"The Universe was created in the beginning.
It angered many, and was generally considered a bad move. "- Douglas Adams
Good evening, I'm Robert the Queen.
No, I'm Brian Green, and I'll make an overture for some of the ideas in the Infinite Worlds program
which we will discuss here tonight.
One way to frame the discussion is to recognize the fact
that over the last few centuries, our understanding of the universe has been seriously increased
and in huge jumps.
The program of the festival has covered a miniature part of a huge amount of knowledge in the last few days
which we were fortunate to achieve.
But there is one unexpected implication of knowledge that we have achieved
which is that we are subject to some kind of setback.
Our species has in some ways consequently gone through a series of regrets through the various types of our discoveries.
Think about it: a long time ago we thought Earth was the center of the universe.
and then people like Copernicus or Galileo came forward and they recognized
that the Earth revolves around the Sun, and then we thought the Sun was the center of the universe
and then we realized that the sun was one of hundreds of billions of stars in our galaxy.
Then, Hubble and others appeared, and realized that it was even our galaxy
just one of many, many galaxies.
What we're going to talk about tonight
is perhaps another step in the process of backtracking from the idea that we are at the center.
And this is the idea that our universe may not be the only universe.
There may be many universes, and we are just one of them.
The picture we could imagine is that the universe is a huge cosmic bubble bath
whereby all bubbles are different universes.
Our universe is then a bubble in that whole.
What I want to do in the next few minutes of this preamble
is to give you a sense of the basic ideas that lead to that play
and then we will move on to a discussion where we explore these ideas in more detail.
The key physics behind all this is gravity physics.
Let's start from there.
Gravity we all know - Newton introduced us
the way we should think about it back in the 17th century.
Basically, he made an interesting formula, Eq
which tells us that any body in the universe is attracted to any other body by force, by the force of gravity
which depends on two things: the size, the mass of the body and the distance between them in space.
A very simple equation that we still teach high school students today
hundreds of years later, and we still use that same equation
when we try to launch spacecraft to land on the moon
or encountered other astrophysical bodies.
So it's a very powerful method of thinking about gravity.
Still, Albert Einstein realized in the early 20th century that something essential was missing
in Newton's vision of gravity.
And that is Newton wrote a formula that describes the force of attraction between two bodies,
but he never explained the way those bodies exert this force of attraction,
how they exert that mutual gravitational pull.
And Einstein deeply wanted to understand the mechanism by which gravity works.
And according to the famous story, he embarked on the path of discovering this mechanism underlying the force of gravity
by turning to Newton's Principia - a book that has all the results of mathematics and physics
that Newton discovered for life, and which you should read for tonight's discussion, you know what it is.
In fact, I was a little surprised to read in the booklet that the book should have been read in the original Latin.
I never did, but you are all one step ahead of me.
So Einstein opens the book, looks under the letter G, finds "The Law of Gravity",
search for a little more, look for the subtitle under the letter M - "The mechanism by which gravity acts".
And he finds something surprising there, because Newton basically says, "I don't know how gravity works."
"I can write an equation that describes her strength, but how she performs it - I don't know."
In fact, his words were; "The answer to that important question - the mechanisms by which gravity works - I leave to the reader for consideration."
Most readers will read this and continue reading.
Einstein was different, and he spent ten long years trying to understand how gravity works.
And finally, by 1915 he came up with an answer in a theory called general relativity.
And the answer is subtle and beautiful. There is a quick way to understand what he has discovered,
and this is just this:
Einstein said that if the sun is here and the earth there and in between is essentially empty space,
the force of gravity must then be mediated in some way by empty space.
Space itself must somehow be that mechanism by which gravity exerts its influence.
And the way to think about it first, I'll show you the visualization in a minute, is to forget about gravity for a second,
use the analogy that physicists adore.
Imagine having a rubber sock tightened in front of you. You take the clicker and roll it over the surface.
It will go in the right line - it's easy to imagine.
If I now take a heavy object and put it in the middle of the stocking, the stocking will distort.
If I roll the clicker now, it won't go in the right line, but it will roll in the wrong trajectory,
rolling on the curved surface of the rubber sheet.
Einstein said, "Apply that simple idea to the universe." Instead of a rubber sheet - on the fabric of the room.
More specifically, the fabric of space and time all around us.
And he also said that when the body is in space, it makes the space bend and thus affect the movement of other bodies,
in a similar way that a distorted rubber sheet affects the movement of the clicker.
In order to get a picture of what this would look like,
Let’s imagine the fabric of space as a lattice area. This is now a three-dimensional space, making it harder to work visually
and so we will move on to a two-dimensional analog showing all ideas.
And you see, space is flat when empty
but when the sun comes up, the fabric curves.
Similarly, if you look at space near Earth, the fabric curves around it.
Pay attention to the moon as this is the main point.
The moon is kept in orbit as it rolls across the valley in the distorted middle that Earth creates.
It is a means of communication of gravity, it is a mechanism of action of gravitational force.
If we move away, we will see that the Earth is also in orbit as it also rolls on the distorted part of the fabric of space
that creates the Sun.
This, according to Einstein, is how gravity works.
He wrote this theory between 1915 and 1916.
Shortly thereafter, people around the world began to think deeply about this general theory of relativity and these ideas,
and in particular, this interesting physicist, a Belgian priest - a priest who is also a physicist,
who came to Einstein's work and decided to apply his ideas not to the sun and earth,
but to the whole universe.
And when he applied Einstein's ideas to the entire universe, he came across something very interesting.
He found that the fabric of space should either expand or narrow. It is not possible for it to be static.
So he predicted that one solution might be that the universe may be growing over time, expanding.
He presented his idea to Einstein, and Einstein told him:
"Math is fine for you, but your physics is abominable."
And what he wasted on was thinking he was already through it. There was an earlier physicist, Alexander Friedman
which looks a lot like my accountant before tax.
Friedman had already discovered this idea of ​​an expanding universe and told Einstein,
Einstein first thought that Friedman had made a mathematical mistake, even stated it in public.
Friedman convinced him there were no mathematical errors.
So when Lemetre introduced the same idea, Einstein said:
"Yes, yes, the math is correct, but your interpretation that the universe is expanding is simply pointless.
Look at the sky, the universe is obviously not expanding. "
So in Einstein's mind it was clear how the universe should behave.
In fact, he was so sure, that he returned to the math of general relativity and adjusted it to get rid of the possibilities
that the universe is expanding.
What followed was wonderful: in 1929, this gentleman, Edwin Hubble, an American-born astronomer, educated at Oxford,
studied the motion of various bodies, galaxies, using this 250cm telescope in an observatory on Mount Wilson,
and discovered that distant galaxies were actually moving away.
And to move away by a certain pattern that is consistent with the textile of the expanding space.
It is as if galaxies are sewn onto the fabric of space, and as the fabric expands,
galaxies are moving away from each other, the universe is expanding.
This has contributed to the development of what we call the Big Bang.
Ideas that the universe began as small and then magnified.
Picture it like this: imagine that the universe started out as a very small, thick, hot lump,
and then it spreads. The space expands, and as the space expands, the hot primordial plasma cools.
As things spread, they cooled, and as cooling began, structures could begin to come together,
structures that will finally create galaxies and stars within galaxies, and that will create things that you can see
in a beautiful, dark, clear night sky.
So this is an image that has finally grown out of this way of thinking about gravity and how the universe evolves over time.
I do not want to give the impression that everyone immediately believed in this way of seeing the universe.
There was definitely a need to find other experiments, other discoveries that would convince people
that this is the right way to think about the origin and evolution of the universe.
And one man, George Gamow, played a particularly important role in this.
George Gamow was an interesting character. 190cm tall, charismatic Russian physicist
who was fast-paced and loved as much fun as he was worth.
He and his wife tried to escape from the Soviet Union in a very interesting way.
They filled the kayak with only brandy and fine chocolate and set out on a journey across the Black Sea.
36 hours after they set off, they were found by authorities floating in a kayak.
They were lucky to bring only alcohol and chocolate
because that supported the story that they just went out for an afternoon paddle, not that they were actually trying to avoid it.
However, a few years later, Gamov succeeded and, having passed under the Iron Curtain, came to America,
and started thinking about cosmology and Einstein's ideas, and came up with the following simple idea:
if the universe started out as very small and hot and then expanded - when things expand, they cool.
This means that there should be some residual heat today in the space all around us that is left over from the Big Bang.
And he said we should look into space and find that residual heat and those residual photons because that would support the image
that the universe began as small and hot.
That work is wonderful, he betrayed it, but he couldn't convince anyone to actually look for that radiation, the heat left behind after the Big Bang.
One of the reasons is that the scientists were mostly focused on quantum mechanics
and other aspects of physics rather than cosmology at that point.
And the other reason why people didn't jump to study this is partly because Gamov had a reputation as a prankster.
He once wrote a work with his student that played a vital role in recognition
that there should be heat left behind by the Big Bang.
The student's name was Ralf Alfer.
And Gamov then persuaded this man on the left of the picture, Hans Bete, to put his name to work
only for the authors to be Alfer-Bete-Gamov.
It can actually pass for a physical joke as the standards are not too high.
But it made an impression on people that he should not be taken as seriously as his work deserves.
And that's why the work he wrote with Alfer and Robert Hermon essentially died.
No one followed him.
A few years later, because in physics, great ideas will eventually be rediscovered
if no one continues at the time they were created,
these two, Robert Dicky at Princeton and Jim Peebles, came up with the same idea -
- that there should be residual heat from the Big Bang. They went through a similar calculation.
They were an interesting couple because Dicky was a great experimentalist.
They started making equipment to try and find that heat left over from the Big Bang.
In the midst of their work, they got a phone call from these guys, Arn Penzias and Robert Wilson,
a phone call that may be the most famous call in the history of cosmology.
I guess it's not that impressive either. It's a bit like you're the cutest kid in fat training, or something.
But this was an incredibly important moment, because these two who were about 30 miles away from Princeton
working at Bel Labs and using that antenna you see behind them in the photo,
they picked up sound, hiss, which they tried to get rid of by all means, cleaned the equipment and failed to get rid of it.
At last they concluded that this hiss must be heat, the radiation lagging behind the Big Bang.
So they called Dickie and told him what they had found. Dickie hung up and said, "They crossed us."
These guys found it and really, they won a Nobel Prize for this discovery.
So this endorsement of the Big Bang idea was a spectacular moment,
but it was also a turning point, for that was the moment when cosmology entered the field of quantitative science.
Because their observations as those of others after them, and the second Nobel Prize awarded
To Mathers and Smut for these observations, they initiated a way to test these ideas.
What I want to do now is show you a graph, a theoretical curve. It doesn't matter if you don't understand exactly what she means.
It shows us the amount of heat at each individual frequency,
the number of photons at each frequency, which should be all around us, lagged behind the Big Bang.
And then I'll show you the measurement data.
If you look at the chart, the curve will go from left to top and right. This is the theory, this is the Big Bang theory.
And now we will see what the experimental observations say. It will be shown in red dots.
You will notice that the red dots are placed exactly along the curve line.
The very impressive overlap between theory and experiment allows people to believe that this is
the right way of seeing the universe.
This is great, but there are still some unresolved issues.
And we will talk about some of these issues at the moment when the discussion begins,
but when people look closely at the Big Bang theory, they see that it explains the way the universe evolved
after it started to expand outside,
but it does not say what triggered the expansion.
She, by the way, omits the bang itself.
That raises the question of what a bang in the Big Bang is, and it's hard to say what it could be.
Usually gravity pulls things inwards, and what then would be pushing them outwards
that would propel the universe toward expansion.
There are many ideas about this, some more convincing than others.
But there are these two guys: Alan Gut and Andre Linde, also Paul Steinhart at Princeton and Adreas Albrecht,
who actually found the answer that we believe today is probably what happened.
And you'll meet these two guys in no time.
But what I want you to conclude from this slide, and the impression is amplified by the introduction of Friedman into it,
is that modern cosmologists are really happy!
But what did these guys find? They discovered the following:
when we come back to Einstein, and that really comes to mind,
gravity, according to Einstein, is not just an attractive force.
Newton thought it was just an attractive force pulling things toward him.
These guys think, reinforcing Einstein's observation, that if there is some kind of energy that permeates the space,
the word field may appear later in the conversation,
so if there is some energy, a field that pervades space,
it can create repulsive gravity.
Gravity that pushes out, which can make the universe, in a sense, shatter
to disassemble, to give a burst to the Big Bang.
The picture you get in a field called inflationary cosmology, which we will discuss for a moment,
is that there is a tiny lump, this is this little shiny area on the left,
a tiny lump of space becomes full of energy, triggering an incredible outburst,
which causes the universe to expand and continue to expand, which we are witnessing today.
This is inflationary cosmology.
What I want to summon here is because the key thing I hope you will bring home with you tonight
is that cosmology is not a bunch of theoretical ideas that people simply put forward
so they hope they are true or false.
It has become a quantitative science.
The most quantitative way to understand, to convince ourselves that this is true, comes from understanding
the heat remaining from the Big Bang, in the following sense:
when the universe is very tiny, there is one feature of quantum physics - you don't have to know much about quantum physics,
but quantum physics says there is always a certain amount of indeterminacy, a certain amount of fluctuating behavior that happens,
and here it happens on the far left of the image when the universe is very small.
But as the universe expands, the tremors of quantum mechanics expand.
And when they do spread, they cause hot spots and cold spots in the sky.
Tiny temperature differences, not large, in the thousandth part, for example,
but these tiny differences in temperature can in principle be measured.
And if you look at the green and yellow parts, they indicate temperature differences.
Here it is shown in blue and red, but it is the same thing.
These are hot spots and cold spots, generated by quantum fluctuations in the early universe.
And the idea is that if you have a device, like this satellite on the right, it can measure hot and cold spots,
because light travels to the satellite, then you will find what I will show you in the last convincing piece of information.
This is a theoretical curve, created in quantum physics and inflationary cosmology.
And this is the data. And I'll step back and let them go.
Eh .. now. This is the data
which were set 13.5 billion years ago.
This curve was generated by us, human beings, 13.5 billion years later
both the data and the curve match to fantastic precision.
If you were to ask me what is the most beautiful image our civilization has created,
yes, some things come to mind such as "Starry Sky", "Mona Lisa".
For me, this would qualify among them.
This picture is so spectacular, this agreement between theory and experiment.
The last thing I want to point out before I finish, which is merging with this program, is this:
the inventors of this inflationary cosmology realized something very interesting a few years after the first discovery.
This kind of inflationary bang is very likely not a unique event.
There can be many such inflationary explosions.
In fact, the picture I like to have in my head is like a big piece of Swiss cheese.
And if Swiss cheese is that cheesy piece of cheese, the energy that permeates the space,
the idea is that the cheese is spreading, but in different places energy is dissipated and creates small openings,
small bubbles that grow over time, and all bubbles in cheese are different universes.
And our universe is one of those bubbles.
This is how so many universes emerge from inflationary cosmology.
I'll show you what it looks like. The last visualization.
You will see a foggy gas-like entity appear, which will be like the cheese I described.
It is this energy, the field that pervades space. And here it comes into view.
The universe is expanding, creating a repulsive gravity that pushes everything apart.
But in different places pockets are opened, regions where energy is weakened
and is converted into more ordinary particles of matter and radiation.
And all these openings in the picture would be different universes created in this huge expanding body.
We call this the multiverse.
Going into one of these would make it look like we had penetrated an ordinary universe like ours.
And here is our universe. Just one of the bubbles in the cheese.
The fact that it's a bubble makes it small on the outside, but it's not huge on the inside either - something we can talk about in a panel discussion.
As you can see, we have galaxies on all sides and this can be our universe.
And if we go out to see what's in another bubble, let's curl around and focus on one,
if we go to another bubble, the world and physics can be a little different.
His features do not have to be identical to ours.
So all these worlds, all these different universes would be out there, embedded in this fast-paced, gaseous empire
and our universe is just one bubble among many.
If this picture of the universe is true and we can see the multiverse from the widest point,
the idea is that we could see a huge assortment of worlds where different lumps of reality take place
world by world as they evolve and change, as they go back and forth, they increase.
The universe would in some sense be a huge assortment of bubbles where our universe is just one melodic beat
in rich cosmic score.
Claire Chase on the flute, Rebecca Heller on the bassoon, Eric Leyman on the flute and Joshua Ruben on clarinet. Thank you.
I'm Robert the Queen, mentioned above, and I want to re-set the stage first,
because when Brian does such things, he does them so well that you are all in the loop: "Oh, yes!".
But I want to be careful here. Because until recently, many of you sitting here, like me, thought
that the universe means everything that exists, everything you can imagine.
And since the universe is everything, then there must be only one thing.
And that's why most of us were perfectly happy with the idea that there was only one universe.
And then this guy comes up with your pictures and all that, and other people you'll meet.
Very very smart people, I must say, will sit on this stage, who believe that there is not one,
but, as you have heard, many universes, and therefore their universe is multiplied,
which is a bit strange, isn't it.
And even more meaningless, these people insist, or suggest, or skillfully describe, many, many, many, many, perhaps infinitely many universes.
And they don't mean the idea in their head or the mathematical equation or abstraction or logic ...
No, they say, as you saw recently, it's real, we suggest that there are real physical universes
with energy and matter and maybe atoms and stars and gases and you know - real things
who are really out there in the vast, perhaps infinite multitude, and collectively call them the multiverse.
That's the theme tonight.
But instead of insisting that this is true, I will reset here, because ...
You will see.
The first thing you need to know is that not everyone agrees.
Nobel Prize winner, physicist from the University of California, Santa Barbara, a highly respected man
he thinks it is, and these are his words: "An inelegant, unprovable and unlikely idea."
And there is a man, perhaps reading about him in Scientifique Ameriken, the mathematician Martin Gardener
calling her "a frivolous fantasy, intellectually bankrupt."
Paul Steinhart, mentioned by Brian, Professor Albert Einstein at Princeton, says:
"This is a dangerous idea that I simply don't have the will to take into consideration."
So what we are going to talk about tonight is not a general agreement object, it is even very debatable.
But because it's a very rich, important, and I must admit, very intriguing idea,
we have fitted the cards by bringing the pluralists of the universe, we call them "i-people" because the word universe is spelled with -i.
I must admit immediately that I am not a scientist, nor am I particularly taught in these matters.
I am here to support many of you who will be asking "What?" if they don't understand some of it
because it is my job to tell these people: What does that mean? What are you talking about? How do you know that? Why do you say that?
This is a science festival not for scientists but for curious people who want to spend an hour or two on spring evenings wondering:
What is and what can be learned about our universe, or our universes?
We'll get to the point. I sit in the most extreme place.
And elsewhere there will be:
Nick Bostrom who is ... I guess it's best for them to go out in the crowd.
They will smile, as Brian predicted.
I don't know, they'll show up already, and I'll tell you who they are.
And here they are! Hi Hello.
This is Nick Bostrom. He is a philosopher who thinks that there may not just be multiple universes,
but many of them can be computer simulations, so everything you see around you right now,
touch your foot if you like, feel the material and texture. That's not really ...
Nick Bostrom is also the director of Oxford University's Institute for the Future of Humanity
what you need to worry about.
Alan Gut is a professor of physics at the Massachusetts Institute of Technology (MIT), world-renowned for his theory of inflationary cosmology.
The story we tell about the universe has changed, in large part, because of the things he discovered and thinks.
Then Brian. Brian is a professor of physics and mathematics at Columbia University. Author of "The Fabric of the Cosmos" and "The Elegant Universe."
He has made important discoveries in his field, and that is the theory of superstring.
And his skill in explaining insanely complicated things like this irritates me, but so many love him.
And Andrew Lind is a cosmologist and professor of physics at Stanford, who believes that the universe is infinitely and eternally multiplying in more and more and more universes.
If you want to blame someone for this, blame him.
Let's start by going back to a few places from Brian's story.
Big Bang: I want us to go back to that.
You said, and I was intrigued, that you could find evidence of microwave radiation and all that.
You also said that the universe is expanding. How do we know then ... if you can describe what happened there.
Why do they call it the Big Bang?
- It was actually a derogatory term. Correct me, but I think Fred Hoyle was the one who didn't believe in that way of thinking.
I think in a radio interview he said, "These guys are constantly talking about some big bang!"
The idea is simply that if you think of something small as it increases and try to compare it to something you see in the world around you,
when things explode, they increase, so it's like a cosmic explosion.
But that kind of thinking is actually cumbersome, because it sounds almost as if there was a universe around where that burst happened
and that's not the typical way we think about it, though when we start to think of the multiverse, it gets a little hazier.
But let's forget about the multiverse for a second and start simple.
Traditional Big Bang theory predicts that everything is in that small lump that started it all.
There is no space outside.
And as it grows, it creates the space that is around us.
- And since space and time, Einstein says, are the same thing, if I ask you, as many would ask
what happened just before the Big Bang, how would he respond?
- There are a lot of issues in cosmology that are very tricky. And that is certainly one of them.
And there is no single answer to it.
When you go to the multiverse image, the question changes. But let's start again from the simple.
In the traditional Big Bang, one way of thinking is that there was no time before the Big Bang
because space and time started their existence with this event.
It's like asking you how to go north of the North Pole.
That question means nothing, does it? Because the north ends there and it starts there.
And so if you ask me what came before the Big Bang, I say, "That question has no meaning."
Admittedly, there are other approaches to this topic and we'll talk about them tonight, where the Big Bang is an interesting event,
but it is not the only creation event, and it is possible that there were events before it.
- Do you all just bypass the issue of events before the Big Bang and move on?
In fact, there is one part from the Calvin and Hobbes comic about this, where Calvin tells Hobbes,
otherwise these are comic book characters, as you know, about a boy and his tiger doll,
and the boy says to his tiger, "Why did they come up with such a name?" Do we have a picture ...?
On the right you will see an alternative name:
A HORRIBLE SPACE KA-BOOM!
Maybe that would be a better name ... But let's move on.
In the beginning, when we have that moment in the beginning, we have a thick soup of things, very hot, and then ...
Alan, I want to ask you, there are problems.
That hot soupy thing that is at the very beginning of time then becomes lumpy
and then it crosses into clouds and galaxies and as Brian's film has shown.
The universe then expands outward but does not turn into a circle, so it seems to turn into some kind of plane to expand.
And if you look around in all directions, like those radio people did, it looks the same wherever you look.
How did you Alan explain the universe's early initial flattery, lumpiness and uniformity
and why did you write in your lab notebook "This idea I just had is a spectacular moment of comprehension"?
- It happened one night when I put together a few things I've been working on for the past six months,
but the key idea is the idea of ​​inflation, inflation, which really ended in one night.
And I realized ...
- In one night?
- One night I put together what was six months of prelude.
I was lucky that a lot of important information fell into my lap during that period.
I was lucky in that knowledge, but I think someone else would have found out sooner.
But the key idea was that I was observing a phase transition that we thought happened in the early universe,
and I considered the idea that the phase transition might have been subjected to a significant amount of supercooling,
motivated by studying something called magnetic monopolies, but I won't go into it now.
- Don't! - No I will not. I never intended.
Anyway, going through some calculations, I realized that supercooling would produce that particular field
which Brian had just targeted, which would have a repulsive gravitational effect.
And that would have huge consequences on the expansive history of the universe.
- Huge consequences? If the universe is extremely tiny, like a proton,
how much did it grow and in what time?
- The weather we're talking about here - we still don't know exactly, but the time we talked about back then still seems convincing,
is 10 at -35 seconds or so silly.
- So much faster than PK!
- Much faster than that. You can't do that. You can try, but you will not succeed.
- I won't even try.
- And during that time the expansion climbed by a factor of 10 to 25 or something.
- So 10 with 25 zeros.
- One with 25 zeros.
- What size is it then?
- Starts at a size more than a billion times smaller than a proton, eventually increasing to about the size of a clicker.
Still very small.
- Clicker?
- Clicker. The whole universe - this way.
- That's mysterious!
- He continued to expand after that, but not to accelerate. It's just an expansion.
- Why it's repulsive PFF! care about?
- It stopped because that thing that pushed him, that field, was unstable.
As radioactive substances, it decomposes into other types of materials, which we consider more normal
and which produce attractive gravity.
- So the opposite of gravity is that the elbow is "bent" instead of being "approached" by a kind of force,
if this repulsive thing creates a table tennis ball-sized universe,
then how does it solve the problems I just mentioned?
How does it make the universe seem flat in order to expand?
How does it create the possibility of lumpy matter so that there are stars?
How does this create the impression of universal uniformity?
- I'll start with the problem in the opposite order. Let's start with uniformity, it's the easiest to understand.
In conventional cosmology, as it existed before inflation was added,
the whole universe was expanding so fast that there was not enough time for the various parts to communicate with each other
even if they could send each other signals at the speed of light.
Therefore, it was concluded that the universe could have started as perfectly uniform,
we don't know exactly how the universe started,
but unless it emerged as perfectly uniform, there was never enough time in conventional cosmology to unify it.
So it stayed lumpy, it started out as lumpy.
In fact, the early universe was very smooth. Nonuniformity is crucially important, but it was only one part in 100,000.
The early universe was simply slick.
Inflation can explain this. Because with that PFF bump! expansion, that means it’s before PFF! rush,
the birth universe was drastically smaller than it would have been under any previous theory.
And while he was drastically smaller, he had plenty of time to get uniformed
in the same way that the air in the room equalizes so we do not have high and low pressure pockets.
But it takes some time for that to happen. And there was enough time on such a small scale.
Then this tiny speck, more than a billion times smaller than protons, believe it or not, we talk about such things and think we believe in them,
it expanded, stretched from inflation itself and increased enough to become a clicker
which then grows enough to include literally everything we see today.
- That the clicker becomes literally everything we see today - is it because there is so much energy in that clicker,
I mean, the energy gradually cools down to become matter, and then you get more space and more time,
and more space and more time ... and then to us.
- That's right. That later part after just sails.
- Then do you solve the problem of clotting in the same way?
- That's a serious problem. The clot problem comes from the smallest quantum fluctuations,
even in this room, we think if we measured things the size of an atom, we would see large fluctuations
in electric, magnetic field, energy, density - everything.
And inflation takes small-scale fluctuations and stretches them. They grow large enough to become the galaxies we see today.
- So tiny groups become galaxies or huge galaxy fields.
- That's right.
- What was the third problem?
- It's flatness. Flatness is a little harder to understand.
We don't know what shape the universe was when it started.
But the picture that is easy to imagine and that can be true is that the universe began as a circular,
what we call a closed universe, which is a three-dimensional analog of the sphere, of what I illustrate with my hands.
- Yeah, you're doing it right.
It is a two-dimensional surface but in a three-dimensional space.
So, the universe started out as such, and then inflation made it drastically higher and in the end looks flat
for the same reason that the Earth's surface acts flat on us, even though the Earth is actually circular.
If you take something that is round and stretch it drastically, it will work straight.
- Andrew, let's move on to the next step. So we have this thing that grows into a bigger thing.
This clarifies some early problems and makes the universe seem a little more familiar to us.
But my next question is called the graceful exit problem.
This indecent form of upside-down gravity pushes itself away.
You said that the universe somehow stopped growing.
But it doesn't seem to stop growing on some kind of tralala-TRAS! the way.
It just keeps disturbing the universe.
And from that flux of repulsive gravity a more interesting question arises. Andrej, the question is for you:
How does one get from one universe to more than one universe if you continue from where Alan left off.
- First, let's try to understand how to get one.
Because Alan suggested the idea of ​​making the universe big, everything in it, etc.
But when the bubbles in his universe ... when the universe starts to vacuum, the energy states start to fall apart,
it produces bubbles, which then collide ...
- Wait. So there is energy. And she pushes everyone outside.
And in Brian's film, energy seems to sigh occasionally.
So the energy level is down, but not up, here and then ...
And every time this repulsive energy makes sense or gives up some space, is that where the universe gets?
- Yes, well, that's how you get the interior of the universe.
You see, in Alan's picture you have a universe similar to Swiss cheese, and bubbles are created which then collide.
Even after they collide, they may somehow disappear, but the universe after that, unfortunately, became inhomogeneous.
And then I had my own night as Alan's,
except it was the night I brought my phone to the toilet
because it was the only place in the house where I would not wake my son.
I called some colleagues and told them I had an idea and asked them if it was stupid.
- Wait, so you got your inspiration, rushed to the toilet, hid your phone?
This is a good story!
- I got my inspiration a little earlier. But it is important that I did not lose it after I went to the toilet.
And I went to the toilet not for the reasons you doubt me,
but because I had to call a colleague to check if I was thinking stupid or not.
And he said he didn't think it was stupid. And then I woke up one-
- Check check. Did you have to say something mathematical or did you say, "I'll tell you something, and you'll think I'm crazy."
- It was pretty mathematical. As much as he can over the phone.
Eventually I woke up and said to the woman, "Look, I think I know how the universe was created."
- It was a big trip to the bathroom!
- I guess we'll all try the same a little later.
But maybe not so successfully this time ...
So the idea was this: you have many bubbles.
But then the blisters can begin to expand continuously internally.
And when the energy goes down, they keep expanding. And the result is that you don’t see all the pieces.
You don't see the opposite walls of the bubble colliding with each other.
Because the interior has grown so much that you don't see disaster.
You only get the benefits of expanding the inner part.
So you get a smooth end to inflation, that slow rolling, inside one bubble.
- Excuse me, I have to translate you into my own language, because it's hard for me to understand.
So in my universe, there is some logic. Things are spreading around me and they seem to be infinitely expanding
and there is some kind of uniformity of creation in my universe.
But if my universe is here and the next universe is there,
the space between us - between my bladder and his bladder - the space between us is increasing rapidly.
So our universes are moving away. Mine is fine, his is fine,
but look! We're moving away. Is that what you want to say?
- This is not a complete story, because if that were the case in the first version of inflationary theory, then your universe would be empty.
So it's not just the case that both of your universes are in order. But because of that smooth decline in energy and the spread of yourself,
not just the distance between your universe and Nick's, but everything that happens around you,
then you are left with a large part of the universe that you can inhabit on your own.
It's like peaceful coexistence. Like when I was in Russia, Alan in the US. Okay, it was a bit of a problem.
But what if Russia and the US are expanding exponentially and not hurting each other at the border,
already expanding from their own resources. That's what we suggest the universe does - expand peacefully, without collision.
- I still don't understand how you start with one universe and then you get another, then another, and another.
Some logic is missing here.
- Maybe I'd better show you. We'll come back to this picture later, but can we see the golden universe?
These are computer simulations. Because when you want high-tech cheating, turn to computers.
On the left is the X-axis, across is the Y-axis. And this is a laser weapon.
And the longitudinal axis shows the energy density level in the universe,
or the value or size of the field - whatever you call it. This is what is responsible for the expansion of the universe.
The higher the spike, the faster the universe expands.
We started the simulation with an almost homogeneous universe,
and then he began to expand at an exponential rate.
A computer cannot expand at an exponential rate, and therefore every new frame displays an exponentially larger part of the universe,
but the computer shrinks it again.
Then these little waves, you see quantum fluctuations in homogeneity here, they freeze at each other
then the universe continues to expand, then new quantum fluctuations freeze over each other, and the universe continues to expand.
And in some places the energy level goes down on average,
and we live somewhere here in this lower left corner where the fluctuations are small.
And when they're small, we launch satellites, watch what's going on, and get interesting curves
and we come across agreement with experiment data.
But there are also parts where these fluctuations accumulate with each new leap, grow and grow
and they use other parts of the universe that are so dense that they expand much faster than the original part of the universe.
And this is where new parts of the universe are created.
So it started from the smallest part of the space, and then, according to the classical theory we all love, it went down
and it could all end there, but due to quantum fluctuations in some regions
the spread continues forever.
By the way, this part that shows low fluctuations is the part that has been experimentally tested
and which will be experimentally tested.
Can we see a movie with Plank's satellite?
This movie shows the recent launch of Planck's satellite, May 14, 2009,
which will generate data in about three years, and will show these little colored dots in the sky
which are the result of small, small scale fluctuations.
And after he finishes and maps all this and, hopefully, agrees with the theory we currently have,
we'll get pictures like the one I want to show you now
and that is the universe of color.
This is a universe similar to the first image with X and Y axes. And here is the density (along), but in different colors.
Different colors indicate that in some parts of the universe there is a space with some kind of properties,
let's call them red,
and in other parts there are different qualities which we shall call green.
And for historical reasons, being from Russia, I started the simulation with a red square.
And as you can see, it all ends with a universe that is multifaceted. But what does that mean?
Let's get some water. So the water can be in solid form, liquid or gaseous.
It's the same water, with the same chemistry and physics in it. This can also be applied to theory.
You can have one fundamental theory for everything, but it can represent different parts of the universe
which have different properties.
You can still have the red universe, or green here, blue here.
But because of the exponential expansion of the universe, the distance between red and blue will be exponentially large.
And if you decide to cross the border, simply start moving from the red universe to the blue.
But you will come to the border, like a wall. A cop is not necessary as it is very very difficult to cross.
But if you are stupid enough, young and brave, and cross the border, you will most likely die instantly. Because...
- Just a moment!
I do not want you to die here in your presentation!
Can I interrupt you for a moment? It looks like we have a carnival in this picture ...
All of us in this panel discussion are very talented, but I would say that you went one chapter further than I would like at this point.
But you Brian have one picture like this, don't you? I don't know if you brought it.
I need a different version of building a universe. Do you have one?
- Do not have. This picture you see is the more scientific version of the visualization I presented at the end of my introduction.
Where each of these colors is actually a separate universe, a separate bubble
in that huge, growing base that holds all the bubbles.
This is a more technical way of pointing out that there can be many different types of universes within different bubbles.
- But I want to go back to the basic idea.
The basic idea is that there is some hesitant, fluctuating thing at the bottom of existence.
And the fluctuating thing is either a robust "get off me!" Or a relaxed, smaller version of it.
And then in some places, robustness breaks out and creates separation of the universe.
You get a lot of distance as the universes move very fast from one another.
And then the universes themselves jump out of this carrying repulsive energy that is always there,
sometimes more, sometimes less, sometimes up, sometimes down ... Is that a general idea?
Do you know how strange and strange this is?
I mean, couldn't you think of something simpler?
- I think it is important to keep in mind that these ideas, when communicated in ordinary language
they really sound complicated and weird, they are unknown.
But if you look at the math behind the versions of these theories that these two gentlemen came up with,
it is actually the simplest mathematics encountered in many physics theories of this kind.
She is really very direct, and really implies. When you look at math,
then really, if these theories are true that we lie in a huge expanding substrate,
and that these openings can happen in what we consider to be a unique universe, which it really is
one opening out of the many possible openings in that huge growing base.
And the features can vary from opening to opening.
- So every universe is one side of that flow, the flux,
and everything in between is a robust separation.
Doesn't that mean that the universe ... Between Nick's universe and my universe
is the distance between us increasing? And is it growing fast?
- Very fast!
- So the universes, his universe and mine, are moving at a speed greater than the speed of light?
- If they were far enough away, they would be faster than the speed of light, yes.
- I thought nothing could move faster than light.
- Einstein told us that nothing can move through space faster than the speed of light.
He said nothing about bodies being pulled away from one another by the expansion of space itself.
So if they are sufficiently far from each other and the space between them expands, then they will move one relative to the other
be in some sense faster than the speed of light.
Which means it will be permanently beyond your ability to talk, communicate with them.
So they are out there somewhere, but permanently beyond your ability to see them or to see you.
- Before we get to that ... You just magnified what I used to call the universe,
you just magnified it enormously. You doubled the speed ... That's ... Uh.
- When these two appeared on the scene, the picture of the vastness of the universe changed dramatically.
It used to be: the universe is 14 billion years old, roughly the transverse distance was
14 billion light-years, more or less, if you insert a factor of three here and there.
But these guys increased it by a factor of about ten to one hundred.
- Or infinite. - Yes, or infinite!
- It should be added that this is not an accurate ... more precisely, the complete picture we are talking about.
Sometimes universes can collide with one another.
- Please, sometimes I can do what?
- Sometimes the main wall comes towards you and hits you, but you don't see it because it moves at a speed approaching the speed of light.
But the moment he collides with you, you stop seeing him, and then ... There you go.
- Andrew, can I just ...
- That's his whole problem!
- Why do you think it will ... You have raised the idea that the universe will go, and go, and go, and go.
So, do you think that there is a beginning of a multiverse, and that it ends?
As in any of these universes, I think you can exhaust yourself and die, and the universe would collapse.
- Yes.
- But it doesn't look like this big thing can collapse.
So, is that what you suggest the eternal universe?
- If we can see the image of that bubble universe again?
As for the beginning, as Alan and several other people have shown,
we still need this bubble below that can't be seen well from the chairs,
this first bubble that appears below. The problem must be something that triggered the tree to grow.
Perhaps, however, growth has not begun simultaneously in the entire universe.
What happens is that once this process of production begins, even more new universes,
the process never ends. So the universe is infinite in the future.
And what does that mean for us? Well, a few things. E.g:
We used to think that this bubble is partially visible from the chairs,
that first bubble is the whole story.
What we and cosmology wanted to explain was:
We see this universe around us, and it is more or less homogeneous, more or less uniform in all directions.
In fact, Albert Einstein believed that the universe must be uniform and homogeneous.
He and some have called it the cosmological principle.
We continue to see this in books on astrophysics. A perfect cosmological principle means
that the universe must be uniform. Even if this is a yellow balloon below - it is a yellow balloon.
I used to joke that people who don't have good ideas have principles.
But I stopped that joke after learning that this cosmological principle was set by Einstein.
Here's what happens: The Greeks had the idea of ​​the universe as a perfect sphere.
We wanted to have a mechanism that made our universe a perfect sphere.
And then inflation came on the scene, and she explained why our universe locally looks like the perfect sphere.
But inflation has claimed that the universe looks fractal globally.
Eternally growing fractal.
So the guiding idea was the perfect sphere for the Greeks.
The concept of beauty in the twentieth century is fractal.
And that is exactly what inflation theory has brought about - the multiverse as a fractal.
And fractal gives all possible colors ...
- But why won't it stop?
- Can not. If it continues to grow, producing more and more as ...
- But is it because ... Why?
- I'll try to show a little better. One way you can look at it is
that, as we said, when we have that energy whose level falls, then that part is not subject to inflation.
But we have two opposing effects - one whose energy drops and one where it does not happen, and that part continues to grow.
So we have a growing effect, more and more of those things that are pushing outside that are being created at all times
and only parts of it experience a decline in energy. So somewhere the energy drops and some parts increase
and the number of those that increase is always, in those models, greater than the number of those where energy has fallen.
And that is why you always have a place out there filled with this repulsive thing that is pushing out.
- If I live in this universe, let's just say it's ours and it has our physics
so it has gravity, atoms and forces, and then if I think of this universe,
then does that universe have the same gravity and atoms as ours? Do you know, do you have a theory?
- No, that's why it's blue.
- Ah!
You're an evil man!
So, there are not only many many universes, but many many types of universes?
- Yes. And do you know how much?
Think like this. 1986 or 1987
people who worked on string theory speculated on how many there were
and concluded that there are probably about 10 in the 1000th degree of different universes.
- Different types of universe?
- Yeah, but nobody took them seriously, because they didn't have any guy that probably exists that would be stable.
String theory is based on the idea that our space is essentially ten-dimensional,
and that six of these ten dimensions are squeezed into something very small,
and that there are four large dimensions remaining - three spatial and one temporal.
But no one managed to prevent those six dimensions from expanding. The universe wanted to be ten-dimensional.
And in 2003 it happened that a few people at Stanford, I was a cosmology consultant at the time,
Kachru, Kalosh and Treveli proposed a mechanism for stabilizing these six dimensions.
Can we see the picture?
This is a picture created by a mathematician, and represents how that six-dimensional space looks.
A six-dimensional space is compressed into five dimensions, but can be compressed in so many different ways,
and there are so many different holes, and since there is so much combinatorial freedom,
the total number of ways it can be compressed is exponentially large.
And for each type of this method, there are different characteristics of our universe that live there,
different laws of particle physics, different energy of empty space, different everything.
And when they calculated the number of these stable compacts, they came to number 10 in the 500th degree.
- Ten to five hundred?
- It's a unit with five hundred zeros behind it. Approximately.
- Oh no!
- Plus or minus something.
At some point they started talking about having infinitely many, but then they reduced it to
- Okay, hold on a second. I have to stop breathing when you speak!
Nick, I haven't asked you anything yet.
Is it a little difficult for you to hear the theory of everything that is open to all possibilities?
I mean, wouldn't a theory be a good theory if ... Just a second, I have a text here ... A good theory ...
- It would be good if the text was good.
- I hope so.
I don't remember where he is.
- You see, you still have nothing against her.
- It seems to me that the theory explaining that anything is possible doesn't really explain anything.
Good theory says why something is, but this guy just said, and these others nodded,
that this multiverse contains every thing of a strange shape imaginable, like what we saw just before,
every way of organizing matter imaginable,
any amount of dimensions imaginable,
every possibility imaginable.
But I say, OK, if that's your idea of ​​science, then go to the toilet and think again, because this is not ...
It's too much!
But I'm just interested in your opinion, Nick.
- You get a similar problem when you only have one universe, if it's big enough.
Let's say it's infinite. Then you will have all kinds of observers that exist somewhere,
and all kinds of illusions.
So whatever measurement you make even in that one infinite universe, you have one observer
somewhere, who imagines making that same measurement.
Then the question is how to test the theories if all the theories you compare predict that
for every possible observation you make, there is an observer who makes that same observation.
Theories seem to support every possible observation.
So this is a problem. And the solution must be to consider not just what the theory says
that certain observations will be made,
but what does the theory say about the frequency of making those observations.
So you have to think this way: if there are all possible observer guns
who make all kinds of observations is interesting
what most observers will see in a given type of universe.
So you mean the faction of observers that will make a certain type of observation.
- Can I ask this question in a different way to you, in fact to all of you?
This universe we are in seems to have a very sensitive set of circumstances.
Gravity is just as it is, the forces that connect atoms are just as they are,
and if you change any of those variables, I think there are six or ten that are very important,
then the universe as we know it would collapse, and we wouldn't be here.
People sometimes ask, like you did a while ago,
how many universes of them all are like ours - where life and intelligent life are possible.
And how come we are in ours?
Are we simply the end result of a set of circumstances,
or are we there because our universe somehow expected us?
- One way to think about it, and what comes from those pictures,
if you have a picture of Andrew with universes of different colors,
if we can only exist in the red universe,
then if you are wondering why we are in the red universe
we are here because we can live here.
We accept this reasoning in other situations as well.
If I ask you why we live on the planet's surface, why we don't live in interstellar space,
the answer is quite clear - we would not be able to survive in interstellar space.
We are on a planet where conditions are receptive to life as we know it, and that is why we are here.
Similarly: why are we in this universe? Simply because we could not exist in others.
And maybe this seems kind of circular, tautological, but what gives it strength
is when you really start to realize that if that picture is true, and there are really huge universes out there,
that it is not just mathematics but reality, then of course we will be in the one in which we can live.
And that's a reasonable explanation if this picture is really true.
- How do you guys know that Andrei is probably right?
Nick, how do you know the answer to your own question?
As you know ... We can't see them, they are moving ever faster than the speed of light.
So how do we answer the question? There is no purpose that can fly over that whole thing.
- I think it would be too much to say that we can know at this point that Andrei is right,
but one of the reasons we take this type of model seriously is just the problem you mentioned -
- fine tuning problem.
So we see that there is some amount of physical constants that seem finely tuned for life.
That's mysterious. Why would they have exactly those values ​​that allow for the emergence of human beings or any complex chemistry.
- And I wasn't even ... I should have told that story much more dramatically, because it's a very specific value.
- There are four different approaches to this topic. It can only be a coincidence,
but by definition it would be highly unlikely that the values ​​would fall out just as they should by mere coincidence.
Of course, if you are religious you may think that God designed it to be as it is
but this explanation creates various kinds of further problems that are well known.
You could be looking for some simple idea basically-
- You may be struck by lightning.
- You could look for some simpler theory that no one came up with, some simple equation
which is simple in itself but from which all these concrete values ​​of persistence would simply jump out.
The problem is, no one has an idea what a simple theory that would be,
and for the fourth time, the one Lind and Gut are exploring,
which is that there is a large ensemble of the universe,
and the values ​​of the constants in these universes vary randomly
and so we get that all or almost all of the possible constellations are values ​​of these constants
implemented or represented in some universes.
But most of these possible universes will not have observers.
Observers will only live in universes where values ​​are conducive to the evolution and existence of life,
complex chemistry.
And that is why all observers will find themselves in universes whose values ​​seem to be finely tuned
because they only see universes that are finely tuned. Everyone else is without observers.
Or at least they have far fewer observers than others.
And that would then explain the impression of fine dining, and the fact that you can explain it through multiverse theory
is one of the reasons behind this theory to be taken seriously.
- You just created a huge array of different types of universes, conveniently getting rid of god
and that can only be a random absurdity. But you have not got rid of the mysterious fact
which you all stick to. And that is, at the heart of this whole system is still that flux,
that gravity that is repulsive and pushes out, sighs and pushes out.
That gravity has a universal presence. Much universal presence.
Why do you all think that this should be taken for granted?
It is an assumption like any other assumption. And you stick to it.
- The thing we bring up here is just the simplest model, and that's why gravity is key.
Of course we can do a lot better, but we'll have to save that for the next reunion, I guess.
Now we are trying to do the simplest job. What we have presented to you
all the time assuming some fundamental law of physics including gravity,
and you already have 10 in the 500th degree of different options. So, that's just the simplest scenario.
"So you're not worried about having to assume there is some basic but universal set of gravitational and physics laws?"
- No, it's a self-limiting rule.
I should probably say something psychological here.
When I lived in Russia, there was one specific rule, and we knew that the right and the only thing was possible.
We will expand that later.
And if we were free from 10 to 500 options, we would be overjoyed.
And then I came to a country that has freedom, and all of a sudden I feel like there is too much freedom, 10 to 500. We need one rule.
I thought: God, what's going on.
- So he likes freedom. What about you Brian?
- The criticism you make, I think can always be addressed.
When you are a theorist, you come up with theories, and even if they are successful you can ask why these ideas.
I think that's a question that can always be asked, and I don't think we can really answer it.
But speaking from my own perspective as a string theorist, I will say why I find these ideas irresistible.
And that's really what Andrew was describing. These guys have developed very interesting cosmological theories,
where all those bubble universes would be out there,
and it is a very interesting cosmology. But let's put that aside for a moment.
We've been working on string theory all these years, and there really is this feature in string theory
where we have more than three dimensions of space. Six, maybe seven other dimensions of space
which, as Andrew said and we saw the pictures, can be curled up into tiny spaces.
And in the eighties, we hoped there was one particular shape for extra dimensions.
And if we get to know him, we will be able to explain all the observed features of the world around us.
Because it turns out that the size and shape of those extra dimensions determine things like the mass of electrons,
or the mass of the quarks, or the force of the forces.
So we had the picture that one day, when we figure out what the shape is for the extra dimensions,
that we will calculate everything, we all agree and finish.
But as we went on, we found more and more shapes for extra dimensions,
we had a catalog of several hundred in the eighties, which grew to several thousand in the nineties,
which then blossomed into, as Andrew put it, 10 in 500 possible different shapes for extra dimensions.
And we were surprised because it turned out not to be the path we thought was going.
But when coupled with a cosmological picture, it becomes very interesting.
You have these 10 in 500 possible shapes, they are realized in all these different bubbles,
and when you have that picture, then the explanation for why things are what they are becomes much simpler:
we see things as they are because we can exist in that particular bubble
with that shape for extra dimensions that is compatible with our biology and chemistry.
- But you didn't describe the biggest bribe we gave you.
- The biggest thing?
- A bribe.
- When was it?
- Here's what happened. In 1998, cosmologists discovered that there was energy in a vacuum.
Empty space is not completely empty, there is something called dark energy, a cosmological constant,
vacuum energy - therefore not empty.
And this is evident in the exponential expansion of the universe at this time.
Five billion years ago, the universe began to expand exponentially.
But exponential expansion is very very slow, don't worry, we have time to finish the discussion.
But the fact is that when string theorists learned about it, they wrote to the director-
No, the director of string theory can't ... OK, one of the main ones ...
- A very, very respected man.
- OK, he mentioned one of the main leaders of string theory in his speech in India
not to know how string theory can account for this exponential expansion of the universe.
And having said that, people were surprised, because Ed doesn't know!
And they were scared, because nobody knows. What's happening? String theory cannot describe our universe.
So everyone got nervous, and went to check how to describe the universe.
And finally we found a way to describe it.
And then we discovered those 10 in 500 different ways to describe it.
But then it turned out to be the value of the vacuum energy that people found through experiments
was absolutely incredibly miniature. It was 10 at minus 120 expected value.
You see, the theorists who count it think this way: if not zero, what is the next number?
The next number was huge, but the experiments came up with something like 10 on -120 of that number.
Which means zero, comma and then 120 zero and then unit.
That seemed absolutely ridiculous.
Still, we now have these 10 in 500 states. Now look at me.
Up here is the theoretically expected value.
It's zero here.
And here is the second, negative theoretically expected value.
Now we will cut 10 into 500 different slits.
And now we are approaching zero. We get to where 10 is at -120.
But we keep cutting, and in this small part, 10 at -120, we have the remaining 10 at 380 slices.
Different types of universes with a cosmological constant, which only stores experimental data.
- I don't know what you said, but it worked out in the end, didn't it?
- String theory allows one to describe the universe using this small vacuum energy value.
And then comes the next step: if the vacuum energy was only a hundred times higher, or even negative - a hundred times higher but negative
in which case we would not be able to live there. This is what the principles of entropy tell us.
Because if the value were up here, the galaxies would have erupted.
If the value were down here, then the universe would have fallen apart before this discussion.
So, we realized that string theory allows one to explain this value of vacuum energy.
So far no other explanation has been proposed.
- Ah, here we are!
So your final defense is that the only explanation that can possibly cover the situation is this explanation
which we cannot test, but which may survive because right near the middle is-
- String theory plus inflation theory together give you the only explanation for the experiment
which was performed ten years ago. So far no one has suggested anything better.
- But if that's your defense - let's have the best explanation ...
Here's an overview of that explanation by Bryce DeWitt. Do you know who he is? He is important I guess.
Bryce DeVit. I'm going where I need to get these quotes.
Although I don't know who I'm quoting.
"I still clearly remember the shock I experienced when I first encountered the concept of multiverse.
The idea of ​​more than 10 in 100 slightly imperfect copies of yourself
which are being shared with even more copies, this idea is not easy to reconcile with common sense. "
"This is schizophrenia with a vengeance," says Brian Stewart.
Martin Gardener, mathematician: "In my layman's view, these are frivolous fantasies.
Certainly the hypothesis is that there is one universe with one creator easier to believe,
but that there are countless billions of billions of worlds whose number is constantly increasing
and which no one has created. "
John Wheeler, Number One whom we all adore in all likelihood, says:
"I don't know. I'm inclined to turn against it. It contains too much physical luggage."
John S. Bell, a physicist from Ireland, says: "It's plain and simply silly."
- Excuse me, if I can break in. One thing we didn't stress too much tonight
is that there are many aromas of parallel universes.
We focused on one that comes from inflationary cosmology.
Most of the comments you make refer to the multiple-world version that comes from quantum mechanics.
The quantum mechanical version of interpreting the idea of ​​multiple worlds is another aroma
the ways in which parallel universes can be obtained, but quite different from the one discussed here.
- In that case, I may not have been fair.
- But there is a criticism that can certainly be addressed. It certainly sounds uneconomical
when you hear that there are all these other universes, but I have to agree with Andrei.
I certainly had the impression in the 1980s and 1990s that there was a universe,
that we will understand his laws, come up with unique predictions, and end it.
This is how it looked to me.
And when that 1998 experiment that Andrey talked about,
who discovered that the universe is accelerating expansion, which means that it is still there today
has those things that push it away, and the amount of that dark energy, as we call it, is so fantastically small,
around 10 to minus 120, we asked ourselves: can we predict ourselves calculating something
starting with some interesting equations that have pi, E, root of 2 - things that appear in natural calculation,
and that at the end of the calculation there appears a zero comma zero zero zero ... 120 zeroes and units.
None of us can ever imagine that we will ever build a computation whose solution is this.
So we're looking for other ways to get that result.
And one of the other ways is that if there are many other universes where the amount of that dark energy
varies from one to the other, then there will be at least one, provided there are enough universes out there,
which has the low value we see.
It's like taking a deck of cards and randomly picking one and throwing out a few,
it's unlikely that anyone will get an ace if I just throw a few cards.
But if there are about 900 people in this room, and even if I had 900 tickets, it means a lot of decks,
and I throw them all out in the audience, I'm sure someone will get an ace pic.
In fact, there are more picks if we have 900 tickets.
- You just explained to us, the reason we're here. If only we were one of those many cards.
- We're just an ace point somewhere. And it's hard for us to imagine calculus in a "unique" universe
in which we get such a crazy small number that is measured.
- But you should be scientists!
Shouldn't you as a scientist try to find some way to test your theory?
If the universe you want to measure ours is moving faster than the speed of light in another direction,
how will you ever know then?
- That's a great question, but another thing to emphasize is-
- Whenever you say the question is great, you never think it.
- No, no, I really mean that.
We described different universes moving away from each other extremely fast,
and this is in some ways a generic case.
But if the two bubbles were very close to each other when they were created, they could shake each other.
And if that happens, it can leave little wrinkles in the radiation we talked about,
on microwave background radiation. And that's why people are looking for these fighters
and that could prove that we were colliding with one of those bubble universes.
So it is not the case that we are completely beyond the ability to test these ideas.
- I'd like to introduce another idea.
People are kind of used to the idea that there should be only one universe.
When we talk about a lot of them, we seem imaginative.
But let's think about it. Let's take all nouns in English, all nouns in the dictionary.
How many are just one? How many are expected to have only one copy of the term?
I know of only two nouns to be found here: "god" and "universe".
So if you have a scientific concept-
- Oh how I wish I could remember another noun.
- If you have the scientific concept of the universe, do you want to put it in the same category as it, or in the same category as "planet", "galaxy" ...
- If you want to get upset, then move on to Mr. Quiet, to Nick.
Because his idea is the most bizarre here. And I don't know how comfortable you will feel after that.
- I'm not sure I want to hold that honorary title.
- That thing is called a problem ... It's called a simulation argument.
I'll summarize and you explain.
You believe it would be possible for the universe to be a stunningly successful computer
who imagines the universe in such a perfect way that everyone in the simulation would
as characters from The Matrix in that little brain, experienced an experience that seems completely real.
I could touch you, and I could feel the texture under my skin.
It would all be a computer simulation. Are you suggesting that a civilization could build such a machine?
- Many have already suggested it. That's one of the options.
The premise of "The Matrix" and the like is that, as we can do simple virtual realities today,
with simple simulated creatures living in them,
in the future, we may be able to build more complex virtual realities on far more powerful computers
with more complex simulated creatures.
Perhaps these creatures would be complex enough to have brains like ours, simulated to such details
such as single neurons and synapses, to make the inhabitants of such simulations aware.
But the simulation argument adds to that
instead of dwelling on the question of how to prove with certainty that we ourselves are not in the simulation,
the simulation argument tries to place a limit on what we can believe in.
And he tries to show that one of the three options is true, but he doesn't tell us which one.
In a sense, this sounds more radical than even some of the multiverse theories we've heard here,
but in another sense it is less radical, for it assumes no unknown physics.
Because we just assume that computers that are much more powerful could be built in the future.
- I think they could be very powerful, because yes I think I'm in a computer simulation
I would look at your face very carefully, because maybe one frame would occasionally skip and then I would notice.
- We can go back to that. People often write to me about such things ...
But never mind. What the simulation argument tries to show is that one of the three possibilities is true.
The first is that almost all civilizations at the stage of our technological development are extinct before they become technologically mature.
Technologically mature in the sense that they have developed all the technologies that we can presently prove to be physically possible
using only physics that can be acquired in a non-controversial way.
- So they make radios, rocket ships, bombs ...
- Yes, we could make big computers the size of a planet and the like,
we could calculate what kind of performance they would have.
We can't make them now, but in maybe a thousand years people will do it.
So, the first possibility is that people at our level simply fail to reach that level of technological maturity.
Maybe they destroy themselves on the way to that.
Alternatively, almost all civilizations that reach technological maturity
they lose interest in creating that kind of ancestral simulation, as I call them.
These would be detailed computer simulations of people like their historical ancestors.
So, they have these powerful computers and the ability to program them,
but they have smarter things to do with their computers and time.
- And here's the third one.
- And the third possibility is that we almost certainly live in computer simulation.
In its full version, this argument requires some theory of probability,
but its essence can be captured very simply and intuitively.
Imagine the first two possibilities are incorrect.
This means that some insignificant factions of civilization at our stage are reaching technological maturity,
and that some negligible factions are interested in creating ancestral simulations,
and devote some nontrivial part of the resources to that end,
in which case you could show that there would be many more simulations of the ancestors,
more than there would have been original streams of history.
Because if you calculate the computing power that technologically mature civilizations would have,
and the computational power necessary to simulate all human brains,
it turns out that these other quantities are a small fraction of the former.
In other words, by allocating a tiny fraction of its computing resources for these purposes,
could create astronomical numbers, billions and billions ...
- So you're saying that if teacher MacGattie gives a school assignment on planet Zentar in another universe:
"Build a universe with extreme precision and make a billion people
with each neuron in its place so that they think they are alive. Start."
And then Perica answered, "Can I use real matter? Can I use energy and math?"
"No, Perice, that would require 50 tons of stuff. We only need to do this bits and bytes."
And then everyone does it in class using bits and bytes, and then next year people just push the "repeat" button?
And then the cost of creating a fictional universe is infinitely less than the cost of building a real one?
- Maybe not infinite, but much smaller. I would go over the question that if you have the ability to use
some advanced form of nanotechnology to transform the planets into computer systems,
using only one planetary computer and only a millionth of its computing power in a tiny fraction of a second,
you could keep many many simulations of human history running.
- So if Perica goes to push a button like this, does that create a high probability that we are in one of such universes?
- Perica may be working on one, but other people will repeat it millions of years later. There would be other simulations over time.
- How do you wake up in the morning?
- To conclude this arc of argument: Assuming the first two assumptions are incorrect
then we come to the conclusion that there are many more simulations than the original.
And if almost all people with our types of experiences are simulated rather than implemented in reality,
we should think of ourselves as being probably typical, simulated people
rather than exceptional people who were part of the original history.
- When you came up with this idea and thought you were more likely to be simulated-
- Except I don't believe it to be true.
- Not? Good.
- I believe the simulation argument will show us that one of these three is true, but it does not tell us which one.
So I think we need to spread our trust across all three options.
We just don't have enough evidence to choose one.
Assuming the discussion works, the third possibility, the simulation hypothesis, is the correct one,
then the reaction of many people is that then we can just go crazy because everything is possible,
but if we think about it, we realize that even if we are in simulation,
the best way to predict what’s going to happen next, to decide what we’re going to do,
that these are still the methods we would use anyway, to observe patterns
in our simulated reality, we derive values ​​from them, and act accordingly.
So the implications are not as radical as they may seem at first glance.
- How much time do we have left?
I don't see anyone stopping us. So good.
Do you guys, collectively, consider the concept of multiverse in which this range of possibilities exists,
including Nick's rather bleak possibility,
that if you think of the universe or more of the universe this way,
do you feel like it's beautiful, or,
to use the Copernican principle of motion, or make us much smaller,
maybe not even real.
- Eh now, I mean, wait ...
- You left us in a rather diminished state, I think, with this idea of ​​so much ...
I liked it more when there was only one, because we were more important in that concept.
- There are many ways to look at it, but I've always felt like every time we downsize
the universe becomes more beautiful.
I mean, it's spectacular for me that we, little beings who are not special to the universe,
we are not in the middle of the universe, we may even be just a simulation, and yet we manage to understand so much.
So to me, this disparity between what we are and the grandeur of what exists,
the greater the distance between the two, the more spectacular our understanding becomes.
I don't feel diminished by it, but it gives me energy.
I also think our aesthetic is evolving and progressing in line with what we learn to be true.
There are many ideas today that, when you asked people 500 years ago what they thought of them,
they would consider them strange, strange and repulsive,
but now we are used to them and our aesthetics have aligned with them, and we now consider those theories beautiful.
Overall, I think we should wait to see if there is evidence for this
or whether we can come up with a better explanation for things that currently have an explanation only within these ideas.
- I'm going to ask this question the other way around.
Sometimes people from Manhattan go to Shanghai and experience it as so big, lush and powerful
that when they go back to Times Square, it seems tiny to them.
They feel like New York has kind of come together.
Let's do it with the universe. Since you all envisioned the multiverse so grandiose and Shanghai-like,
Does the universe you live in seem a little tiny?
We're nearing the end of the program, so I'm just throwing out what comes to mind.
- Even if you have a single universe, if it is infinite then you already have more vastness
than you would ever hope it could be.
Adding other universes to this can have interesting observational consequences.
But if you're only interested in size, you've already got it with standard Big Bang cosmology
where you have an open universe.
- Oh God.
I didn't think I'd get to this.
Do you...
Not!
Bhagavad Gita ...
I'm sorry.
In one of the famous books of the Mahabharata, the Bhagavad Gita,
there is a story about the famous warrior Arjuna.
He addressed Krishna, and asked him, "Can you show me your universal form?"
Krishna refused. But the warrior continued to pray to show him his universal form.
In the end, Krishna consented and showed him his universal form,
and this is the god who devours all, and destroys all, and gives all,
and he is also a lion, and a tiger, and an elephant ...
And he's everything!
And then Arjuna asked him, "Oh no. Please show your normal face!"
And that's the current situation.
Nature is much richer than previously thought.
But with each subsequent step of our realization, she becomes more and more beautiful.
It's actually absolutely exciting and thrilling when you're trying to figure it all out.
And, yes, when you look at it, it somehow seems dangerous. You look at her face and you don't understand what it is.
You might think it's better to do something else.
And that's why a lot of people go into finance.
- But that didn't work.
- See, that's why inflation is better in our theory!
- I can't think of a better way to end the discussion than to stop right here.
I want to thank all of you for your participation.
If you have the final word - feel free, but I think this one was quite good.
Thank you all for coming.