th.

Mindmap

Keywords

πŸ’‘Black Hole

A black hole is a region in space where the gravitational pull is so strong that nothing, not even light, can escape from it. In the video, Alice and Bob explore the concept of black holes to understand the fundamental structure of spacetime and its connection to quantum entanglement. The black hole serves as a backdrop for the thought experiment, where Alice jumps into Sagittarius A*, a supermassive black hole at the center of the Milky Way, to test the principles of quantum mechanics and general relativity.

πŸ’‘Quantum Entanglement

Quantum entanglement is a phenomenon in quantum physics where pairs or groups of particles interact in such a way that the state of each particle cannot be described independently of the state of the others, even when the particles are separated by large distances. The video discusses how quantum entanglement might be the underlying fabric of space, with the entire structure of space possibly emerging from entanglement. This concept is central to the thought experiment conducted by Alice and Bob.

πŸ’‘Hawking Radiation

Hawking radiation is a theoretical process through which black holes can lose mass and eventually evaporate. Named after physicist Stephen Hawking, this phenomenon occurs due to quantum effects near the event horizon of a black hole. In the video, Bob waits for the black hole to evaporate through Hawking radiation, hoping to recover the quantum information that Alice and the experimental Cubit carried, which is a critical aspect of the black hole information paradox.

πŸ’‘Event Horizon

The event horizon is the boundary around a black hole beyond which nothing can escape the black hole's gravitational pull. It is the point of no return for any matter or radiation falling into the black hole. In the video, Alice crosses the event horizon, and Bob observes the effects of this crossing, including the freezing of time and the scrambling of information, which leads to the central paradox of the video.

πŸ’‘Quantum Information

Quantum information refers to the information that is processed or stored in a quantum system. It is the fundamental concept behind quantum computing and quantum cryptography. In the video, the experimental Cubit, which contains a single electron with its spin frozen, represents a bit of quantum information. The fate of this quantum information as it interacts with the black hole is a key focus of the narrative.

πŸ’‘Unitarity

In quantum mechanics, unitarity is the principle that the total probability for a system must equal 1 (or 100%), reflecting the conservation of probability. It is a fundamental requirement for a quantum theory to be consistent. The video discusses the potential violation of unitarity if quantum information is either duplicated or deleted, which is a significant issue in the black hole information paradox.

πŸ’‘Equivalence Principle

The equivalence principle is a cornerstone of general relativity, stating that the effects of gravity are locally the same as those of acceleration. It implies that an observer in free fall cannot locally distinguish whether they are in a gravitational field or are in free space. In the video, Alice's experience of free fall into the black hole is described using this principle, which leads to the apparent contradiction between her perspective and Bob's.

πŸ’‘Spaghettification

Spaghettification is a term used to describe the elongation of objects due to tidal forces when they are stretched out towards a black hole's event horizon. In the video, Bob initially fears that Alice might experience spaghettification, but due to the scale of the black hole, this effect does not occur as Alice approaches the event horizon.

πŸ’‘Dion Sphere

A Dion sphere, mentioned in the video, is a hypothetical structure that would completely surround a black hole to collect the Hawking radiation emitted by the black hole. Bob constructs a Dion sphere to collect and analyze the Hawking radiation in the hope of recovering the quantum information that Alice and the Cubit carried.

πŸ’‘Black Hole Complementarity

Black hole complementarity is a concept in theoretical physics that attempts to reconcile the apparent paradox between the principles of quantum mechanics and general relativity as they relate to information falling into a black hole. The video hints at this concept as a potential solution to the paradox that arises from the differing perspectives of Alice and Bob regarding the fate of the quantum information.

πŸ’‘No Cloning Theorem

The no cloning theorem is a fundamental principle in quantum mechanics that states it is impossible to create an identical copy of an arbitrary unknown quantum state. This theorem is relevant to the video's discussion of the black hole information paradox, as it raises questions about the fate of quantum information that seemingly needs to be both inside the black hole and emitted as Hawking radiation.

Highlights

New limited edition merchandise available at the merch store featuring Alice and Bob, famous explorers of theoretical physics.

Alice and Bob embark on a mission to explore the abstract landscapes of theoretical physics by jumping into a black hole.

The thought experiment aims to determine the fundamental structure of spacetime and its connection to quantum entanglement.

Previous episodes discussed the holographic principle and the idea that space could be encoded on its boundary.

Quantum entanglement is proposed as a method to encode the emergent dimension on the boundary of a black hole.

The fabric of space may be emerging from entanglement, with space being knit together by mutual information of its contents.

The ER=EPR conjecture suggests a deep connection between entanglement and wormholes.

Black hole complementarity challenges our intuition about where information exists within a black hole.

Alice carries a clock and a box containing a single electron to track her position and the flow of time as she descends into the black hole.

From Bob's perspective, Alice appears to slow down, speed up, and then merge with the black hole's event horizon.

Alice's and the box's descent seem to freeze only very close to the event horizon, with Alice appearing to flatten from Bob's viewpoint.

Alice experiences no spaghettification due to the scale of the black hole and her position relative to the event horizon.

Bob loses sight of Alice and the box as their photons become indistinguishable from the black hole's Hawking radiation.

Bob constructs a detector to surround the black hole to collect all future Hawking radiation in an attempt to preserve quantum information.

Alice, in freefall, experiences no significant gravitational forces and observes the black hole as a vast black surface moving away from her.

Upon crossing the event horizon, Alice does not experience any unusual phenomena, consistent with the equivalence principle.

The experiment reveals a contradiction in the perspective of Alice and Bob regarding the fate of the quantum bit, challenging the principles of quantum mechanics.

Bob, after an immense wait, detects a pattern in the Hawking radiation, suggesting that black holes do not swallow quantum information.

Bob uses advanced technology to reconstruct Alice's consciousness, providing a potential resolution to the paradox.

The paradox identified in the experiment may lead to new insights in theoretical physics, including the concept of a firewall at the event horizon.

Limited edition merch items include a black hole enamel pin and a Star Wars inspired SpaceTime t-shirt and sweatshirt.

Transcripts

00:00

before we get started I want to let you

00:01

know that there's some new limited

00:02

edition merch for sale at the merch

00:04

store meet Alis and Bob famous explorers

00:08

of the abstract Landscapes of

00:09

theoretical physics Heroes of the dunkan

00:12

experiment the thought experiment whose

00:16

life mission is to find contradiction in

00:18

the deepest layers of our theories and

00:21

so lead us deeper today our intrepret

00:24

pair are jumping into a black hole again

00:27

why well to determine the fundamental

00:29

structure of SpaceTime and its

00:30

connection to quantum entanglement of

00:37

[Music]

00:39

course in recent as well as less recent

00:41

episodes we've seen how thinking about

00:43

black holes leads to weird ideas like

00:46

the fact that there's a minimum

00:48

meaningful distance in space or that all

00:50

the information of a volume of space

00:52

fits on its boundary we also saw a

00:55

simplistic manner in which an entire new

00:57

spatial Dimension can actually be

00:59

encoded on that boundary leading to the

01:01

notion of the holographic Universe we

01:04

even saw one idea for how gravity could

01:06

emerge from the thermodynamics on that

01:08

boundary in a couple of the recent

01:10

episodes we talked about how the

01:12

emergent Dimension could be encoded in

01:14

the scale of patterns on the boundary

01:17

but these days most physicists working

01:19

in that area think there's a better way

01:21

to do that encoding and that's with

01:23

quantum entanglement the subtle

01:25

correlations between the bits of

01:27

information that define the properties

01:29

of part articles in fact as we'll see in

01:32

upcoming episodes it's starting to look

01:34

like the entire fabric of space may be

01:37

emerging from entanglement that space is

01:39

sort of knit together from the network

01:41

of mutual information of its

01:44

contents this idea of the role of

01:46

entanglement came from thinking about

01:48

black holes in parallel to the stuff

01:51

that led to this minimal plank length

01:53

and the holographic principle in

01:55

particular in thinking about what

01:57

happens to Quantum information in a

01:58

black hole this is ultimately going to

02:01

lead to a deep connection between

02:03

entanglement and wormholes in the ER

02:06

equals epr conjecture and the same line

02:09

of reasoning is going to completely mess

02:11

with our intuition about where

02:14

information exists leading to black hole

02:18

complimentarity we'll get to these in

02:20

upcoming episodes but today we want to

02:22

set up the contradiction that drives all

02:24

of these and for that we need Alice and

02:27

Bob to jump into a black hole well just

02:30

Alice actually she's always been a bit

02:33

more adventurous than Bob so Alice and

02:36

Bob head to Sagittarius AAR the super

02:39

massive black hole at the center of the

02:41

Milky Way Alice suits up and prepares to

02:44

jump Bob prepares to watch from a safe

02:46

distance Alice carries a clock that

02:48

emits pulses of high energy Gamay with a

02:51

regular period so that Bob can track her

02:53

position and also how her flow of time

02:56

changes Alice also carries a box in

02:59

which there's a single electron with its

03:02

spin Frozen this is our Cubit our bit of

03:06

quantum information in this case the

03:08

information is about whether that

03:09

electron spin is pointing up or down the

03:12

box also emits regular pulses of Gamay

03:14

so it can be tracked

03:16

independently excited to be the first

03:18

human to see below an event horizon

03:20

Alice high-fives Bob and leaps head

03:22

first towards sag a star and as she

03:25

begins her descent she throws the Cubit

03:27

box to fall just ahead of her let's

03:30

start with Bob's perspective he watches

03:32

Alice and the Box fall training his

03:34

Gamay telescope on them to monitor their

03:36

flow of time those Gamay photons arrive

03:39

with increasing separation due to

03:42

gravitational time dilation and at the

03:44

same time the photons are

03:45

gravitationally red shifted stretched to

03:47

longer wavelengths Bob has also switched

03:50

on detector sensitive to all wavelengths

03:52

from x-ray to visible to radio he

03:55

settles in expecting to watch Alice slow

03:58

down as she approaches the event Horizon

04:00

to witness her seconds stretch to hours

04:03

years

04:04

Millennia but that doesn't happen

04:08

instead he observes Alice fall quickly

04:10

speed up and then suddenly slow down and

04:13

merge with the black holes Event Horizon

04:15

so what happened to the time dilation

04:17

approaching Infinity at the Event

04:19

Horizon well it's true that for any

04:23

black hole you can find a distance from

04:25

The Event Horizon with any ridiculously

04:28

high time dilation that you want on like

04:30

a millisecond stretching to 100 trillion

04:32

years but the thing is a Free Falling

04:35

Observer like Alice is moving very very

04:38

fast by the time she reaches these

04:40

points she's approaching the speed of

04:42

light the time dilation increases but

04:45

the amount of time spent at each point

04:47

decreases now ultimately the formal

04:50

winds and both Alice's and the Box's

04:53

descent seem to slow down and freeze but

04:57

really only very close to the event

04:59

horizon

05:00

Bob sees the Box slow down and freeze

05:02

first which means Alice appears to catch

05:04

up to the box and then Alice's head

05:07

slows down before her feet so from Bob's

05:10

perspective she appears to flatten now

05:13

Bob had been worried about the opposite

05:15

effect that Alice might get

05:17

spaghettified elongated by the tidal

05:20

forces pulling on her head harder than

05:22

her feet but that doesn't happen here

05:24

because human scale tidal forces for a

05:26

black hole this massive are only deep

05:29

inside the black hole instead by the

05:32

time the top of Alice's head is just

05:35

above the Event Horizon her entire body

05:37

is also just above the Event Horizon now

05:40

this effect doesn't have a term but Bob

05:42

wonders if pancake ification might be

05:46

appropriate at this point Alice's

05:48

photons are much fainter than the

05:50

ambient glow of the universe the cosmic

05:52

microwave background and the wavelengths

05:54

of those photons are are much longer

05:56

than the CMB those photons are barely

05:59

detectable even by Bob's giant radio

06:02

antenna and then Bob loses sight

06:05

altogether the last thing he sees is

06:08

that all of Alice's cubits along with

06:10

the experimental Cubit get scrambled

06:12

over the entire event horizon now any

06:15

light from Alice is indistinguishable

06:17

from the black hole's own Hawking

06:19

radiation and may actually be equivalent

06:21

to it Hawking radiation is the faint

06:24

glow that every black hole produces due

06:26

to its non-zero temperature for sadj

06:28

star that temperature is 10 to the power

06:31

of -4 Kelvin resulting in Hawking

06:34

photons with wavelengths over 100

06:36

million km long but Bob is desperate to

06:39

not lose track of the experimental Cupid

06:42

the only way is to collect all future

06:45

Hawking radiation emitted by the black

06:47

hole he begins the construction of a

06:50

detector that will surround the entire

06:51

black hole a type of Dion sphere he also

06:55

goes ahead and uploads his mind to the

06:56

ship's computer so that he can outlift

06:58

the black hole and he settles in for the

07:00

long game in the meantime let's look at

07:03

what happened to Alice from her own

07:05

perspective plummeting towards sjar take

07:08

some hours but most of that time is

07:10

spent far from The Event Horizon she

07:13

rapidly accelerates and by the latter

07:15

part of the journey whizzers

07:17

exponentially quickly there's no GeForce

07:21

from that acceleration and no tidal

07:23

forces from the black Hall Alice is in

07:26

freeall towards an event horizon vastly

07:28

larger than she is so she feels like

07:31

she's floating this is a consequence of

07:34

Einstein's equivalent principle which

07:35

tells us that for an observer in

07:36

freefall their local patch of SpaceTime

07:39

behaves exactly like space in the

07:41

absence of a gravitational

07:43

field Alice sees the black hole beneath

07:46

her as a vast black surface oddly though

07:49

that surface appears to move away from

07:52

her as she approaches see the true Event

07:55

Horizon looks black from a great

07:57

distance due to the infinite gravity

07:59

ational red shift of photon struggling

08:01

to depart it that red shift results from

08:04

the full trajectory out of a black

08:07

hole's gravitational well but Alice can

08:09

still encounter photons that were

08:11

emitted a hair above the Event Horizon

08:13

because she's deep in that gravitational

08:15

well effectively she's coming to them

08:18

rather than waiting for them to reach

08:19

her also as Alice approaches The Event

08:22

Horizon her own Extreme Velocity sort of

08:26

D redshifts the outward pointing photons

08:28

that she passes through she sees the

08:31

record of objects that fell ahead of her

08:34

including the Cubit

08:36

box now comes the critical part of the

08:38

experiment from Alice's perspective at

08:41

some point the cubid Box crosses the

08:43

true Event Horizon ahead of her even if

08:45

she sees no marker of that Horizon in

08:48

her reference frame does she still see

08:51

the Box well yes but the Box she sees is

08:55

the box as it was just before crossing

08:58

the horizon she could only catch photons

09:01

emitted by the box from below the

09:03

Horizon if she crosses that Horizon

09:06

herself she is first and foremost a

09:09

scientist so turns her mind back to the

09:11

experiment and plummets through the

09:13

Event Horizon and nothing weird happens

09:16

remember the equivalence principle that

09:18

tells us that there's no experiment you

09:19

can do or observation you can make on

09:21

the local patch of space that

09:23

distinguishes whether that patch is Free

09:25

Falling or free floating this principle

09:28

is the Bedrock of relativity and

09:30

physicists are very uncomfortable by

09:32

anything that appears to violate it now

09:34

remember this because we may have to

09:36

break the equivalence principle later

09:38

and that should make you uncomfortable

09:40

also but assuming the equivalence

09:42

principle holds Alice can't see things

09:44

freeze at the Event Horizon not the

09:46

Cubit not herself nor does she catch up

09:48

to the Cubit so now Beneath The Horizon

09:52

the Cubit is still below her and still

09:54

gaining ground towards the dark surface

09:57

that also always appears below

10:00

but now that dark surface is growing and

10:03

stretching around behind her also the

10:06

outside universe is a shrinking fisheye

10:08

view above Alice's sense of up iris's

10:13

closed and all directions become an

10:15

enveloping down all directions lead to a

10:19

Terminus of space and time Alice can't

10:22

ever leave to tell Bob the result of the

10:24

experiment but from her perspective it's

10:27

a huge success she she now knows with

10:30

short that black holes can swallow

10:33

Quantum bits let's go back to Bob

10:35

remember he's now in the business of

10:36

catching Hawking radiation and looking

10:38

for signs of the experimental Cubit

10:41

though if we're being honest he's also

10:42

looking for signs of

10:44

Alice the black hole radiates it would

10:48

lose Mass this way if it weren't for the

10:50

fact that it eats more Cosmic microwave

10:52

background than it spews up but after

10:54

about 100 billion years or so the

10:56

universe has expanded enough to dim the

10:58

CMB below the temperature of the black

11:00

hole and finally Sagittarius AAR starts

11:03

to shrink assuming it doesn't eat

11:06

anything else Bob is aware that the

11:09

black hole will eventually completely

11:10

evaporate through this radiation he's

11:13

also aware of the law of conservation of

11:14

quantum information and the black hole

11:17

information Paradox from watching

11:18

ancient PBS SpaceTime episodes he knows

11:22

that quantum mechanics and perhaps his

11:24

own heart won't allow the Eraser of

11:26

Alice's information nor the experimental

11:29

Cubit from the universe but there's a

11:31

risk of that happening if the black hole

11:33

evaporates to nothing and so just like

11:35

many long dead 21st century physicists

11:38

Bob concludes that the information must

11:40

be hidden in the Hawking radiation many

11:43

lifetimes of the universe pass and the

11:45

Hawking radiation appears completely

11:48

random Bob has had to build several

11:50

starssized computers metrios brains to

11:54

store and analyze the data no big deal

11:57

really because Bob has nothing but time

11:59

on his

12:00

hands after the black hole has lost half

12:03

of its mass 10 to the power of 87 years

12:06

later when incidentally all the stars

12:08

have gone out and their Cellar remnants

12:10

have scattered to the void it's now just

12:13

Bob and the black hole then Bob analyzes

12:16

the next in the endless stream of

12:19

information Baron Hawking radiation but

12:22

this time he detects the first sign of a

12:25

faint

12:27

pattern the subtlest of correlations

12:30

starts to emerge between all past

12:32

radiation hinting at some profoundly

12:35

scrambled order in the randomness of the

12:39

bits stuck on the black hole Event

12:41

Horizon newly excited by his sophan task

12:45

Bob continues to collect eventually he

12:48

manages to recover the object of the

12:50

experiment the quantum bit proving

12:53

incontrovertibly that black holes do not

12:56

swallow Quantum information and just

12:58

before the black hole evaporates

13:00

entirely Bob also recovers all of the

13:02

bits that were once Alice revealing the

13:04

true source of his long patience he

13:06

brings to Bear the full might of the

13:08

enormous black hle powered matrioska

13:10

brains and reverse Engineers all of

13:12

Alice's cubits and reconstructs her

13:14

Consciousness in digital form and the

13:16

two live happily ever after digital

13:18

ghosts in a dead Universe how

13:22

sweet this might seem like a happy

13:24

ending and it is for Bob and for the

13:26

version of Alice encoded in the event

13:29

Horizon but not necessarily so for the

13:32

version of Alice that fell in nor for

13:34

physics let's get back to our experiment

13:37

what really happened to the Cubit Bob

13:39

saw it freeze on the horizon and then

13:41

eventually caught it when it emerged as

13:44

Hawking radiation but Ellis saw it fall

13:47

through the Horizon and then merge with

13:49

the singularity just before she did the

13:50

same in physics we often make progress

13:53

by identifying contradictions in a

13:55

theory this is perhaps the primary value

13:57

of the G Duncan experiment

14:00

so it seems we've identified a

14:01

contradiction two different observers

14:03

end up with irreconcilably different

14:05

answers for the question where is the

14:08

Cubit there's a reason we used a cubit

14:10

instead of just asking for example where

14:12

is Alice that's because the Cubit allows

14:15

us to break very specific rules in

14:17

quantum mechanics and so it sharpens our

14:20

contradiction I already talked about the

14:22

prohibition against deleting Quantum

14:24

information which is why Bob concluded

14:27

that the Cubit must be preserved in the

14:29

Hawking

14:30

radiation but there's another related

14:32

rule the no cloning theorem states that

14:34

Quantum bits can't be

14:36

duplicated if the bit Escapes in the

14:39

Hawking radiation then how can it also

14:41

be inside the black hole the problem

14:43

with deleting or duplicating Quantum

14:45

information is that it breaks what may

14:46

be the most fundamental tenant of

14:48

quantum mechanics as foundational as the

14:51

equivalence principle is to general

14:53

relativity and that's

14:56

unitarity the quantum wave function

14:58

describes probabilities probabilities

15:00

have to add up to one add up all the

15:02

probabilities of say an object's

15:04

possible position and they can't add up

15:06

to more than 100% because what would

15:08

that even mean deleting or duplicating a

15:11

cupid breaks unitarity and so is a no no

15:14

but it seems we have to either Break

15:16

unitarity by duplicating the cubit in

15:19

the Hawking radiation or by deleting it

15:22

as the black hole evaporates or we have

15:25

to break the equivalence principle by

15:27

saying that Alice and her it never got

15:29

past the Event Horizon to find out which

15:32

is the case you're going to have to wait

15:34

another week remember Bob waited 10 to

15:37

the^ of 87 years so a week isn't so bad

15:39

then we'll start to see some of the

15:42

possible solutions to this Paradox from

15:44

black hole complimentarity to the idea

15:47

of the firewall at the Event Horizon and

15:50

we will continue to sharpen the tools we

15:52

need to knit entangled cubits into the

15:56

very fabric of SpaceTime hey everyone

15:59

before we go I wanted to let you know

16:01

that we have two new limited edition

16:03

merch items up at the merch store first

16:06

up is our first ever black hole enamel

16:08

pin this is a 1 and 1/2 in enamel pin on

16:12

Hol foil backing card designed by the

16:15

SpaceTime gfx team these pins are

16:17

limited edition pre-sale with the pins

16:20

shipping during the second week of June

16:22

once we're out of stock from the

16:23

pre-sale that's it next up is our Star

16:26

Wars inspired SpaceTime t-shirt and and