New discoveries cause astronomers to question if the Big Bang really happened, and using the latest science, they investigate if it wasn't just the start of the universe but many mysterious multiverses.
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LearningTranscript
00:00the Big Bang the story of everything time the universe us the Big Bang one has
00:14a cool name and two it's the history of our universe this is it it's all of us
00:20it's all things that's the traditional view but is it right more and more
00:28scientists aren't sure and the old outdated Big Bang Theory our universe
00:34just popped into existence from nothing we talk about it as the beginning of
00:41the universe but what it really is is the end of our understanding astronomers
00:46are ripping up the old rules but that creates new problems how can we
00:52possibly say that the universe expanded faster than the speed of light
00:57but are they asking questions with no answers what was the origin is there
01:03even a sense to asking was there a time before time we don't know we got none
01:09folks well we got some things but it's tough it's tough it doesn't tell us what
01:15happened really at the begin this is still an absolute puzzle so just how did
01:22it all start the Big Bang Theory there's a good story but is it true
01:30to begin at the beginning no space no time everything in the known universe compressed into a dot smaller than an atom
01:57so the big bang is the observed truth but there are details that haven't been quite worked out
02:10the story of our universe starts with a big bang or does it so the big bang is the observed truth but there are details that haven't been quite worked out
02:22there are a lot of things that may have happened it's just one explanation
02:27science isn't about being right all the time it's about being wrong and we
02:36could absolutely be wrong about a major component in our understanding of the
02:41universe we're putting one of science's greatest stories to the test the big bang
02:47sure sounds like an explosion but was it an explosion is a sudden release of energy from one point
02:56usually generating light heat pressure and the bang
03:04but did the big bang even explode when you hear the term bang you think of a noise but you have to
03:14realize that it's sound waves propagating through air so after the Big Bang there's no air there was
03:19no air there's no way to hear anything so in that sense it was silent so the Big Bang didn't bang but
03:27to make the universe it must have pushed out stuff lots of stuff
03:36every explosion has an ignition point what about the Big Bang so if you were to only think of the Big Bang as an explosion
03:45you would very rightly ask well where's the center of that explosion where is the center of the
03:51universe there was no central point there's nowhere in the sky you can point and say that's where the
03:56Big Bang was the Big Bang is everything the Big Bang happened here where I'm sitting the Big Bang happened on the
04:04other side of the planet the Big Bang happened in the Andromeda Galaxy the Big Bang occurred throughout the
04:10the universe simultaneously during an explosion debris fires out from the center
04:20this debris spreads out unevenly with different sized pieces landing at different distances from the blast center
04:30but did the Big Bang shoot material out in this explosive manner
04:36the Big Bang shoot material out in the sky for clues you need to search the night sky one of the
04:42things that's really very striking about the universe when you simply take a telescope and start looking
04:47in different directions is that it roughly speaking looks the same in all directions although the universe
04:54is peppered with individual galaxies and galaxy clusters the big picture is what astronomers call homogeneous
05:02when we say the universe is homogeneous it means it's almost exactly the same on very large scales
05:09with very very little differences it's perfectly smooth
05:15if we believe the classic Big Bang story the same amount of material was shot out over the same distance
05:23in all directions our smooth homogeneous universe doesn't appear to be the result of what we know as an explosion
05:33it wasn't big and it wasn't a bang the Big Bang was not an explosion like a grenade or a bomb or dynamite
05:42where there is material rushing out from a common center it's not like there's a ring of galaxies that
05:49came out from some explosion a firecracker explosion is triggered by a fuse so what set off the Big Bang what I
05:59would say is there's no such thing as what triggered the Big Bang you know we tend to think when
06:03something happens when there's an effect there was a cause right there's something that made it happen
06:09but here we're talking about the whole universe there's nothing outside the universe to bring it into
06:13existence the science is clear the universe did not start with an explosion but if there was no bang then how did
06:22everything start so small and get so big the young universe we do understand and the old contemporary
06:33universe we also understand we've stitched together this story where we don't fully understand the first
06:40few paragraphs of the story but we know the rest of the book
06:45how can we get to the bottom of the Big Bang story when we can't even read the first page of the book
06:52the only hope we have is to search back in time line by line
06:58one of the amazing things about being a cosmologist is that telescopes are time machines it takes a while
07:08for light to get here so if we look farther out into space we're really looking back into the history
07:15of the universe and that's amazing the first clues to unraveling the Big Bang mystery came with the
07:22introduction of advanced telescopes in the 1920s edwin hubble was studying the light coming from distant
07:32galaxies and what he realized was the more distant the galaxy was the more reddened the light was why
07:38should that be well it turns out that light reddens if a galaxy is moving away from us it's called the red
07:44shift so what he discovered was pretty much every galaxy in the sky was moving directly away from the milky way
07:52this was truly one of science's landmark moments hubble had proved one of the basic principles of the
08:00big bang story our universe is continuously expanding there was only one conclusion to draw
08:08if you extrapolate that back in time it looks like everything was coming from one point at one time
08:15that's the big bang hubble's discovery grabbed the headlines but the idea of an expanding universe
08:22had been proposed two years earlier by a belgian priest and physicist the real idea of the big bang
08:30comes from george lemaitre he realized that if you ran time backwards back to the beginning of time
08:37maybe everything coalesced into a single atom the primeval atom
08:40lemaitre believed the infant universe was extremely small and dense squeezed into a single point
08:54the primeval atom later scientists would define this point
09:00as an infinite entity called a singularity but there's a problem the singularity and the laws of physics don't mix
09:12it may be one infinitely small point but it causes some impossibly big problems
09:28the big bang for almost a century it's been science's leading account of how everything began
09:45but there was no explosion no bang and it wasn't big
09:50in fact the father of the big bang george lemaitre claimed everything originated from one tiny point
09:59he called the primeval atom i think one of the hardest things to grasp about the idea of the big bang
10:05is that everything you see everything you've ever known everybody every house every tree every planet
10:12every moon every star every galaxy in the entire universe at some point 13.8 billion years ago was
10:19compressed down into a tiny little dot in fact far smaller than a tiny dot infinitely small a point called a singularity
10:33and this singularity has been causing astronomers headaches for decades it's all because of one word
10:41infinite as soon as you start getting the word infinity things are infinitely large or infinitely
10:47small in physics it means that you don't understand everything einstein's general relativity predicts
10:54the theoretical existence of singularities but in practice a singularity is where our current laws of
11:01physics break down we do not understand singularities these are some of the theoretical questions that are real
11:10conundrums and people are trying to figure out what to do the universe is telling us something is going on
11:16here that we don't understand quite yet with our math our mathematics are incomplete this is a sign
11:23that general relativity is not up to the task of describing the earliest earliest moments of the universe
11:31general relativity predicts singularities but in reality it doesn't work when things are really tiny
11:39in reality Einstein's picture of general relativity is incredibly successful at describing the motion of
11:48planets around the sun the bending of light around massive objects the the growth and expansion of the
11:56universe itself but it breaks down when gravity gets too strong and gets too small general relativity may
12:05not be the best tool for understanding the origin of the universe say for example you want to weigh some
12:12spices in your kitchen you can use a kitchen scale that works really fine but now say on the other hand you wish to
12:18weigh your truck that's just not the right tool for it so forget relativity maybe another fundamental branch of
12:27theoretical physics can help out quantum mechanics this deals with the small the very small but what about
12:37the infinitely small can quantum mechanics prove the existence of a singularity general relativity seems to say
12:45that singularities exist they're a very straightforward prediction of general relativity that doesn't fit well
12:51with what quantum mechanics says quantum mechanics tends to fuzz things out it doesn't really like singularities
12:57in some theories of quantum mechanics the science of the small there's a limit to how small you can go
13:05for example i'm not going to be able to fold up this paper more than seven times
13:11one two three four i'm feeling good five oh man six can i do it
13:21can i do it can i break the laws of physics no i can't there's a limit i just can't go past it
13:27you can't keep folding paper or space into smaller and smaller fragments and according to most laws of
13:35quantum mechanics you can't have anything infinitely small and infinitely dense
13:43singularities seem to be doomed so is the big bang story wrong or are we just
13:50too dumb to work it out our laws of physics are our best attempts to model with mathematics
14:00all of our observations of the universe the universe doesn't care what we think the universe doesn't
14:08care how we understand it this is just our attempts to explain the behavior that we see and the
14:15earliest moments of the big bang is a big example of where our understanding falls short
14:27maybe the answer lies in a combination of general relativity and quantum mechanics
14:33but they won't play ball imagine the rules of quantum mechanics are like the rules that lacrosse
14:48players might use to play their game and the rules of general relativity are the rules that baseball
14:55players would use to play their game if you're just watching a baseball game then they're just following
15:02the rules of baseball or general relativity if you're just watching a lacrosse game you're watching
15:07the rules of lacrosse play out you're watching the rules of quantum mechanics but if you take one
15:13team from lacrosse and one team from baseball and put them together and ask them to start playing they
15:19don't even know how to interact with each other it's fundamentally different rules that simply don't connect
15:26each of these pillars of modern science quantum mechanics and general relativity are wonderful in
15:34their domain but when we try to marry them which is what we need to do to describe the earliest moments
15:41of the universe it all goes haywire perhaps both teams playing with a unified set of rules will shed some
15:49light on the big bang merging together quantum mechanics and general relativity is the gold
15:56standard it's what every theoretical physicist would really love to do in the modern age we haven't done
16:01it yet we have ideas so when i say we haven't done it yet we don't agree on what the right idea is
16:07what will ultimately reconcile quantum mechanics with gravity is there even a reconciliation between them
16:16what do we need do we need more surprising more powerful observations new data that we weren't expecting
16:24another genius or a thousand geniuses to come along and find the route through the mathematics to marry it
16:32it's probably all of the above
16:37so a major premise of the big bang story remains unproven
16:42but what about monsignor lemaitre's other assertions was the infant universe the primeval atom intensely hot
16:52and if so just how hot was it
17:12the story of the big bang is based on the discovery that the universe is continuously expanding
17:22and if we go back in time this leads to one inescapable conclusion
17:30so if you run the clock backwards and let the universe get younger it'll get smaller and smaller
17:35smaller and then everything is basically compressed into one point the big bang story claims this point
17:41was infinitely small but scientists have not been able to prove the existence of such singularities
17:50in our universe we see all galaxies receding from all other galaxies on average imagine if you were looking
17:59at trains leaving a station if you ran the clock backwards the trains would converge to the same station
18:06now did these trains come from the same station probably did they come from the exact same platform
18:14probably not you can't fit all the trains onto the same platform
18:18but while physicists can't prove everything came from an infinitely small and dense
18:24singularity they're convinced the observable universe did expand from one small point and this point
18:31was incredibly dense and incredibly hot imagine that you and a bunch of friends are in a very large room
18:39and you're all hanging out and it all seems normal but now you're all crammed together in a very small
18:44elevator and it starts to feel much warmer because you're interchanging all this heat it's sort of like
18:50that in the early universe everything is smashed together everything is very hot
18:56it makes sense theoretically that this period was intensely hot but how do you prove it
19:03how do you take the temperature of the early universe which began 13.8 billion years ago
19:11you can't but you can take the temperature of the coldest parts of the universe now
19:17so if you go away from all the stars and get away from all the galaxies you might think space was
19:22infinitely cold absolute zero but it turns out it's not empty space has a temperature of roughly 455 degrees
19:31fahrenheit below zero five degrees higher than absolute zero where did these mysterious extra five degrees come
19:41from big bang believers thought they had the answer they claimed this faint trace of heat was left over
19:50from the incredibly hot infant universe getting the proof took decades but it came in 1964 by pure accident
20:02penzius and wilson were bell labs engineers and they were given an assignment to measure certain radio signals
20:09for the idea of sending wireless signals via telephone so rural areas could have telephone
20:14they used a radio antenna shaped like a giant horn the problem was no matter where they pointed this horn
20:22they kept hearing kind of a static just a radio noise coming from every direction
20:28and they thought okay maybe it's a satellite but it didn't match up with any satellite positions
20:34there's a nearby army base and they called up the army base said hey are you
20:38broadcasting at this frequency and they said no we're not they thought maybe it's pigeon poop
20:44well you know there are these pigeons nesting inside the antenna and their droppings are creating
20:49this noise in your telescope so they actually went inside and scraped out all these pigeon droppings
20:54but no matter what they did the noise remained they tried everything they could to remove this
21:00background noise and they finally realized it was coming from the sky it was real
21:05what they were hearing was not radio waves but a different form of radiation microwaves a heat signature
21:15left over from the big bang
21:20they had discovered the cosmic microwave background a ghostly snapshot of the early universe
21:28different colors highlight subtle variations in temperature
21:34the cooler blue areas will develop to form stars and galaxies
21:40the warmer orange areas will eventually make up the vastness of intergalactic space
21:47the cosmic microwave background is a literal baby picture of our universe it's the equivalent of a picture of you
21:57when you were seven seconds old we can date the cosmic microwave background to 380 000 years after the big bang
22:07the temperature here is estimated to be 5 000 degrees fahrenheit
22:13but how hot was the big bang as we run the clock backwards the universe gets smaller and the temperature increases
22:26we know what the temperature of the cosmic microwave background was but prior to that time we know
22:30the universe was getting smaller and smaller and smaller and therefore it had to get hotter and hotter and hotter
22:36but can we find out how hot
22:38in the early universe it was much smaller denser and hotter than it is today and in fact it was so hot it could fuse hydrogen into helium
22:5125 of the mass in the early universe is fused into helium in this time scale of just a few minutes
22:57so it's trillions and trillions of times more than the amount of fusion that's going on in the sun
23:08extremely high temperatures are required to fuse hydrogen into helium scientists estimate
23:15fusion started 100 seconds after the big bang when temperatures reached 1 billion degrees fahrenheit
23:23during the very first fractions of the very first second of the big bang some estimate the temperature
23:31could have reached 250 million trillion trillion degrees fahrenheit but what sparked this massive release
23:40of energy here at the birth of the big bang the initial moments of our universe are a source of
23:50frustration because it'd be really nice to know that but also a source of curiosity this is the
23:56frontiers of physics this is where we're really pushing things to try to understand the fundamental
24:03aspects of reality but even if we can back up the big bang story by proving the way everything came
24:11from a tiny hot point there's still another problem where did everything that made up that tiny point
24:18come from you can't get something from nothing right we all know that except it looks like we got
24:25everything from nothing the entire universe seems to have appeared out of nowhere how can that work
24:30the big bang no space total darkness nothing
24:51suddenly the universe sparks into life
24:55really surely everyone knows you can't get something from nothing
25:06it's really the ultimate question how did the universe come into being and the thing is we
25:12don't want just everything to come from nothing it seems like a trick but here we are we exist
25:17so something must have happened and we just don't understand the physics of it yet
25:22this is one of the big open questions in cosmology um the origin of the universe
25:28and i think that people have variously said stuff like oh the universe has come from nothing like
25:34ta-da now there's a universe but remember we don't have data about the earliest moments of the universe we
25:44we don't know what was going on we're struggling in the dark to get insight into what may have happened
25:54before the big bang that period of apparent nothingness physicists look to empty space
26:02but does empty really mean there's absolutely nothing there it's not that there's something coming from
26:10nothing because that old-fashioned idea of nothing just doesn't apply to what we think of as empty space
26:18it turns out empty space is far from empty the vacuum of space is really a writhing sea
26:26awash with charged quantum particles and electromagnetic fields
26:31the vacuum of space itself it can be a very dynamic thing
26:35matter can spontaneously appear out of the vacuum and then spontaneously annihilate the vacuum is full
26:41of particles and anti-particles that are whizzing into existence and then disappearing colliding with each
26:47other space is full of virtual particles popping in and out of existence and there's no question that
26:55they're real their effects are absolutely visible we can see them
27:02in extreme physics things can get strange maybe nothing is something after all
27:12if empty space contains particles that apparently come from nothing
27:17could some sort of similar process have triggered the big bang
27:20the quantum vacuum itself can randomly spontaneously without any input just
27:33have a lot of energy perhaps enough energy to spark something that we would call a big bang
27:43there are many speculative theories about the origin of the universe
27:48but is its sudden appearance out of nothingness the only trick it pulled off
27:54it also made matter from energy the universe is full of galaxies stars planets and comets
28:02where did they all come from according to the big bang narrative from one tiny dot
28:09when the universe began there was actually no room for matter at all the temperature was so high
28:15the spaces were so compressed that matter couldn't exist so how did the universe manage to become full of matter
28:25in the primeval atom there was no room for matter but it was crammed full of energy
28:32and as einstein tells us all we need to create matter is energy
28:37according to e equals mc squared energy and matter are interchangeable
28:48einstein taught us with special relativity that energy and matter are two sides of the same coin
28:56you can convert matter into energy by say blowing something up
29:01the most fearsome example of converting matter into energy was the atomic bomb developed in the 1940s
29:14but with the big bang this process was reversed energy created matter
29:21matter matter that expanded out and out to fill a whole universe
29:31and in cosmic terms the universe where matter would develop grew remarkably fast
29:38right after the universe was born it had an unbelievable growth spurt basically going from
29:43being a toddler to a teenager in the single tick of a clock how could the universe get so big so quickly if we
29:53believe the big bang story it appears to have broken one of the most fundamental laws of physics
30:01did the early universe really grow faster than the speed of light
30:13the big bang in the classic big bang story the observable universe expands from a ball of energy smaller than an atom
30:34today the universe is estimated to be 93 billion light years in diameter
30:40think about the vast universe that we see all around us today and it was once a tiny tiny little volume
30:47unimaginably dense the universe must have gone through a colossal growth spurt
30:55with a steady rate of expansion there simply hasn't been enough time for the universe to grow to its current size
31:01regions of the universe that were close neighbors in the past are now so far apart that their separation
31:11can't be explained by normal expansion
31:17and the huge size of the cosmos is not the only strange thing we've discovered the universe is what
31:24astronomers call flat our universe is lumpy and bumpy at small scales there's galaxies there's black holes
31:35there's people there's all sorts of junk but at large scales global scales truly universal scales our universe is flat
31:46could this universal flatness and the super rapid growth somehow be connected
32:00we know that the big bang wasn't an explosion or matter in the universe would be unevenly distributed
32:07yet something pushed everything outwards and fast but what
32:18in 1980 alan guth a young stanford cosmologist came up with a potential answer
32:26his theory of inflation says the observable universe expanded from being smaller than an atom to the size of
32:34a basketball almost instantaneously in this tiny fraction of a second at the beginning of the
32:41universe like a millionth of a second but a millionth of that a millionth of that and a millionth of that
32:47the universe expanded by take the size of the universe at that time and multiply it by a one with
32:53say roughly 50 zeros behind it inflation drove the accelerated expansion in the universe made it get
33:01really really really big really really fast and then it stopped inflation seems to solve two big bang
33:10headaches how the universe got so huge so quickly and why it's so flat because it inflated everywhere at
33:21once all the energy in the universe which would turn into matter was pushed out evenly at the same time
33:29and same pace the four stars grow together to become the first galaxies even here us in the solar system
33:39we're born we're seated in the event of inflation
33:48parts of the universe that are now separated by 93 billion light years once had the same cosmic zip code
33:55to have expanded so quickly inflation must have broken one of the fundamental rules of physics
34:05we all know that one rule the universe sticks to all the time is that nothing can travel faster than the
34:10speed of light so how can we possibly say that the universe expanded faster than the speed of light
34:15time but inflation says the universe expands into nothingness there was no outside of the universe the universe was everything
34:28so space itself was inflating and space can move as fast as it wants you can't go faster than the speed of light through space
34:38space but space itself is allowed to stretch and expand as fast as it wants and that's what our universe is doing
34:45the idea of inflation smooths out the universe in kind of a peculiar way you can kind of think of it
34:50as having a sheet with a lot of wrinkles in it and if you take that sheet and snap it really hard
34:56those wrinkles very suddenly flatten out the theory of inflation is
35:00it's one of the craziest sounding ideas in the history of science so crazy that it might just be right
35:09inflation helps us to understand the inexplicable but there's a problem we don't know
35:16what triggered or powered inflation the inflationary universe idea imagines that the universe was
35:23suffused with some kind of ultra dense energy at early times something that pushed the universe
35:29apart what caused there to be that hot expanding stuff we have to be humble and acknowledge that
35:37we don't know for sure but whatever started it inflation was over in a split second it didn't last very
35:46long and this is difficult to understand how did inflation stop
35:52we don't know we got none folks well we got some things but it's tough it's tough
36:04but has the process of inflation really stopped
36:09one radical theory proposes if the force called inflation kick-started the expansion of one universe
36:17then why not another and another and another and another
36:23is inflation creating a whole series of new universes is there a multiverse
36:31that's a big bang
36:45if we believe the big bang story a dot smaller than an atom expanded to make a universe 93 billion light
36:54years across a theory called cosmic inflation claims to explain this stupendous growth
37:08but inflation may create more questions than answers
37:14inflation gave us more than we had bargained for we tried to come up with a mechanism that would just
37:18create our universe and stop and then quickly realized that actually just like most car factories don't
37:24produce one car and then stop but produce many cars inflation tends to produce one universe and another
37:31and a vast number of them a multiverse it's a process called eternal inflation it proposes
37:39that while inflation ended in our universe and led to formation of stars and galaxies
37:45we're just one small part of a vast continuously inflating multiverse
37:52imagine a series of bubbles next to each other those are the different universes and so our bubbles
37:59expanding and we're bumping into our neighboring universe and we're going to expand into it
38:04if the multiverse theory is correct a big bubbling multiverse sounds like science fiction
38:14but there is prospective evidence to back up the theory scientists have spotted an unusual mark on the cosmic microwave background
38:23that snapshot of the infant universe there's a spot in the southern hemisphere that's not necessarily the coldest spot
38:37or the biggest spot but it's the coldest biggest spot and it's strange we don't know how to fully explain it
38:46one unproven but intriguing theory is that this area is a kind of cosmic dent surface damage from an impact
38:56with another universe i work in the building with the people that discovered this giant cold area and
39:03they were pointing it out and saying well that doesn't make any sense why would the microwave background
39:07be like that hey maybe that's evidence of another universe interacting with our own that's something that
39:13when you go to lunch makes you pause if you buy into the idea of a crowded multiverse cosmic bangs and
39:22scrapes are not only perfectly possible they're probable there may be many universes outside expanding
39:30under the force of inflation right now one analogy is think about a superhero that just can't be killed
39:36they keep regenerating if the multiverse narrative is correct it places a giant question mark over the
39:45story of the big bang the possibility of a multiverse suggests not just one but a whole series of big bangs
39:57but not all physicists buy into this thesis the community is divided on the idea of the multiverse
40:04uh predictably uh predictably because there are some of us who believe that this sort of this leap of
40:09imagination is justified and there are others sort of hardliners who think that till we have empirical
40:15evidence this is not a scientific idea others welcome the fact that when it comes to explaining
40:22everything we're not simply stuck with the good old big bang narrative
40:27i would have felt kind of claustrophobic if it turned out that all that existed was earth
40:34and i was happy that we discovered there was part of something bigger the solar system the galaxy
40:39a cluster of galaxies our universe so i'd feel even better if there's still more space out there
40:45and in parallel universes the more the merrier while it's an appealing notion without empirical evidence
40:54it's a theory requiring a leap of faith there's no reason to think that the tiny little creatures
41:02that we are actually perceive the vast true nature of reality this is still an absolute puzzle we have
41:09ideas i have ideas other people have proposed models right but we have no data really that helps us
41:16distinguish between these ideas and to be honest the ideas themselves aren't fully fleshed out
41:20support for the classic big bang model seems to be increasingly shaky the latest thinking proposes
41:29not one but a whole series of big bangs
41:35as scientists continue to rewrite the traditional story more and more questions are being asked but
41:42for now many remain unanswered what was the origin is there even a sense to asking was there a time
41:52before time and i think the answer is yes you know our science and our math they're just incomplete
41:58someday we may have the mathematics to describe the earliest moments of the universe someday we may
42:03be able to make predictions that we can connect to observations just because that day isn't today
42:09doesn't mean that that day will never come we've learned an enormous amount in the last hundred years but
42:15now we're left with some pretty serious puzzles that are going to be really tough to solve so i'm waiting
42:21for the next einstein