All language subtitles for Cosmos_ Possible Worlds.en

We inhabit a cosmos
of undiscovered dimensions

and paradoxical realities.

We live on one
level of perception,

but there are others.

Every once in a while,
a searcher happens upon

the doorway to one
of these other levels.

One of them discovered a
paradox about reality that

proved to be so profound,
we have yet to understand

how it could be possible.

The universe,
or perhaps we should say,

universes have
never been the same.

Nature writes her most
intimate secrets in light.

The light from our star that
powers all life on this world.

The light that
plants eat to make sugar.

The light that is the
yardstick of the universe,

stitching diamonds into
the fabric of space and time.

The imprisoned light
that defines black holes.

The absence of light
that prevents us from knowing

what dark matter
and dark energy are.

"Seeing the light" usually
refers to a religious epiphany,

but no one is more
light-obsessed than astronomers.

And as soon as they
began studying light,

it challenged even
the very best of them.

Take Isaac Newton, for example.

He was so desperate to understand
the nature of light and colors,

he was willing to
stick needles in his eyes.

No, I mean literally.

Newton was only in his mid-20s,

but he had already laid the foundations of a
new branch of mathematics called "calculus,"

and he was conducting a series

of experiments that led him to
conclude that color was an aspect of light.

Newton wanted to find out
which of the things we see

are properties of light and
which are caused by our nerves.

Was color hiding
inside the light?

Or was it in our eyes?

With a burning desire to know,

he took a needle
called a bodkin and

Newton carefully
noted that if he conducted

the experiment in a
room filled with light,

even with his eyes shut,
some light would pass through

his eyelids and he would see
a great, broad blue-ish circle.

It may not sound like much of
a result considering the pain,

but it was with simple
homemade experiments such

as this one that Isaac Newton became
the first person to explain rainbows,

and how white
light hides a whole

palette of colors inside itself.

Most people thought of
the events Newton studied as

being just the way things were.

The way an apple falls.

The way a ray of light
shines through a window.

Newton's greatness stemmed
from his questioning of the

"why" and "how" of
ordinary things.

Newton asked,
what was light made of?

If you could break light apart
into its tiniest components,

what would you see?

Newton noticed that light
moved in straight lines.

How else to explain
the edges of shadows?

Or the straightness of
the inspiring rays of sunlight

that poke through a cloud?

Or the darkness that resulted
from a total solar eclipse?

From these observations,
Newton reasoned that light

must consist of a
stream of particles,

or corpuscles as he called them,

that a ray of light was like
a stream of bullets striking

the retina of the eye.

But there was one
man over in Holland,

who vigorously disagreed with
Newton's particle theory of light.

Christiaan Huygens shared
Isaac Newton's insatiable curiosity,

and when it came
to changing the world,

he was no slouch himself.

Despite a lifelong
struggle with depression,

he managed to get a lot done.

While looking through a telescope
that he designed and built himself,

he discovered
Saturn's moon, Titan.

Huygens invented
the pendulum clock.

He worked out the mathematical
formulas necessary to create

a pendulum with an arc
that would accurately and

consistently measure out
uniform increments of time.

Huygens sketched a
prototype for a new machine

that he thought
might have some promise.

It was what he called
a "magic lantern."

A few hundred years would
pass before it evolved into

a working motion
picture projector.

But back in the 17th century,

Christiaan Huygens already
had an idea for a movie,

possibly influenced
by his gloomy disposition.

Huygens, like Newton,

also invented his own
new branch of mathematics,

a predictive theory of the
outcomes of games of chance,

probability theory.

A way to call heads or tails.

And like Newton, Christiaan
Huygens had his own theory of light,

but it was very different.

He didn't think light
consisted of particles like

bullets firing
along a single path.

Huygens saw light as a wave,

spreading out in all directions.

It was already known in that time
that sound must travel as a wave.

How?

Because a voice could be heard
around a door when it was slightly ajar,

so sound must travel around
the door as water would,

like a wave.

Huygens thought that light
moved the same way sound did,

spreading out as waves.

So, which genius was right?

The answer to that question
of whether light was a particle

or a wave would
prove to be complicated.

Now enter Thomas Young.

The man who exposed the
enigma at the heart of light

and unraveled the fabric of the
cosmos that we thought we knew.

Come with me to one of the greatest
mysteries in the history of science.

It's a story about a man who
could do just about anything,

and Thomas Young did.

For 1500 years, no one had been
able to decipher Egyptian hieroglyphics.

By identifying six major sounds
that the hieroglyphics represented,

he was able to
decrypt six of the symbols,

which led to the complete
translation of the ancient

Egyptian language by others.

He was the first to chart the family
tree of the Indo-European languages.

As a physician, he identified a
deformity in the shape of the eye,

the defective vision
he named astigmatism.

But it was Young's design
of an experiment that sent

physics down the rabbit
hole we still live in.

It looks simple, right?

How could three sheets of cardboard
set such a catastrophe in motion?

A green glass shade like this one
will only allow the green light through,

so that only a single color,

or frequency of light
will pass through the slits.

Why was that important?

Because he assumed that the
many overlapping colors would

result in the same light
wave that Huygens imagined,

called an interference pattern.

He forced that single
color of light to travel through

two separate slits to see
what kind of pattern the light

would make on that
last piece of cardboard.

If light was a particle,
you'd expect to see two distinct

clumps of light
on the opposite wall,

where the individual
particles of light ended up

after they passed
through the slits.

But that's not what happened.

Instead, a
completely unexpected pattern.

The one that two waves would
make when they overlapped,

or interfered with each other.

That's why they're called
an interference pattern.

Young had demonstrated
that light was actually a wave.

That Newton, the greatest genius in
the history of science was half wrong.

That light was not a particle
as he confidently proclaimed.

There's a reason that
arguments from authority

hold little weight in science.

Nature and nature
only settles the argument.

And she has so many
tricks up her sleeve,

only a fool would ever consider
our understanding of nature complete.

Newton had missed
something fundamental.

Surprising, but we haven't gotten
to the really disturbing part yet.

Thomas Young left
a time bomb with a long fuse.

One that took 100 years
to burn down before it exploded.

It wasn't until the end of
the 19th century that science

developed the necessary tools to
find an opening to a hidden universe,

a realm of deeper mystery.

You can hear the discoverer's
astonishment in his own account.

Could anything, at first sight,

seem more impractical than
a body which is so small that

its mass is an insignificant fraction
of the mass of an atom of hydrogen?

Which itself is so small that

the crowd of these atoms equal

in number to the population of
the whole world would be too small

to have been detected by any
means then known to science.

That voice, that
particular organization of

sound waves frozen in
time nearly 100 years ago,

belongs to J.J. Thomson.

He's remembering his discovery of the
electron in his cathode ray experiment.

He had heated up a metal
electrode until it spit out an electron.

And another, and another.

For the first time,
an elementary particle of

the atom was made visible.

Science was breaking into
nature's vault where she had

kept her most
closely held secrets,

and that's when
things got really crazy.

If even the smallest
units of matter, atoms say,

had even smaller components,
such as an electron,

then could the same
thing be true of light?

Scientists, in their never-ending
fascination with light,

set out to devise
ways of isolating smaller

and smaller units of it.

It proved to be the passage
way through the looking glass.

It was the crossing of a
threshold into a wonderland

where the known rules
of physics do not apply.

For the first time, they were able
to isolate the tiniest unit of light,

a single photon.

And to perform Young's double
slit experiment on a whole new level,

tracing its precise path either
through the right slit or the left slit.

We'll pull over to the side of the road
for the best possible view of which slit,

the right or the left,

the photon passes through
to get to the far wall.

Left slit, right slit.

Another right slit.

Left slit.

If we watched them all day long,

the pattern would be random.

About half would go
through either slit.

Wait a second.

Where are the waves?

Where is Young's
interference pattern?

This is where the weird begins.

I cannot explain to you
what you're about to see.

That's because no one
on earth understands it yet.

If you can't live with that,

then you're not gonna be
happy with what lies up ahead.

On the smallest possible scale
that we've ever discovered,

the quantum universe, the mere
act of observation changes reality.

Okay, photons, keep on coming,
and this time we promise not to look.

You're not gonna believe this,
but we can change the pattern

on the far wall simply by
not watching which slit the

photons pass through.

I know it sounds crazy, but
in every trial ever conducted,

the outcome depends on whether
or not the experiment was observed.

So, the reason we didn't
get the interference pattern

earlier wasn't because we chopped
up the light into single photons,

it was because we
were observing which slit

the photons passed through,

but how can a photon
know if someone is watching?

A photon doesn't have eyes.

A photon doesn't have a brain.

How could it know
it was being watched?

You might reasonably conclude
that a single photon is such

a tiny thing that it's very hard to
see without using complex technology.

This machinery does
violence to the delicate photon.

It changes it, but that
doesn't explain why photons

behave like particles when we're
watching but waves when we're not.

If light is
fundamentally a particle,

then it should never
create a wave pattern,

whether we're
observing it or not.

And how can individual photons
know where to take their places,

so that as a group they create
the interference patterns of waves?

This is a maddening conundrum
at the heart of quantum physics.

Isaac Newton and
Christiaan Huygens were both

equally right and equally wrong.

Light is both a wave
and a particle, and neither.

Until we make an observation,

the photon exists in
a state of uncertainty,

governed by laws of probability.

And when we do observe it,

it becomes something
completely different.

We would be lost in the quantum
universe without Christiaan Huygens.

His probability theory
provides, even now,

the only key we have to grasping
the laws of quantum reality.

Every particle is at
the mercy of random chance

and shifting probabilities.

Thinking about it is like
looking at an optical illusion,

you can only grab
hold of it for moments at

a time before it pops
back into something else.

In the quantum universe,
there's an undiscovered

frontier where the laws of
our world give way to the ones

that apply on the
tiniest scale we know.

They're divorced from
our everyday experience.

How can you think about a world
that has different rules than ours?

It's not easy.

That's why I want to take you
to this place where it's not

only possible to make
such a leap, it's mandatory.

It's a world very
much like our own,

except in one respect.

It just happens to be
missing a spatial dimension,

the third one.

Ie

We have to be able to
imagine another dimension.

That's very hard to do.

It's much easier to wrap
your mind around a world that's

missing one of the three
dimensions that we take for granted.

The beings of the world we're
about to enter have only two.

This world was first imagined
by a man named Edwin Abbott.

Everyone and everything here
and everyone they know

and love is flat.

Their houses are flat.

Some are squares,
others are triangles.

Some have more complex shapes,
say octagons.

But all are completely flat.

They scurry about on
foot or in little vehicles,

in and out of
their flat buildings,

busy with their flat lives.

Everyone on this
world has width and length,

but no height whatsoever.

These Flatworlders know about
left-right and forward-back,

but have no hint, not
an inkling, about up-down,

except for one tiny group,

the mathematicians,
who imagine something more.

The mathematicians dream of
a world in three dimensions,

but it's too hard for most of
the Flatworlders to think about.

The mathematician says,

"Listen, it's really very easy."

We all know left-right.

We all know forward-back.

"So let's just imagine another dimension
at right-angles to the other two."

But the Flatworlders say,

"What are you talking about?"

At right angles
to the other two?

Everybody knows that there
can only be two dimensions.

Go ahead, wise guy, show
us that third dimension.

"Where is it?"

So the mathematician
draws a picture.

Poor teacher.

Nobody listens
to mathematicians.

Every creature on flatworld sees
its fellows as merely short lines,

which are the nearest
sides of their oblong bodies.

But the insides of a Flatworlder
are forever mysterious,

unless exposed by some
terrible accident or autopsy.

And then one day, we came along.

Hello? How are you?

Hi, I'm a visitor from
the third dimension.

Hello? I feel
sorry for the little guy.

To him, it appears that my greeting
is emanating from his own flat body,

an alien voice from within.

That's because
nothing can come from above.

There is no above in this world.

A three-dimensional
creature like me can only exist

on Flatworld where my feet
touch the surface of the plane.

Sorry, little guy.

I know how weird
this must be for you.

Don't worry.

You'll have a perfectly safe
trip to the third dimension.

Nothing's gonna harm you.

But this is your chance
to see a whole new perspective

on where you live.

At first, our Flatworlder can make
no sense of what is happening.

It's utterly outside the
realm of Flatworld experience.

But eventually he realizes
that he's viewing Flatworld

from a totally new
vantage point above.

Now, he can see
into closed rooms.

He can see into
his flat fellows.

This unprecedented
three-dimensional view of

his two-dimensional
universe is devastating.

Traveling to another dimension
provides as an incidental benefit,

a kind of X-ray vision.

Just as the Flatworld
houses can have no roofs,

their inhabitants
can have no sky,

because that sky could only
exist in a third-dimension.

Little guy's suffered enough.

Better put him down.

From the point of
view of its spouse,

this Flatworlder has
distressingly disappeared,

then unaccountably
materialized from out of nowhere.

It's easier to imagine the
universe in fewer dimensions

than our comfort zone of three.

A zero-dimensional
universe is just a point.

A dot with no dimension at all.

Or a one-dimensional universe
where everyone is a line segment.

Or the
two-dimensional Flatworld.

Or 3D, where we all live.

We can laugh at
the cluelessness of

two-dimensional creatures.

Unable to imagine a
three-dimensional world.

But, when it comes to quantum
reality, that inability,

resembles the problems we have.

The best we can do for
now is to imagine this

three-dimensional cube as
a four-dimensional hypercube.

We're living in
our own Flatworld,

just like the 19th Century
writer, Edwin Abbott,

in his book
Flatland, was trying.

It's the rarest of events,

when a searcher happens
on a hole in the curtain

that hides the matrix.

It was not until Isaac Newton
that we began to understand

the motions of the worlds.

The variety of living
things always astonished us,

but Charles Darwin discovered
how time and the environment

sculpted these
forms, including us,

from life's first living cell.

We had no idea that the
quantum universe even existed

until Albert Einstein
revealed it.

The mysterious laws of this
paradoxical cosmos deeply disturbed him.

And we have yet to
understand them ourselves.

At its heart, was a
relationship that seemed

to violate the speed of light.

The backbone of modern
physics and reality itself.

That blue photon, a
quantum packet of light,

will divide into two.

Splitting its energy and
emerging as a pair of red photons.

These new red photons are married
in the most profound physical sense or,

as quantum physicists
say, entangled.

And no matter how far
they wander from each other,

in space and in time, the
bond between them will endure.

It's a little like Plato's Ancient
Greek explanation of love.

A single being splits
into two and separates.

For the rest of their existence,

each remains the one and
only soul mate of the other.

Exquisitely attuned to
the inner life of its partner.

Even if they are separated from
each other by a whole universe.

Observe the spin of one photon
and you will instantly know

the spin of its
entangled partner.

It's not something special
about these particular photons.

As far as we know,
it's the rule.

This kind of long distance
relationship has been going

on for the whole
history of the universe.

Two photons born in the early
universe nearly 14 billion years ago,

separate and head
in opposite directions.

They could end up tens of
billions of light-years apart and yet,

over all that time
and across all that space,

the bond between them endures.

What is it about a photon
or an electron or any other

elementary particle,
once entangled,

that makes them capable
of such lasting fidelity?

And to me, an
even stranger fact,

is that all it takes to
sever that awesome commitment,

is the simple
act of measurement.

All I have to do is measure
the spin of one of them.

How can it be that only
one seemingly innocuous act

by a third party can forever sever
such a deep and enduring bond?

There she is.

Half of our cosmic couple.

Somewhere, at this very moment,

many billions of
light-years away from us,

her soul mate is suddenly
feeling something different.

The thrill is gone.

The bond has been broken.

They are no long
entangled with each other.

Our simple act of observing
one of them has ruined

a marriage that has lasted
since the beginning of time.

But, how could that be?

And that's not the only
crazy thing about this.

How could one photon,
a cosmos away from its partner,

send a break-up message
across the universe and have

the other photon
receive it instantaneously?

Faster than the speed
of light could possibly carry

such a message between them.

These are two of the greatest
unanswered questions in science.

So, don't worry
if they bother you.

These questions haunted a mind as great
as Einstein's for the rest of his life.

There's nothing more intriguing
to a scientist than a paradox.

If light, the
fastest thing there can be,

has a cosmic speed limit,
then it would be impossible

for one photon to communicate with
another instantly across such vastness.

Einstein found it almost unbearable
to live in this kind of universe.

Where what he called, "spooky"
action at a distance was possible.

Remember those particles
in the double slit experiment?

Taking either the
left or the right slit?

Those choices amounted to
nothing more than random chance,

but even random chance
must follow certain rules.

That's the basis for
Huygens's probability theory and

for calculating the odds in
flipping a coin or throwing dice.

When Einstein applied
probability theory to the

problem of entangled protons,
he was deeply disturbed.

If these photons could brazenly
violate the speed of light,

then the universe and
all of creation was nothing

more than a casino where the
laws of nature can be broken.

Einstein dealt with his
discomfort by clinging to the

idea that the dice was somehow
loaded in a way we didn't yet understand.

We had passed this way before.

More than 100,000 years ago,
our ancestors domesticated fire.

They didn't know what fire was,

but they used it anyway
to build a civilization.

And so it was
with quantum physics.

We didn't need to understand
it to exploit its countless

practical applications,
scientific and technological.

Much as our ancestors used fire
without understanding how it worked,

we lived with this
mystery for decades.

We have entered a territory
beyond the reach of classical physics.

Where the elementary particles
that make up everything,

including us, respond to events
they can't possibly know about.

In the outlaw casino
of the quantum universe,

there is no objective reality.

And that's where
we're headed next.

We are made of atoms.

The bizarre quantum
universe is inside us,

tugged on by undiscovered moons.

Performing its impossible magic
on every level of life and experience.

What is this?

A smattering of
stars or something else?

We are sending an image
made of light to your eyes.

It's arriving at your
retina at this very moment.

The cells in your retina
are changing chemically right

now because we are stimulating
some of them with photons.

Your retina stores these
changes for a fraction of a second.

Now, it's erasing them in readiness
for the next barrage of photons.

Your retina doesn't
detect all of them, it can't.

It picks up on only a small percentage
of photons that come your way.

It's impossible to predict
which particular cell in your

retina will catch a photon.

Even when it comes to
something as vital as our vision,

all we have is
our probabilities.

Now, we're shooting
many more photons at you.

More like, half a million.

What are you looking at?

The surface of some
planet orbiting another star?

We need still more of
those photons to know for sure.

Say, a couple
of million or more.

Only when we send all
of those photons your way,

tens of millions of them,

does reality
begin to take shape.

Over time, probabilities become
likelihoods and eventually,

likelihoods become certainties.

But is there really any
such thing as certainty.

If everything,
even our own vision,

is governed by probabilities,

can there be any
absolute reality?

Is there any hope of
rescuing our classical idea

of reality in the
quantum universe?

Scientists have come up
with one way to preserve our

traditional understanding
of cause and effect called

"The Many Worlds Hypothesis."

That's a misnomer because it
can't be tested scientifically,

but it goes like this.

Every probability that
can happen does happen in

some parallel cosmos
that is foreclosed to us.

An infinite number of
ever branching realities.

Unfolding at every
possible juncture.

Every probability that
can happen does happen

in some parallel cosmos...

♪ Oh, we need the funk ♪

♪ Gotta have that funk ♪

♪ Oh, we want the funk ♪

Or is probability
just an illusion itself?

A phantom of our ignorance?

It is, if we live in a
universe where every single

event was already foreordained
at the beginning of time.

What is called,
superdeterminism.

In a superdeterministic
universe,

the catastrophic failure
of treaties, a sneeze.

The asteroid that
wiped out the dinosaurs,

one particular bee pollinating
one particular flower.

You listening to me right now,
all of these events were set

in lockstep motion at the
moment the universe began.

When it was all no
larger than a marble.

Superdeterminism has
an additional virtue.

It can explain
mystery of entanglement.

The ability of entangled particles to
communicate across the vastness,

apparently violating
the speed limit of light.

In a superdeterministic cosmos,

entangled partners
separated by whole galaxies,

don't need to hear from
each other to change their spin.

They were always destined
to do so at that precise moment.

And so were their partners.

And so was the intruder,

who severed their bond
by observing one of them.

Think of it.

All these events
and trillions of others,

inscribed in the potential of
the first moment of the universe.

Since everything in the
universe is made of those

same elementary particles,
including us,

we are subject to the
same laws as those that rule

the quantum universe.

And so it is,
for what will happen next.

And what will happen after that.

The good news is
superdeterminism gives us

a solution to the
mystery of entanglement,

the bad news is,

it seems to rob
us of all agency.

Are we just going
through the motions,

acting out a script that
was written for us nearly

14 billion years ago?

All the while,

telling ourselves how
clever we were in that argument.

How selfish, how brave.

If you could only change that
one little thing about yourself.

In a universe
devoid of free will,

are we nothing more
than deterministic robots?

We have found a way to hitch
a ride on the uncertainties.

To forge technologies that
would otherwise be unattainable.

We have built a quantum clock.

One that you never have to wind.

It will only lose a single second
in the next 15 billion years.

A three-dimensional lattice
of laser light keeps isolated

atoms of the element strontium,

suspended in space.

For all we know, we
may be near collections

of preprogrammed particles
in a deterministic universe.

But I say, let's
not live like we are.

Besides, we have no way
of knowing if that's true.

And to think that,
in some sense,

our freedom to explore
the quantum realm begins

with Thomas Young.

Remember, it was Young
who also found the key to

decrypting the lost language
of the ancient Egyptians.

With quantum encryption,
we are creating codes that

vanish the moment someone
tries to hack into them.

The key to the code, can
be sent via entangled photons.

The observer effect is
our insurance policy that no

spy can decipher the
message without causing the

entanglement to break apart.

Rendering the
message unintelligible.

We still don't know how a
photon can be both a particle

and a wave at the same time.

What I love about science,
is that it demands of us,

a tolerance for ambiguity.

It requires us to live with
humility regarding our ignorance,

withholding judgement
until the evidence comes in.

That needn't prevent us
from using the little we do know

to search for and decrypt
new languages of reality.

In this vast cosmos,
we are all Flatworlders.

Science is the struggle
to imagine and find above.

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