Horizon (1964–…): Season 46, Episode 15 - Is Everything We Know About the Universe Wrong? - full transcript
14 billion years ago
there was nothing.
No stars, no galaxies,
no planets or people.
Then suddenly, without warning,
everything exploded into existence.
The universe was born.
That is what science says actually
happened at the moment of creation.
Everything was created from nothing.
It's cosmology's
greatest achievement,
the discovery of how we came to be.
The atoms that make up me
were once created inside a star.
Not only am I in the universe, but
the universe is in me.
Cosmologist's have uncovered
the universe's deepest secrets,
revealing strange and exotic events
only dreamed of before.
Events that formed the night sky.
But a new generation of cosmologists
are questioning our basic
understanding of the universe.
We need to understand
what's the origin of time and space.
What was the universe actually like?
I think these are the big questions.
I wish I knew what dark matter was.
Actually, I've been worrying about
it for years.
They are beginning to wonder if
there is a greater reality.
It's some kind of proxy
for a deeper idea.
Too crude
to be the real thing that really
happened in the early universe.
Could it be that everything we think
we know about our universe is wrong?
Somewhere out in the universe
there seems to be a disturbing
force that we can't explain.
A force of astonishing power
that appears to have bent
trillions of stars to its will.
Gripping not just galaxies but
whole clusters of galaxies spanning
billions of light years of space.
And it's dragging everything
towards a single point.
This mysterious phenomenon
is known as dark flow.
And it shouldn't be happening.
It seems as though a very,
very large region of
the universe around us,
about a billion light years across,
is moving at a
phenomenal speed in the cosmos.
It's an unsettling discovery,
a unique movement
on an unimaginable scale.
Galaxies simply aren't meant to race
across space in the same direction.
It left us quite unsettled
and jittery at times because
this is not something we planned to
find or expected to find in any way.
Dark flow is a new enigma.
It's the latest in a long line of
mysteries that reveal our universe
is far more exotic than
science had predicted.
Anomalies that have to be resolved
to reveal the true nature
of the universe.
There are a lot of things
we know more than ever.
At the same time there are big
mysteries that we don't
really quite know what's going on.
Cosmologists have come up with
a series of controversial theories
designed to make
sense of the universe.
Like the theory of inflation,
which claims that the universe
suddenly expanded a
quadrillion, quadrillion times.
We don't know what caused
the universe to inflate.
We don't know what kind of energies,
what kind of stuff was around
in the early universe.
Or dark matter theory,
which says the cosmos is filled with
matter that's totally invisible.
It's cheating in this sense that
maybe it's not like that.
And maybe we should just
take things face value.
And even dark energy.
The strange energy of nothing
that dominates everything.
It is a very unwelcome
actor on the cosmic scene.
Nobody asked for it, nobody
wanted it, nobody understands it.
Despite these uncertainties,
scientists have written
their own version
of the greatest story ever told.
It's the story of creation
and it starts with a bang.
The big bang.
The most violent explosion
there has ever been
bought everything into existence.
This early universe was hot,
so hot, it contained
only raging energy.
After just one second,
some energy was transformed
into the seeds of matter
and the universe
filled with a dense fog.
400,000 years passed as the
universe grew and eventually
the fog settled to form atoms.
There were no stars to shine
just vast clouds of gas.
After a billion years one cloud
became so dense,
it burst into life
and the first star was born.
Stars grouped into galaxies
and finally, the night sky looked
as it does today.
It's a great story, and for
cosmologists, it's no fairytale.
This story of creation
has been built with the most
important tool in science.
The ability to turn physical events
into mathematical equations.
Mathematics is like Plasticine.
It's flexible, it allows you to
take ideas and move them around.
It allows you
to explore them further.
The power of relating
physical phenomena
and converting them into an equation
is that it lets you apply
these relations
in different situations.
By creating equations that
describe how things work today,
the cosmologists could then
change their formulas to see how
the universe behaved in the past.
Traditionally, we use physics
to start with a present
that predict the future.
You can also do
it backwards and start with
what we see around us
in the present day
and calculate what the universe
must have been like in the past
in order to end up like this.
And that's exactly how we've
come to the conclusion
that there was a big bang.
This has allowed cosmologists
to create a mathematical
replica of the universe.
It's called the standard model
of cosmology.
The standard model of cosmology
describes the entire evolution of
the cosmos from an instant after
the big bang, to the present day.
The standard model allows
cosmologists to travel through time.
They can wind the maths back and see
the universe as it was in the past.
It described the big bang
and how the universe has expanded
ever since.
It's a remarkable theory because it
really does allow us
to understand
literally everything that we can see.
It works perfectly.
The problem is that it doesn't
quite explain everything .
The more cosmologists look at the
night sky, the more they realise
that their model isn't an exact copy
In fact the standard model is
something that's very, very simple,
and that's its appeal,
that's why it's lasted so long,
that's why people really
want to sign up to it.
Scientists
do like things to be simple.
The problem is there are certain
observations that we have that
don't quite fit,
If the observations don't fit,
it means the whole model
could be undermined.
Now, a new generation of
cosmologists are questioning
the great model itself.
They think that the orthodox
science could be very wrong.
Professor Joao Magueijo
is a theoretical physicist.
We probably are on the threshold
of a new era in physics
and all these things are
just symptoms that not all is well
with the current theory.
Dr Kathy Romer
is an astrophysicist who
specialises in studying galaxies.
Everything that we've learnt,
everything we've gathered is just a
theory and it might well be wrong.
In fact, the fun is in the chase.
In fact, the greatest thrill of all
would be to prove something wrong,
Max Tegmark
is professor of physics at MIT.
We always have a love-hate
relationship with
the standard model.
We like all the predictions
it can make for us
when we're doing practical things,
even though we mostly suspect
in our heart of hearts that that's
probably not the final truth.
Professor Pedro Ferreira,
from Oxford, is a cosmologist.
I think we're at an interesting
time where we're up against
how perfect a model it might be.
Maybe the standard model is
wrong and we have to come
up with a better model.
For all its intricate mathematics,
the standard model has flaws.
Built into it are
a series of theories
designed to explain observations
that don't make any sense.
Theories that are incomplete
and unproven
but without which, cosmology's story
of creation is just another story.
The standard model runs into its
first problem when the universe
is less than a second old.
The universe begins with a bang.
A mass of seething energy that
expands from a single point.
It keeps expanding for just a
quadrillionth of a second...
..when everything grinds to a halt.
Even though the classic big-bang
theory of a hot expanding plasma
early on explained a lot of things,
it forced us to assume
some very contrived
initial conditions for our universe.
In physics, we hate
unexplained coincidences.
If there's an unexplained
coincidence in nature,
it usually tells us
that we're missing something,
our theory is wrong or incomplete.
Big-bang theory says
that the universe was
created in an explosion.
But an explosion would produce
a universe that was lumpy and messy,
with patches that were vastly
different temperatures
from one area to another.
The real universe
is nothing like this.
In all directions, the
temperature appears to be
almost exactly the same.
This temperature problem
made the idea of the big bang itself
seem completely impossible.
Something was very wrong
with the standard model.
Re-writing the history of the
universe is a daunting challenge.
But luckily, in 1980,
one man stepped up to the task.
His name is Alan Guth, professor of
particle physics, and his creation
was the theory of inflation.
When I started working in cosmology
there was a standard theory of
cosmology, the big-bang theory.
We still, basically, think that the
big-bang theory is correct.
But there are things
that were just left out.
There's no understanding of the
uniformity that we see in the
universe.
The universe
looks essentially the same if you
look that way or that way.
No normal explosion would ever
do that.
The problem is that all explosions
produce a chaotic pattern.
Areas of extreme heat
jostle with patches of cold.
And that doesn't match the smooth
uniformity of our universe.
But Guth's theory of inflation has
an answer.
Inflation gets around this problem,
essentially, by varying the expansion
history of the universe so that
the universe starts out essentially
dawdling with very low expansion rate
for a period of time
before inflation.
By allowing the universe
to be small for longer,
Guth had found a way to let it
all become the same temperature.
And it's during that time when
the universe is incredibly tiny
and not expanding that rapidly that
it can come to a uniform temperature.
Then inflation takes over and
suddenly magnifies that tiny region
to become large enough to include
literally everything that we see and
very likely regions far beyond.
Guth's theory of inflation
said that, out of the blue,
our fledgling universe
dramatically increased in size.
It expanded from something, which is
quite small and crinkly, to something
incredibly large.
It happened almost in an instant
a very small fraction of a second.
Inflation says the
universe started small
allowing the temperature to
become the same everywhere.
Then in an instant
it underwent a massive expansion
that left everything
perfectly smooth and uniform.
Inflation explained a lot,
but it was still a hypothesis.
To try and prove it, cosmologists
scoured the heavens for evidence.
Using satellites, they photographed
light from the very early universe.
The pictures that emerged showed a
special kind of radiation called
the cosmic microwave background.
This cosmic microwave background,
this CMB, as we call it, we think of
as the afterglow of the heat
of the big-bang explosion itself.
The remarkable images allowed
cosmologists to see the universe
as it was 13 billion years ago.
These photons allow us to construct
an image of what the universe
looked like,
at 380,000 years
after the big bang, which is
an incredibly early time.
As expected,
they found that the temperature
was the same in all directions.
When we look at this microwave
background, we see that it has
pretty much the same properties,
you know,
one end of the sky to the other.
The temperature of the universe
is almost perfectly uniform,
except for some tiny variations
of one ten thousandth of a degree.
Variations that were actually
predicted by Guth's theory.
Inflation predicted not only the
range of temperatures that should be
present today,
but also the
distribution of those temperatures.
That's what this graph shows...
in theory.
The real test came
when satellites accurately measured
the actual temperature of the CMB.
The data points lie perfectly
on top of the curve.
It's an incredible match between
theory and observation.
It's one of those things that you
look at and on the one hand it's very
satisfying, but also unexpected.
Its powerful evidence,
but not conclusive proof.
The most basic aspects of inflation
can't be explained.
The theory can't say
what actually caused it.
We don't know
how inflation happened, we don't know
what drove the universe to inflate.
It's caused some to wonder if
this is really what happened
to the early universe.
Inflation is not really very deep.
It's something really simple.
In a way, it's too crude to be
the real thing that happened
in the early universe.
If inflation really happened,
it would have needed a kind of force
far more powerful than
has ever been seen.
Right now, we're nowhere near being
able to create enough energy
in our laboratories to create
inflation or anything like it.
Even Guth doesn't
have all the answers.
I think it's important
to understand that this is not
something that any of us working
on it would say we know for sure.
It is a proposal, a theory.
We don't yet fully understand
the physics of these energies,
we are making large extrapolations
in what we're talking about.
Inflation seemed to happen by magic
and then stopped just in time
before it blew the universe apart.
I'm not a great fan of inflation.
Whenever I teach it in my cosmology
class...
I actually wrote in my notes,
"Your lecturer doesn't really like
this theory."
I don't like it because
it seems too much of an add-on.
But saying that,
it's the easiest way for us
to get from the standard model
to some unexplained observations.
Inflation, in a way,
is an acquired taste for cosmology.
It's something which, if you're
really trying to explain the early
universe, especially if you're
very lazy and you just want to get
papers out, it's perfect because it
gives you an answer.
But the maths does appear to work.
It creates a universe that looks
as neat and ordered as our own.
Inflation could be sending all
of science down a blind alley,
But published in 1980,
the theory has become a key
part of the standard model.
The new story of creation
still begins with a bang.
In a fraction of a section,
inflation expands the universe a
quadrillion quadrillion times.
As it cools the building
blocks of matter are formed.
Then gravity begins
to takes effect.
But it's at this point that the
standard model hits another problem.
When the cosmologists look at the
night sky, they see something weird.
Galaxies
aren't behaving the way they should.
What's interesting is when you
look at galaxies, they seem to
be spinning around too quickly.
According to Newton's Law of
Gravity, stars on the edge of
a galaxy should move more slowly
than those closer to the centre.
It's a process clearly
seen in our solar system.
The further a planet is from the sun
the slower it moves.
The planets' speeds produce a
line known as a rotation curve.
Galaxies should produce
exactly the same curve.
But they don't.
Remarkably, when the speed of stars
at the edge of galaxies
are measured,
they turn out to be moving just
as fast as those close to centre.
The rotation curve
isn't a curve at all.
It's more of a straight line.
This should lead to disaster
all across the universe.
The galaxy would just fly apart
at these very high rotation speeds.
To make the galaxies work the way
the laws of physics dictated, the
cosmologists needed more gravity.
The only way to get more gravity
was to add more matter to galaxies.
But they couldn't find any,
so they decided to invent some.
And so dark matter was born.
A key architect of this idea
is Professor Carlos Frenk.
When we look at the way things
move in the cosmos, we soon reach
a very profound conclusion.
There isn't enough gravity
in the stuff we can see,
the stars or the galaxies,
to explain how objects move
in the universe, there must be
something else, that is responsible
for these movements, and that
is what we call dark matter.
The new matter was called dark
because they couldn't see it.
There has got to be something extra
in these galaxies bulking them up,
so that there's enough stuff
for there to be enough gravity
for them to be spinning around.
But this stuff is dark,
this stuff is dark, it's invisible.
Dark matter explained the flat
rotation curves and meant that the
laws of physics still made sense.
Dark matter is the easiest way to
explain why the galaxies work,
the way they do and everything else.
When the calculations were done
to work out how much unseen matter
the universe should have,
the results were shocking.
We expect that for every kilogram
of normal matter, there's another
five kilograms of dark matter
and we expect that dark matter to be
everywhere clustered around us.
The universe doesn't seem
to be made from the same
stuff that we're made from.
It's made of something else,
something strange, something alien
that we can't see.
Dark matter is wonderful stuff.
Wonderful stuff.
Without dark matter, the universe
wouldn't look anything like it does.
Dark matter in general, I think, is
one of the pillars of the standard
model of cosmology.
It is needed -
there's no doubt about that.
It's a persuasive theory
but there is a fundamental flaw.
Cosmologists
don't know what dark matter is.
All they know for certain
is it can't be ordinary matter.
Because ordinary matter either
emits light or reflects it.
Dark matter
has to be totally invisible.
We have to not be able to see it at
all wavelengths,
so you wouldn't see it with
an optical telescope, but
you wouldn't see it with
an X-ray telescope, or radio
telescope either. It really is dark
at all frequencies.
But dark matter had to
be more that just dark.
It needed to be a
special form of matter,
a kind of particle that
had never been seen before.
What's even worse, it's not just
invisible matter, it's exotic
matter.
Things which are not atoms,
which are not the things we know.
The idea of finding a new particles
isn't as strange as it seems.
Physicists have found lots
of particles over the years.
They all have different roles.
Some build atoms,
while others make up light.
Particle physics has its own
standard model, which catalogues
these different particles.
Today, we have the standard
model of particle physics, in which
there are 24 elementary particles.
They all have their own values of
mass, electric charge and spin.
They interact with each other
in different ways so that
in the standard model,
these particles are
grouped into different families.
It's just that dark matter
can't be one of these.
None of the particles would be a
good candidate for the dark matter
because, essentially, the ones that
are massive enough would not be dark
because they would form into atoms
that, in principle,
could omit light.
But particle physics is also
good at fixing standard models.
To make their model work
they invented whole
range of new particles.
If there was another set of 24
particles, identical to these ones,
of the standard model, but with just
one difference, the difference in
the way in which the particles spin,
this idea
goes by the name of super symmetry.
Super symmetry predicts there are
24 new particles that have yet
to be discovered by scientists.
And they're invisible...so
dark matter could be one of these.
Not only are they invisible,
they can pass right
through solid objects.
Even stars and planets should
be no barrier to dark matter.
Astrophysicist Dan Bauer is in
charge of a special experiment.
He's hunting for dark matter.
He's not looking for it in space.
Instead he's buried his
equipment ½ mile under the
frozen plains of Minnesota.
It's strange at first,
but you get used to it
and once you pass through these doors
it looks like any other lab.
You could be
in one of those and not even know
that you have a mile underground.
As dark matter should be able
to pass through solid rock,
Dr Bauer has no trouble running
his experiment underground.
You'd think it's easier to detect
dark matter at the surface,
why do we bother to come down this
far, it's obviously inconvenient.
It's because that there's
a lot of normal matter particles
hitting the Earth's
surface from space.
It would overwhelm any
possible signal we could see.
But Bauer is facing a problem.
His dark matter detector
is made of normal matter.
The kind of normal matter that
dark matter passes right through.
If we are right about this dark
matter particles streaming through
us all the time, millions of them
are passing by here every second, and
they're doing absolutely nothing,
in fact their passing through the
entire Earth without doing anything.
Turn on the lights.
This massive block here
is the actual experiment.
There's millions of dollars worth
of the most advanced technology
imaginable
waiting to record the first evidence
of the theoretical particles.
If they are real, and one of them
so much as nudges Bauer's detectors,
it would set of a signal that
could provide the proof that
cosmology's been waiting for.
Occasionally one of these particles
will however
do something in one of the detectors
buried deep within this pile.
It will cause a little bit
of heat and charge.
If we're very lucky
then we will have detected
a particle that makes up dark matter.
Theoretically, millions of
particles have been streaming
through Dr Bauer's machine
every day
for the five years it's been here,
but frustratingly
they've always left no trace.
But then something did happen.
Just this last December
we saw the first two events that have
the characteristics we might expect
from dark matter.
But it's too few events
for Bauer to be certain
he's really found dark matter.
Despite the years of research
and investigation,
cosmologists don't seem to be
much closer to uncovering
what dark matter actually is.
If I, If I knew the answer to the
question, "What is dark matter?"
I would already be sitting
very comfortably with a medal,
being from the Nobel Committee.
There is very little doubt
that the dark matter exists.
The question is, "What is it?"
It's cheating in a sense that
maybe it's not like that
and maybe we should just
take things face value and in fact
what's out there is what there is...
there's no dark matter,
no ghosts around the universe.
But despite the doubts,
cosmology needs dark matter.
It's the missing ingredient that
makes the universe work the way
the maths predicts it should.
And it puts the standard model
story of creation back on track.
Creation starts with a bang,
Inflation takes over
and everything expands.
After one billion years
the first star is born.
Then dark matter kicks in.
It creates the gravity
that makes galaxies form.
The universe continues to expand.
As the epochs pass
the expansion slows.
Soon, the universe
will come to a stop.
The trouble is this
isn't what is actually happening.
The universe isn't stopping at all.
At the top of a mountain
range in New Mexico
is a very special instrument.
It's a finely-tuned device
that scans the heavens.
This telescope is
measuring the universe.
It's designed to work out
how space itself is moving.
And what it's discovered
has shocked cosmology.
Using the Sloan telescope,
astrophysicist Saul Perlmutter
recorded a new phenomenon.
The big surprise that we found, 10
years ago now, was that the universe
apparently has been speeding up
in the last half of its life,
for the last seven billion years
or so, there's been an acceleration
in that expansion.
Everyone had been expecting
that the universe was expanding.
But the standard model said
the expansion should be slowing.
The universe was meant
to be coming to a stop,
but it wasn't.
This was a great scandal and it was
a great scandal in a way because
you know anyone reasonable
would have expected that somehow
gravity is attractive therefore the
universe should be slowing down.
The pull of gravity from all
the matter in the universe
should be acting as a brake,
bringing expansion to a stop.
Perlmutter's observations
told a different story.
It's rare that you get to catch
the universe in the act
of doing something which doesn't fit.
So having the chance to have seen
the universe do something that's
completely surprising
is, is tremendous.
Inflation theory had
already established the
big bang was no ordinary explosion.
Now Perlmutter was saying
it was stranger still.
The explosion hasn't stopped.
The big bang is still banging.
Perlmutter's discovery created
a new mystery to be resolved.
It suggested a new force
was powering the universe.
And it needed a name.
They called it dark energy.
What is dark energy?
Well, I know, but I'm
not going to tell you.
Well, it's dark and it's expanding.
I guess it's a pictorial
way to describe dark energy.
We don't know what it is so we
might as well say it's this.
Actually, no, I've
no idea what it is.
I hope it goes away, I don't like it.
We have no idea what dark energy is.
Dark energy is basically a fancy
word for ignorance of what makes up
75 per cent of our universe.
I wish I knew what dark energy is.
I don't know and nobody else
knows either.
It is a very unwelcome actor
in the cosmic scene.
Nobody asked for it, nobody
wanted it, nobody understands it,
This ignorance didn't
stop the ideas coming in.
What could dark energy be?
Was it an odd kind of gravity?
Dark energy causes this type of
anti-gravity
where distant things
are repelled from each other.
Or something entirely new.
If the universe is accelerating,
something must be causing it
and dark energy is just
defined to be whatever it is that's
causing the universe to accelerate.
Even a weird bit of maths.
When Einstein proposed his theory
of space and time,
he proposed this thing called
the cosmological constant,
which is this constant thing
that pervades all of space,
which would
counterbalance the pull of matter.
Whatever dark energy is, whether
anti-gravity, weird energy or maths,
it seems to have magical properties.
Not only does dark energy
make the universe expand.
But the more expanded the universe
becomes, the more dark energy
is created to fill the gaps.
This could only mean one thing.
There must be something in nothing.
Although we used to think that
nothing was the simplest thing
you could have,
just complete emptiness,
we now realise that there is no such
thing as a completely empty vacuum.
If you take out all the air
molecules from this space
and take out all the light
particles, there's still
something left.
The very fabric of space itself
isn't empty.
Deep space,
the space between galaxies,
is meant to be perfectly empty.
There shouldn't be anything there,
not even the tiniest particle.
Instead, it seems this
space is full of energy.
It might also
explain the dark energy.
Maybe the vacuum itself
has this energy
which we can gravitationally
measure throughout our space.
You take a space and you stretch
it into more space...
Well, that new stretched-out
space has to have the same
properties as the old space
cos a stretched vacuum
is still a vacuum.
It's yet another explanation for
what dark energy might actually be.
So that's one of the prime
contenders for what dark energy
is - the energy of nothing,
which is not nothing.
"Nothing"
is taking over the universe.
It's creating more
and more empty space,
filled with even more nothingness.
Counterintuitive
though it is, just like inflation,
cosmologists need dark energy.
Even though we don't know much about
it, it's the simplest explanation
we have for some of
the observations in the universe.
Like dark matter,
dark energy isn't a solution,
it's a description of a problem.
We're pretty much in the
dark about dark energy.
There isn't
a theory, a compelling theory.
There are hundreds of theories.
We don't know where it comes from,
we don't know how it relates to
the other particles in the universe,
but that's an interesting challenge.
It means, you know, maybe this
is going to be the next big thing.
The mystery is driving science on,
making cosmologists
re-evaluate what's really
happening in the universe.
The dark energy seems to me
really mysterious, and I think it's
very unlikely that my generation
of physicists will come to see the
solution to the dark energy problem.
Mysterious though dark energy is,
it's become an important
part of the standard model.
It makes the maths fit
with the real universe.
But more importantly, it seems to
be the final piece in the jigsaw.
However counterintuitive
the universe now is,
it's the best model that we have,
the most complete description
of creation there's ever been.
The universe starts with a bang.
Then it suddenly inflates.
Dark matter forms...
..and helps galaxies to emerge.
And the universe's expansion slows.
Finally, dark energy takes over,
stretching the universe
more and more.
After 13.7 billion years,
cosmologists look up at the sky
and understand the
story of creation.
It's all thanks to the
beautiful equations
and elegant descriptions that
make up the standard model
of cosmology.
Today we have a very compelling
standard model that describes
a huge amount of observations
and measurements.
Some pretty spectacular, like the
fact that the universe was once hot,
the fact that the universe is
expanding, it explains why
the...we're made of the elements
that we're made, it explains
where the atoms come from,
and it also explains, for example,
where galaxies originate, how they
ended up being the way they are.
So it's a very powerful
standard model.
The unlikely combination
of inflation, dark matter
and dark energy has come good.
Cosmology's standard model works.
Except...that it now
has a new challenge.
Another darkness to account for.
That new phenomenon, dark flow.
For Dr Sasha Kashlinsky,
most days start the same way -
taking the kids to school
on the way to the office.
His office is at NASA's
Goddard Space Flight Center.
Kashlinsky is a cosmologist.
What made me choose this career?
I guess, in my childhood, it was
reading too much science fiction.
I dreamt then
of doing space travel and eventually
instead of space travels,
I ended up doing cosmology
as a desk job.
Say "bye-bye", gentlemen.
His desk job involves poring
through pages and pages of data
about the cosmic
microwave background.
The picture of temperature
differences in the
afterglow of the big bang.
Hidden in these numbers,
he's found something that
shouldn't be happening.
This very nice map
that they produced, is, um,
is a nuisance for us, an obstacle.
Kashlinsky is looking for
movements hidden in the map.
So we remove most of the signal that
they detect, and then we concentrate
only on about one per cent
of this map associated
with clusters of galaxies.
By stripping away the information,
he's found distortions in the light
coming from the microwave
background.
Distortions that
appear to show movement.
Whole clusters of galaxies seem to
be moving in an inexplicable way.
It left us greatly puzzled when we
found it, so puzzled that we, er, we
didn't know what to do with it.
We sat on it for a year,
checking everything, but
ultimately it is in the data.
The CMB is the saviour of cosmology.
It had provided the evidence that
validated the theory of inflation
and allowed the standard
model to work again.
Now the very same data
could undermine everything.
It could easily point to something
very exciting, a breakdown of our
understanding of the universe.
Like dark matter and dark energy,
these galactic movements
were another mystery.
So Kashlinsky decided
to call them dark flow.
He immediately sought to find a
cause for this strange phenomenon.
A new, unseen force
that could power dark flow.
He came up with a theory
for what this could be.
All he needed was another universe,
one that exists outside our own.
So, therefore we believe that
in order to explain this flow,
we should be looking outside
of our universe very far
beyond what is
the gasmological
horizon of the universe.
For Kashlinsky,
our universe isn't everything,
it's part of an even larger whole.
This apparently crazy idea
is actually predicted by one of the
pillars of the standard model.
Alan Guth's theory of inflation.
In almost all versions of our
theories, inflation never
ends completely,
it ends in places and in
those places where inflation ends,
normal universes happen,
but in other places the inflation
continues and then ends again and
another normal universe happens.
Guth thinks our universe is
part of a bigger structure.
We're in a small piece of it,
a bubble created by inflation.
So we end up with a picture of
a multiverse consisting of many
different universes which we,
in this context, tend to call pocket
universes, ah, we would be living
in one of these pocket universes.
Ah, but inflation tends to produce
not just one pocket universe,
but an infinite number for the
same price as the one.
It could mean that dark flow
is evidence that our
universe is not alone.
This would make it one of the
most important discoveries ever.
Despite large parts of the standard
model being built only on theory,
it won't be easy for dark flow
to change the science
and join the model.
I think it's good
to have a healthy dose of scepticism,
we don't want to be,
jump on fly-by-night theories, um,
we want to make sure that if theory
is going to change, it's a change for
the better, and by better, I mean
it explains our observations better.
Many modern cosmologists have
devoted their careers to trying
to find theories that could
replace the standard model.
They have even tried to change
some of the fundamental
principles of physics.
I work a lot on trying to
come up with alternatives which
don't have this dark universe.
I've been involved with
varying speed of light theory.
You want to bring everything into
contact in the early universe,
raise the speed limit.
They are hoping to find
a deeper truth that will reveal
how the universe really behaves.
I think the way that science works
is there's always one big thing
that most people work on
and then there are always these side
projects that other people look at
and every now and then, one of
these side projects is right
and the big thing is wrong.
It's just that these cosmologists
haven't been very successful.
I would say there's no shortage of
alternatives, it's just none of them
is compelling in a way that might
make the whole community change
and start working on them.
These attacks have meant that
cosmology's standard model has gone
from strength to strength.
The more they fail,
the stronger the model becomes.
You get famous in science if you can
be the one who shoots down the
theory everybody else believes in.
So if the theory has withstood
all this artillery fire
from a lot of smart physicists
and experimentalists for many years,
that gives it a lot of street cred.
This is the key test for
a theory in cosmology.
It's the hurdle that must be passed
to enter the standard model
and it's where dark flow
currently falls down.
It hasn't yet been pushed to the
brink of destruction and survived.
You really have to be very rigorous,
and anything that you come up with
has to be corroborated.
It has to be demonstrated to be the
case, not just by one measurement,
one experiment but by many
different groups.
That's the essence of the
scientific method, repeatability,
rigour, accuracy and relevance.
It's not enough to make one
measurement, find one thing
that looks strange and say,
"Ah, this is true
so there's a problem."
You have to come at it
with many different ways.
A lot of these results are tentative.
Some of these results
are inconsistent with each other.
So, I think it's premature
to incorporate these results
as hard facts
about the universe as we know it.
I think it's fair to say
that it's, it's controversial.
For a long time it was controversial
among ourselves, in fact, we did not
think it was possible.
But ultimately,
it's the data that decides
and the data, to us, show very
unambiguously that this is there.
The battle between resolving
the mysteries of the universe
and searching for new ones
has driven cosmology on.
It's been a struggle to
explain the unexplainable.
and has resulted in a powerful tale
built on mystery.
So for now, the standard
model remains unchanged.
It's successfully described so much.
It tells us how the universe began.
How matter and energy formed.
How gravity created stars and
galaxies and planets like the Earth.
It's the best we have,
and it's so nearly a perfect fit.
It's just that it could be
totally wrong.
There's a feeling we need an extra
clue, and we don't have it yet.
And I think that's what
we're waiting for, somehow.
Subtitles by Red Bee Media Ltd
there was nothing.
No stars, no galaxies,
no planets or people.
Then suddenly, without warning,
everything exploded into existence.
The universe was born.
That is what science says actually
happened at the moment of creation.
Everything was created from nothing.
It's cosmology's
greatest achievement,
the discovery of how we came to be.
The atoms that make up me
were once created inside a star.
Not only am I in the universe, but
the universe is in me.
Cosmologist's have uncovered
the universe's deepest secrets,
revealing strange and exotic events
only dreamed of before.
Events that formed the night sky.
But a new generation of cosmologists
are questioning our basic
understanding of the universe.
We need to understand
what's the origin of time and space.
What was the universe actually like?
I think these are the big questions.
I wish I knew what dark matter was.
Actually, I've been worrying about
it for years.
They are beginning to wonder if
there is a greater reality.
It's some kind of proxy
for a deeper idea.
Too crude
to be the real thing that really
happened in the early universe.
Could it be that everything we think
we know about our universe is wrong?
Somewhere out in the universe
there seems to be a disturbing
force that we can't explain.
A force of astonishing power
that appears to have bent
trillions of stars to its will.
Gripping not just galaxies but
whole clusters of galaxies spanning
billions of light years of space.
And it's dragging everything
towards a single point.
This mysterious phenomenon
is known as dark flow.
And it shouldn't be happening.
It seems as though a very,
very large region of
the universe around us,
about a billion light years across,
is moving at a
phenomenal speed in the cosmos.
It's an unsettling discovery,
a unique movement
on an unimaginable scale.
Galaxies simply aren't meant to race
across space in the same direction.
It left us quite unsettled
and jittery at times because
this is not something we planned to
find or expected to find in any way.
Dark flow is a new enigma.
It's the latest in a long line of
mysteries that reveal our universe
is far more exotic than
science had predicted.
Anomalies that have to be resolved
to reveal the true nature
of the universe.
There are a lot of things
we know more than ever.
At the same time there are big
mysteries that we don't
really quite know what's going on.
Cosmologists have come up with
a series of controversial theories
designed to make
sense of the universe.
Like the theory of inflation,
which claims that the universe
suddenly expanded a
quadrillion, quadrillion times.
We don't know what caused
the universe to inflate.
We don't know what kind of energies,
what kind of stuff was around
in the early universe.
Or dark matter theory,
which says the cosmos is filled with
matter that's totally invisible.
It's cheating in this sense that
maybe it's not like that.
And maybe we should just
take things face value.
And even dark energy.
The strange energy of nothing
that dominates everything.
It is a very unwelcome
actor on the cosmic scene.
Nobody asked for it, nobody
wanted it, nobody understands it.
Despite these uncertainties,
scientists have written
their own version
of the greatest story ever told.
It's the story of creation
and it starts with a bang.
The big bang.
The most violent explosion
there has ever been
bought everything into existence.
This early universe was hot,
so hot, it contained
only raging energy.
After just one second,
some energy was transformed
into the seeds of matter
and the universe
filled with a dense fog.
400,000 years passed as the
universe grew and eventually
the fog settled to form atoms.
There were no stars to shine
just vast clouds of gas.
After a billion years one cloud
became so dense,
it burst into life
and the first star was born.
Stars grouped into galaxies
and finally, the night sky looked
as it does today.
It's a great story, and for
cosmologists, it's no fairytale.
This story of creation
has been built with the most
important tool in science.
The ability to turn physical events
into mathematical equations.
Mathematics is like Plasticine.
It's flexible, it allows you to
take ideas and move them around.
It allows you
to explore them further.
The power of relating
physical phenomena
and converting them into an equation
is that it lets you apply
these relations
in different situations.
By creating equations that
describe how things work today,
the cosmologists could then
change their formulas to see how
the universe behaved in the past.
Traditionally, we use physics
to start with a present
that predict the future.
You can also do
it backwards and start with
what we see around us
in the present day
and calculate what the universe
must have been like in the past
in order to end up like this.
And that's exactly how we've
come to the conclusion
that there was a big bang.
This has allowed cosmologists
to create a mathematical
replica of the universe.
It's called the standard model
of cosmology.
The standard model of cosmology
describes the entire evolution of
the cosmos from an instant after
the big bang, to the present day.
The standard model allows
cosmologists to travel through time.
They can wind the maths back and see
the universe as it was in the past.
It described the big bang
and how the universe has expanded
ever since.
It's a remarkable theory because it
really does allow us
to understand
literally everything that we can see.
It works perfectly.
The problem is that it doesn't
quite explain everything .
The more cosmologists look at the
night sky, the more they realise
that their model isn't an exact copy
In fact the standard model is
something that's very, very simple,
and that's its appeal,
that's why it's lasted so long,
that's why people really
want to sign up to it.
Scientists
do like things to be simple.
The problem is there are certain
observations that we have that
don't quite fit,
If the observations don't fit,
it means the whole model
could be undermined.
Now, a new generation of
cosmologists are questioning
the great model itself.
They think that the orthodox
science could be very wrong.
Professor Joao Magueijo
is a theoretical physicist.
We probably are on the threshold
of a new era in physics
and all these things are
just symptoms that not all is well
with the current theory.
Dr Kathy Romer
is an astrophysicist who
specialises in studying galaxies.
Everything that we've learnt,
everything we've gathered is just a
theory and it might well be wrong.
In fact, the fun is in the chase.
In fact, the greatest thrill of all
would be to prove something wrong,
Max Tegmark
is professor of physics at MIT.
We always have a love-hate
relationship with
the standard model.
We like all the predictions
it can make for us
when we're doing practical things,
even though we mostly suspect
in our heart of hearts that that's
probably not the final truth.
Professor Pedro Ferreira,
from Oxford, is a cosmologist.
I think we're at an interesting
time where we're up against
how perfect a model it might be.
Maybe the standard model is
wrong and we have to come
up with a better model.
For all its intricate mathematics,
the standard model has flaws.
Built into it are
a series of theories
designed to explain observations
that don't make any sense.
Theories that are incomplete
and unproven
but without which, cosmology's story
of creation is just another story.
The standard model runs into its
first problem when the universe
is less than a second old.
The universe begins with a bang.
A mass of seething energy that
expands from a single point.
It keeps expanding for just a
quadrillionth of a second...
..when everything grinds to a halt.
Even though the classic big-bang
theory of a hot expanding plasma
early on explained a lot of things,
it forced us to assume
some very contrived
initial conditions for our universe.
In physics, we hate
unexplained coincidences.
If there's an unexplained
coincidence in nature,
it usually tells us
that we're missing something,
our theory is wrong or incomplete.
Big-bang theory says
that the universe was
created in an explosion.
But an explosion would produce
a universe that was lumpy and messy,
with patches that were vastly
different temperatures
from one area to another.
The real universe
is nothing like this.
In all directions, the
temperature appears to be
almost exactly the same.
This temperature problem
made the idea of the big bang itself
seem completely impossible.
Something was very wrong
with the standard model.
Re-writing the history of the
universe is a daunting challenge.
But luckily, in 1980,
one man stepped up to the task.
His name is Alan Guth, professor of
particle physics, and his creation
was the theory of inflation.
When I started working in cosmology
there was a standard theory of
cosmology, the big-bang theory.
We still, basically, think that the
big-bang theory is correct.
But there are things
that were just left out.
There's no understanding of the
uniformity that we see in the
universe.
The universe
looks essentially the same if you
look that way or that way.
No normal explosion would ever
do that.
The problem is that all explosions
produce a chaotic pattern.
Areas of extreme heat
jostle with patches of cold.
And that doesn't match the smooth
uniformity of our universe.
But Guth's theory of inflation has
an answer.
Inflation gets around this problem,
essentially, by varying the expansion
history of the universe so that
the universe starts out essentially
dawdling with very low expansion rate
for a period of time
before inflation.
By allowing the universe
to be small for longer,
Guth had found a way to let it
all become the same temperature.
And it's during that time when
the universe is incredibly tiny
and not expanding that rapidly that
it can come to a uniform temperature.
Then inflation takes over and
suddenly magnifies that tiny region
to become large enough to include
literally everything that we see and
very likely regions far beyond.
Guth's theory of inflation
said that, out of the blue,
our fledgling universe
dramatically increased in size.
It expanded from something, which is
quite small and crinkly, to something
incredibly large.
It happened almost in an instant
a very small fraction of a second.
Inflation says the
universe started small
allowing the temperature to
become the same everywhere.
Then in an instant
it underwent a massive expansion
that left everything
perfectly smooth and uniform.
Inflation explained a lot,
but it was still a hypothesis.
To try and prove it, cosmologists
scoured the heavens for evidence.
Using satellites, they photographed
light from the very early universe.
The pictures that emerged showed a
special kind of radiation called
the cosmic microwave background.
This cosmic microwave background,
this CMB, as we call it, we think of
as the afterglow of the heat
of the big-bang explosion itself.
The remarkable images allowed
cosmologists to see the universe
as it was 13 billion years ago.
These photons allow us to construct
an image of what the universe
looked like,
at 380,000 years
after the big bang, which is
an incredibly early time.
As expected,
they found that the temperature
was the same in all directions.
When we look at this microwave
background, we see that it has
pretty much the same properties,
you know,
one end of the sky to the other.
The temperature of the universe
is almost perfectly uniform,
except for some tiny variations
of one ten thousandth of a degree.
Variations that were actually
predicted by Guth's theory.
Inflation predicted not only the
range of temperatures that should be
present today,
but also the
distribution of those temperatures.
That's what this graph shows...
in theory.
The real test came
when satellites accurately measured
the actual temperature of the CMB.
The data points lie perfectly
on top of the curve.
It's an incredible match between
theory and observation.
It's one of those things that you
look at and on the one hand it's very
satisfying, but also unexpected.
Its powerful evidence,
but not conclusive proof.
The most basic aspects of inflation
can't be explained.
The theory can't say
what actually caused it.
We don't know
how inflation happened, we don't know
what drove the universe to inflate.
It's caused some to wonder if
this is really what happened
to the early universe.
Inflation is not really very deep.
It's something really simple.
In a way, it's too crude to be
the real thing that happened
in the early universe.
If inflation really happened,
it would have needed a kind of force
far more powerful than
has ever been seen.
Right now, we're nowhere near being
able to create enough energy
in our laboratories to create
inflation or anything like it.
Even Guth doesn't
have all the answers.
I think it's important
to understand that this is not
something that any of us working
on it would say we know for sure.
It is a proposal, a theory.
We don't yet fully understand
the physics of these energies,
we are making large extrapolations
in what we're talking about.
Inflation seemed to happen by magic
and then stopped just in time
before it blew the universe apart.
I'm not a great fan of inflation.
Whenever I teach it in my cosmology
class...
I actually wrote in my notes,
"Your lecturer doesn't really like
this theory."
I don't like it because
it seems too much of an add-on.
But saying that,
it's the easiest way for us
to get from the standard model
to some unexplained observations.
Inflation, in a way,
is an acquired taste for cosmology.
It's something which, if you're
really trying to explain the early
universe, especially if you're
very lazy and you just want to get
papers out, it's perfect because it
gives you an answer.
But the maths does appear to work.
It creates a universe that looks
as neat and ordered as our own.
Inflation could be sending all
of science down a blind alley,
But published in 1980,
the theory has become a key
part of the standard model.
The new story of creation
still begins with a bang.
In a fraction of a section,
inflation expands the universe a
quadrillion quadrillion times.
As it cools the building
blocks of matter are formed.
Then gravity begins
to takes effect.
But it's at this point that the
standard model hits another problem.
When the cosmologists look at the
night sky, they see something weird.
Galaxies
aren't behaving the way they should.
What's interesting is when you
look at galaxies, they seem to
be spinning around too quickly.
According to Newton's Law of
Gravity, stars on the edge of
a galaxy should move more slowly
than those closer to the centre.
It's a process clearly
seen in our solar system.
The further a planet is from the sun
the slower it moves.
The planets' speeds produce a
line known as a rotation curve.
Galaxies should produce
exactly the same curve.
But they don't.
Remarkably, when the speed of stars
at the edge of galaxies
are measured,
they turn out to be moving just
as fast as those close to centre.
The rotation curve
isn't a curve at all.
It's more of a straight line.
This should lead to disaster
all across the universe.
The galaxy would just fly apart
at these very high rotation speeds.
To make the galaxies work the way
the laws of physics dictated, the
cosmologists needed more gravity.
The only way to get more gravity
was to add more matter to galaxies.
But they couldn't find any,
so they decided to invent some.
And so dark matter was born.
A key architect of this idea
is Professor Carlos Frenk.
When we look at the way things
move in the cosmos, we soon reach
a very profound conclusion.
There isn't enough gravity
in the stuff we can see,
the stars or the galaxies,
to explain how objects move
in the universe, there must be
something else, that is responsible
for these movements, and that
is what we call dark matter.
The new matter was called dark
because they couldn't see it.
There has got to be something extra
in these galaxies bulking them up,
so that there's enough stuff
for there to be enough gravity
for them to be spinning around.
But this stuff is dark,
this stuff is dark, it's invisible.
Dark matter explained the flat
rotation curves and meant that the
laws of physics still made sense.
Dark matter is the easiest way to
explain why the galaxies work,
the way they do and everything else.
When the calculations were done
to work out how much unseen matter
the universe should have,
the results were shocking.
We expect that for every kilogram
of normal matter, there's another
five kilograms of dark matter
and we expect that dark matter to be
everywhere clustered around us.
The universe doesn't seem
to be made from the same
stuff that we're made from.
It's made of something else,
something strange, something alien
that we can't see.
Dark matter is wonderful stuff.
Wonderful stuff.
Without dark matter, the universe
wouldn't look anything like it does.
Dark matter in general, I think, is
one of the pillars of the standard
model of cosmology.
It is needed -
there's no doubt about that.
It's a persuasive theory
but there is a fundamental flaw.
Cosmologists
don't know what dark matter is.
All they know for certain
is it can't be ordinary matter.
Because ordinary matter either
emits light or reflects it.
Dark matter
has to be totally invisible.
We have to not be able to see it at
all wavelengths,
so you wouldn't see it with
an optical telescope, but
you wouldn't see it with
an X-ray telescope, or radio
telescope either. It really is dark
at all frequencies.
But dark matter had to
be more that just dark.
It needed to be a
special form of matter,
a kind of particle that
had never been seen before.
What's even worse, it's not just
invisible matter, it's exotic
matter.
Things which are not atoms,
which are not the things we know.
The idea of finding a new particles
isn't as strange as it seems.
Physicists have found lots
of particles over the years.
They all have different roles.
Some build atoms,
while others make up light.
Particle physics has its own
standard model, which catalogues
these different particles.
Today, we have the standard
model of particle physics, in which
there are 24 elementary particles.
They all have their own values of
mass, electric charge and spin.
They interact with each other
in different ways so that
in the standard model,
these particles are
grouped into different families.
It's just that dark matter
can't be one of these.
None of the particles would be a
good candidate for the dark matter
because, essentially, the ones that
are massive enough would not be dark
because they would form into atoms
that, in principle,
could omit light.
But particle physics is also
good at fixing standard models.
To make their model work
they invented whole
range of new particles.
If there was another set of 24
particles, identical to these ones,
of the standard model, but with just
one difference, the difference in
the way in which the particles spin,
this idea
goes by the name of super symmetry.
Super symmetry predicts there are
24 new particles that have yet
to be discovered by scientists.
And they're invisible...so
dark matter could be one of these.
Not only are they invisible,
they can pass right
through solid objects.
Even stars and planets should
be no barrier to dark matter.
Astrophysicist Dan Bauer is in
charge of a special experiment.
He's hunting for dark matter.
He's not looking for it in space.
Instead he's buried his
equipment ½ mile under the
frozen plains of Minnesota.
It's strange at first,
but you get used to it
and once you pass through these doors
it looks like any other lab.
You could be
in one of those and not even know
that you have a mile underground.
As dark matter should be able
to pass through solid rock,
Dr Bauer has no trouble running
his experiment underground.
You'd think it's easier to detect
dark matter at the surface,
why do we bother to come down this
far, it's obviously inconvenient.
It's because that there's
a lot of normal matter particles
hitting the Earth's
surface from space.
It would overwhelm any
possible signal we could see.
But Bauer is facing a problem.
His dark matter detector
is made of normal matter.
The kind of normal matter that
dark matter passes right through.
If we are right about this dark
matter particles streaming through
us all the time, millions of them
are passing by here every second, and
they're doing absolutely nothing,
in fact their passing through the
entire Earth without doing anything.
Turn on the lights.
This massive block here
is the actual experiment.
There's millions of dollars worth
of the most advanced technology
imaginable
waiting to record the first evidence
of the theoretical particles.
If they are real, and one of them
so much as nudges Bauer's detectors,
it would set of a signal that
could provide the proof that
cosmology's been waiting for.
Occasionally one of these particles
will however
do something in one of the detectors
buried deep within this pile.
It will cause a little bit
of heat and charge.
If we're very lucky
then we will have detected
a particle that makes up dark matter.
Theoretically, millions of
particles have been streaming
through Dr Bauer's machine
every day
for the five years it's been here,
but frustratingly
they've always left no trace.
But then something did happen.
Just this last December
we saw the first two events that have
the characteristics we might expect
from dark matter.
But it's too few events
for Bauer to be certain
he's really found dark matter.
Despite the years of research
and investigation,
cosmologists don't seem to be
much closer to uncovering
what dark matter actually is.
If I, If I knew the answer to the
question, "What is dark matter?"
I would already be sitting
very comfortably with a medal,
being from the Nobel Committee.
There is very little doubt
that the dark matter exists.
The question is, "What is it?"
It's cheating in a sense that
maybe it's not like that
and maybe we should just
take things face value and in fact
what's out there is what there is...
there's no dark matter,
no ghosts around the universe.
But despite the doubts,
cosmology needs dark matter.
It's the missing ingredient that
makes the universe work the way
the maths predicts it should.
And it puts the standard model
story of creation back on track.
Creation starts with a bang,
Inflation takes over
and everything expands.
After one billion years
the first star is born.
Then dark matter kicks in.
It creates the gravity
that makes galaxies form.
The universe continues to expand.
As the epochs pass
the expansion slows.
Soon, the universe
will come to a stop.
The trouble is this
isn't what is actually happening.
The universe isn't stopping at all.
At the top of a mountain
range in New Mexico
is a very special instrument.
It's a finely-tuned device
that scans the heavens.
This telescope is
measuring the universe.
It's designed to work out
how space itself is moving.
And what it's discovered
has shocked cosmology.
Using the Sloan telescope,
astrophysicist Saul Perlmutter
recorded a new phenomenon.
The big surprise that we found, 10
years ago now, was that the universe
apparently has been speeding up
in the last half of its life,
for the last seven billion years
or so, there's been an acceleration
in that expansion.
Everyone had been expecting
that the universe was expanding.
But the standard model said
the expansion should be slowing.
The universe was meant
to be coming to a stop,
but it wasn't.
This was a great scandal and it was
a great scandal in a way because
you know anyone reasonable
would have expected that somehow
gravity is attractive therefore the
universe should be slowing down.
The pull of gravity from all
the matter in the universe
should be acting as a brake,
bringing expansion to a stop.
Perlmutter's observations
told a different story.
It's rare that you get to catch
the universe in the act
of doing something which doesn't fit.
So having the chance to have seen
the universe do something that's
completely surprising
is, is tremendous.
Inflation theory had
already established the
big bang was no ordinary explosion.
Now Perlmutter was saying
it was stranger still.
The explosion hasn't stopped.
The big bang is still banging.
Perlmutter's discovery created
a new mystery to be resolved.
It suggested a new force
was powering the universe.
And it needed a name.
They called it dark energy.
What is dark energy?
Well, I know, but I'm
not going to tell you.
Well, it's dark and it's expanding.
I guess it's a pictorial
way to describe dark energy.
We don't know what it is so we
might as well say it's this.
Actually, no, I've
no idea what it is.
I hope it goes away, I don't like it.
We have no idea what dark energy is.
Dark energy is basically a fancy
word for ignorance of what makes up
75 per cent of our universe.
I wish I knew what dark energy is.
I don't know and nobody else
knows either.
It is a very unwelcome actor
in the cosmic scene.
Nobody asked for it, nobody
wanted it, nobody understands it,
This ignorance didn't
stop the ideas coming in.
What could dark energy be?
Was it an odd kind of gravity?
Dark energy causes this type of
anti-gravity
where distant things
are repelled from each other.
Or something entirely new.
If the universe is accelerating,
something must be causing it
and dark energy is just
defined to be whatever it is that's
causing the universe to accelerate.
Even a weird bit of maths.
When Einstein proposed his theory
of space and time,
he proposed this thing called
the cosmological constant,
which is this constant thing
that pervades all of space,
which would
counterbalance the pull of matter.
Whatever dark energy is, whether
anti-gravity, weird energy or maths,
it seems to have magical properties.
Not only does dark energy
make the universe expand.
But the more expanded the universe
becomes, the more dark energy
is created to fill the gaps.
This could only mean one thing.
There must be something in nothing.
Although we used to think that
nothing was the simplest thing
you could have,
just complete emptiness,
we now realise that there is no such
thing as a completely empty vacuum.
If you take out all the air
molecules from this space
and take out all the light
particles, there's still
something left.
The very fabric of space itself
isn't empty.
Deep space,
the space between galaxies,
is meant to be perfectly empty.
There shouldn't be anything there,
not even the tiniest particle.
Instead, it seems this
space is full of energy.
It might also
explain the dark energy.
Maybe the vacuum itself
has this energy
which we can gravitationally
measure throughout our space.
You take a space and you stretch
it into more space...
Well, that new stretched-out
space has to have the same
properties as the old space
cos a stretched vacuum
is still a vacuum.
It's yet another explanation for
what dark energy might actually be.
So that's one of the prime
contenders for what dark energy
is - the energy of nothing,
which is not nothing.
"Nothing"
is taking over the universe.
It's creating more
and more empty space,
filled with even more nothingness.
Counterintuitive
though it is, just like inflation,
cosmologists need dark energy.
Even though we don't know much about
it, it's the simplest explanation
we have for some of
the observations in the universe.
Like dark matter,
dark energy isn't a solution,
it's a description of a problem.
We're pretty much in the
dark about dark energy.
There isn't
a theory, a compelling theory.
There are hundreds of theories.
We don't know where it comes from,
we don't know how it relates to
the other particles in the universe,
but that's an interesting challenge.
It means, you know, maybe this
is going to be the next big thing.
The mystery is driving science on,
making cosmologists
re-evaluate what's really
happening in the universe.
The dark energy seems to me
really mysterious, and I think it's
very unlikely that my generation
of physicists will come to see the
solution to the dark energy problem.
Mysterious though dark energy is,
it's become an important
part of the standard model.
It makes the maths fit
with the real universe.
But more importantly, it seems to
be the final piece in the jigsaw.
However counterintuitive
the universe now is,
it's the best model that we have,
the most complete description
of creation there's ever been.
The universe starts with a bang.
Then it suddenly inflates.
Dark matter forms...
..and helps galaxies to emerge.
And the universe's expansion slows.
Finally, dark energy takes over,
stretching the universe
more and more.
After 13.7 billion years,
cosmologists look up at the sky
and understand the
story of creation.
It's all thanks to the
beautiful equations
and elegant descriptions that
make up the standard model
of cosmology.
Today we have a very compelling
standard model that describes
a huge amount of observations
and measurements.
Some pretty spectacular, like the
fact that the universe was once hot,
the fact that the universe is
expanding, it explains why
the...we're made of the elements
that we're made, it explains
where the atoms come from,
and it also explains, for example,
where galaxies originate, how they
ended up being the way they are.
So it's a very powerful
standard model.
The unlikely combination
of inflation, dark matter
and dark energy has come good.
Cosmology's standard model works.
Except...that it now
has a new challenge.
Another darkness to account for.
That new phenomenon, dark flow.
For Dr Sasha Kashlinsky,
most days start the same way -
taking the kids to school
on the way to the office.
His office is at NASA's
Goddard Space Flight Center.
Kashlinsky is a cosmologist.
What made me choose this career?
I guess, in my childhood, it was
reading too much science fiction.
I dreamt then
of doing space travel and eventually
instead of space travels,
I ended up doing cosmology
as a desk job.
Say "bye-bye", gentlemen.
His desk job involves poring
through pages and pages of data
about the cosmic
microwave background.
The picture of temperature
differences in the
afterglow of the big bang.
Hidden in these numbers,
he's found something that
shouldn't be happening.
This very nice map
that they produced, is, um,
is a nuisance for us, an obstacle.
Kashlinsky is looking for
movements hidden in the map.
So we remove most of the signal that
they detect, and then we concentrate
only on about one per cent
of this map associated
with clusters of galaxies.
By stripping away the information,
he's found distortions in the light
coming from the microwave
background.
Distortions that
appear to show movement.
Whole clusters of galaxies seem to
be moving in an inexplicable way.
It left us greatly puzzled when we
found it, so puzzled that we, er, we
didn't know what to do with it.
We sat on it for a year,
checking everything, but
ultimately it is in the data.
The CMB is the saviour of cosmology.
It had provided the evidence that
validated the theory of inflation
and allowed the standard
model to work again.
Now the very same data
could undermine everything.
It could easily point to something
very exciting, a breakdown of our
understanding of the universe.
Like dark matter and dark energy,
these galactic movements
were another mystery.
So Kashlinsky decided
to call them dark flow.
He immediately sought to find a
cause for this strange phenomenon.
A new, unseen force
that could power dark flow.
He came up with a theory
for what this could be.
All he needed was another universe,
one that exists outside our own.
So, therefore we believe that
in order to explain this flow,
we should be looking outside
of our universe very far
beyond what is
the gasmological
horizon of the universe.
For Kashlinsky,
our universe isn't everything,
it's part of an even larger whole.
This apparently crazy idea
is actually predicted by one of the
pillars of the standard model.
Alan Guth's theory of inflation.
In almost all versions of our
theories, inflation never
ends completely,
it ends in places and in
those places where inflation ends,
normal universes happen,
but in other places the inflation
continues and then ends again and
another normal universe happens.
Guth thinks our universe is
part of a bigger structure.
We're in a small piece of it,
a bubble created by inflation.
So we end up with a picture of
a multiverse consisting of many
different universes which we,
in this context, tend to call pocket
universes, ah, we would be living
in one of these pocket universes.
Ah, but inflation tends to produce
not just one pocket universe,
but an infinite number for the
same price as the one.
It could mean that dark flow
is evidence that our
universe is not alone.
This would make it one of the
most important discoveries ever.
Despite large parts of the standard
model being built only on theory,
it won't be easy for dark flow
to change the science
and join the model.
I think it's good
to have a healthy dose of scepticism,
we don't want to be,
jump on fly-by-night theories, um,
we want to make sure that if theory
is going to change, it's a change for
the better, and by better, I mean
it explains our observations better.
Many modern cosmologists have
devoted their careers to trying
to find theories that could
replace the standard model.
They have even tried to change
some of the fundamental
principles of physics.
I work a lot on trying to
come up with alternatives which
don't have this dark universe.
I've been involved with
varying speed of light theory.
You want to bring everything into
contact in the early universe,
raise the speed limit.
They are hoping to find
a deeper truth that will reveal
how the universe really behaves.
I think the way that science works
is there's always one big thing
that most people work on
and then there are always these side
projects that other people look at
and every now and then, one of
these side projects is right
and the big thing is wrong.
It's just that these cosmologists
haven't been very successful.
I would say there's no shortage of
alternatives, it's just none of them
is compelling in a way that might
make the whole community change
and start working on them.
These attacks have meant that
cosmology's standard model has gone
from strength to strength.
The more they fail,
the stronger the model becomes.
You get famous in science if you can
be the one who shoots down the
theory everybody else believes in.
So if the theory has withstood
all this artillery fire
from a lot of smart physicists
and experimentalists for many years,
that gives it a lot of street cred.
This is the key test for
a theory in cosmology.
It's the hurdle that must be passed
to enter the standard model
and it's where dark flow
currently falls down.
It hasn't yet been pushed to the
brink of destruction and survived.
You really have to be very rigorous,
and anything that you come up with
has to be corroborated.
It has to be demonstrated to be the
case, not just by one measurement,
one experiment but by many
different groups.
That's the essence of the
scientific method, repeatability,
rigour, accuracy and relevance.
It's not enough to make one
measurement, find one thing
that looks strange and say,
"Ah, this is true
so there's a problem."
You have to come at it
with many different ways.
A lot of these results are tentative.
Some of these results
are inconsistent with each other.
So, I think it's premature
to incorporate these results
as hard facts
about the universe as we know it.
I think it's fair to say
that it's, it's controversial.
For a long time it was controversial
among ourselves, in fact, we did not
think it was possible.
But ultimately,
it's the data that decides
and the data, to us, show very
unambiguously that this is there.
The battle between resolving
the mysteries of the universe
and searching for new ones
has driven cosmology on.
It's been a struggle to
explain the unexplainable.
and has resulted in a powerful tale
built on mystery.
So for now, the standard
model remains unchanged.
It's successfully described so much.
It tells us how the universe began.
How matter and energy formed.
How gravity created stars and
galaxies and planets like the Earth.
It's the best we have,
and it's so nearly a perfect fit.
It's just that it could be
totally wrong.
There's a feeling we need an extra
clue, and we don't have it yet.
And I think that's what
we're waiting for, somehow.
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