The Universe: Cosmic Clusters Fill Our Galaxy (S4, E7) | Full Episode | History

among the swirling gas and dust in the arms of the  milky way stars flash into existence not alone but   in clusters held together by the force of gravity  gravity is like the sculpture of the universe now   take a grand tour of the galaxy's star clusters  the treasure maps of space holding critical clues   to the mysteries of the milky way's 400 billion  suns star clusters really allowed us to get a   handle on how stars go through their lives how  they live and die it's a violent chaotic existence   where our search for cosmic clusters may end up  revealing a universe in darkness for eternity about a thousand stars are visible to the naked  eye during a dark night on planet earth while the   glistening display may impress us there are places  in the galaxy where the view would blow us away imagine the sun on the edge of a  giant cluster made up of a million   other suns filling the heavens horizon to  horizon the stellar density is really high   the distances between stars can be  just a few hundredths of a light year   something like that the galaxy's magnificent  clusters are more than just beautiful to look   at you may not realize it but they hold the  very secrets to the way stars are created   and how they're destroyed in massive supernova  explosions that generate the very elements of life our search for cosmic clusters begins not through  the eyepiece of a telescope but in the cockpit of   an interstellar spacecraft our mission to traverse  the galaxy and find out why clusters are so   valuable why they are keys to unlocking  the mysteries of the stars our first stop   the pleiades the most famous star cluster of all  440 light years from earth known since antiquity   it contains a thousand stars though only a  handful can be seen from earth the pleiades   are the so-called seven sisters a bright easily  noticeable grouping of stars in the winter skies   well it turns out only six of the stars are easily  visible you can see six and really sharp eyed   people can see eight or nine or ten rarely have  i met anyone who can see precisely seven stars   so maybe in antiquity there was a star that was  considerably brighter than it is now but it has   faded since then so now there are only six easily  visible stars there are actually hundreds of stars   in the pleiades perhaps up to a thousand we circle  the pleiades in search of clues that can reveal   the secrets of the universe because clusters  hold the key to understanding how stars are born   how they live and die the secrets of creation  like all clusters we see that the stars in the   pleiades are so close to each other they are  all virtually the same distance from earth   of course the stars in a cluster are not  all exactly at the same distance from us   but they're so far away that the slight  differences in distance are really pretty   small they're inconsequential a nice analogy is  viewing a stadium full of people from a blimp high   above from the perspective of the blimp most of  the people are at about the same distance most of   what we know about stars their size weight and age  comes from figuring out their inherent brightness   but you can't judge a star's true brightness  without knowing how far away it is   that's where the cluster comes in the fact that  all stars in the star cluster are basically the   same distance from us is very important it gives  us a sample of stars where we can actually see   what the intrinsic real brightness of these stars  are unless we know these stars are all the same   location we don't know whether we're looking  at a bright star that's far away or a dimmer   star that's close to us there's no way to tell  but in a cluster all together you can see that   the same rules that apply to stars in  the sky also apply to cars on the road what we have here are two  cars same make same model   so we know the headlights on each car  are exactly alike and equally bright   from where i'm standing here one car's headlights  look just like the other that makes sense but now   let's make these cars act like stars in the  universe same stars but at different distances okay amy back it up look at these headlights  now the ones over there are much dimmer than   the ones here even though we know they're  the same this is the inverse square law   if that car is twice as far away then  the headlights are four times dimmer   if it's four times farther away the headlights are  16 times dimmer and so on as far as you care to go but sometimes a light that  appears to be dimmer actually is this flashlight and headlights are just like  stars in a star cluster the flashlight next to   the headlight looks dimmer and that's because  it is dimmer not because it's farther away   a dim star next to a bright star in a cluster  looks dimmer because the star itself is dimmer   not because it's farther away up close we see the  pleiades has a mix of bright stars and dim stars   and it's this very variety of different stars in  a cluster all in the same place that solves the   puzzle of stellar evolution star clusters really  allowed us to get a handle on how stars go through   their lives how they live and die think of it  this way if an alien wanted to learn how humans   live and die but they could only watch us for 30  seconds they flew by earth and they took pictures   of millions of humans even though they couldn't  watch a single human live and die as a group they   could piece together our story they looked at some  babies looked at older people a star cluster is   just that it's a single snapshot in time but there  are stars at every different part of their lives   and that was the tool astronomers needed to  piece together what a stellar lifetime is   like we know that the biggest brightest stars  are the most dangerous so we keep our distance   these are the live hard die young stars of the  universe those that expand to giant size before   going supernova the dangers lurk even in clusters  with appealing names like the jewel box but the   next stop on our journey is a place in the sky  very familiar to people in the northern hemisphere   we are 80 light years from earth approaching  the closest cluster to our planet   the ursa major moving group as  we bring our starship around   we see five of the central stars in ursa  major form what we know as the big dipper   people noticed that they actually move across the  sky together with most constellations the stars   even though they look like they're part of the  same constellation they're actually completely   unrelated to each other they have nothing to  do with each other gravitationally however   the stars in the ursa major moving group actually  formed at the same time and are part of the same   moving group in time the movement will change  the appearance of the familiar pattern of stars we're visiting ursa major to  explore another cluster question   why are some more spread out than others irregular in shape and scattered in appearance  they're called open clusters an open star cluster   is a relatively loosely bound aggregation of  stars they form in the spiral arms of a spiral   galaxy and then they gradually move away and then  they disperse scientists believe virtually all   stars are born in clusters but as time goes on  the stars in open clusters get scattered apart   by the gravity of other passing stars that  means most clusters are young because otherwise   their stars would no longer be in clusters  a star cluster is kind of like this pile of   confetti on my hand gravity gradually pulls  the stars away and disperses the cluster   well i can blow on this pile of confetti  and disperse the pile let's do it now if this were a star cluster  instead of a pile of confetti   then gravity would be the agent  that gradually pulls the stars away   dispersing the cluster over time  until there's little if anything left as explorers these young clusters are important  to us with a lot of stars in one place it's as if   we can take a pole and figure out how common or  rare different kinds of stars are in the galaxy   in most clusters we see quickly that there are a  few very big bright stars maybe a larger number   of ordinary stars like our sun and lots and lots  of small dim stars barely visible in the crowd   but how crowded are they really stars and  clusters are many billions of miles apart   but when we add up their  distances in our starship computer   we find they're much closer  together than we're used to at home the density of stars in the  sun's neighborhood is little   more than one star for every 50 cubic light years in a typical open cluster there  would be 500 stars in the same space we were once in an open cluster but we've  been around the galaxy so many times now   that our sister stars may be all the  way on the other side of the milky way   what would it have been like for the  sun when it was part of a cluster   to find out we file a flight plan for a place  where stars are forming in a cluster right now we're headed 1500 light years from earth to  the orion nebula which looks like a fuzzy star   in orion's sword up close though  it's a spectacular light show   the orion nebula is one of the great stellar  nurseries that we know of it's forming stars   right now if you were to fly through the orion  nebula you would see a whole bunch of stars   but near the middle there are four particularly  bright stars they form a configuration called the   trapezium and if you were to fly past these stars  you would see these four newly formed brilliant   stars and a whole bunch of little guys all  floating around it would be a wonderful journey   we head toward the trapezium stars the four  brightest in a cluster that's a hectic laboratory   of star formation thousands of other stars  have formed or are in the process of forming   but as it's happening scientists believe  the cluster is imposing a kind of   birth control on the whole cycle only about 10  of the mass of a cloud which will form stars   actually becomes stars so why is it that so little  of the matter in a cloud actually turns into stars   what we've come to believe now is that there  may be a feedback process so once you form   stars they feed back on the cloud acting like a  thermostat and actually limiting the amount of   star formation that can form in the trapezium  cluster you've got those four massive stars   that are producing enormous amount of ultraviolet  radiation as well as winds that stream into the   surrounding area and they will affect the gas  that wants to form stars so even though you   have another thousand stars forming around  the trapezium the star formation rate in   that area is being affected by the ultraviolet  radiation and the winds from those massive stars if nebulas are the stellar nurseries of  the cosmos then clusters are their grade   schools where stars stay together until  life and the galaxy drives them apart   but it's clear not all clusters are alike   we're due now to encounter clusters that make  up some of the most extreme environments in the   entire galaxy where stars are so massive they are  on the verge of blasting themselves into oblivion when it comes to star clusters one of  the first things most people want to know   is what's the biggest which ones really stand out   it's no different than looking at a big city  you want to know about its tallest buildings   its most distinctive landmarks if there's  an empire state building of star clusters   we'd have to travel ten thousand light years  to find it it's called westerland one a super   cluster with a total mass a hundred thousand  times our sun westerland one right now holds   the world's record for the biggest known young  cluster it has about a hundred thousand stars   and what's really odd is for a long time  we didn't even know it was that massive   astronomers have known about westerland one for  a long time but only about five years ago did we   first get a glimpse of all the stars in the  cluster because that's when we had infrared   detectors that could peer through the dust in the  galaxy that's situated between the earth and the   cluster recent advances in infrared astronomy  revealed a space only six light years across   packed with a thick population of stars the  biggest and brightest are galactic freaks   super giant stars in a range of sizes and  colors from blue to red and even yellow the   blue super giant phase and the yellow and red  supergiant phase represent phases during the   lifetime of a massive star they start blue they  become red in some cases they go back and forth   between blue and red as the outer layers are  lifted and we see deeper to the hotter material   in between the red and the blue phases they're  yellow and so we call them yellow supergiants the sun which so often is called an ordinary star  is tiny when compared to supergiants of any color   suppose our sun which is over a  hundred times the diameter of the earth   we're scaled down to the size of  this little yellow pinhead here   less than an eighth of an inch in diameter so  we're really scaling down the sun a lot in that   case the largest stars the red supergiants would  be about the size of this telescope dome behind me   they're huge compared with the sun and yet the  sun itself is already huge compared with the earth supergiant stars whether blue yellow or red  are collectively called evolved massive stars   that means they've burnt out  their nuclear hydrogen fuel   and are transforming into giants that  may eventually explode as supernovas supernovas are so bright it's easy  to see them from great distances   but david y from wing pennsylvania wants to  ask the universe if a supernova can cause   space and time to warp enough to make us  notice a change david we sure hope that a   supernova will create a big enough disturbance  a warping in space and time to be noticeable   but it won't be easily noticeable you won't be  jostled around but we hope that the current and   future generation of gravitational wave detectors  will detect these slight ripples in the fabric   of space and time that's the new unexplored window  of astrophysics gravitational wave astronomy   our own sun will evolve into a red giant it  will expand enough to engulf earth's orbit but   it won't reach the size of jupiter's orbit like  supergiants and it won't explode in a supernova having supergiants in a cluster gives us clues  to the cluster's age now those incredibly massive   stars are important because they have very  short lives they only live for maybe five or   six million years so if you see a star a massive  star that's evolved it's near the end of its life   you know that the cluster can't be  more than five or six million years old   because if it were that massive  star would already have blown up   to date astronomers have discovered only a  handful of these extremely massive clusters   and like westerland one all of them were virtually  unknown until very recently just to express how   ignorant we are realized that only 10 years  ago we didn't know about any of these massive   clusters every young cluster we knew about more  than 10 years ago all had less than 10 000 stars   we know of thousands of those kinds of smaller  clusters right now we only know of a dozen of the   massive clusters because our galaxy is so filled  with dust most star clusters discovered so far   exist in an area surrounding our  particular place in the milky way   we can see barely as far  as the center of the galaxy   but as technology improves our view will extend  further and further into the more distant spiral   arms westland one won't be the most massive  young cluster known for a long time we're still   discovering these other clusters all the time  a few super clusters are near the galactic core   where the gravitational tides of the milky way's  giant black hole may rip them apart in just a few   million years for now though their massive bright  stars are being studied intensely our next stop is   the quintuplet cluster a massive four million year  old cluster named for five supergiants dominating   its center it is also home to the pistol star  one of the brightest stars in the entire galaxy   the cluster has five mysterious supergiants  whose secrets are shrouded by red dust clouds   in 2006 puzzled scientists tried  to get a closer look at them   using the keck telescope in hawaii  what they found was startling   two of the stars are surrounded by bizarre  spirals which means the supergiants are not alone   in the quintuplet star cluster there are several  massive stars that are in fact in binary systems   and they're in the process of gently blowing  away their outer envelopes and those envelopes   are colliding and forming this spiral pattern it's  very unusual to find several of these things in   the same place such stars are very rare if you  look elsewhere in our galaxy you'll find one   every once in a while here and there but not  several of them in one concentrated location it's only a matter of time before these and  any of a hundred other supermassive stars   light up the cluster with supernova explosions  blowing away their own planets and wiping out   any civilizations on neighboring worlds with  deadly radiation similar dangers lurk inside   another cluster close to the galactic center it's  called the arches cluster 25 000 light years from   earth and just a hundred light years from the  milky way's core the arches cluster was the first   young massive cluster discovered in the galaxy  it is the densest young cluster in the galaxy   our own sun's neighborhood is practically  empty compared to the arches cluster   in the 50 cubic light years around the sun the  only neighbor is the alpha centauri system if   we were in the arches cluster the stars are so  tightly packed this same space would contain   more than a million stars lighting up the sky  of any planet both night and day if we lived on   a planet surrounding a star in the arches cluster  or a cluster that's similarly dense we would see   thousands of stars in the night sky in fact some  of those stars would be so bright that they would   individually be much brighter than the full moon  the night sky would be very bright it would be   comparable to the light level in an office during  the day the arches cluster is a major landmark in   our galaxy because it was used by scientists  to figure out just how big a star can get our search for cosmic clusters has taken us to  the arches one of the most important clusters   in our galaxy it's here that scientists  discover just how massive a star can get that seems like a simple question but we didn't  know up until a few years ago how massive a star   could actually be the arches had everything  scientists needed to answer this question   first in such a big cluster there were  surely many massive stars to study   second at roughly two and a half million  years old the cluster was young enough   that its massive stars wouldn't have  exploded yet so the biggest star in   the cluster would probably be a good guide for  how massive stars can get in the wider universe   what we saw in the arches is a  collection of many many low-mass stars   not so many maybe hundreds of medium-sized stars  and then a dozen or so very massive stars with 130   times the mass of the sun in them beyond that  we saw nothing it was like falling off a cliff   if star is more massive than about 130 solar  masses can form and live then they would have   been there in the arches so apparently nature  has placed a limit on the maximum mass of a star   it's probably somewhere between 130 and 150  solar masses as we travel away from the very   young arches cluster we chart a course  for a very different part of the galaxy   out in the milky way's quiet suburbs are  its senior citizens the globular clusters   a globular cluster sounds so wonderful  it's one of my favorite words a glop and   that's exactly what it is often up to a  million stars in a tight large cluster   these things are really mysterious because they  seem to be very old some of the oldest stars in   the galaxy in fact some of the stars are so old  they're practically as old as the universe itself though they are visually stunning it's the age of  the globular clusters that makes them so exciting since they are nearly as old as the universe  itself they raise the question of the galaxy's age is the milky way as ancient as the universe itself  we have good evidence that the universe is about   13.7 billion years old given that the oldest  globular clusters are about 13 billion years old   this means that they formed within the  first billion years after the big bang   this essentially marks the birth of our  galaxy and we think other galaxies as   well in many cases were formed within the first  billion years after the birth of the universe scientists don't know how globular clusters  form it's one of today's enduring mysteries of   astronomy because they are found in other galaxies  too it may have something to do with galaxy   formation itself because we see that individual  stars in globular clusters are very old in some   cases being dated to 13 billion years old we know  that the globulars are that old and we know that   they were formed right at the time when the galaxy  was forming it's still unclear whether the system   formed first and then the galaxy condensed out  of the remaining molecular cloud or if they   condensed and collapsed and formed at the same  time finding globular clusters takes us outside   the chaotic disk of the galaxy where most of the  stars reside into a place called the galactic halo   the halo of our milky way galaxy is a vast  roughly spherically shaped distribution of stars   that's around it envelops the disc of our spiral  galaxy it's where the globular clusters live there are about 160 globular clusters now known  but it's believed there were once many more   of them their presence in the halo outside the  influence of the galactic disk may figure into the   way they keep their spherical form it may be that  any globulars near the disk dissipated long ago but there's at least one cluster out in the  halo that's in danger of being ripped apart   a cluster that has lost 80 percent of  the stars it had when it was first formed   we set our course for globular cluster m12  to get an up-close view of the devastation   m12 instead of orbiting outside of our galaxy  or going through the outer edges actually passed   close to the center of our galaxy and when it did  that the gravitational interaction with all the   other stars inside the milky way was strong enough  to pull off some of the low-mass stars inside the   cluster so what's happening is that m12 is slowly  losing its lowest mass stars with every successive   passage through our galaxy and eventually there's  not going to be anything left because it will have   been completely devoured by the milky way for  now most globular clusters remain very crowded   60 000 times as dense in stars as our own  galactic neighborhood but because the clusters   are old any massive bright stars they once had  have long since burned out the globular cluster   sky would be crowded but its glow would remain  subtle if we were on a planet around a star in   a globular cluster we would see thousands of  stars but the average illumination at night   would be comparable to the illumination you'd  experience in a room with some candles lit up   orbiting out in the halo globular clusters are to  the galaxy something like moons are to a planet   globular clusters on the  outskirts of other galaxies   show that this is something  many galaxies have in common now our route through space takes us far outside  our own galaxy 60 million light years away   to a massive elliptical galaxy called m87 that  looks something like a globular cluster itself most of the fuzzy dots in this photo  from the hubble space telescope   are globular clusters orbiting m87  the giant galaxy has 15 000 of them but m87 represents the upper  end of the clustering phenomenon   it sits at the core of a cluster not of stars  but of galaxies where our starship now travels   to witness the violence of giant star systems  colliding at speeds of a million miles an hour   all it takes is a few quick looks at star clusters  to see how obvious gravity's effect is in holding   stars together gravity is like the sculpture of  the universe it influences large regions around it   so it can cause galaxies to cluster together  just like stars cluster together but on a much   much bigger scale on scales of millions of light  years that's fantastic it's a process that begins   right in our own astronomical backyard where  our spaceship prepares to fly outside the galaxy   the milky way is a large but relatively typical  spiral galaxy and we're located in a small galaxy   group which is a very typical kind of environment  for material to be located in the universe only   about five percent of galaxies are located in rich  clusters but more than half of them are located in   small groups of galaxies our galaxy's home cluster  is called the local group a trip across three   million light years takes us past its two big  members the milky way and m31 the andromeda galaxy   the triangulum galaxy is the next largest and  a few dozen dwarf galaxies circulate among them the galaxies within an individual cluster tend  to gradually merge with time so in the next four   five six billion years our milky way galaxy  is going to merge with the andromeda galaxy   right now if we view the whole universe from  earth orbit our view screen looks like this   our own galaxy's plane dominates  stretching across the center   but when we merge with andromeda  the sky will look vastly changed   at a very spectacular event it's likely to result  in an elliptical galaxy which looks very very   different than either of the two component  spirals andromeda will fly by several times   as it and the milky way do a gravitational dance  the merger will destroy their elegant disc shapes   in the end they'll settle  into a giant rounded blob   the typical form of elliptical  galaxies across the universe the local group is tiny compared to the  big galaxy clusters across the universe   the nearest big cluster is the next  stop on our voyage our local group is   about 60 million light years away from a much  bigger cluster the virgo cluster of galaxies   consisting of thousands of galaxies not just a few  dozen and our local group in the virgo cluster and   a bunch of other clusters are part of an even  bigger structure called the local supercluster such clusters are violent places with  galaxies moving at incredible speed we're talking about speeds of hundreds of  kilometers per second or another way of   saying that would be something in the vicinity  of a million miles an hour we take our trip   into the high velocity realm of these giant  clusters to solve a mystery about galaxies   why some have stars forming in clusters and  others don't the answer is found in galactic gas   galaxies are sometimes gas rich and sometimes gas  poor gas rich galaxies tend to be forming stars   fairly actively in the gas poor ones don't   it turns out that the action in galaxy  clusters is something like a war zone   where the million mile an hour speeds put any  gas-rich galaxy in danger of being strangled   the galaxy strangulation occurs when a galaxy  that's not part of a cluster comes close to a   cluster and the gravitational pull the tidal pull  of that cluster can remove or suck gas out of that   incoming galaxy that leaves the galaxy deficient  in gas and so it's unable to form many new stars   it gets strangled and once a galaxy travels deep  inside the cluster it faces trouble from what's   called ram pressure stripping as it speeds through  the thin gas floating in the cluster's base   when zooming through that gas the pressure  of the gas can actually strip gas away from   the galaxy itself leaving it relatively gas  free and unable to form many new star clusters if we flew through the cluster  looking for the intergalactic gas   we wouldn't see it it is so very thin that  on earth we'd consider it a perfect vacuum   but if we turn on our spaceship's x-ray detectors  it would show up as a massive eerie glow   the galaxies that we see in visible light if we  look with an ordinary telescope aren't the only   component of galaxy clusters indeed they're not  even really the dominant component the dominant   component is a hot thin gas and the gas was heated  by shocks during the formation process of the   clusters and is now so hot that it glows in x-rays  and this is completely invisible to normal light   the hot gas exerts more gravitational influence on  the cluster than the visible galaxies themselves its overwhelming gravity helps draw  cluster galaxies to a common center   and when we look at galaxy clusters we see a  preview of our own future in the cluster center   is often a giant elliptical galaxy the result  of countless gravity-driven mergers like the   one that will join the milky way with andromeda  that's a common trend for clusters of galaxies   the galaxies within them are merging together  forming a few and finally one super galaxy is the universe destined to be  filled with isolated super galaxies   will gravity continue its unending pull to find the answers we enlist supercomputers  as time machines taking us into the future   the scenario they predict may be far  more grim than anyone ever suspected the world's greatest telescopes  and satellite observatories   routinely serve up awesome  pictures of cosmic clusters but essentially these are only snapshots in  time to truly watch the universe as it evolves   we need a time machine human lives are short  compared with cosmic time scales but we can   watch effectively how galaxies and galaxy clusters  evolve by simulating them on powerful computers the supercomputer turns our starship into a  time machine for the next leg of our mission to   find out how the universe evolved and where it's  going to end up this simulation shows how a galaxy   cluster may form 12.3 billion years of stellar  evolution is condensed into less than a minute   supercomputer visualizations like these are  important tools to help all of us understand   the workings of the universe and where  the future will take us the simulations   where we can actually play how a galaxy cluster  evolves over billions of years always leave me   breathless it's amazing to watch cosmological  time play in these beautiful elegant simulations   here's how the supercomputers do it they start  with something that scientists call the n-body   problem n stands for the number of bodies  the bodies are planets stars or galaxies   and the problem is to do some simple math to  figure out how isaac newton's basic laws of   gravity make the planets or stars move in space  such simulations are remarkably powerful ways   to study how complex systems like clusters  of galaxies and galaxies evolve with time peter tubin a simulation specialist  at the university of maryland   programs the gravity formulas into  a supercomputer named deep thought it's easy for instance to figure  the orbit of a planet around a star   that's called a two-body problem a college math  student can do it in a snap but suppose you have   to work out the motions of a swarm of stars in a  star cluster the ant body problem is a little bit   like a juggling act if you have a two body problem  here we have one ball i can do one ball relatively   easy but i'm not a juggler i don't know if i can  two balls oops well clearly i cannot do two balls   and it takes a lot of effort and interpretation  by the brain how to correctly juggle two balls   now imagine that we have to do three balls  or four balls i cannot do that there are   people who can do that but the complexity  ends at some point nobody can do 20 balls surprisingly the math behind the problem is fairly  easy but the reason you need a super computer is   that there's just so much of it to do it's pure  grunt work all right guys write your position   as tube and students demonstrate when trying  to do it for 12 stars without a computer   number one is at six four and the two choose  that three four number three three is at two   four in calculations like these each star's  starting position gets coordinates on a chart   number eight is at 4-4 each star also gets its  own speed and the rest is up to the students   using newton's laws they have to figure out how  each star's gravity acts on each one of the others   to determine where each star's position will be at  the next point in time number one these students   would need to work for 300 years non-stop to  do what a supercomputer can do in one second calculations for galaxy clusters ramp up  to millions even billions of end bodies   but fortunately supercomputers are increasingly  available to astronomers eager to simulate the   past present and future of the universe the  current state-of-the-art supercomputers are   actually off-the-shelf computers that you and i  use at home desktop computers the only thing is   we put them all together they're easy to build  they're cheap to build so there's many available among the most complex of the current simulations   is the millennium run in europe where 10 billion  galaxies were manipulated in a supercomputer   running continuously for 28 days  utilizing 343 000 processor hours   one result is a remarkable 3d fly through across  2.4 billion light years of space showing hundreds   of millions of galaxies clumped together in  clusters along vast strands of dark matter using supercomputers scientists not only study  the past but they can predict the future of the   universe i think it's amazingly cool that we can  actually take what we know about the present day   conditions in the universe and we can basically  use these computer simulations to play time   forward we can use this to extrapolate what's  going to happen to us in the end this simulation   starts with the quantum foam left over from the  big bang and flies us through 13 billion years   as it all condenses into the galaxy  clusters and superclusters along the   network of filaments and voids  like those we can detect today this is the cosmic clustering phenomenon  driven by gravity to its greatest extreme   but gravity's pull is counterbalanced by  the mysterious dark energy that is driving   the galaxy clusters of the universe apart  about a decade ago astronomers discovered   that the universe is not just expanding in  fact its expansion is accelerating with time   gravity will keep galaxy clusters together  only on a local level our local galaxy group   will coalesce into one super galaxy but all other  galaxies in the universe will race away from us   a hundred billion years from now this corner  of space will be left virtually in the dark as soon as the distant galaxies around us  will expand away and reach the speed of light   even light from them will never be able to reach  us anymore and so these galaxies will expand into   vast regions of space and disappear from view  our galaxy will be an island embedded in darkness clouds of gas will continue to  form into star clusters nearby   but astronomers of the future will see nothing  in the sky beyond the borders of our own galaxy   unless the work of today's  cosmologists is preserved   there will be no clues to tell them that there  was once a big bang and a cosmic expansion nothing   to let them know of the vast existence beyond  the place we know today as the universe you

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Id: nTeFUmQftJ8

Length: 45min 2sec (2702 seconds)

Published: Mon Mar 15 2021