How the Universe Works (2010) s03e02 Episode Script
The End of the Universe
The universe was born to die.
But how and when will it all end? That's the reason i became a cosmologist.
I wanted to be the first person that would know How the universe would end.
Two cosmic heavyweights wrestle for control.
The winner seals our fate.
The tug of war is gravity, Which is trying to shrink it down, And the expansion of space and time itself.
Will gravity triumph? The universe will get smaller and smaller, hotter and hotter.
Or will expansion get the upper hand? Even the electrons around your atoms will be ripped apart.
The end is coming, And it could be sooner than you think.
Captions paid for by discovery communications The universe is everything All space, all time, all matter.
The earth is a speck by comparison, A grain of rock orbiting just one of the 200 billion stars In our home galaxy, the milky way.
In turn, this enormous structure is just a drop In an ocean of galaxies that stretch For 90 billion light years.
And all of this, From the biggest galaxy to the smallest atom, Will one day die.
We don't see evidence of anything being eternal.
Eternity doesn't exist.
Even space and time will come to an end.
The universe has been expanding since its birth, Gradually burning through the fuel that lights its stars.
But what happens when the fuel runs out? Will it all just fade away? Stars die out, use up their nuclear fuel.
We have an empty, cold, desolate universe.
Just dead remnants of stars -- Black holes, neutron stars.
Eventually, they decay away, And you're left with a thin haze of very low energy light.
That's it.
We used to think the universe Would cruise gently into old age.
But over the past few decades, Astronomers have revealed a very different And disturbing picture.
The universe isn't cruising.
It's fighting for its life.
It may seem peaceful here on earth on a nice, sunny day, But in fact, above us and all around us, Throughout the universe, a battle is raging, And it has raged since the beginning of time.
Two deadly forces grapple for control.
The first, expansion, pulls galaxies apart, Cooling the universe and threatening it With a frozen extinction.
The second, gravity, tries to crush everything back together, Annihilating the universe in a dense ball of fire.
Will gravity or expansion win? Or will it end in a tie? These two colossal forces yield three endgames.
One is the big freeze.
Expansion wins, and the universe just expands forever.
The second is that there is a delicate balance Between the expansion And the amount of gravitational attraction, And the universe gets to a particular size, And it pretty much stays there.
And the third outcome is that The gravitational attraction wins, And the expansion stops, And the universe begins to get smaller Until, eventually, it goes back to a big crunch.
So far, the universe seems balanced On a tightrope between expansion and contraction.
But will it keep its equilibrium until it runs out of steam, Or will something tip the balance? I don't think there's any bigger question than, Where is the universe going? To predict the future, cosmologists have always looked To the past, back to the beginning of expansion, The beginning of gravity, the beginning of everything.
an infinitely dense, Hot speck ignites and suddenly expands outward -- The big bang.
All energy, all space, and all matter the building blocks of the universe we see today, Are created and set in motion.
Think of it.
Everything you see around us Concentrated into a primordial fireball that exploded, Sending all the galaxies into motion.
That outward blast, the birth of expansion, Is still going on today.
Without it, we wouldn't have a universe big enough For stars and galaxies to exist in.
Expansion is an astonishing force of nature.
It works by inflating the fabric of space-Time.
Space between galaxies expands, And it pushes the galaxies apart.
Space carries objects with it like a surfer on a wave.
It's going on in every part of space.
Even inside your body right now, There's a pressure for space to expand.
Expansion generated the vast, moving stage On which today's universe plays out.
But left unchecked, it could have been a force For utter annihilation.
If the universe had been expanding much faster, It would have emptied out so fast, You wouldn't have had time to make galaxies, Planets, people.
The fact that we're here Means that something must have put on the brakes.
It was, of course, our universal glue -- Gravity.
Gravity and matter go hand in hand.
The more massive the object, The more pull it exerts on everything around it.
It draws atom to atom, particle to particle building stars, nebulas, Galaxies -- The hardware of the universe we see today.
But gravity is a double-Edged sword.
Too much, and the early universe would never have gotten Out of the starting blocks.
If it had been expanding more slowly, It would have re-Collapsed into another singularity.
And again, you wouldn't have had the time to make galaxies, Planets, or people.
So we live in the goldilocks universe.
We live in the universe that lasts long enough That we can be here, but expands gently enough That we have time to form.
The universe has lasted for 13.
8 billion years, Thanks to the opposing forces of gravity and expansion.
But just how stable is this balancing act? Does our universe have just the right amount of stuff in it To keep it from runaway expansion Or catastrophic collapse? In the 1920s, scientists did the math, And the results were anything but reassuring.
The more matter you have, the more gravity you have.
If you have lots of matter in a very dense universe, Perhaps the universe begins to re-Collapse.
Or, if you have very little matter, The universe would freeze to death.
So what is the critical density, the border between the two? It's approximately five hydrogen atoms per cubic meter.
So think of a cubic yard, and put just five hydrogen atoms Inside, and that is the tipping point.
If you put more than five atoms, Then the universe will begin to collapse.
If you have less than five atoms, Then the universe just keeps on going.
If we thought the universe was balanced On a tightrope before, the critical density question Showed us that the rope was more like a razor blade.
Yet, when astronomers took additional measurements, They liked what they saw.
The universe appeared to contain just the right amount Of matter to stay at the critical density.
More and more, the indirect evidence And the theoretical arguments suggested That the universe must be exactly at the boundary Between a universe that would collapse And one that would expand forever, That we were teetering on the hairy edge of expansion.
The universe seemed so perfectly balanced That it would head quietly into old age.
Then, in the 1970s, astronomers made an observation That shocked them.
The cosmos was filled with invisible stuff, And its gravity could cause a catastrophic collapse.
The universe is balanced on a tightrope.
On each side of the drop lies an early death -- A big freeze, fueled by the runaway stretching of space, Or a big crunch, the result of gravity overcoming expansion.
believed we'd stay balanced Between these fates for eternity.
Now things have changed tremendously, Because we've discovered something we never knew about In the 1970s, astronomers are stunned.
Some unknown form of matter, invisible to telescopes, Dwarfs what we thought was out there, Not a fraction more, but five times more.
We used to think that gravity came from stars And objects you can see -- End of story.
Now, we realize that that naive picture is actually wrong.
Astronomers make the discovery, Studying the clockwork nature of our universe.
The huge gravity of the sun holds the earth And all the other planets in a delicate circular dance.
The sun's mass controls the speed of these orbits.
If it were more massive, the planets would orbit Much more quickly.
And if it were smaller, it would take much longer For a planet to complete an orbit.
Galaxies run like clockwork, too.
The vast mass at the center pulls the outer stars Into circular, planet-Like orbits.
Astronomers make precise measurements Of these galactic orbits in the 1970s.
The results change everything.
The galaxies were spinning too fast.
Way too fast.
Even accounting for the supermassive black holes At their center, nine-Tenths of their mass was missing.
By rights, the galaxy should fly apart.
By rights, the earth should have been flung Into intergalactic space billions of years ago.
We should have no milky way galaxy, and yet, Our universe is full of galaxies.
An immense additional source of gravity Must be holding galaxies together.
But no matter where astronomers point their telescopes, They see nothing.
Not a glimmer, not a shadow.
Whatever this new stuff is, it doesn't emit light, Reflect light, or even block light.
They call it dark matter.
What we've learned is that most of the matter in the universe Is not ordinary stuff.
It's not atoms.
It's not particles we've yet detected in any experiment Done here on earth.
It's some new kind of particle that we call the dark matter.
Dark matter fills the universe, Outstripping normal matter by 5-To-1.
Vast filaments spread out throughout the cosmos, And bright galaxies cluster where dark matter is thickest.
Dark matter provides the scaffolding that underlies How the matter in the universe structures itself, Where it goes, and what it does.
So, dark matter dictated How the universe unfolded.
It seems as if out of the hot big bang, Dark matter condensed first, before atoms, And dark matter began to become clumpy.
The clumpiness then began to attract atoms As they were formed later, and that formed galaxies.
And in some sense, the dark matter therefore Provides kind of a womb that allows the birth of our galaxy.
Dark matter holds the universe together, But it also threatens to destroy it.
One of the most amazing discoveries Of the past few decades is dark matter, The fact that there's much more matter in the universe Than we were aware of.
And all of that matter has a lot of gravity.
So all this new matter, all this new gravity Must be slowing down the expansion of the universe.
Dark matter may even tip the cosmic scales In favor of gravity, Defeating expansion and pulling the entire universe Towards a death by fire.
It's called the big crunch, And this is how it would play out.
For a fraction of a second, the universe stalls, Poised between expansion and contraction.
Then, gravity kicks off a cataclysm.
When you looked out, the very first things As it began to turn around that you began to see Is that galaxies, instead of moving away from us on average, Would begin to be moving towards us on average.
The whole universe would look like it was coming to get us.
As space contracts further, The density of matter increases, gravity gets stronger, Temperatures soar as the crunch gathers momentum.
Galaxies begin to collide, Gas clouds begin to collide, Planets slam into the earth.
Black holes will execute a death dance around each other.
Temperatures, of course, will continue to skyrocket.
Matter, space, and time implode Until everything in the universe is compressed Into a tiny speck of infinite mass, heat, and pressure.
For the last stages of the big crunch, Galaxies will collide and form a primordial atom.
And then, life as we know it will be impossible.
We're back to where it all began, Back at the big bang.
The universe that we live in will cease to exist.
But some believe a big crunch could herald a new beginning.
We don't know what the end point of a big crunch would be, Because the laws of physics break down.
It's possible, and indeed, philosophically very pleasant, To imagine that that crunch would somehow end up evolving Into an expansion again, and you could have a cyclic universe Which goes on forever.
Perhaps at that point, we will recreate another big bang.
It's conceivable that as everything comes together In the crunch, something sort of keeps it from just continuing And pushes out in a hot, dense, smooth state, And from the other side, it looks like a big bang, And a new universe has been created.
Our big bang might have been someone else's big crunch.
But just when scientists came to terms With dark matter's big crunch, the universe threw them Another, even bigger curve.
Some ghostly force seemed to be sending us hurtling toward A completely different death.
My postdoctoral scholar showed me the results.
I nearly fell off my chair.
Gravity and expansion battle for control Of our universe for 14 billion years expansion pushing it outwards, Gravity pulling it in.
With dark matter in its corner, Gravity seems to be the inevitable winner.
The extra mass will drag the universe into a big crunch, Until a stunning discovery Revolutionizes our understanding of the universe.
Around 1990, two teams of researchers decided to measure The expansion history of the universe To determine whether it's been slowing down so much That it'll eventually have a big crunch, Or whether it hasn't been slowing down much And will eternally expand.
Astronomer alex filippenko was on one team.
Saul perlmutter led the other.
We realized that it was possible for the first time To go and actually make a direct measurement Of how much the universe had been slowing down in the past.
Both teams want to measure The speed of distant galaxies.
But because the galaxies are too dim and too far away, They look for something brighter.
Billions of light years from earth, a star detonates.
This is a supernova, A dying star's brilliant final gasp.
It burns brightly, 5 billion times brighter than the sun, But briefly.
Perlmutter and filippenko have a window Of just one or two weeks to measure How much the galaxy it sits in is slowing down As it moves away from us.
The teams look for supernovas for eight years.
They measure 42, and the results seem impossible.
We plotted the points on the graphs, Andit didn't make any sense.
They were not slowing down at all.
They were actually speeding up.
What both groups found stunned the world.
In the last 4 or 5 billion years, The universe has actually been speeding up in its expansion.
An accelerating universe, Propelled by something mysterious.
For so long, we've been arguing whether the universe would Expand forever or collapse back in on itself, But nobody thought the answer was going to be That the universe was accelerating, Going faster and faster all the time.
The acceleration bewilders the scientists.
It seems to defy the laws of physics.
Imagine i've got a baseball And i throw it straight up.
And instead of slowing down once it leaves my hand, Which is what normally it will do, It begins to slow down at first, But then it starts speeding away.
Somehow, it's getting energy.
The new energy seemed to be coming from nothing, The vacuum of space.
The word "vacuum" to a scientist means completely empty space, No particles there at all, no temperature, No energy to speak of.
But there's an intrinsic energy in space and time.
Empty space has energy, and that energy produces A gravitational repulsion, a kind of anti-Gravity.
Without a clue what this force is or how it works, All scientists can do is give it a name -- Dark energy.
We could have called it we-Don't-Know energy.
We could have called it anything.
But we don't know what it is, and dark or not, It's the biggest mystery in physics.
Nasa calibrates its finest space telescopes To measure how much dark energy is out there, And the result is mind-Blowing.
It dominates the mass of the universe by nearly 3-To-1.
And the more space expands, The more dark energy there seems to be.
Dark energy is the energy of nothing, And it's repulsive.
Therefore, as this dark energy repels galaxies, There's more of it, there's more vacuum.
And so there's more repulsion, And perhaps that's the reason why the universe is accelerating Right now rather than slowing down.
Dark energy seems to kill the big crunch theory, But scientists aren't yet sure how dark energy, Expansion, and space are connected.
If a volume of space doubles in size, Does the dark energy inside it double, too? Or does it increase more? A 1-To-1 relationship leads to a steady expansion.
The universe ends in a big freeze.
But if dark energy increases above and beyond expansion, A new, even more terrifying end awaits the universe -- A big rip.
In a big rip scenario, the expansion is so great That even the galaxies begin to expand internally, Which means that literally Our bodies are going to be ripped apart.
Scientists calculate Just how the big rip will play out.
One by one, the galaxies in the night sky will blink out As space pulls them away from the earth Faster than the speed of light.
dark energy overcomes gravity On smaller and smaller scales.
First galaxies start to rip apart, Then insides of galaxies will begin to rip apart, And then solar systems will begin to rip apart then planets and then rocks, people, atoms.
The end will be mercifully quick.
In the space of a few minutes, All the stars and planets in the universe will be destroyed, Their remains pulled apart into ever-Smaller pieces Until finally, when the universe has Less than a second to live, The subatomic particles that made all matter Will be destroyed, And all that remains will be individual photons Becoming scarcer and scarcer As the space between them expands.
All you're left with is very low energy light That gets stretched and stretched Until it might as well not exist at all.
The last thing to go -- The empty vacuum of space itself.
It'll be pulling on the universe so hard, It could tear the fabric of the universe apart.
Reality could dissolve.
Will the universe end with a big rip, Or a big freeze? The answer is locked inside the mystery of dark energy.
Solve that, and the fate of the universe becomes clear.
The end of the universe is coming.
But how will it play out? For a time, a big crunch was the likely answer.
Dark matter, the invisible bulk of the universe, Causes space to fall in on itself.
Galaxies collide.
Planet merges with planet.
Everything becomes hotter and hotter, denser and denser.
The universe is like one giant star.
Dark energy kills the big crunch theory.
It acts like rocket fuel for the expansion of space Between galaxies.
They're not just coasting.
They're getting pushed outward.
Only two possible fates remain -- A big rip or a big freeze.
Both scenarios rely on dark energy.
For the universe to be torn to shreds in a big rip, Dark energy must increase exponentially in the future.
But a big freeze requires a steady increase In dark energy, Pushing galaxies away from each other.
We can't write the last chapter of our universe Until we understand the nature of dark energy.
May 2009.
The european space agency launches the planck satellite To search for the birth of dark energy.
Its ultra-Sensitive telescope peers through space and time Back through billions of years, Towards the beginning of everything, to capture this.
This is our universe as it appeared Over 13 billion years ago, after the big bang.
So what planck has done is take a picture Of the early universe And told us about what the early universe is like And given us our most detailed and accurate picture Of that moment in time.
The universe in this picture Is a hot soup of protons, electrons, and photons.
Hydrogen atoms have just started to form, And it's the light from this genesis of matter That we see here.
Blue areas are colder.
Reds are warm.
Eventually, those hot spots, Those red spots you see in the map, Are going to form large superclusters Made up of hundreds or thousands of galaxies.
Each one of those galaxies will contain billions of stars.
Gravity and expansion alone Appear to drive the formation of these embryonic galaxies.
Dark energy doesn't seem to have switched on yet.
So, when did dark energy take control of the universe? Astronomer brenda frye is part of a team Using massive ground-Based telescopes Like this one at kitt peak, arizona.
She peers back in time to capture the universe Through its childhood as it was growing.
Right.
So this is an aluminum plate, And into this plate are drilled 640 individual holes.
Each one is put at a very specific place on the mask Which will correspond to one particular galaxy in the sky.
During each observation, The light from 640 individual galaxies is collected Using fiber optic cables.
The speed and relative position of each galaxy is measured To pinpoint exactly where it is in space.
So far, the team has accurately mapped Around a million galaxies in 3d, And this is what they look like.
Each one of these fuzzy patches Is a fully grown galaxy Containing around This is a very basic measurement, And we think that this will be able to help us To get a grasp into the nature of dark energy.
Scientists compare this adolescent universe To its baby pictures.
It shows dark energy emerging When the universe is half as old as it is today.
About 8 billion years after the big bang, This expansion of the universe begins to accelerate, And we're in the middle of this acceleration.
The data also shows that as space expands, Dark energy increases in lockstep with it.
If you had a box and you put some dark energy in it, And then you went and you weighed that box now you take the box, you make it twice as big.
You don't open it.
You don't put anything in it.
You weigh it again, it's gonna weigh twice as much.
This remarkable observation means That we should be safe from a big rip.
Dark energy will continue to increase gradually.
The universe is heading for a big freeze, And scientists can finally calculate a timeline For the end of everything.
It now seems that we live In an almost perfect universe, With just enough gravity to hold the galaxies together And just enough dark energy that it will expand forever Without ripping itself to shreds.
Cosmologists can finally envision the end of it all.
it was debatable.
But now, it appears that the universe most likely Will suffer a deep freeze.
If you look at the data, it stares out at you.
In a big freeze, Dark energy pushes galaxies further and further apart, But they remain intact.
The stars inside them fade away.
Every star you see in the sky, including our sun, Is burning through its nuclear fuel.
The gas will run out, stars will stop being made, And the ones that exist are it.
Those are the last ones.
A hundred trillion years from now, The biggest stars will be the first to go extinct.
Big stars burn bright and die hard.
The star's core collapses, Unleashing a supernova.
Then gravity crushes the dead star down To a single dense spot.
The bright star is now a black hole.
Sun-Like stars go next.
As their supply of hydrogen runs out, They swell to a bloated fireball Over 200 times their current size.
And when the core has no more hydrogen, It's going to bloat up into a red giant star.
Now, red giant stars are so big, they will actually Eat up their own planets.
We know of examples of red giants That go all the way out to where the orbit of jupiter is In our solar system.
Its fuel exhausted, The sun-Like star gives in to gravity And shrinks to a white dwarf, A dense ball of matter Just a few thousand miles in diameter.
It will glow with heat for a further 10 billion years Before cooling to a black dwarf, A ball of compressed carbon, perhaps even diamond.
As the biggest stars die, The universe will slowly turn red.
The blue stars will blow up, And then the slightly less blue stars will blow up, And then stars like the sun will fade away and die, Leaving just the red stars to exist.
Red stars are the smallest And coolest in the universe.
They burn their fuel slowly.
But, after another Even these smallest of dwarf stars Will use up their fuel.
Stars as we know them will cease to burn energy, And the night sky will turn black.
Black holes, the corpses of dead stars, And cold clouds of gas and dust are all that remains.
The age of stars is over.
The age of black holes begins.
Black holes become the fundamental building block Of the universe.
A galaxy will basically be a supermassive black hole In the center, with smaller black holes orbiting it.
In some ways, it's kind of a ghost universe.
It's the corpses, the zombie stars, That will take us into the future.
Zombie galaxies filled with black holes Continue to evolve.
They sweep up the dead remains of stars.
Black hole merges with black hole.
They'll eat each other and they'll get bigger, And maybe they'll fall into the supermassive black hole And it'll get bigger.
The universe will still be an exciting, dynamic place, It's just that the time scales you're talking about Are now trillions of years Instead of thousands or millions of years.
Any material that evades the pull of a black hole Eventually dies away as its protons disintegrate.
A proton, one of the fundamental building blocks Of atomic matter, of what makes us up, Can just spontaneously fall apart, And it turns out this takes a tremendously long time.
But even that will go away.
All that will be left is a sea of black holes.
Scientists used to think black holes were immortal, But even these will one day die.
Now we're talking about time scales Of unimaginable length -- Quadrillions of years into the future.
But on that time scale, Even the black holes begin to evaporate.
They'll get smaller and smaller and smaller, And then, poof, they'll be gone.
The universe will end When the last remaining black hole dies.
As it gets smaller, the evaporation rate Increases exponentially.
Before long, it reaches a size A billionth of a trillionth of a trillionth of an inch.
At that instant, the laws of physics break down, And the last black hole explodes in a flash of gamma rays, Leaving nothing.
And it will die in a sudden burst of light, The last burst of light In the entire history of the universe.
The big freeze is coming.
The universe will suffer a cold, slow, dark death Which will play out Over trillions upon trillions of years.
But quantum physics leaves the door open For an alternative end, An event so powerful, so destructive, That it could destroy everything we see in the blink of an eye.
And it could happen tomorrow.
The end of the universe -- It's coming.
Dark energy accelerates the space between galaxies, Pushing everything we see to a long, cold, And very slow death.
Unless, that is, something bizarre happens first.
A monster called phase transition Is lurking in the shadows, And it could annihilate the fabric of space and time At any moment.
When we cool down water, it turns into ice.
The properties change.
If you lived in the water, when it changed to ice, Your world would be very different.
Water phase changes into ice when it loses energy.
I once left a water bottle in my car overnight.
It was still liquid, but the moment i touched it, The slight imperfection, The little bit of ice that it formed, spread, Poof, and filled up the whole bottle.
That rapid change to something new Is called a phase transition, And bizarrely, the same thing could happen to empty space.
We've really come to understand That we shouldn't take for granted thatvacuum, What we call nothing, is actually stable.
It could be that the energy stored in empty space Is just waiting to be released in a phase transition.
If it is, the laws of physics will change.
A spontaneous glitch in the fabric of space-Time Could trigger a phase transition of space, A tiny bubble of new universe that spreads out, Overwriting the old.
We know it can happen, because it's happened before.
At the moment of the big bang, The universe that's first created Is completely different to the one we see today.
Hot and without form, There's no matter, no time.
The laws of physics are different.
Suddenly, less than a trillionth of a second later, A glitch triggers a phase transition.
A tiny bubble of the universe we live in today forms, And it races outward, Destroying everything it touches Like ice spreading through water.
The energy that spills out creates the space and time That we exist in, The building blocks of matter and the forces that govern them.
All that energy was released, producing all the matter And radiation we observe in the universe today.
The old universe gives up its energy To create the new.
But it holds some back.
The vacuum of space still has energy bound to it.
Perhaps this is the dark energy we see today.
Physicists believe that someday in the future, A brand new glitch in the fabric of space-Time May trigger another phase transition, One that wipes us and everything we see Out of existence.
This is a way to destroy an entire universe, Because within your universe Are the seeds of its own destruction.
It would spread out at the speed of light in a death bubble, Ruining all the galaxies as it passes through, And ultimately completely destroying our universe.
Nothing can survive the expanding phase transition.
Planets, nebulas, galaxies -- All are ripped apart As the boundary of the bubble reaches them.
Inside this bubble, protons are unstable, Atoms begin to rearrange in a new form of matter.
As these bubbles begin to expand, A new universe is being born In the corpse of the old universe, And the beginning of a new law of physics.
And so, the expanding universe we now see May end in a phase transition, but we won't know what hit us, 'Cause the laws of physics will change, And we will essentially most likely disappear At the instant it happens.
This bubble will expand at the speed of light, And as the bubble passes you, All the atoms of your body rearrange themselves, And you would never know it.
You would have no warning, because the bubble itself Is expanding at the speed of light.
You can't predict precisely when it could happen.
You only have a probability.
So what you really are predicting is a rate.
Does it happen once a year? Once every 10 billion years? Once every googol years? Or whatever.
It's very possible that these bubbles get nucleated And grow about once every So it hasn't happened yet because we got lucky.
It's unlikely it would happen the next year or the next day, But the laws of physics absolutely allow it.
A phase change may happen, or it may not.
The universe plays its cards close to its chest.
And, like dark energy and dark matter, There may be more surprises to come surprises that will only add to the mystery and wonder Our universe holds for us.
Whatever the universe is up to, We still don't know enough.
We're in an age of discovery right now.
Perhaps there is something else out there That we don't know about.
So, i'm not going to draw any conclusions Until things are conclusive.
We don't understand the nature of dark energy.
And without that understanding, virtually anything is possible.
The future is still uncertain, And that means there's still a mystery.
And for me, that's the most exciting possibility of all.
But how and when will it all end? That's the reason i became a cosmologist.
I wanted to be the first person that would know How the universe would end.
Two cosmic heavyweights wrestle for control.
The winner seals our fate.
The tug of war is gravity, Which is trying to shrink it down, And the expansion of space and time itself.
Will gravity triumph? The universe will get smaller and smaller, hotter and hotter.
Or will expansion get the upper hand? Even the electrons around your atoms will be ripped apart.
The end is coming, And it could be sooner than you think.
Captions paid for by discovery communications The universe is everything All space, all time, all matter.
The earth is a speck by comparison, A grain of rock orbiting just one of the 200 billion stars In our home galaxy, the milky way.
In turn, this enormous structure is just a drop In an ocean of galaxies that stretch For 90 billion light years.
And all of this, From the biggest galaxy to the smallest atom, Will one day die.
We don't see evidence of anything being eternal.
Eternity doesn't exist.
Even space and time will come to an end.
The universe has been expanding since its birth, Gradually burning through the fuel that lights its stars.
But what happens when the fuel runs out? Will it all just fade away? Stars die out, use up their nuclear fuel.
We have an empty, cold, desolate universe.
Just dead remnants of stars -- Black holes, neutron stars.
Eventually, they decay away, And you're left with a thin haze of very low energy light.
That's it.
We used to think the universe Would cruise gently into old age.
But over the past few decades, Astronomers have revealed a very different And disturbing picture.
The universe isn't cruising.
It's fighting for its life.
It may seem peaceful here on earth on a nice, sunny day, But in fact, above us and all around us, Throughout the universe, a battle is raging, And it has raged since the beginning of time.
Two deadly forces grapple for control.
The first, expansion, pulls galaxies apart, Cooling the universe and threatening it With a frozen extinction.
The second, gravity, tries to crush everything back together, Annihilating the universe in a dense ball of fire.
Will gravity or expansion win? Or will it end in a tie? These two colossal forces yield three endgames.
One is the big freeze.
Expansion wins, and the universe just expands forever.
The second is that there is a delicate balance Between the expansion And the amount of gravitational attraction, And the universe gets to a particular size, And it pretty much stays there.
And the third outcome is that The gravitational attraction wins, And the expansion stops, And the universe begins to get smaller Until, eventually, it goes back to a big crunch.
So far, the universe seems balanced On a tightrope between expansion and contraction.
But will it keep its equilibrium until it runs out of steam, Or will something tip the balance? I don't think there's any bigger question than, Where is the universe going? To predict the future, cosmologists have always looked To the past, back to the beginning of expansion, The beginning of gravity, the beginning of everything.
an infinitely dense, Hot speck ignites and suddenly expands outward -- The big bang.
All energy, all space, and all matter the building blocks of the universe we see today, Are created and set in motion.
Think of it.
Everything you see around us Concentrated into a primordial fireball that exploded, Sending all the galaxies into motion.
That outward blast, the birth of expansion, Is still going on today.
Without it, we wouldn't have a universe big enough For stars and galaxies to exist in.
Expansion is an astonishing force of nature.
It works by inflating the fabric of space-Time.
Space between galaxies expands, And it pushes the galaxies apart.
Space carries objects with it like a surfer on a wave.
It's going on in every part of space.
Even inside your body right now, There's a pressure for space to expand.
Expansion generated the vast, moving stage On which today's universe plays out.
But left unchecked, it could have been a force For utter annihilation.
If the universe had been expanding much faster, It would have emptied out so fast, You wouldn't have had time to make galaxies, Planets, people.
The fact that we're here Means that something must have put on the brakes.
It was, of course, our universal glue -- Gravity.
Gravity and matter go hand in hand.
The more massive the object, The more pull it exerts on everything around it.
It draws atom to atom, particle to particle building stars, nebulas, Galaxies -- The hardware of the universe we see today.
But gravity is a double-Edged sword.
Too much, and the early universe would never have gotten Out of the starting blocks.
If it had been expanding more slowly, It would have re-Collapsed into another singularity.
And again, you wouldn't have had the time to make galaxies, Planets, or people.
So we live in the goldilocks universe.
We live in the universe that lasts long enough That we can be here, but expands gently enough That we have time to form.
The universe has lasted for 13.
8 billion years, Thanks to the opposing forces of gravity and expansion.
But just how stable is this balancing act? Does our universe have just the right amount of stuff in it To keep it from runaway expansion Or catastrophic collapse? In the 1920s, scientists did the math, And the results were anything but reassuring.
The more matter you have, the more gravity you have.
If you have lots of matter in a very dense universe, Perhaps the universe begins to re-Collapse.
Or, if you have very little matter, The universe would freeze to death.
So what is the critical density, the border between the two? It's approximately five hydrogen atoms per cubic meter.
So think of a cubic yard, and put just five hydrogen atoms Inside, and that is the tipping point.
If you put more than five atoms, Then the universe will begin to collapse.
If you have less than five atoms, Then the universe just keeps on going.
If we thought the universe was balanced On a tightrope before, the critical density question Showed us that the rope was more like a razor blade.
Yet, when astronomers took additional measurements, They liked what they saw.
The universe appeared to contain just the right amount Of matter to stay at the critical density.
More and more, the indirect evidence And the theoretical arguments suggested That the universe must be exactly at the boundary Between a universe that would collapse And one that would expand forever, That we were teetering on the hairy edge of expansion.
The universe seemed so perfectly balanced That it would head quietly into old age.
Then, in the 1970s, astronomers made an observation That shocked them.
The cosmos was filled with invisible stuff, And its gravity could cause a catastrophic collapse.
The universe is balanced on a tightrope.
On each side of the drop lies an early death -- A big freeze, fueled by the runaway stretching of space, Or a big crunch, the result of gravity overcoming expansion.
believed we'd stay balanced Between these fates for eternity.
Now things have changed tremendously, Because we've discovered something we never knew about In the 1970s, astronomers are stunned.
Some unknown form of matter, invisible to telescopes, Dwarfs what we thought was out there, Not a fraction more, but five times more.
We used to think that gravity came from stars And objects you can see -- End of story.
Now, we realize that that naive picture is actually wrong.
Astronomers make the discovery, Studying the clockwork nature of our universe.
The huge gravity of the sun holds the earth And all the other planets in a delicate circular dance.
The sun's mass controls the speed of these orbits.
If it were more massive, the planets would orbit Much more quickly.
And if it were smaller, it would take much longer For a planet to complete an orbit.
Galaxies run like clockwork, too.
The vast mass at the center pulls the outer stars Into circular, planet-Like orbits.
Astronomers make precise measurements Of these galactic orbits in the 1970s.
The results change everything.
The galaxies were spinning too fast.
Way too fast.
Even accounting for the supermassive black holes At their center, nine-Tenths of their mass was missing.
By rights, the galaxy should fly apart.
By rights, the earth should have been flung Into intergalactic space billions of years ago.
We should have no milky way galaxy, and yet, Our universe is full of galaxies.
An immense additional source of gravity Must be holding galaxies together.
But no matter where astronomers point their telescopes, They see nothing.
Not a glimmer, not a shadow.
Whatever this new stuff is, it doesn't emit light, Reflect light, or even block light.
They call it dark matter.
What we've learned is that most of the matter in the universe Is not ordinary stuff.
It's not atoms.
It's not particles we've yet detected in any experiment Done here on earth.
It's some new kind of particle that we call the dark matter.
Dark matter fills the universe, Outstripping normal matter by 5-To-1.
Vast filaments spread out throughout the cosmos, And bright galaxies cluster where dark matter is thickest.
Dark matter provides the scaffolding that underlies How the matter in the universe structures itself, Where it goes, and what it does.
So, dark matter dictated How the universe unfolded.
It seems as if out of the hot big bang, Dark matter condensed first, before atoms, And dark matter began to become clumpy.
The clumpiness then began to attract atoms As they were formed later, and that formed galaxies.
And in some sense, the dark matter therefore Provides kind of a womb that allows the birth of our galaxy.
Dark matter holds the universe together, But it also threatens to destroy it.
One of the most amazing discoveries Of the past few decades is dark matter, The fact that there's much more matter in the universe Than we were aware of.
And all of that matter has a lot of gravity.
So all this new matter, all this new gravity Must be slowing down the expansion of the universe.
Dark matter may even tip the cosmic scales In favor of gravity, Defeating expansion and pulling the entire universe Towards a death by fire.
It's called the big crunch, And this is how it would play out.
For a fraction of a second, the universe stalls, Poised between expansion and contraction.
Then, gravity kicks off a cataclysm.
When you looked out, the very first things As it began to turn around that you began to see Is that galaxies, instead of moving away from us on average, Would begin to be moving towards us on average.
The whole universe would look like it was coming to get us.
As space contracts further, The density of matter increases, gravity gets stronger, Temperatures soar as the crunch gathers momentum.
Galaxies begin to collide, Gas clouds begin to collide, Planets slam into the earth.
Black holes will execute a death dance around each other.
Temperatures, of course, will continue to skyrocket.
Matter, space, and time implode Until everything in the universe is compressed Into a tiny speck of infinite mass, heat, and pressure.
For the last stages of the big crunch, Galaxies will collide and form a primordial atom.
And then, life as we know it will be impossible.
We're back to where it all began, Back at the big bang.
The universe that we live in will cease to exist.
But some believe a big crunch could herald a new beginning.
We don't know what the end point of a big crunch would be, Because the laws of physics break down.
It's possible, and indeed, philosophically very pleasant, To imagine that that crunch would somehow end up evolving Into an expansion again, and you could have a cyclic universe Which goes on forever.
Perhaps at that point, we will recreate another big bang.
It's conceivable that as everything comes together In the crunch, something sort of keeps it from just continuing And pushes out in a hot, dense, smooth state, And from the other side, it looks like a big bang, And a new universe has been created.
Our big bang might have been someone else's big crunch.
But just when scientists came to terms With dark matter's big crunch, the universe threw them Another, even bigger curve.
Some ghostly force seemed to be sending us hurtling toward A completely different death.
My postdoctoral scholar showed me the results.
I nearly fell off my chair.
Gravity and expansion battle for control Of our universe for 14 billion years expansion pushing it outwards, Gravity pulling it in.
With dark matter in its corner, Gravity seems to be the inevitable winner.
The extra mass will drag the universe into a big crunch, Until a stunning discovery Revolutionizes our understanding of the universe.
Around 1990, two teams of researchers decided to measure The expansion history of the universe To determine whether it's been slowing down so much That it'll eventually have a big crunch, Or whether it hasn't been slowing down much And will eternally expand.
Astronomer alex filippenko was on one team.
Saul perlmutter led the other.
We realized that it was possible for the first time To go and actually make a direct measurement Of how much the universe had been slowing down in the past.
Both teams want to measure The speed of distant galaxies.
But because the galaxies are too dim and too far away, They look for something brighter.
Billions of light years from earth, a star detonates.
This is a supernova, A dying star's brilliant final gasp.
It burns brightly, 5 billion times brighter than the sun, But briefly.
Perlmutter and filippenko have a window Of just one or two weeks to measure How much the galaxy it sits in is slowing down As it moves away from us.
The teams look for supernovas for eight years.
They measure 42, and the results seem impossible.
We plotted the points on the graphs, Andit didn't make any sense.
They were not slowing down at all.
They were actually speeding up.
What both groups found stunned the world.
In the last 4 or 5 billion years, The universe has actually been speeding up in its expansion.
An accelerating universe, Propelled by something mysterious.
For so long, we've been arguing whether the universe would Expand forever or collapse back in on itself, But nobody thought the answer was going to be That the universe was accelerating, Going faster and faster all the time.
The acceleration bewilders the scientists.
It seems to defy the laws of physics.
Imagine i've got a baseball And i throw it straight up.
And instead of slowing down once it leaves my hand, Which is what normally it will do, It begins to slow down at first, But then it starts speeding away.
Somehow, it's getting energy.
The new energy seemed to be coming from nothing, The vacuum of space.
The word "vacuum" to a scientist means completely empty space, No particles there at all, no temperature, No energy to speak of.
But there's an intrinsic energy in space and time.
Empty space has energy, and that energy produces A gravitational repulsion, a kind of anti-Gravity.
Without a clue what this force is or how it works, All scientists can do is give it a name -- Dark energy.
We could have called it we-Don't-Know energy.
We could have called it anything.
But we don't know what it is, and dark or not, It's the biggest mystery in physics.
Nasa calibrates its finest space telescopes To measure how much dark energy is out there, And the result is mind-Blowing.
It dominates the mass of the universe by nearly 3-To-1.
And the more space expands, The more dark energy there seems to be.
Dark energy is the energy of nothing, And it's repulsive.
Therefore, as this dark energy repels galaxies, There's more of it, there's more vacuum.
And so there's more repulsion, And perhaps that's the reason why the universe is accelerating Right now rather than slowing down.
Dark energy seems to kill the big crunch theory, But scientists aren't yet sure how dark energy, Expansion, and space are connected.
If a volume of space doubles in size, Does the dark energy inside it double, too? Or does it increase more? A 1-To-1 relationship leads to a steady expansion.
The universe ends in a big freeze.
But if dark energy increases above and beyond expansion, A new, even more terrifying end awaits the universe -- A big rip.
In a big rip scenario, the expansion is so great That even the galaxies begin to expand internally, Which means that literally Our bodies are going to be ripped apart.
Scientists calculate Just how the big rip will play out.
One by one, the galaxies in the night sky will blink out As space pulls them away from the earth Faster than the speed of light.
dark energy overcomes gravity On smaller and smaller scales.
First galaxies start to rip apart, Then insides of galaxies will begin to rip apart, And then solar systems will begin to rip apart then planets and then rocks, people, atoms.
The end will be mercifully quick.
In the space of a few minutes, All the stars and planets in the universe will be destroyed, Their remains pulled apart into ever-Smaller pieces Until finally, when the universe has Less than a second to live, The subatomic particles that made all matter Will be destroyed, And all that remains will be individual photons Becoming scarcer and scarcer As the space between them expands.
All you're left with is very low energy light That gets stretched and stretched Until it might as well not exist at all.
The last thing to go -- The empty vacuum of space itself.
It'll be pulling on the universe so hard, It could tear the fabric of the universe apart.
Reality could dissolve.
Will the universe end with a big rip, Or a big freeze? The answer is locked inside the mystery of dark energy.
Solve that, and the fate of the universe becomes clear.
The end of the universe is coming.
But how will it play out? For a time, a big crunch was the likely answer.
Dark matter, the invisible bulk of the universe, Causes space to fall in on itself.
Galaxies collide.
Planet merges with planet.
Everything becomes hotter and hotter, denser and denser.
The universe is like one giant star.
Dark energy kills the big crunch theory.
It acts like rocket fuel for the expansion of space Between galaxies.
They're not just coasting.
They're getting pushed outward.
Only two possible fates remain -- A big rip or a big freeze.
Both scenarios rely on dark energy.
For the universe to be torn to shreds in a big rip, Dark energy must increase exponentially in the future.
But a big freeze requires a steady increase In dark energy, Pushing galaxies away from each other.
We can't write the last chapter of our universe Until we understand the nature of dark energy.
May 2009.
The european space agency launches the planck satellite To search for the birth of dark energy.
Its ultra-Sensitive telescope peers through space and time Back through billions of years, Towards the beginning of everything, to capture this.
This is our universe as it appeared Over 13 billion years ago, after the big bang.
So what planck has done is take a picture Of the early universe And told us about what the early universe is like And given us our most detailed and accurate picture Of that moment in time.
The universe in this picture Is a hot soup of protons, electrons, and photons.
Hydrogen atoms have just started to form, And it's the light from this genesis of matter That we see here.
Blue areas are colder.
Reds are warm.
Eventually, those hot spots, Those red spots you see in the map, Are going to form large superclusters Made up of hundreds or thousands of galaxies.
Each one of those galaxies will contain billions of stars.
Gravity and expansion alone Appear to drive the formation of these embryonic galaxies.
Dark energy doesn't seem to have switched on yet.
So, when did dark energy take control of the universe? Astronomer brenda frye is part of a team Using massive ground-Based telescopes Like this one at kitt peak, arizona.
She peers back in time to capture the universe Through its childhood as it was growing.
Right.
So this is an aluminum plate, And into this plate are drilled 640 individual holes.
Each one is put at a very specific place on the mask Which will correspond to one particular galaxy in the sky.
During each observation, The light from 640 individual galaxies is collected Using fiber optic cables.
The speed and relative position of each galaxy is measured To pinpoint exactly where it is in space.
So far, the team has accurately mapped Around a million galaxies in 3d, And this is what they look like.
Each one of these fuzzy patches Is a fully grown galaxy Containing around This is a very basic measurement, And we think that this will be able to help us To get a grasp into the nature of dark energy.
Scientists compare this adolescent universe To its baby pictures.
It shows dark energy emerging When the universe is half as old as it is today.
About 8 billion years after the big bang, This expansion of the universe begins to accelerate, And we're in the middle of this acceleration.
The data also shows that as space expands, Dark energy increases in lockstep with it.
If you had a box and you put some dark energy in it, And then you went and you weighed that box now you take the box, you make it twice as big.
You don't open it.
You don't put anything in it.
You weigh it again, it's gonna weigh twice as much.
This remarkable observation means That we should be safe from a big rip.
Dark energy will continue to increase gradually.
The universe is heading for a big freeze, And scientists can finally calculate a timeline For the end of everything.
It now seems that we live In an almost perfect universe, With just enough gravity to hold the galaxies together And just enough dark energy that it will expand forever Without ripping itself to shreds.
Cosmologists can finally envision the end of it all.
it was debatable.
But now, it appears that the universe most likely Will suffer a deep freeze.
If you look at the data, it stares out at you.
In a big freeze, Dark energy pushes galaxies further and further apart, But they remain intact.
The stars inside them fade away.
Every star you see in the sky, including our sun, Is burning through its nuclear fuel.
The gas will run out, stars will stop being made, And the ones that exist are it.
Those are the last ones.
A hundred trillion years from now, The biggest stars will be the first to go extinct.
Big stars burn bright and die hard.
The star's core collapses, Unleashing a supernova.
Then gravity crushes the dead star down To a single dense spot.
The bright star is now a black hole.
Sun-Like stars go next.
As their supply of hydrogen runs out, They swell to a bloated fireball Over 200 times their current size.
And when the core has no more hydrogen, It's going to bloat up into a red giant star.
Now, red giant stars are so big, they will actually Eat up their own planets.
We know of examples of red giants That go all the way out to where the orbit of jupiter is In our solar system.
Its fuel exhausted, The sun-Like star gives in to gravity And shrinks to a white dwarf, A dense ball of matter Just a few thousand miles in diameter.
It will glow with heat for a further 10 billion years Before cooling to a black dwarf, A ball of compressed carbon, perhaps even diamond.
As the biggest stars die, The universe will slowly turn red.
The blue stars will blow up, And then the slightly less blue stars will blow up, And then stars like the sun will fade away and die, Leaving just the red stars to exist.
Red stars are the smallest And coolest in the universe.
They burn their fuel slowly.
But, after another Even these smallest of dwarf stars Will use up their fuel.
Stars as we know them will cease to burn energy, And the night sky will turn black.
Black holes, the corpses of dead stars, And cold clouds of gas and dust are all that remains.
The age of stars is over.
The age of black holes begins.
Black holes become the fundamental building block Of the universe.
A galaxy will basically be a supermassive black hole In the center, with smaller black holes orbiting it.
In some ways, it's kind of a ghost universe.
It's the corpses, the zombie stars, That will take us into the future.
Zombie galaxies filled with black holes Continue to evolve.
They sweep up the dead remains of stars.
Black hole merges with black hole.
They'll eat each other and they'll get bigger, And maybe they'll fall into the supermassive black hole And it'll get bigger.
The universe will still be an exciting, dynamic place, It's just that the time scales you're talking about Are now trillions of years Instead of thousands or millions of years.
Any material that evades the pull of a black hole Eventually dies away as its protons disintegrate.
A proton, one of the fundamental building blocks Of atomic matter, of what makes us up, Can just spontaneously fall apart, And it turns out this takes a tremendously long time.
But even that will go away.
All that will be left is a sea of black holes.
Scientists used to think black holes were immortal, But even these will one day die.
Now we're talking about time scales Of unimaginable length -- Quadrillions of years into the future.
But on that time scale, Even the black holes begin to evaporate.
They'll get smaller and smaller and smaller, And then, poof, they'll be gone.
The universe will end When the last remaining black hole dies.
As it gets smaller, the evaporation rate Increases exponentially.
Before long, it reaches a size A billionth of a trillionth of a trillionth of an inch.
At that instant, the laws of physics break down, And the last black hole explodes in a flash of gamma rays, Leaving nothing.
And it will die in a sudden burst of light, The last burst of light In the entire history of the universe.
The big freeze is coming.
The universe will suffer a cold, slow, dark death Which will play out Over trillions upon trillions of years.
But quantum physics leaves the door open For an alternative end, An event so powerful, so destructive, That it could destroy everything we see in the blink of an eye.
And it could happen tomorrow.
The end of the universe -- It's coming.
Dark energy accelerates the space between galaxies, Pushing everything we see to a long, cold, And very slow death.
Unless, that is, something bizarre happens first.
A monster called phase transition Is lurking in the shadows, And it could annihilate the fabric of space and time At any moment.
When we cool down water, it turns into ice.
The properties change.
If you lived in the water, when it changed to ice, Your world would be very different.
Water phase changes into ice when it loses energy.
I once left a water bottle in my car overnight.
It was still liquid, but the moment i touched it, The slight imperfection, The little bit of ice that it formed, spread, Poof, and filled up the whole bottle.
That rapid change to something new Is called a phase transition, And bizarrely, the same thing could happen to empty space.
We've really come to understand That we shouldn't take for granted thatvacuum, What we call nothing, is actually stable.
It could be that the energy stored in empty space Is just waiting to be released in a phase transition.
If it is, the laws of physics will change.
A spontaneous glitch in the fabric of space-Time Could trigger a phase transition of space, A tiny bubble of new universe that spreads out, Overwriting the old.
We know it can happen, because it's happened before.
At the moment of the big bang, The universe that's first created Is completely different to the one we see today.
Hot and without form, There's no matter, no time.
The laws of physics are different.
Suddenly, less than a trillionth of a second later, A glitch triggers a phase transition.
A tiny bubble of the universe we live in today forms, And it races outward, Destroying everything it touches Like ice spreading through water.
The energy that spills out creates the space and time That we exist in, The building blocks of matter and the forces that govern them.
All that energy was released, producing all the matter And radiation we observe in the universe today.
The old universe gives up its energy To create the new.
But it holds some back.
The vacuum of space still has energy bound to it.
Perhaps this is the dark energy we see today.
Physicists believe that someday in the future, A brand new glitch in the fabric of space-Time May trigger another phase transition, One that wipes us and everything we see Out of existence.
This is a way to destroy an entire universe, Because within your universe Are the seeds of its own destruction.
It would spread out at the speed of light in a death bubble, Ruining all the galaxies as it passes through, And ultimately completely destroying our universe.
Nothing can survive the expanding phase transition.
Planets, nebulas, galaxies -- All are ripped apart As the boundary of the bubble reaches them.
Inside this bubble, protons are unstable, Atoms begin to rearrange in a new form of matter.
As these bubbles begin to expand, A new universe is being born In the corpse of the old universe, And the beginning of a new law of physics.
And so, the expanding universe we now see May end in a phase transition, but we won't know what hit us, 'Cause the laws of physics will change, And we will essentially most likely disappear At the instant it happens.
This bubble will expand at the speed of light, And as the bubble passes you, All the atoms of your body rearrange themselves, And you would never know it.
You would have no warning, because the bubble itself Is expanding at the speed of light.
You can't predict precisely when it could happen.
You only have a probability.
So what you really are predicting is a rate.
Does it happen once a year? Once every 10 billion years? Once every googol years? Or whatever.
It's very possible that these bubbles get nucleated And grow about once every So it hasn't happened yet because we got lucky.
It's unlikely it would happen the next year or the next day, But the laws of physics absolutely allow it.
A phase change may happen, or it may not.
The universe plays its cards close to its chest.
And, like dark energy and dark matter, There may be more surprises to come surprises that will only add to the mystery and wonder Our universe holds for us.
Whatever the universe is up to, We still don't know enough.
We're in an age of discovery right now.
Perhaps there is something else out there That we don't know about.
So, i'm not going to draw any conclusions Until things are conclusive.
We don't understand the nature of dark energy.
And without that understanding, virtually anything is possible.
The future is still uncertain, And that means there's still a mystery.
And for me, that's the most exciting possibility of all.