All language subtitles for How.the.Universe.Works.S10E03.Hunt.for.Dark.Matter.1080p.WEB.h264-KOMPOST

Scientists believ there is a
hidden substance deep in space

that keeps the cosmos runnin

But is that substance real?

We've never seen dark
matter, it's completely invisible,

but we know that
it has to be there.

Not only can you not see it, you couldn't
really touch it or taste it, or smell it,

and yet it is all around us it
affects everything that we do.

After searching for decades,

we still don't understand
this inexplicable substance

We know dark matte is there because
we feel its strong gravitational pul

but it just doesn't
want to talk to us.

There's evidence
that dark matter

makes up 85% of all
the matter in the universe.

We can see dark matter
holding galaxies together

and ripping other structures
apart, we even see it bending light.

Dark matter itself has been around
since the beginning of the universe.

Without dark matter,
we wouldn't be here.

But if you can't see dark matter

and if you can't touch
it, does it really exist?

The Hyades star cluster.

This family of 700 stars
is 150 light years from Eart

At the scale of the
universe it's in our backyard.

Hyades is actually
close enough to Earth

that you could see it
with your naked eye.

When you look
up at the night sky,

Hyades is in that
V-shape in Taurus the Bull.

For most of its
650-million-year lifetime,

the Hyades enjoyed
a peaceful existence.

But something is
breaking the calm.

The Hyades cluster is one of the
most well-studied clusters of stars

we have in the entire sky
and yet there's something

very deeply mysterious going on.

Two star tails extend
from the cluster center,

they should be roughly equal
but one tail is hemorrhaging stars.

Something is disrupting it, there's
something exerting a force on it

that's ripping stars
out of their orbits.

Something with
immense gravitational pull

has passed by the cluster

and robbed it of stars.

In order to be gravitationally pulling
stars out of an object like Hyades,

you need to have an
incredibly massive structure,

as much as 10 million
times the mass of the sun.

This monstrous cosmic
mugger should still be visible,

but when we point our telescopes

to where it should be,
that region is empty.

There's nothing there
and I mean nothing.

And not a little bit or something
dark, or something small,

but there's literally
nothing that we can see.

We know somethin is out
there, invisible and powerful.

And whenever we witness
these unseen assaults,

a prime suspect gets called in,

a phantom of physics,

dark matter.

So what can we confidently s about
this mysterious cosmic substance?

It does not emit light, it does not
reflect light, it does not absorb light.

The only thing we know about
dark matter is that it has gravity.

We're not even really
sure it's matter at all.

It's just that that's the only
thing we know, that it has gravity.

We may not be abl to
see or touch dark matter

but we are very good at finding
its fingerprints all over the universe.

We can see dark matter's use of
gravity to break and bind structures

and we've been spotting
its handiwork for decades.

Let's rewind back to 1933.

Swiss-American physicist, Fritz
Zwicky tracks strange movements

in a far off collection of
galaxies called the Coma cluster.

He knows he's not
seeing the whole picture.

Some galaxies are speeding around
the cluster at inexplicably fast rates.

Zwicky is looking
at these galaxies

and if the only mass that was there
were the other galaxies you can see,

you would expect these galaxies to
be moving at about 50 miles a second,

then they would stay bound
to each other and not fly apart.

Instead, he sees them
moving at 1,000 miles a second.

At these velocities,

galaxies should be flying of the
cluster like sparks from fireworks.

Zwicky realized there
had to be extra stuff,

in his words, Dunkle Materie

Dark matter.

Dark matter.

Dark matter.

It becomes clear that Zwicky's
Coma cluster isn't an isolated case.

Astronomers begin seeing the same
dynamics within galaxies themselves.

In systems governed
exclusively by gravity,

objects farthest
away from the center

would take the longest
to complete an orbit.

But in many galaxies, stars
on the outside are orbiting

at almost the same
rate as those in the core.

It's almost like a
photograph record.

Every part of that record
spins around like a solid disc.

The stars are going too fast to stay
bound to the gravity of the galaxy.

They should just fly
right off into space.

Physicists come u
with an explanation.

Galaxies sit in a giant hal or
ball of invisible dark matter.

And it's that extra mass that
allows the stars to turn fast

all the way out
to the galactic rim.

Think about actual
taking a disc of dough

and spinning it to make a pizza.

The more you spin it, the more those
outer regions go farther and farther away.

Eventually, the dough
just goes flying everywhere,

that's what would happen to a
galaxy if it weren't for dark matter.

Uh, as you spin pizza dough
and you spin it faster and faster,

it does hold itself together

because there's all this yummy
gluten that's acting as a glue.

Dark matter is the
gluten of our universe.

By calculating the
mass needed to bind

those speeding outer
stars to the galaxy,

physicists are able to estimate

how much visible matter there
is compared to dark matter.

The results are staggering.

All the stuff we thought existed
was just maybe 15% of our universe.

That's like if you
go to a restaurant

and leave like the measly 15%
tip, you know, that's what we are.

I mean, not even the
majority substance.

We may not be able to see it,

but dark matter makes
up some 85% of all matter.

Wherever we look, we can
se its gravity having effects.

It glues galaxies like
our Milky Way together

And a close look reveals dark
matter can also bend light itself.

It's called
gravitational lensing.

A massive object can
bend space and time,

and light must follow the
curves of that space and time.

Gigantic clumps of any matter
create a gravitational lens.

Dark matter showed its
space-warping power in a trick it played

with a gigantic explosion
in a far off galaxy cluster

Supernova Refsdal was first
detected in November of 2014

Supernova Refsdal is actually
one of my favorite recent results

in all of the
astronomical literature.

That result blew me away.

So a star explodes, light
is emitted in all directions,

and some of it makes
its way towards the Earth.

So far so good.
This is very standard.

So the flash appears

and then, another flash appears.

We see it again,
and again, and again.

We see the explosion go
off in four parts of the sky.

And then, a year later,
a fifth explosion goes off

in a totally different
part of the sky.

What's going on?

Analysis proves that these multiple
explosio are the same supernova.

But between this one
dying star and our telescope

sits a giant mass
of dark matter,

a huge gravitational lens.

What that means is that some of
these rays of light will take much longer,

more complicated paths
through this region of space time.

The dark matter lens
turns one supernova

into a fireworks display
lasting an entire year.

Dark matter affected the trajectory
of light from this supernova so much

that for some of
those trajectories,

it added a whole light year,

it took a whole extra
year for light to reach us.

Something is ver
definitely out there

distorting our
view of the cosmos.

It's a potent clue that
dark matter is real.

Now, new evidence suggests that
without it, we might not exist at all.

The cosmos is filled
with an unseen substance,

its mass even bends starligh

Gravitational lensing sugges dark
matter holds our entir universe together.

For decades, this specter
of space has haunted us.

We've never been
able to pin it down.

In 2021, an international te ran a
virtual experiment to try to predict

where dark matter should
be by letting computers

map out where we think it lives.

Because we think we
know how it behaves,

we can model what it should be
doing in supercomputer simulations.

The team taught the computer
how dark matte bends light,

then applied computational power
to 17,000 unexplored galaxies.

The model created
a dark matter map.

I think a lot of people, when they
imagine the universe on the larger scales,

think it's sort of boring,
everything's uniform.

But that's not what we see.

What's amazing is that on the
larger scales of the universe,

we see a very
particular pattern.

When we zoom out, we
see this magnificent structure,

this cosmic web that's
created by dark matter.

The interweaving tendrils
of dark matter stretch

for thousands of light
year across the cosmos.

At the junctions where matte is
concentrated, we find galaxies form,

illuminating the dark scaffold.

If dark matter exists,
scientists believe

it makes up 85% of the
matte in the universe,

and also controls the
remaining 15% regular matter,

like stars, planets, us.

If they're right, dark
matte played a critical role

in actually building the
universe we see today.

2021.

Astronomers using the
SkyMapper observatory in Australia

trains specialist optics on a
dwarf galaxy called Tucana II.

The SkyMapper's filters split up the
starlight into a spectrum of wavelengt

revealing some
very ancient light.

One of the best clocks that
we can put on the universe

is the progress of chemistry.

Right?

The build-up of more
complex elements over time.

Stars are nothing if not
factories of chemical complexity.

They slam, uh, particles together
and create heavier elements,

right, through a
process called fusion.

The later the generation of star,
the more chemicall complex it is.

Tucana II's spectral signature
reveals its stars contain

very few of these
heavy complex elements.

A clue that lets astrophysicists
calculate the age of the galaxy.

These are very, very old stars from
the very early days of the universe

when the gas in the universe
was not that chemically complex.

Tucana II might be one
of the oldest known structur

that we can see in
our local universe.

It could be as old
as 13 billion years.

You know, almost as
old as the universe itself.

This grand old la of
a galaxy is a tiny thing

Barely 3,000 stars.

And yet, way out
on her galactic rim,

stars hurdle around
at breakneck speed.

When you look at the mass
of this ultra-faint dwarf galaxy,

it only has a few thousand
times the mass of the sun.

That's really small.

And at the speed it's
moving, it should fly apart.

Tucana II doesn' break up
because it's glued together,

apparently by an incredible
amount of dark matter.

When you look at a
galaxy like our Milky Way,

it's about 85% dark
matter, which is a lot.

But with Tucana II,
it's more like 99%.

Tucana II is old among the
oldest galaxies in the universe

and it is packed
full of dark matter.

Simulations suggest this dark matter
played a ke role in shaping Tucana II

and other very early galaxie
right from the beginning,

gathering regular matter into
clumps and building the first galaxies.

The importance of dark
matter really can't be overstated.

It has actually controlled
the way matter has evolved

since the beginning
of the universe.

It brings matter together.

You need this underlying structure
of dark matter to make it all happen.

Scientists think that for billions of
years as the early universe grew,

dark matter called the shots

Without its gravity, structures like
the Milky Wa wouldn't have formed.

We've seen dark matter's
light-bending effects.

We've even deduced
where it should be.

Dark matter really
does appear to exist,

but this evidence is
indirect, circumstantial

To get conclusive proof
that dark matter exists,

don't we need to find some?

If we could find a
lump of dark matter,

um, that would be one of the
greatest discoveries in all of nature,

in all of our history, right?

Because we would understand

one of the most fundamental
components for how our universe works.

Dropping the
title, they love that.

It's time to hun for
dark matter itself.

Could it be hiding in
the darkest place of all

Black holes.

Scientists believ an
invisible substance

is pulling the strings
in our universe.

But until we see it, sense
I perhaps even touch it,

dark matter is just a theory

Sometimes though,
ideas dreamed up

by scientists come true

like black holes.

Once the stuff of science
fiction and children's nightmares,

black holes today
are confirmed reality.

So black holes and dark matter
have a ton of similarities, right?

You know, an unseen
collection of matter

that creates an enormous
gravitational field, check.

It bends light and causes
gravitational lensing, check.

Tests the boundaries
of known physics, check.

It seems crazy to even ask,

but could our
search for dark matter

end in an idea more
than 100 years old?

Could dark matter
be black holes?

Black holes appear
when stars explode.

And their remaining mass
crunches down into a sphere

so dense even light
can't escape its gravity.

But that's where the black
hole dark matter theory stumbles.

We know that black holes
happen. We know how they form.

And we also know that there's nowhere
near enough of them to be dark matter.

Not enough stars have lived
and died in the history of the univer

to create 85%
of the matter in it.

If dark matter is made
up of black holes,

they would have to
be an entirely new type.

It's possible that these black holes are
of a type that we've never seen before.

They could be
primordial black holes.

Primordial black
holes are an idea.

A theoretical
concept at this point

that we've never seen,
but they could exist.

If primordial black holes are real then
the universe is flooded with black holes.

The smallest coul have
the mass of Mount Evere

packed into the
size of one atom.

The biggest could be hundreds of thousands
or millions of times the mass of the sun.

Stephen Hawking first suggested
that primordial black holes

could be dark matter
back in the 1970s.

The idea centers on what happened
during that intangible momen

13.8 billion years
ago, the big-bang.

Theory says that primordial black
holes formed in the first fraction

of a second of
the early universe.

It's that time between
when the universe

goes from a pinprick to
this giant inflating ball of gas.

In these first moments of
the universe's existence,

matter is packed
incredibly tightly.

But it's not quite
evenly spread.

Even the tiniest fluctuation in density
could trigger gravitational collapses.

In other words, black holes
would be forming everywhere,

theoretically, in huge numbers.

By the time one second
has passed in our universe,

you're already
making black holes

thousands, hundreds of thousands
of times more massive than our sun.

The collective ma of
these objects could be va

but could they be 85%
of the universe's matter?

If primordial black
holes really do exist

there might be enough
to explain the dark matter.

It's a tantalizin possibility, but
there's on pretty big problem.

For most scientists, the
physics of the very early universe

is incomplete and hard to trust.

Generations of physicists
dismissed primordial black holes

as myths, fantasies,
astrophysical unicorns,

until that is, an
earthshaki crash in space.

May, 2019.

A violent cosmic
event rocks the USA.

How violent?

Well, the physical distance between
Louisiana and Washington state

is stretched by nearly the width of
an atom which is bigger than it sounds.

The Laser Interferometer
Gravitational-Wave Observato

detects this wobble
in space time.

This is the biggest gravitational
wave event that LIGO has seen.

This cosmic disturbance seems
to come from colliding black holes

but crucially not the
ordina dead star type.

In this LIGO detection, one of
the black holes is 85 solar masses.

There's no way that a star
could've made that black hole.

Physicists believ
there's a range of masses

where dying stars can't
collapse into black holes.

Instead, stars in this zone become
insanely hot and rip themselves apart

leaving nothing to crunch
do into a black hole.

Eighty-five solar masses
sits right in the middle

of this so called
forbidden mass range.

The black hole that LIGO
detected can't be a dead star,

but in theory it
could be primordial.

Could this discarded theory of
dark matter be back in fashion?

The LIGO detections
come up and everyone says,

"Oh, right, primordial
black holes.

Maybe we should pay
more attention to that."

Primordial black holes
can be really appealing

because they would solve
the dark matter problem.

But unfortunately,
it's not that simple.

The thing with flooding the
universe with primordial black holes

is that you expect
a lot of collisions.

And so LIGO shouldn't
have seen one,

it should have seen a thousand
of these collisions and we don't.

Many scientists doubt what LIGO
saw was a primordial black hole

To them, these beasts
remai fairytales of physics,

red herrings in the quest for
solid evidence of dark matter.

Does dark matter exist?

Or are we chasing shadows?

Some scientists
think it's not only real,

but the dark matter
is within our grasp,

and that it's flying through
our bodies right now

We think 85% of the
universe's matter is dark.

And yet, we've never
found a speck of it.

We can't prove
dark matter exists.

Regular matter is made up of everyday
particles, like electrons and protons.

Scientists wonder if dark
matter is also a type of particle.

One of the leading
candidates for dark matter

are these things called Weakly
Interacting Massive Particles.

They're massive particles like protons
and electrons and things like that.

But they don't interact well with normal
matters, so they're weakly interacting.

And they just have this name because
it's awesome to call them WIMPs.

For decades,
scientists have struggled

to find these shy
theoretical particles.

The very first physics
research I ever did in my life

was about actually measuring
directly dark matter particles,

these so called WIMPs.

And if they exist, then there
will be a flux of millions of them

through my hand right now,
just by holding out right here.

If dark matter is actually made
of WIMPs, if these particles exist,

then we're actually living
basically in a sea of them.

It surrounds and penetrates
us and it bin the galaxy together.

WIMPs don't play by our rules.

They barely interact with
the world of regular matter,

so they're hard to detect.

But when they
play with each other,

sparks fly, intense flashes
that we just might be able to see.

As the theory goes,
WIMPs will self-annihilate.

WIMP A and WIMP B get
too close together, poof,

they explode and they
create gamma rays.

Gamma rays are high energy
light, making them easy to spot.

Scientists point their detectors
at the cente of the Milky Way,

where they believe the WIMP
collision rate should be especially high.

We have a 4 million
solar mass black hole there

There are billions
of stars there.

That's where most of the
mass of the galaxies is densest.

So any WIMPs orbiting the
galaxy will feel this natural attraction

towards the center
and fall toward it.

The Fermi Large Area
Telescope scoured

the center of our galaxy
for more than 10 years.

It detected lots of gamma rays,

but scientists couldn't tel if
they came from colliding WIMPs.

The Galactic Center is a mess.
It's like downtown of a city, right?

That's where everything is,
where all the hustle and bustle is.

There are stars exploding there,

just tons of stars, gas,
magnetic fields, a black hole,

a lot of sources of gamma rays,

so it's very difficult
to tease out the signal.

Downtown Milky Wa was a washout.

So the scientists turned
their attention to planets

living in less noisy ZIP codes,

where WIMP collisions
should be easier to spot.

One place where you might
see evidence for WIMP collisions

is actually the
cores of exoplanets.

Turns out exoplanets might be the
best dark matter detector we have.

You can use giant
planets orbiting distant stars

as laboratories to
understand dark matter.

We know gravity
should attract WIMPs.

The more gravity, the more
dark matter particl come together.

Scientists suggest that WIMP
congregate inside the cores

of the Milky Way's
largest gas planets.

In these super-sized gas giants,

WIMPs could collide, annihilate,
and release gamma rays.

If there are these WIMPs
that are collecting the centers

of mass of exoplanets, the
annihilation of that dark matter

can heat those exoplanets up.

If you have a WIMP-heated
exoplanet, and that's just fun to say,

this thing is going to be warm,

it's gonna be warmer than the
heat of space, which is very cold.

So what you need is
an infrared telescope,

something that sees an infrared
light and is sensitive enough

to be able to measure the
temperatures of these things.

But a dedicated telescope
like this won't launch until 2028.

For some dark matter
hunters that's too long to wait.

They argue that WIMPs
do have one characteristic

that should allow us to
detect them right here on Earth.

The key to detecting WIMPs
is in their name, it's the W-I.

They're weakly interacting.
They're not not interacting.

They do interact, it's
just very weak with matter.

And that means that
there are the rare occasions

where it will smack into
a particle of normal matter

and then there are effects
that we can observe.

Scientists in Gran Sasso in Central
Italy watch for a spark of energy

generated when a WIMP
hits an atom of regular matter.

Their detector, a tank
of super cooled xenon

built thousands of feet
beneath the Earth's surface

The beauty of putting this detector under
a mountain is that you've got all of this

rock and soil and
everything else

which is blocking a
lot of background noise.

When you're looking
for a WIMP interaction,

you're looking for something that's
very rare and something very subtle,

so you don't want
other things going on.

You don't want other particles coming
in and messing up your experiment.

These Weakly Interacting Massive Particles
will pass right through that mountain,

and then if they smack into a
xenon atom, we can look at it and go,

"Ah, that was a
dark matter particle."

Detecting a WIMP could be
definitive proof that dark matter exists.

In 2020, the scientists
spotted something in the results.

But was it the elusive evidence

or a ghost among the stars?

Scientists believ they can
prove dark matter is real

by detecting WIMPs.

An experiment buried deep
beneath an Italian mountain

spotted unusual activity
in a tank of regular matter

pure liquid xenon.

So a WIMP detector,
like the XENON1T,

waits for a little WIMP,
tiny, tiny little particle

to hit an atom of normal matter,

and that creates a vibration.

And we can see this
entire block of xenon shake

just a little bit from that
little, subatomic collision.

The intensity of the vibration

from the particle
collision is critical.

In theory, a WIMP striking a xenon
atom should generat a powerful shock.

The vibrations XENON1T
detected were too weak.

When a WIMP comes through,
it smashes into the atom.

It seemed like here something
was just sort of rattling the electrons

on the outside of the atom.

So whatever is causing
these detections was likely

something much
smaller than a WIMP.

Let's take these
results at face value

It... If they're
correct, it's telling us

that the dark
matter isn't a WIMP,

but something much, much smaller

and something
much, much lighter.

The results sugge
that what hit the xenon

was actually a much smaller
theoretical particl called an axion.

Axions are really weird
particles, incredibly light.

In fact, almost zero mass
is possible for an axion.

An axion is no bigger

than 150 billionth
the size of an electron.

Compared to a WIMP, an axion is
like a soccer ball compared to our sun.

The sheer tinines of
axions makes them seem

like an unlikely
candidate for dark matter.

If dark matter is real, it makes up
85% of the matte in the universe.

To account for all that mass we would
need an almost unfathomable number of axion

142 trigintillion
of them, in fact.

That's 140 with
93 zeros after it.

If axions exist, space
must swimming with them.

They must be packed into
every corner of the cosmos.

When regular matter
clumps together, it forms stars.

So, to prove dark matter exists,

maybe we should be
looking for dark stars.

There's no reason
they can't exist.

There's even a name for them

Ghost stars.

They're very weird objects.

These ghost stars are like nothing
we would ever see in the night sky.

We've never seen a ghost star.

They are theoretical object
made of hypothetical axions

But in theory, ghost stars
should form like any other star,

pulled together by gravity.

They would be gigantic, super
dense objects floating through space.

They could reach the mass
of tens of millions of suns

But because they are
made of dark matter,

ghost stars would produce
no energy and emit no light

They would be transparent
to both light and matter.

If you were right next to it, you
wouldn't even notice it, right?

If we sent a probe through
it, it'd sail right through it

uh, and once it passed through, it
would be pulled back by its gravity.

85% of the matte in our universe
could consis of transparent orbs

made of infinitesimally
small, dark matter particles

But do these
invisible stars exist?

The evidence is thin, but..

Rewind back to th
LIGO detection in 2019.

The gravitational wave
detector picked up the signa

of two massive
objects colliding.

We call the event GW190521.

Most scientists agree
this w a black hole collision.

But could it have been
clashing ghost stars?

If there are ghost
stars out there

and they can interact with
each other gravitationally,

they may collide.

And when they do, they
would emit gravitational waves

and it would look a lot like
two black holes colliding.

In fact, it would look theoretically
very much like GW190521.

One collision, two explanations.

Primordial black
holes or ghost stars,

LIGO can't tell them apart.

Do these ideas bring us closer to
proving the existence of dark matter

Or are we just hurtling further
down a weird physics rabbit hole

Primordial black holes,
ghost stars, axions,

this is all very exotic physics.

We can't take for granted that
any of this is real or that it's not real.

We just don't know.

Dark matter is irritating.

We know it's out there.
We see its effects, right?

But we can't see the dark
matter and that's frustrating.

And it's like a lot of
young fields in astronomy.

We have way more ideas
than we do hard observations.

We have ideas, we have theories,

but without direct observations, we
just can't back them up with solid proo

The more we look, the
harder it is to find dark matter.

Maybe it's primordial black
holes from the early universe.

Maybe it's a sea of particle that
flow right through us every day.

Or maybe it's gigantic,
transparent ghost stars.

Perhaps it's the combined ma of Santa's
sleigh and the Easter Bunny's baske

Or maybe all our physics is
based on questionable mat

85% of the stuff in the
universe is missing in action.

The search for this dark
matter looks hopeless.

This problem of dark
matter is really a tough one.

Everything that we've predicted

and then gone and
looked for, we're not finding.

It's starting to become
a huge embarrassment.

Surely something so fundamental

to our cosmology
should be detectable.

And yet, it remains elusive.

We're stumbling blindly around
the limits of our understanding.

As of right now, there are
zero direct observations.

Maybe dark matter
doesn't exist after all.

Instead of searching
for an invisible substance

affecting the universe
with its gravity,

maybe it's gravity we
don't quite understand.

If you're looking in a galaxy
and it's spinning way too quickly,

either there's a new
ingredient in the galaxy,

like dark matter, that
holds it all together.

Or you're misunderstanding
the laws of physics.

To describe the
effects of gravity,

we use the nearly 350-year-o
math of Sir Isaac Newton.

Maybe to explain the excess
gravity we see in the universe,

it's not extra matter we nee

It's better math.

Although we understand
very well how gravity works

here on Earth and
in our Solar System,

perhaps when you get
up to galactic scales,

it actually behaves
just slightly differently.

And if that were the case,
you can kind of tweak that idea

until it fits the data we see of
how galaxies are spinning around

without needing dark matter.

Questioning the math of a legend

of physics might
sound like sacrilege,

but to solve the dark matter
conundrum, it has been done.

It's called Modified
Newtonian Dynamics or MOND.

Modeling galaxies with this math
produces very different results.

On its surface, MOND
is not a bad idea.

In the same way that we would
normally program a computer

to include dark matter
in our simulations,

you can take that out,
and instead program it

with a different law
of gravity with MOND.

And then, you can set up a
kind of spinning mass of gas

and it does seem to
be possible with MOND

to get things settled down
and look a bit like a real galaxy.

Changing the law of
gravity accurately recreates

the super-fast spin astronomers
see through their telescopes.

No need for dark
matter. It doesn't exist.

Case closed?

Not by a long shot.

With anything
bigger than a galaxy,

this artificial
physics breaks down.

MOND does really
well on galaxy scales,

but when you zoom
out and you go to larger

and larger structures
in our universe,

like clusters of galaxies,
big, big structure,

you see that MOND by itself can't
reproduce all of our observations.

There's something missing.

Dark matter.

Dark matter, dark
matter, dark matter.

Dark matter.

In MOND, you still have to invoke
the existence of material you can't see.

It basically introduces

some of its own
dark matter as well,

which kind of negates the point
of having MOND in the first place.

MOND doesn't
replace dark matter.

The universe still needs
something to hold it togethe

We just don't know what it I

But there are plenty of
new ideas flying around.

In my theory, the dark
matter is a super fluid.

It's a radical new
theory of dark matter,

particles not
acting individually,

but flowing as one invisibl
mass around the galaxies.

A super fluid is like an
ordinary fluid that flows,

but in this case, it flows without
any resistance or viscosity.

If I pour honey, it
will flow very slowly.

It has high viscosity.

A super fluid will just flo
and never stop flowing.

As the super flui dark matter
flows around the universe,

eddies and waves form large
enough to engulf entire galaxies.

The gravity of the fluid
holds the stars together.

But like most theories on dark
matter, there's no direct evidence.

If these waves are
on the size of galaxies,

then we have to find detectors that
can detect those types of huge waves.

They don't exist at the moment.

Which brings us
back to square one.

We just can't prove
that dark matter is real.

Primordial black holes,
ghost stars, WIMPs,

a super fluid sloshing
about the cosmos,

or maybe we're just
using the wrong math.

What's your money on?

If I had to wager $20
on what dark matter is.

Hmm.

I would never place money
on what dark matter is.

I just think we have no idea.

My money is on dark
matter itself is real,

but it's not the whole picture.

I would say left
socks in dryers.

I would say remote controls that
fall into sofa cushions and disappear.

I would love there to be

dark matter, ghost stars,
planets, even dark matter people.

I'm going all black.

I think no current
ideas are correct.

I think dark matter is something
that we haven't thought of yet.

Does dark matter exist?

Watch the space.