All language subtitles for HTUW S05x08 The Dark Matter Enigma

SUB BY : DENI AUROR@
https://aurorarental.blogspot.com/

Everything we see,

from people to cities to the millions of stars

that fill the night sky,

they're all made of the same stuff:

Atoms of matter.

But there's something else out there,

invisible dark matter.

It fills our universe, too.

And it could be the key

to the existence of everything,

including us.

Captions paid for by discovery communications

There's something about our universe

that might surprise you.

We exist side by side with cosmic ghosts.

Normal matter, the stuff that makes stars, planets

and people, accounts for just a fraction

of what's really out there.

An invisible web of strange material

connects the galaxies

that make up our universe.

We can't see or feel this mysterious stuff.

But we're pretty sure it's there

because we can measure its gravity.

It's a little weird, uh, to ...

to discover that what you see,

what you know, everything in your experience

is actually the tiniest, teeniest fraction

of what's actually out there in the universe.

Most of the matter in the universe

is made of a substance

that we have not even discovered yet.

This strange ghostly stuff

is called dark matter.

Most scientists believe dark matter

is a kind of elementary particle,

hanging in vast networks

of clouds or halos

that link the 2 trillion galaxies

that make up our universe.

If ... if you could put on some sort of ...

some sort of mask or goggles that could detect dark matter,

you would see millions of them passing through you

every second, millions of them, billions,

all around you all the time.

You can't see them, but their effect is very real.

Crucially, we are now beginning to understand

the ghostly tendrils of dark matter

have shaped everything we see in our universe today.

They may have even played a key role

in the evolution of us.

Dark matter is kind of like a ...

an invisible puppet master with invisible strings

controlling the movement of everything we can see.

It is the central reason for our existence.

The fact that our galaxy exists

for us to exist in is due to the fact

that dark matter exists.

If you were to think about it,

dark matter is the matter that matters.

So how did dark matter shape the universe we see today?

Best way to find out:

Take a trip back to the beginning

of everything, the big bang.

13.8 billion years ago,

an infinitely hot and infinitely dense speck

bursts into existence.

This speck is the infant universe.

It's hot and filled with nothing but pure energy.

As it expands, it cools.

And some of the energy condenses

to form tiny subatomic particles.

But these aren't the protons or electrons

that make up you and me.

They're particles of dark matter.

If dark matter is made up of strange subatomic particles,

these were probably created in the very,

very early universe,

moments after the big bang itself.

Even normal matter may not have existed yet

when dark matter did.

The universe is still less than a second old.

It's incredibly dense and hot.

In this confined space,

the dark-matter particles are crammed tightly together.

Collisions are inevitable.

The particles annihilate each other

as they smash together,

releasing a burst of energy

plus, something new:

Subatomic particles of ordinary matter,

the stuff that makes up the universe we can see.

It's very plausible that two dark-matter particles

that collided and annihilated

in the very early universe produced an electron

that's now a part of my body.

So I might actually be a child of dark matter,

you know, even in a very direct and literal sense.

Did colliding dark matter particles

really make all the ordinary matter

we see in the universe today?

It depends on what dark matter particles are made of.

The best best is that dark matter

is a particle 100 times the mass of a proton.

But unlike ordinary matter,

it doesn't interact with light or anything else.

One of the top contenders for dark matter

is something called a wimp,

a weakly interacting massive particle.

This was a particle that was made in the big bang

that's left over today.

Wimps are the leading contender

because if you plug their properties

into computer simulations of the big bang,

you end up with a universe

that looks just like the universe we see today

with 84 percent dark matter

and just 16 percent ordinary matter.

We get numbers that correspond roughly to the amount

of dark matter we infer in the universe.

So there's good evidence,

indirectly, that these particles may be the dark matter.

If current thinking is right,

the subatomic building blocks

of the universe were forged from colliding wimps.

But dark matter's role in building the cosmos

was just getting started.

In fact, dark matter may answer

one of the great mysteries of cosmology,

how the primordial gas

that filled the early universe clump together

to form the first stars.

The mystery begins when the universe

is less than a second old.

It suddenly expands.

In a period of about a millionth of a billionth

of a billionth of a billionth of a second,

our universe puffed up

by over 90 orders of magnitude in volume

and went from the size of a single atom

to the size of a basketball

in a fraction of a fraction of a fraction of a second.

This rapid expansion creates

a vast sea of evenly spread particles,

which cool to form atoms of hydrogen and helium,

the gases that will one day collapse

under the force of gravity

to become the first stars.

But there's a problem.

The gas of the early universe

is too evenly spread,

too smooth for gravity

to pull on some parts more than others

and trigger regions of the gas to collapse and clump.

If the universe was completely smooth,

it would be beautiful but boring because no ...

nothing would exist that we could see.

Something must have made

the smooth sea of gas collapse

and build the first stars,

something weird operating on the tiniest of scales.

One thing that really is interesting about that

is that on very small scales,

due to the Heisenberg uncertainty principle,

strange things can happen.

When we see a car, a runner or even a spacecraft,

we can calculate their motions.

In the tiny quantum world of the infant universe,

that certainty is missing.

Nothing has a definite momentum or position.

And because nothing was locked in place,

fluctuations or grooves

could develop in the expanding universe.

And when the universe inflated rapidly,

these fluctuations because frozen in place,

creating dense points around

which the gas clouds could collapse,

acting like gravitational seeds for star formation.

Fortunately, there were these tiny seed fluctuations,

which acted like a kind of cosmic DNA,

determining where and when

and how the structural layer grew into the stars,

the planets and all the other awesome structure

we see around us in today's world.

I think it's one of the most beautiful ideas

of all of science, that something

like the Heisenberg uncertainty principle,

which we thought applied only to tiny things

in quantum mechanics, ultimately is responsible

for the biggest structures

that we know of in the cosmos.

So thank you, Heisenberg.

The development of the fluctuations

seems to solve the mystery of

how the universe evolved its structure.

But there's another problem.

If you do the math,

the mass of gas alone

doesn't pack enough gravity

to create all the stars

we see in the universe today.

Something else must have added mass

to the collapsing gas clouds.

Could that something have been dark matter?

Today, cosmologists are grappling

with a puzzling paradox,

how did the gas that once filled the universe collapse so quickly

to form the stars we see today

when there wasn't enough gas to begin with?

The only answer: Something other than normal matter

must have been out there,

adding mass to the gas clouds,

helping them collapse into stars.

If you only have the normal matter,

it turns out things just don't grow fast enough.

You don't have enough structure in the universe.

We can calculate that there wouldn't have been enough time

since the beginning of the universe

for normal matter to collapse to form galaxies,

stars, planets and people.

Many scientists now believe

the extra push speeding up the formation of stars

was the gravity of invisible dark matter.

Even though dark matter and normal matter

can't really interact directly,

they do interact via gravity.

And it turns out that is

critically important to our existence.

If you put that dark matter in, everything works out.

And it's really kind of amazing how well, uh,

we can make the universe work.

As the early universe expands, it also cools.

It's now a sea of hydrogen and helium gas.

There's also lots of dark matter around,

which is built up in the fluctuations or grooves

in the expanding universe,

creating regions of high gravity.

Tegmark: The dark matter was free to actually start doing

its own thing and started growing its patterns

and its clustering before the ordinary matter did.

And that's why dark matter

actually played such a key role in ...

in creating this much more interesting universe

that we live in today.

The gravitational pull of these clumps

of dark matter drags in huge clouds

of hydrogen and helium.

The clouds get denser and denser

until they trigger nuclear fusion.

And the first stars in our universe are born

thanks to dark matter.

It clumped and collapsed.

And that would later allow all the normal matter to fall in.

Dark matter is what gave the initial kick to form stars,

black holes, planets,

aliens, people and everything else.

You really have to understand that dark matter

is the dominant form of matter in the universe.

At the very beginning of the universe,

that's what got everything started.

And regular matter was just along for the ride.

Dark matter explains how the first stars

in the universe burst into life.

But when astronomers gaze back to the early universe,

they see these stars weren't alone.

They lived alongside monsters,

supermassive black holes.

A real puzzle is that we see some of these

supermassive black holes in the very early universe.

So there really wasn't enough time between the big bang

and when we're studying these things for them

to grow to such large sizes.

Supermassive black holes are the heavyweights

of the early universe.

Some weigh in at 12 billion times

the mass of our sun.

How they grew so gigantic so quickly has been one

of the biggest mysteries in cosmology

until perhaps now.

Some scientists believe the beginnings of these early

black holes could have been formed

by a strange superstar called a dark star.

Dark stars would be the very first stars

to form in the universe.

So they form when the universe

is about 200 million years old.

And these are very early objects.

So they are made of ordinary matter.

They're made of hydrogen and helium.

But they're powered by dark matter.

Katherine freese believes

that as these giant early stars

formed in the early universe,

their enormous gravity

dragged dark matter particles into their cores.

These particles smashed into each other,

releasing bursts of energy.

Whenever they encounter each other,

they annihilate and turn into something else.

That means a lot of heat is released, a lot of energy.

And it's that energy that could power stars.

Bullock: So it's possible that in some stars,

their internal reactions

are actually being powered by dark matter.

Effectively, dark matter annihilation

is providing energy to keep these stars lit up.

It's quite remarkable because

you only need one part

in 10,000 of dark matter

to power an entire giant star.

The energy from dark matter annihilations

allowed the dark stars

to become super large.

These early objects are really strange.

They're very cool.

And they're really, really big.

They're ... the size of these things

is 10 times the size

the distance between the sun and the earth.

So they're really, really big puffy,

cool and powered by dark matter annihilation.

But when their dark matter fuel ran out,

these huge stars had nothing left to hold them up.

There's nothing to sustain this big, puffy object.

It's gonna collapse.

If it's big enough, you collapse directly to a black hole.

Because the collapsing star was so huge,

the new black hole it formed was also super massive.

Freese: If dark stars exist,

then black holes could be born big.

So because of dark matter, you could start with very,

very massive black holes early in the universe.

But that's only because you have the dark matter

to power these early stars.

Dark matter may have helped form

the basic units of our universe,

stars and black holes.

But did the reach of this mysterious puppet master

stretch even further?

There are patterns in the distribution

of galaxies and galaxy clusters

that normal matter alone can't explain.

Our home star, the sun,

is just one of 200 billion stars

that make up our galaxy.

But how did this vast collection of stars first form?

View the milky way with imaginary dark matter goggles.

And you'll find a clue:

A halo of dark matter surrounding the galaxy.

A dark matter halo helps the galaxy form

simply by providing gravity

to pull things together, catalyzing it.

And that may have allowed our galaxy to form.

The gravity from this huge construct

brought regular matter in to form

the milky way in the middle.

Astronomers used to think

the distribution of galaxies

throughout the universe was random.

But recent observations

have discovered something extraordinary:

Walls of interlinked galaxies

that stretch through space for millions

and millions of light-years.

One of the most amazing discoveries

of the last few decades

is that galaxies form these vast superstructures

that actually span the known universe.

The great wall is a filament of galaxies

that stretches hundreds of millions of light-years.

To understand how these vast

galactic structures formed,

astronomers use telescopes like the

atacama large millimeter array,

or Alma for short.

It's an array of 66 radio telescopes

and so powerful it can peer back billions of years

to the formation

of the earliest galactic structures.

Now, Alma can actually look back

into the history of the universe

and see similar structures being formed

by these giant baby galaxies,

sort of a proto great wall.

Alma gives us a snapshot

of how the adolescent universe evolved.

It shows us that as the universe expanded,

the newborn galaxies aligned with their neighbors.

It was as if the expanding universe

was producing sticky filaments.

And the materials building new galaxies

were sticking to these threads like flies to a spider's silk.

It turns out these invisible filaments are dark matter.

It's like a scaffolding of dark matter

that was pulling normal matter into it.

As the universe expanded,

the original clumps of dark matter

didn't expand as quickly as the rest.

They stuck together like sticky Taffy

with their powerful gravity

shaping them into filaments.

The filaments formed a sprawling web

of dark-matter strands,

stretching throughout the universe.

The gravity of this dark matter web

then dragged in normal matter,

which built up where the filaments meet

and eventually collapsed to form galaxies.

The thicker filaments pulled in the most gas,

providing the building blocks for galaxy clusters.

They actually fall along these tremendous filaments

across the universe,

hundreds of millions of light-years across.

We're talking about tremendously large structures.

But they would not exist if it weren't for dark matter.

And the galaxies themselves were able to form

because of this structure.

There are galaxies and stars and planets

and you here today.

That's because of the dark matter

providing the framework.

Bullock: Just like a grid system in a city defines

where buildings are going to be,

galaxies assemble themselves around the cosmic grid.

It seems like city planners here on earth

have been following the lead of the universe,

except those planners used roads

in place of dark matter.

New York is the perfect example.

Freese: Let's imagine New York City without roads.

There would be no structure, no foundation.

Then the whole thing would fall apart.

When people first designed the city,

they laid down the grid.

They built the roads.

And that was really the foundation.

And then later on, they built the buildings.

Just like the dark matter web

transported the building materials

for galaxies,

New York's grid of roads brought the steel

and concrete to build its city blocks.

It's the dark matter that gives you the foundation.

And it gives you the cosmic structure.

And then later on,

the normal matter fell into the galaxies

and the clusters that we see today.

The elegance of this newly discovered structure

of the universe really astounds me.

You have this web of dark matter,

and it almost creates highways for regular matter

to fall into these nexuses.

And that's where you form the biggest, brightest galaxies.

The more cosmologists study dark matter,

the more they see the crucial role

it's played in shaping the universe we see today.

But despite these insights into our origins,

scientists still don't know

what dark matter actually is.

How do you measure something that you can't see or feel?

In the last 50 years,

astronomers have discovered something

incredible about our universe.

It's controlled by an invisible puppet master

called dark matter.

Dark matter created and organized

the large-scale structure of our universe.

It may have even created the atoms

that make up your body.

But it remains a mystery because we can't see it,

feel it or measure it directly.

One of the properties of dark matter

that we know for sure is that it doesn't interact with light.

It doesn't shine. It doesn't reflect light.

And so if you shine, uh, a laser beam on dark matter,

the laser beam goes right through.

It doesn't do anything.

The term dark matter might actually be

a little bit misleading.

Maybe the real term for this stuff

is transparent matter.

But somehow that doesn't sound quite as cool as dark matter.

So if we can't see dark matter,

why are scientists so sure it's there?

We know dark matter's there the same way

we know many things are there that we can't see.

We use gravity.

Dark matter may not interact with light,

but it interacts with gravity.

Bullock: It's only by studying the motions of stars,

even the motions of galaxies and the clustering of galaxies

do we know that there's a lot of extra stuff

out there that has mass

that's directing these stars

and galaxies to move in ways that are somewhat unexpected.

The first person to detect this unusual movement in galaxies

was astronomer Fritz zwicky in the 1930s.

Using a custom-built 18-inch telescope,

he studied how multiple galaxies interact inside a tight

grouping of galaxies known as a cluster.

Fritz zwicky, studying the motions

of galaxies and clusters.

And what he saw is that these galaxies

were moving too fast.

Every concentration of matter

has associated with it an escape velocity.

And if you're moving faster than the escape velocity,

you should no longer be a part of that system.

Just as a rocket can escape earth's gravity

if it's traveling fast enough,

a galaxy should break away from a galaxy cluster

if it's moving with enough speed.

Zwicky noticed that the galaxies in the coma cluster

should be moving fast enough

to escape the gravitational pull of their neighbors.

But instead of speeding off

into different parts of the universe,

the galaxies remained bound together.

Zwicky thought some unknown material was adding mass

and, therefore, extra gravity to the system,

holding the galaxies in place.

Maybe there's something extra there

that's providing more gravity

than we can account for based on what we see.

At the time, zwicky's ideas

for this unexplained source

of extra gravity fell on deaf ears.

Zwicky was a very unlikable fellow and,

I think, uh, infuriated many of his colleagues.

And that perhaps was one another reason

why they were less willing to accept his suggestion.

The other is that I think he was so far ahead

of his time as a scientists

that it just took time

for the rest of the community to catch up.

It took another 30 years

and a crucial discovery by astronomer Vera rubin

before dark matter made it into the text books.

Vera rubin was looking at galaxies themselves.

Now, galaxies are collections of gas and stars and dust.

And they have an overall motion.

Our milky way galaxy's a disc.

And that disc is moving around the center of the galaxy.

Bullock: The stars in the middle of the galaxy you expect

to go around very fast.

And the stars at the outskirts of the galaxy,

you expect to go around very slowly,

just like the inner planets go around the sun very quickly

and the outer planets go around the sun much more slowly.

What she found is that the outskirts of the galaxy

were spinning around the galaxy

at the same speed as parts that were closer in.

And that didn't make any sense.

The stars of the galaxy appeared to be fixed,

almost as if they were glued to a giant spinning wheel.

Bullock: And the only way that can be is

if there's some additional gravity there,

some additional stuff there that's adding mass,

that's adding gravity, that's making those

outer stars go faster.

The only conclusion was that the spinning wheel

was being affected by something very massive

and completely invisible.

When astronomers turn their telescopes

to see for themselves

if this invisible mass was real,

they found evidence for it almost everywhere they looked.

As more and more other people were able to replicate

what they had done, people started to realize,

"whoa. You know, Fritz and Vera were right.

This weird stuff is really out there."

But there's not only just a little bit.

Every galaxy we can see, essentially,

is dominated by dark matter.

Now, we know that dark matter is out there.

But we're still no closer to working out what it actually is.

We think it may be a particle called a wimp.

But it could be a whole family of particles

that forms dark atoms and dark molecules.

Perhaps an entire dark universe is out there,

filled with invisible dark planets

and illuminated by the dark light

of their dark stars.

Scientists are struggling to uncover

the true identity of dark matter.

To date, the best candidate

is a theoretical particle known as a wimp.

But because wimps can pass through

ordinary matter like a ghost,

the researchers have been left empty-handed.

Not only could dark matter be going through me right now,

but it almost certainly is

and I'm just not noticing it.

And this is why we're building

these very fancy detectors here on earth,

to try to catch them.

Until scientists can capture

and analyze a wimp, all bets are off.

Tegmark: The main challenge for the wimp theory is

that we simply haven't found any wimps yet.

And we've been looking pretty hard for ...

for a lot of years. And pretty soon,

it's gonna start to get embarrassing.

Perhaps dark matter isn't made of wimps.

Perhaps the stuff that makes up dark matter

is stranger and more complex

than we ever thought possible.

We know that regular matter comes in many different forms.

There are electrons and protons,

neutrons, quarks, all of those.

Why should we assume there's only one kind of dark matter?

Our approach could be all wrong.

Instead of looking for a single type of particle,

there could be an entire zoo of dark matter particles.

Particles of ordinary matter interact

with each other to form atoms and molecules,

the stuff we touch and see.

If dark matter is made from different particles,

it could do the same,

interacting and building dark atoms of dark stuff,

perhaps even a universe of dark materials.

If we can show that dark matter interacts with itself,

that means their really could be dark matter galaxies,

dark matter stars, dark matter planets

and people all around us right now

that we were not aware of.

Could this shadowy dark universe really exist?

In 2012, the chandra X-ray telescope

gave astronomers the first clue

to whether dark matter interacts.

The telescope observed the collision

of two galaxy clusters,

each packed with hundreds of galaxies.

Astronomers hope to see what would happen

to the dark matter inside the clusters.

Would it show any signs of interacting?

What does the dark matter do when these clusters collide?

Well, that's the big question.

When the clusters come together,

does the dark matter smack and drag

or does it go right on through?

If we can measure that difference,

we can tell does the dark matter self-interact or not?

The galaxies pass through each other.

But something is left behind:

A tangle of dark matter.

It looks like there's some extra dark matter

that's been left behind in the middle.

So it looks like as these two dark matter balls

have come together, there has been some extra drag.

And that drag has deposited,

has left a bit of dark matter kinda sitting in between.

To produce the drag,

the dark matter in the colliding galaxy clusters

must have interacted.

If this observation turns out to be correct,

it means that some dark matter interacts with itself.

If that signal holds up,

then it could be a really smoking gun

detection of self-interacting dark matter.

And that would be a game changer.

Perhaps there could be dark matter planets

and dark matter living entities.

There could be a hidden ... hidden dark matter universe,

if you wish, of ... of hidden dark matter objects.

It's ... it stretches the limit of plausibility,

but it's ... it's, uh, it's not impossible.

If this dark sector really exists,

there could even be dark light.

So imagine you have this dark matter universe

and it has this dark radiation.

And this dark radiation can travel in waves

that we call dark light,

then maybe you could put on your dark glasses

and actually view this dark universe

via the dark light.

Interacting dark matter

suggests invisible worlds

next to our own.

But are these visions real or just a Sci-Fi fantasy?

I think dark matter stars, dark matter planets,

dark matter people are more in the realm of science fiction

at this point.

It would require a plethora of tooth fairies

to imagine that the dark sector

is that complicated

to actually reproduce something like our sector.

So in order to have, uh, dark planets

and dark people and dark TV shows,

it's... people have imagined it.

And I'm not saying they haven't.

But it certainly stretches the realm of,

uh, credibility.

There is so much dark matter out there

that it controls the very fate of our universe.

If even a tiny fraction of it could interact

with other forms of dark matter,

then maybe all bets are off.

Even a tiny percentage of dark matter

interacting could have huge implications

for the future of life on earth

because a controversial new idea

suggests that in the future self-interacting dark matter

could send a hail of comets our way.

How do we know?

Because dark matter may have done it before.

Dark matter is the dominant

creative force in our universe.

But could it have helped to create us, too?

Some scientists believe that a key moment

in human evolution

may have been directly affected by dark matter

in the milky way.

This controversial theory is inspired

by one of the most violent days in earth's history.

65 million years ago,

an object the size of mount Everest

slammed into the earth.

The impact turned the sky black

and set the continents on fire.

Rampino: The amount of energy released in that explosion

is about a billion times the Hiroshima bomb ...

atom bomb that was dropped

in world war ii, a billion times.

This catastrophic event

ended the age of dinosaurs and paved the way

for our mammalian ancestors to flourish.

But was it a one-off?

Mass extinctions have happened

on earth multiple times.

So an obvious question to ask,

is there any pattern?

Is there any time that we know is more dangerous,

more likely to have a mass extinction event?

And is there anything we can link it to

in the larger universe?

Geologist Mike rampino thinks there is a pattern.

And it could be linked to dark matter.

Rampino: We were looking at the possibility of cycles

in the geological record.

And we found what seemed to be a 30-million-year cycle

in many kinds of geological phenomena.

Now, what could be causing this kind of

a cycle of 30 million years?

A clue comes from the passage

of the sun around the milky way.

It takes the sun about a quarter billion years

to move once around the milky way galaxy.

But as we spin around the galaxy's center,

we also kind of Bob up and down

through the larger disk of the galaxy.

Weaving like a carousel horse,

our sun passes through the galactic plane

around once every 30 million years.

And as it does this,

it may also be passing through a layer

of self-interacting dark matter.

Bullock: It's a little bit speculative, but the idea

is that a very small fraction of the dark matter

is able to form a disk along

with the disk of our galaxy.

So in between the stars,

in the disk where the sun lives,

there's a very, very thin disk of dark matter,

and this could do very exciting things.

This disk has a strong gravitational pull.

When our solar system passes through it,

the disk's gravity may disrupt the orbits of comets

in the outer solar system

and send them hurtling towards the earth.

Perhaps the object that killed the dinosaurs

and paved the way for human evolution

was just one of a series of extinction-level events

triggered by dark matter.

We've called this the Shiva hypothesis

because the god Shiva in the hindu religion

is the god of destruction and renewal.

So one world is destroyed.

The dinosaur world is destroyed.

And the world of mammals and birds, uh, begins.

If that's true,

then dark matter has played an important role in us

being here from the very beginning,

right after the big bang,

all the way through the evolution

of humans themselves.

The idea that dark matter

caused mass extinctions

on earth is, frankly, terrifying.

The solar system is still bobbing up and down

through the galactic plane.

Perhaps the next disruptive comet

will have our name on it.

Fortunately for us,

the theory that dark matter

helped wipe out the dinosaurs

is just that.

We are talking about speculation on top of speculation.

If dark matter exists in this manner,

if it's made of some sort of particle

that interacts with itself

just enough that it forms a disk

and if this disk exists, if, if, if, if,

this idea is interesting.

If I were the book maker here in New York,

I would bet against dark matter killing the dinosaurs.

But I think it's great that people are doing the math

more careful and ...

and really testing these scenarios.

The outlook is unclear.

But one thing's for sure:

Without dark matter, we wouldn't even be here.

The fact that there's a universe full of matter and stars

and galaxies is due to the fact that dark matter exists.

So if some young person in some ways asks me,

"where do I come from?"

I'd have to say, "from dark matter."

Dark matter dictates how the galaxies form

and how they move and where we'll go in the future.

We're actually in dark matter's universe, not ours.