How the Universe Works - S10E01 - Secrets of the Cosmic Web - video Dailymotion

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Transcript

00:00The night sky, countless stars, and the majestic sweep of the Milky Way.

00:09But beyond our local neighborhood, across the cosmos, there are over two trillion more

00:17galaxies.

00:18When we first began to observe galaxies, we collected them like butterflies.

00:22Little by little, we realized that they formed a web.

00:25The cosmic web is the infrastructure that connects every corner of the universe.

00:32You don't know anything about our universe if you don't understand the cosmic web.

00:35It feeds galaxies, it forms galaxies, it is made of galaxies.

00:42It's the architect of everything, and our cosmic future depends on it.

00:49The cosmic web is one of the most important parts of our universe.

00:52It plays a key role in the evolution of the cosmos.

00:56Without the cosmic web, there would be no stars, no planets, nowhere in the universe

01:02where the conditions of life could exist.

01:04How did the universe go from a hot soup of gas to a cosmic web sprinkled with galaxies,

01:12planets, and us?

01:22The universe may appear random.

01:32Two trillion galaxies spread across the cosmos.

01:39But in this cosmic chaos, scientists detect order.

01:45When we first saw that the universe was full of galaxies, it seemed like overwhelming chaos.

01:51But it's not, they are all connected.

01:55Galaxies link up in a gigantic cosmic network spanning the entire universe.

02:02How this pattern emerged may be cosmology's biggest puzzle.

02:08In some senses, you don't understand something unless you understand how it comes into existence

02:13and how it's formed.

02:16And galaxies are the basic building block of our universe.

02:20To solve this mystery, scientists need to go deep, to the very edge of the observable

02:26universe, and study light from the first galaxies.

02:33Chile, 2021.

02:38Scientists point the VLT, or Very Large Telescope, towards the Hubble Ultra Deep Field.

02:46It's a patch of sky famously photographed by the Hubble Space Telescope in 1995.

02:52The VLT's power allows astronomers to see much deeper into space.

02:58Imagine you take a grain of sand, and you put it on your fingertip, and you hold your

03:03arm out like this, and you block a part of the sky looking at that grain of sand.

03:09That's the size of the Hubble Ultra Deep Field, and yet it contains thousands of galaxies

03:15in it.

03:17The telescope stares at those galaxies for 155 hours, and picks up the faintest of glows.

03:28Ancient hydrogen gas concentrated along a strand of space 15 million light years long.

03:37The filaments are just one tiny section of the cosmic web, the largest known structure

03:44in the universe.

03:49The scale of the cosmic web is enormous.

03:50It is, by definition, the largest thing that we can see in our universe.

03:55Today, the cosmic web is a lattice of filaments, linked streams of hydrogen gas, that form

04:04an intergalactic network spanning the entire universe.

04:09Inside the nodes of the cosmic web, you'll find galaxies, stars, black holes.

04:15Along the filaments, you'll find gas that connects these nodes, and the gas will connect

04:19to the other galaxies and clusters of galaxies.

04:23It's this beautiful superhighway of large cities that are connected through these filaments.

04:32We can see the cosmic web about as far back as we can look, and really, galaxies are forming

04:37along that web all the way back.

04:40This cosmic infrastructure dates back to the earliest days of the universe, 13.8 billion

04:50years ago.

04:52The universe ignites in a tiny ball of superhot energy.

04:59It expands and begins to cool.

05:04Energy transforms into primitive subatomic particles of matter.

05:10The heat from the Big Bang is so intense, gravity is effectively powerless.

05:16The very early universe was superhot, super energetic, and regular particles of matter

05:22were zipping around so fast that not even gravity could hold them together.

05:27But regular matter wasn't the only thing in the early universe.

05:30In the background, gravity is working on something else.

05:36Regular matter's ghostly cousin, the invisible substance known today as dark matter.

05:43It makes up about 85% of all the matter created in the early universe.

05:50Normal matter and dark matter both existed around the time of the Big Bang, but the way

05:54they played out was very different.

05:57Just 10 seconds after the Big Bang, the infant universe is billions of degrees Fahrenheit.

06:03Still, far too hot for regular matter particles to clump together.

06:08But dark matter plays by different rules.

06:12Dark matter isn't affected by the Big Bang's intense radiation in the same way that regular

06:17matter is.

06:18And so because it's able to cool, it clumps together in a way that regular matter doesn't.

06:25As dark matter clumps grow, they exert a gravitational pull and begin to form shadowy

06:31structures.

06:32As soon as the dark matter gets a foothold, we have a place where there's a bit more stuff.

06:38Then that attracts more and more dark matter.

06:42380,000 years after the Big Bang, the intense heat drops to a few thousand degrees.

06:49Normal particles of matter move around more slowly.

06:54Electrons and electrons bind together and form atoms of hydrogen and helium gas.

07:01Then gravity from dark matter starts to work on regular matter.

07:06Before you know it, you have this very clumpy universe with these huge dark matter halos

07:12that can now start to draw in also ordinary matter in the form of gas.

07:18A billion-year building project begins.

07:22The dark matter clumps pull in clouds of gas, the foundations of the cosmic web and

07:30the galaxies.

07:32Just as when you build a building, you know, there's a lot of work that happens before

07:36the building goes up.

07:37Our universe spent a lot of time laying the groundwork for this cosmic web before it switched

07:42on the lights.

07:45The foundations are complete, but the job isn't finished.

07:50How did those clouds of gas transform into the greatest structure in the universe?

07:58The secretive dark matter that brought the gas together is also on site, managing the

08:04build.

08:05It was really the dark matter that called the shots in cosmic clustering because it

08:10outweighed the ordinary stuff by a big factor.

08:16In essence, the cosmic web is made of dark matter.

08:18The kindrals of material are stretched out across the cosmos.

08:22As the sprawling structure builds, its gravitational pull strengthens, pulling in more dark matter.

08:30The clumps begin to collapse and shrink down into filaments.

08:36These meet at even more tightly packed clusters, creating a huge dark scaffold that drags

08:42in more hydrogen gas.

08:45Imagine drops of dew on a spider web.

08:48That's like hydrogen blobs being pulled into dark matter's cosmic web.

08:54After tens of millions of years of construction, strands of gas stretch across the cosmos.

09:03Fast forward to now.

09:05The web appears in all its star-spangled glory, lit up with galaxies.

09:11We know at some point stars and galaxies formed.

09:14The big question is when.

09:15What were the first galaxies like?

09:18That's a big mystery.

09:19So how then did the lights of the cosmos switch on?

09:24Evidence suggests that as the universe assembled its web of dark matter and hydrogen gas, the

09:30biggest stars that have ever lived set the cosmos ablaze.

09:462018.

09:47Scientists study an ancient galaxy, the catchily named MACS 1149-JD1.

09:55There, they find some of the oldest stars ever detected.

10:02This particular galaxy is exciting because it's forming stars just a very short time

10:07after the Big Bang.

10:10Those stars could hold clues as to how the cosmic web that supports the universe first

10:16lit up.

10:17But as astronomers study starlight from when the universe was just 250 million years old,

10:24they get a shock.

10:27The stars are not just made up of hydrogen and helium produced in the Big Bang.

10:32They also contain what astronomers call metals.

10:38Metals in astronomy is everything heavier than hydrogen and helium.

10:43No matter where it is on the periodic table, if you're not hydrogen or helium, you are

10:47a metal, even though that makes no sense.

10:51If I were king of astronomy, metals is right out.

10:55The Big Bang only made hydrogen and helium.

10:59Anything heavier than that was churned up in the cores of dying stars.

11:05The bright stars of this ancient galaxy, dating back to just 250 million years after

11:11the Big Bang, contain chemicals that were created in even earlier stars.

11:19Some of them seem to be nearly the age of the universe, extremely old.

11:23And yet they contain elements that guarantee they can't have been the first generation.

11:29As old as these stars are, there must have been something that came before.

11:34The earlier first generation of stars remains cloaked in mystery.

11:39How did the first stars ignite?

11:42And did they kickstart the formation of the first galaxies?

11:49It sounds like a classic creation myth.

11:53It's out of the darkness, out of nothing.

11:56Structure arrived and from that structure, the galaxies, the lights in the universe turned

12:02on.

12:04We've never seen a first generation star, but physicists have a theory of how they formed

12:11and what they were like.

12:14Let's step even further back in time to around 100 million years after the Big Bang.

12:20The early cosmic web is dark.

12:23There are no stars to illuminate it.

12:28But the universe is ready for stellar ignition.

12:34Cooled down after millions of years of expansion, the gas clouds clinging to the dark matter

12:40scaffold begin to contract.

12:45As the hydrogen gas clumps together, larger clouds form super dense, ultra hot cores.

12:52If you can bring hydrogen together and actually get it hot and dense enough, hydrogen will

12:59begin to fuse into helium.

13:01There'll be a nuclear fusion reaction going on.

13:05Simulations suggest that some gas clouds are hundreds of times the mass of the sun.

13:13The stars they produce are unlike anything that exists today.

13:20So the stars around us today really top out at masses between, let's say, 70 to 100 times

13:26the mass of our sun.

13:27There's nothing larger than that.

13:30These first stars were up to a thousand times more massive than the sun.

13:36So if you plopped it in our solar system, it would extend all the way past Jupiter.

13:41So think about that.

13:42That is incredibly big.

13:44That scale is mind blowing.

13:48So what happened to these stellar behemoths?

13:52The lifetime of a star has a lot to do with its mass.

13:55The more massive a star is, the more gravity crushes the interior up to high temperatures

14:00and it burns through its nuclear fuel even faster.

14:03So incredibly, the more mass there is, the shorter a lifetime you get for a star.

14:09The first generation of stars are sort of like the rappers and rock stars of the universe.

14:16They live fast, they die young.

14:21First generation stars didn't live long enough to form complex galaxies, but they did set

14:27the process in motion.

14:30The lives of the first stars may have been rock and roll, but their explosive deaths

14:36in supernovas pumped the universe full of heavy metal.

14:42In the galaxy today, we see a supernova maybe every couple of years, close to us every couple

14:47of decades.

14:49This must have been a firework show.

14:51Giant supernovas going off all the time, all around you.

14:56That act of destruction is actually an act of creation.

15:00What a star does in its core is it creates heavier elements from lighter elements.

15:08The first generation of stars must have been absolutely incredible, simply exploding so

15:13quickly and unloading all of this wonderful new chemistry into the galaxy.

15:19Two hundred million years after the Big Bang, the remains of the first stars flood the interstellar

15:25medium with heavier elements like carbon, oxygen, silicon, and iron.

15:34Crucial ingredients for the next wave of stars.

15:38It's such a beautiful story because suddenly the whole process of star formation changed

15:43and it literally became easier to make a star.

15:48Heavy elements suck heat out of the surrounding gas.

15:52Cooler clouds crunch down much faster.

15:55The smaller, second generation stars form rapidly and in much greater numbers.

16:02Somehow this mess of stars transformed into a network of young galaxies.

16:08But it wasn't easy, because as these baby galaxies formed, a breed of matter-hungry

16:14monsters appeared in the young cosmic web.

16:2613.6 billion years ago, the dark scaffold that supports all the regular matter in the

16:33universe emerges, ablaze with stars.

16:39But how did this stellar array evolve into a structure littered with organized galaxies?

16:45It seems they formed under constant threat of destruction.

16:54October, 2020.

16:56Astronomers discover a monster lurking among the cosmic web's earliest structures, dating

17:03to 900 million years after the Big Bang, a supermassive black hole.

17:10Six galaxies surround this cosmic giant, caught in its grip, seemingly linked to the supermassive

17:17black hole by filaments of the developing cosmic web.

17:23It's like the universe has given supermassive black holes an umbilical cord.

17:29It's like an all-you-can-eat buffet right there.

17:34Supermassive black holes are hungry beasts.

17:37They feast on any matter that gets too close to them.

17:42Supermassive black holes are likely some of the most powerful objects in the universe.

17:47They can be anywhere between 100,000 to 10 billion times the mass of the sun.

17:55Supermassive black holes have been a nemesis for generations of scientists, not because

18:00of their fearsome nature, but because nobody knows how they grew so large so early.

18:07I wish I knew where supermassive black holes came from.

18:10If I knew, I would have a Nobel Prize hanging around my neck, and I would wear it every

18:14single day.

18:16As someone who deeply loves supermassive black holes, whose career is based on studying supermassive

18:24black holes, it is very frustrating to not know where they come from.

18:29Regular stellar black holes are the collapsed cores of dead stars, ranging from three to

18:36thousands of solar masses.

18:38But supermassive black holes?

18:41Those are a different beast.

18:4313 billion years ago, not enough stars had lived and died to build something as huge

18:50as a supermassive black hole.

18:53Now, the cosmic web offers scientists clues about the black hole conundrum.

19:02We now know supermassive black holes grow among the lattice of the young cosmic web,

19:08gorging on the hydrogen gas that travels along the filaments.

19:14At the same time, when the cosmic web is lighting up, supermassive black holes appear to be

19:20stealing star fuel from the young universe.

19:24You might think that would kill a growing galaxy.

19:28And yet, most mature galaxies have a supermassive black hole.

19:33They really dominate the physics of what happens in the centers of galaxies.

19:37And even how galaxies can evolve.

19:41We think these galactic monsters have been around from the start.

19:45How then did the web's young galaxies develop around supermassive black holes?

19:52The Milky Way's supermassive black hole is called Sagittarius A star.

19:58It's around 27 million miles wide and weighs in at just over 4 million solar masses.

20:08The environment around Sagittarius A star is very dynamic.

20:12It can actually be a really hellish place.

20:16There's this accretion disk that's full of plasma seated to thousands of degrees.

20:21So you wouldn't necessarily think that that's a great place for star formation to happen.

20:28But that's exactly where astronomers decided to look.

20:33Using the Atacama Large Millimeter Array, or ALMA for short, scientists scanned the

20:39heart of the Milky Way for dense cores of gas and dust, stellar embryos.

20:46They found more than 800 within just 1,000 light years of Sagittarius A star, including

20:54More than 40 embryos with energetic jets blasting from their cores.

20:59The telltale sign of the birth of stars.

21:06It's really surprising to find those stars there.

21:08It's like hearing babies' cries from a wolf's den.

21:14It's not the place you would expect this to happen.

21:17But in fact, stars are forming there.

21:20It's not as efficient as it is out here in the suburbs where things are quieter, but

21:24it works.

21:26Baby stars igniting and thriving around a supermassive black hole.

21:32The kind of hostile environment we know existed in the young cosmic web.

21:37Star birth is a key part of kick-starting young galaxies.

21:41This evidence suggests that star formation is more resilient than researchers thought.

21:49And they've developed a theory to explain it.

21:53Gas and dust race around the black hole in the accretion disk.

21:57Heated to incredible temperatures, plumes of gas break off and blast into space.

22:03The gas rapidly cools, collapses, and forms baby stars.

22:08These accretion disks are the most chaotic of stellar nurseries.

22:14You see this mechanism that you think is violently inhibiting star formation, and at the same

22:19time it's triggering the birth of new stars.

22:23Matter clumps at the cosmic web's intersections, feeding the supermassive black holes.

22:30Around them, stars burst into life, slowly building galaxies.

22:36This could be how our own Milky Way formed among the filaments of the young cosmic web.

22:44But new research suggests that growth in these baby galaxies requires murder and mayhem.

22:51And without them, we wouldn't exist.

23:04The infant universe is a dramatic place.

23:09Stars ignite and stars die, even in the violent surroundings of supermassive black holes.

23:17Baby galaxies form with the cosmic web.

23:22But how do they grow?

23:24Scientists believe the critical factor is galactic turmoil.

23:28The universe does need to churn things up.

23:32You need to break some eggs to make an omelet.

23:34You need to introduce some chaos into your galaxy to rapidly form stars or grow black holes.

23:41Smashing things together is how the universe came to be.

23:46The Hubble Space Telescope discovers many distorted galaxies, twisted, battered, and

23:53torn, victims of violent collisions on a cosmic scale.

24:01Galaxies are never sitting quietly doing nothing.

24:04They're always undergoing change.

24:06They're constantly encountering and slamming into and colliding with and mixing with other galaxies.

24:14You can see images in Hubble of total car wrecks of galaxies that are trying to merge

24:18with each other.

24:22We know that galaxies collide now.

24:25But what about in the early universe, when the cosmic web was beginning to take shape?

24:31Astronomers study a strange galaxy named Himiko, born just 800 million years after the Big Bang.

24:41Three bright light sources suggest intense star formation.

24:46Detailed analysis reveals not one galaxy, but three baby galaxies, not yet fully formed.

24:56Scientists call these youthful star systems protogalaxies.

25:01The trio that make up Himiko are in mid-collision.

25:07Computer simulations of the early universe suggest protogalaxies smash together with

25:13frightening regularity.

25:16These violent shake-ups trigger star birth.

25:21Protogalaxies are rich in gas.

25:23When they collide and merge, those gas clouds collide and collapse and form stars, sometimes

25:28at prodigious rates.

25:29And after a billion years or so, all of that structure forms and you get a formal galaxy.

25:36Picture the early universe, 500 million years after the Big Bang.

25:41It's smaller and more compact than today.

25:44Cosmic collisions are common.

25:48Imagine taking a bunch of cars and just letting them drive around in Nevada, where there's

25:52nothing but space, right?

25:53You're not going to get too many collisions.

25:55Now squeeze them into a tiny little city block someplace and you're just going to have accidents

26:00everywhere.

26:01Well, it's the same thing with the universe.

26:02When the universe was younger, it was smaller and these protogalaxies were everywhere.

26:07It was crowded.

26:08You were bound to get collisions between them back then.

26:12More and more baby galaxies form at the growing web's gas-rich intersections.

26:18A collision between small protogalaxies might trigger modest amounts of star formation when

26:24regions of dense matter come together.

26:30But a merger involving protogalaxies with rich reserves of gas can rev up the rate of

26:36stellar ignition, supercharging a growing galaxy.

26:41Gas-rich mergers can generate starburst galaxies where we see incredibly vigorous events of

26:47star formation.

26:50Astronomers think one such smash-up, around 10 billion years ago, kick-started the growth

26:55of the Milky Way.

26:57A group of stars called the Gaia Enceladus Cluster in the outer reaches of the galaxy

27:03behaves strangely compared to other stars around it.

27:07The stars in the Gaia Enceladus Cluster, they're different.

27:12They move differently.

27:13They act different.

27:15They're like kids from the next town over showing up at your school.

27:18You just know that they don't belong.

27:21The Milky Way had already largely formed.

27:25And then this massive cluster comes screaming in.

27:28It was a violent event that eventually ended up absorbing the stars from this cluster into

27:36the body of the Milky Way itself.

27:39Galaxies are built from these kinds of collisions.

27:44Less than a billion years after the Big Bang, the dark scaffold of the cosmic web begins

27:51to glow.

27:52Matter channeled down the web's tendrils creates dense clumps of gas.

27:58Even in the turbulent neighborhoods of supermassive black holes, stars burst into life.

28:06Baby galaxies collide, and the young universe sparkles with light.

28:13But an important question remains.

28:16In the mayhem of the early universe, how did galaxies like our Milky Way survive and thrive?

28:26Galaxy evolution is very dynamic.

28:29Our understanding of galaxy evolution is very dynamic.

28:32And there's so much that we still don't know.

28:35There's a lot of different competing theories right now as to how galaxies grew into the

28:40galaxies that we see today.

28:43It's a huge open question and it's something that's a big deal in science right now.

28:49New research suggests that life and death in the cradle of the universe lay within the

28:55cosmic web.

29:0614.6 billion years ago, a proto-galaxy, the infant Milky Way, forms in the tendrils of

29:13the young cosmic web.

29:17Today it bears the scars of many collisions.

29:21Each one could have torn it apart.

29:23So what controls if a young galaxy lives or dies?

29:29Today, 2020, scientists image a graceful galaxy that existed just 1.4 billion years

29:37after the Big Bang.

29:40Analysis of its light shows this is a starburst galaxy, pumping out newborn stars.

29:48Galaxies like our Milky Way are old and rather stately, and they don't form stars very rapidly,

29:53about the equivalent of the mass of the sun every year.

29:57Well, starburst galaxies, yeah, they form them a lot more quickly, hundreds of solar

30:02masses per year.

30:03But BRI 1335-0417, 4,650 times the mass of the sun every year.

30:11It is blasting out stars.

30:16Some young galaxies in the early universe appear to be supercharged with star fuel.

30:22How can they grow at such an incredible pace?

30:28Scientists think the answer lies in the mysterious substance that's controlled the flow of gas

30:34since the beginning, the dark structure whose tendrils stitch the universe together.

30:42But exploring this cosmic network is no easy task.

30:46When it comes to dark matter, we're flying blind.

30:54May 2021, an international team of researchers investigates dark matter in the local universe

31:01by observing its effect on the path of light.

31:07Gravity affects light.

31:09A massive object causes light to curve through space, even if that object is invisible, like

31:17dark matter.

31:18We can't see the dark matter directly, but we can see what it's doing to the light.

31:23It's stretching it.

31:24It's bending it.

31:25It's creating arcs in ways that would never happen unless the dark matter were there.

31:31Using an AI program, the team analyzes 100 million visible galaxies, looking for warped

31:38galactic light.

31:40Because the model is artificially intelligent, it gets better and better at finding dark

31:45matter.

31:49What's very clever about this kind of algorithm is that it's learning as it goes.

31:55It uses the information that it has to predict the existence of new structures.

32:02As the model teaches itself to see the dark matter behind the stars, it maps out new dark

32:09structures, never before seen highways between galaxies.

32:14There's a lot more filaments.

32:16There's a lot more intricacies.

32:17There's a lot more cosmic web there than what meets the eye.

32:22It's like, if you look how Manhattan is connected to the land around it, you can see all the

32:29bridges, but now we're also seeing the underwater tunnels.

32:34The new layout of dark matter reveals the local universe is a bird's nest of hidden

32:39channels feeding galaxies with gas.

32:46Galactic structures seem to thrive at the cosmic web's most densely knotted intersections.

32:55Because multiple filaments are intersecting in those locations, and that is the location

32:59of very enhanced gravity relative to other locations, then material will be drawn in.

33:05So these galaxy clusters are likely feeding off the cosmic web.

33:11This connectivity could be the key to the rapidly forming galaxies in the early universe.

33:19But there's a catch.

33:21Sitting right at the densest regions of the cosmic web can be really good for galaxy growth.

33:27You have all of this gas being funneled in for new star formation, but being that plugged

33:32into the network isn't all good news.

33:35There is evidence that though the cosmic web gives life, it can also take life away.

33:43Scientists studying some of the universe's most heavily connected galaxies found something

33:47unexpected, plummeting rates of star birth.

33:52In some ways it's a little bit counterintuitive, right?

33:55If these nodes are meeting grounds for all of this gas, right, why aren't you forming

34:01more stars there?

34:03One explanation?

34:05In the all-you-can-eat buffet of the cosmic web's matter-rich junctions, a young galaxy

34:11might overindulge.

34:14As the cosmic web funnels more matter towards a junction and its growing galaxies, the gas

34:20influx doesn't just boost star formation.

34:24It fattens up the supermassive black hole at the galaxy's core.

34:30For a young galaxy, that's dangerous, because when this monster overeats, it produces high-energy

34:37jets and belches out super hot wind.

34:43These black holes radiate tremendous amounts of energy when they grow, and that radiation

34:48can slam into the material around them in the galaxy and blow it all out of the galaxy,

34:52wash it away, or heat it up to super high temperatures.

34:56Star formation requires stuff.

34:58So if you blow that stuff away, how are you going to form a star?

35:05And what's left behind would be what we call a quenched galaxy that basically can't form

35:10any new stars.

35:11The researchers found that although connectivity within the cosmic web can boost galactic growth,

35:18it was the super-connected galaxies that died the quickest, choked and stunted like

35:24over-watered plants.

35:27Perhaps our Milky Way got lucky.

35:32You could say that the Milky Way galaxy is sort of in this Goldilocks zone of galaxy

35:36formation.

35:37It's been receiving enough gas over time that it's been able to keep up with its star formation,

35:42but not so much gas that its central black hole has been fed enough that it would clear

35:48the galaxy out of gas.

35:51The cosmic web determined if galaxies lived or died.

35:56Its construction project brought order to chaos.

36:01The cosmic web is the architect, the engineer, the builder, the construction worker, even

36:07the interior designer of the cosmos.

36:12But now, work is shut down.

36:15An invisible force threatens to tear apart the very fabric of the cosmic web.

36:21What does this mean for galaxies and for us?

36:37The cosmic web brought order to the early universe.

36:40The gravitational attraction of its dark scaffolding helped build galaxies and fueled

36:46their development.

36:48But growth tops out at the level of galaxy clusters.

36:52Nothing bigger will ever form.

36:57Something has stopped the formation of structure in our universe.

37:02To understand what's going on, we need to return to the Big Bang and the formation of

37:07the cosmic web.

37:1013.8 billion years ago, the universe sparks into life.

37:18A tiny ball of pure energy cools and expands.

37:25The energy transforms into regular matter and dark matter.

37:30But another force appears at the same time.

37:35Dark energy.

37:39Dark energy, as far as we understand it, which is not much, has always been here.

37:45It's always been a part of the universe, but it's been silent in the background.

37:51Dark energy is everywhere.

37:53It's over here, it's over there, it's between you and me.

37:56It's absolutely everywhere.

37:59One theory is that dark energy never formed, that it's just a constant in the laws of physics,

38:04has always been there and always will be.

38:08Some physicists believe that dark energy is simply the force of emptiness.

38:15People used to take for granted that space was empty, vacuum.

38:21But the discovery of dark energy has made some people wonder if space is actually more

38:26of a substance, and that space also might have pressure that causes things to push apart.

38:33So, yeah, whatever space is, it might be more interesting than we thought.

38:38Dark matter dominates the young universe.

38:43But as the dark scaffold of the cosmic web grows, it sows the seeds of self-destruction.

38:51As the network of matter takes shape, pockets of emptiness form between the filaments, cosmic

38:58voids.

39:01In these expanding hollow spaces, dark energy grows.

39:07The weirdest thing about dark energy is that it has constant density.

39:12Constant density means the more volume you have, the more dark energy you have.

39:18So the larger the voids get, the more dark energy they contain.

39:24Dark energy pushes against the cosmic web, opening up huge chasms in the architecture

39:31of the universe.

39:32Five billion years ago, dark matter's strength of attraction is finally overwhelmed.

39:39Like bridge cables in a hurricane, the cosmic web's filaments stretch and snap, and the

39:46universe's substructure fails.

39:50Cosmic construction freezes as the universe expands.

39:54But darker times are ahead for the cosmic web.

40:00As time goes on, not only is it expanding, but this expansion gets faster and faster

40:05and faster.

40:08As the dark energy in the voids increases, the entire structure of the cosmic web begins

40:13to break up.

40:17The effects of dark energy will get stronger and stronger with time, until the very fabric

40:23of space-time gets torn apart.

40:26This isn't a superhero movie.

40:28The bad guy wins.

40:30The future of the cosmic web is looking bleak.

40:34Ultimately, it's going to be a cold, lonely universe.

40:40Our closest galaxies will accelerate away until they're just tiny pinpricks of light.

40:46Then, the universe will go dark again.

40:51Everything will fade out.

40:53So the universe started with a bang, but it will die with a whisper.

40:59The cosmic web transformed the universe from a hot mess to a sparkling structure.

41:05It gave birth to billions of galaxies and us.

41:10Without it, space would be a much less interesting place.

41:15This giant structure, the largest thing that we know of in the universe, is responsible

41:20for nourishing the galaxies, creating the stars, making the conditions right to form

41:25life.

41:26We would not be here talking right now if it were not for this cosmic web.

41:32Understanding the cosmic web is understanding dark matter, is understanding dark energy,

41:38is understanding our past, is understanding our future.

41:42Really, everything that we know about how the universe works is directly tied to the

41:47cosmic web.

41:49It's amazing to think that the overall structure of the universe that we witness today began

41:55in the earliest times of the universe and has yielded beings like ourselves who can

42:02now discover it and ponder about its existence.

42:06That's pretty dope.

How the Universe Works - S10E01 - Secrets of the Cosmic Web

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