What Happens If You Jump Into A Black Hole?

before we get started I want to let you

know that there's some new limited

edition merch for sale at the merch

store meet Alis and Bob famous explorers

of the abstract Landscapes of

theoretical physics Heroes of the dunkan

experiment the thought experiment whose

life mission is to find contradiction in

the deepest layers of our theories and

so lead us deeper today our intrepret

pair are jumping into a black hole again

why well to determine the fundamental

structure of SpaceTime and its

connection to quantum entanglement of

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course in recent as well as less recent

episodes we've seen how thinking about

black holes leads to weird ideas like

the fact that there's a minimum

meaningful distance in space or that all

the information of a volume of space

fits on its boundary we also saw a

simplistic manner in which an entire new

spatial Dimension can actually be

encoded on that boundary leading to the

notion of the holographic Universe we

even saw one idea for how gravity could

emerge from the thermodynamics on that

boundary in a couple of the recent

episodes we talked about how the

emergent Dimension could be encoded in

the scale of patterns on the boundary

but these days most physicists working

in that area think there's a better way

to do that encoding and that's with

quantum entanglement the subtle

correlations between the bits of

information that define the properties

of part articles in fact as we'll see in

upcoming episodes it's starting to look

like the entire fabric of space may be

emerging from entanglement that space is

sort of knit together from the network

of mutual information of its

contents this idea of the role of

entanglement came from thinking about

black holes in parallel to the stuff

that led to this minimal plank length

and the holographic principle in

particular in thinking about what

happens to Quantum information in a

black hole this is ultimately going to

lead to a deep connection between

entanglement and wormholes in the ER

equals epr conjecture and the same line

of reasoning is going to completely mess

with our intuition about where

information exists leading to black hole

complimentarity we'll get to these in

upcoming episodes but today we want to

set up the contradiction that drives all

of these and for that we need Alice and

Bob to jump into a black hole well just

Alice actually she's always been a bit

more adventurous than Bob so Alice and

Bob head to Sagittarius AAR the super

massive black hole at the center of the

Milky Way Alice suits up and prepares to

jump Bob prepares to watch from a safe

distance Alice carries a clock that

emits pulses of high energy Gamay with a

regular period so that Bob can track her

position and also how her flow of time

changes Alice also carries a box in

which there's a single electron with its

spin Frozen this is our Cubit our bit of

quantum information in this case the

information is about whether that

electron spin is pointing up or down the

box also emits regular pulses of Gamay

so it can be tracked

independently excited to be the first

human to see below an event horizon

Alice high-fives Bob and leaps head

first towards sag a star and as she

begins her descent she throws the Cubit

box to fall just ahead of her let's

start with Bob's perspective he watches

Alice and the Box fall training his

Gamay telescope on them to monitor their

flow of time those Gamay photons arrive

with increasing separation due to

gravitational time dilation and at the

same time the photons are

gravitationally red shifted stretched to

longer wavelengths Bob has also switched

on detector sensitive to all wavelengths

from x-ray to visible to radio he

settles in expecting to watch Alice slow

down as she approaches the event Horizon

to witness her seconds stretch to hours

years

Millennia but that doesn't happen

instead he observes Alice fall quickly

speed up and then suddenly slow down and

merge with the black holes Event Horizon

so what happened to the time dilation

approaching Infinity at the Event

Horizon well it's true that for any

black hole you can find a distance from

The Event Horizon with any ridiculously

high time dilation that you want on like

a millisecond stretching to 100 trillion

years but the thing is a Free Falling

Observer like Alice is moving very very

fast by the time she reaches these

points she's approaching the speed of

light the time dilation increases but

the amount of time spent at each point

decreases now ultimately the formal

winds and both Alice's and the Box's

descent seem to slow down and freeze but

really only very close to the event

horizon

Bob sees the Box slow down and freeze

first which means Alice appears to catch

up to the box and then Alice's head

slows down before her feet so from Bob's

perspective she appears to flatten now

Bob had been worried about the opposite

effect that Alice might get

spaghettified elongated by the tidal

forces pulling on her head harder than

her feet but that doesn't happen here

because human scale tidal forces for a

black hole this massive are only deep

inside the black hole instead by the

time the top of Alice's head is just

above the Event Horizon her entire body

is also just above the Event Horizon now

this effect doesn't have a term but Bob

wonders if pancake ification might be

appropriate at this point Alice's

photons are much fainter than the

ambient glow of the universe the cosmic

microwave background and the wavelengths

of those photons are are much longer

than the CMB those photons are barely

detectable even by Bob's giant radio

antenna and then Bob loses sight

altogether the last thing he sees is

that all of Alice's cubits along with

the experimental Cubit get scrambled

over the entire event horizon now any

light from Alice is indistinguishable

from the black hole's own Hawking

radiation and may actually be equivalent

to it Hawking radiation is the faint

glow that every black hole produces due

to its non-zero temperature for sadj

star that temperature is 10 to the power

of -4 Kelvin resulting in Hawking

photons with wavelengths over 100

million km long but Bob is desperate to

not lose track of the experimental Cupid

the only way is to collect all future

Hawking radiation emitted by the black

hole he begins the construction of a

detector that will surround the entire

black hole a type of Dion sphere he also

goes ahead and uploads his mind to the

ship's computer so that he can outlift

the black hole and he settles in for the

long game in the meantime let's look at

what happened to Alice from her own

perspective plummeting towards sjar take

some hours but most of that time is

spent far from The Event Horizon she

rapidly accelerates and by the latter

part of the journey whizzers

exponentially quickly there's no GeForce

from that acceleration and no tidal

forces from the black Hall Alice is in

freeall towards an event horizon vastly

larger than she is so she feels like

she's floating this is a consequence of

Einstein's equivalent principle which

tells us that for an observer in

freefall their local patch of SpaceTime

behaves exactly like space in the

absence of a gravitational

field Alice sees the black hole beneath

her as a vast black surface oddly though

that surface appears to move away from

her as she approaches see the true Event

Horizon looks black from a great

distance due to the infinite gravity

ational red shift of photon struggling

to depart it that red shift results from

the full trajectory out of a black

hole's gravitational well but Alice can

still encounter photons that were

emitted a hair above the Event Horizon

because she's deep in that gravitational

well effectively she's coming to them

rather than waiting for them to reach

her also as Alice approaches The Event

Horizon her own Extreme Velocity sort of

D redshifts the outward pointing photons

that she passes through she sees the

record of objects that fell ahead of her

including the Cubit

box now comes the critical part of the

experiment from Alice's perspective at

some point the cubid Box crosses the

true Event Horizon ahead of her even if

she sees no marker of that Horizon in

her reference frame does she still see

the Box well yes but the Box she sees is

the box as it was just before crossing

the horizon she could only catch photons

emitted by the box from below the

Horizon if she crosses that Horizon

herself she is first and foremost a

scientist so turns her mind back to the

experiment and plummets through the

Event Horizon and nothing weird happens

remember the equivalence principle that

tells us that there's no experiment you

can do or observation you can make on

the local patch of space that

distinguishes whether that patch is Free

Falling or free floating this principle

is the Bedrock of relativity and

physicists are very uncomfortable by

anything that appears to violate it now

remember this because we may have to

break the equivalence principle later

and that should make you uncomfortable

also but assuming the equivalence

principle holds Alice can't see things

freeze at the Event Horizon not the

Cubit not herself nor does she catch up

to the Cubit so now Beneath The Horizon

the Cubit is still below her and still

gaining ground towards the dark surface

that also always appears below

but now that dark surface is growing and

stretching around behind her also the

outside universe is a shrinking fisheye

view above Alice's sense of up iris's

closed and all directions become an

enveloping down all directions lead to a

Terminus of space and time Alice can't

ever leave to tell Bob the result of the

experiment but from her perspective it's

a huge success she she now knows with

short that black holes can swallow

Quantum bits let's go back to Bob

remember he's now in the business of

catching Hawking radiation and looking

for signs of the experimental Cubit

though if we're being honest he's also

looking for signs of

Alice the black hole radiates it would

lose Mass this way if it weren't for the

fact that it eats more Cosmic microwave

background than it spews up but after

about 100 billion years or so the

universe has expanded enough to dim the

CMB below the temperature of the black

hole and finally Sagittarius AAR starts

to shrink assuming it doesn't eat

anything else Bob is aware that the

black hole will eventually completely

evaporate through this radiation he's

also aware of the law of conservation of

quantum information and the black hole

information Paradox from watching

ancient PBS SpaceTime episodes he knows

that quantum mechanics and perhaps his

own heart won't allow the Eraser of

Alice's information nor the experimental

Cubit from the universe but there's a

risk of that happening if the black hole

evaporates to nothing and so just like

many long dead 21st century physicists

Bob concludes that the information must

be hidden in the Hawking radiation many

lifetimes of the universe pass and the

Hawking radiation appears completely

random Bob has had to build several

starssized computers metrios brains to

store and analyze the data no big deal

really because Bob has nothing but time

on his

hands after the black hole has lost half

of its mass 10 to the power of 87 years

later when incidentally all the stars

have gone out and their Cellar remnants

have scattered to the void it's now just

Bob and the black hole then Bob analyzes

the next in the endless stream of

information Baron Hawking radiation but

this time he detects the first sign of a

faint

pattern the subtlest of correlations

starts to emerge between all past

radiation hinting at some profoundly

scrambled order in the randomness of the

bits stuck on the black hole Event

Horizon newly excited by his sophan task

Bob continues to collect eventually he

manages to recover the object of the

experiment the quantum bit proving

incontrovertibly that black holes do not

swallow Quantum information and just

before the black hole evaporates

entirely Bob also recovers all of the

bits that were once Alice revealing the

true source of his long patience he

brings to Bear the full might of the

enormous black hle powered matrioska

brains and reverse Engineers all of

Alice's cubits and reconstructs her

Consciousness in digital form and the

two live happily ever after digital

ghosts in a dead Universe how

sweet this might seem like a happy

ending and it is for Bob and for the

version of Alice encoded in the event

Horizon but not necessarily so for the

version of Alice that fell in nor for

physics let's get back to our experiment

what really happened to the Cubit Bob

saw it freeze on the horizon and then

eventually caught it when it emerged as

Hawking radiation but Ellis saw it fall

through the Horizon and then merge with

the singularity just before she did the

same in physics we often make progress

by identifying contradictions in a

theory this is perhaps the primary value

of the G Duncan experiment

so it seems we've identified a

contradiction two different observers

end up with irreconcilably different

answers for the question where is the

Cubit there's a reason we used a cubit

instead of just asking for example where

is Alice that's because the Cubit allows

us to break very specific rules in

quantum mechanics and so it sharpens our

contradiction I already talked about the

prohibition against deleting Quantum

information which is why Bob concluded

that the Cubit must be preserved in the

Hawking

radiation but there's another related

rule the no cloning theorem states that

Quantum bits can't be

duplicated if the bit Escapes in the

Hawking radiation then how can it also

be inside the black hole the problem

with deleting or duplicating Quantum

information is that it breaks what may

be the most fundamental tenant of

quantum mechanics as foundational as the

equivalence principle is to general

relativity and that's

unitarity the quantum wave function

describes probabilities probabilities

have to add up to one add up all the

probabilities of say an object's

possible position and they can't add up

to more than 100% because what would

that even mean deleting or duplicating a

cupid breaks unitarity and so is a no no

but it seems we have to either Break

unitarity by duplicating the cubit in

the Hawking radiation or by deleting it

as the black hole evaporates or we have

to break the equivalence principle by

saying that Alice and her it never got

past the Event Horizon to find out which

is the case you're going to have to wait

another week remember Bob waited 10 to

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

then we'll start to see some of the

possible solutions to this Paradox from

black hole complimentarity to the idea

of the firewall at the Event Horizon and

we will continue to sharpen the tools we

need to knit entangled cubits into the

very fabric of SpaceTime hey everyone

before we go I wanted to let you know

that we have two new limited edition

merch items up at the merch store first

up is our first ever black hole enamel

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

Hol foil backing card designed by the

SpaceTime gfx team these pins are

limited edition pre-sale with the pins

shipping during the second week of June

once we're out of stock from the

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

Wars inspired SpaceTime t-shirt and and

sweatshirt designed by our very Star

Wars nerdy director this limited edition

design will be available until May the

4th be with you to put that order in

just head over to pbsp time.com sshop or

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