[MUSIC PLAYING] SPEAKER 1: Your new book,
"Until the End of Time," is quite broad and
ambitious in its scope. It's literally
about the beginning to the end of the universe. So I was wondering if you
could talk a little bit about the project of the book
and what you were setting out to accomplish. BRIAN GREENE: Well, I think
you summarized it quite well. My previous books all
focused on particular areas of scientific insight,
you know, try and describe string theory or insights
into the nature of spacetime or the possibility of
parallel universes. Those are the kinds of
things I tackled in the past. This book is really
meant to try to lay out in a coherent fashion the
entirety of the development from the beginning, the
Big Bang, if you will, to the closest that science
can take us to the very end. And within that narrative-- and this is very
different from things that I've written about
before, and no doubt you're familiar from having
looked at the book itself-- there's a focus on what
happens when life emerges, and in particular what happens
when conscious life emerges, and more particularly
what happens when self-aware life emerges, stands
up, looks around, and tries to make sense of not only how
we got here, but tries to make sense of what we should
do while we're here and what's going to happen
into the far future. And the bottom-line
message, if you will, is that our footprint on
the cosmological timeline is incredibly tiny when
seen within the context of the totality, and how
do we deal with that. And that's the
theme of the book. SPEAKER 1: Starting
at the beginning, I was reading the first
few chapters of the book and I was struck by
the incredible elegance of the explanation of how
the universe unfolded. Just as you've described
it, it can basically be boiled down to two natural
forces, entropy and evolution. I was wondering if you could
talk a bit more about that. BRIAN GREENE: Yeah. When you have a project
as big as trying to summarize from the
beginning to the end, the natural thing is to find
the overarching principles that allow you to organize a great
many apparently seemingly distinct phenomena,
but to find them all fitting into some
coherent pattern. And the two qualities
that you described are the two that I used to
organize how things unfold. And I think many of these
ideas are familiar, certainly, to this audience, but
just to be complete, the second law of
thermodynamics, as we teach our students,
our physics students, describes how there's a
tendency of the universe to go from states of order
toward disorder, states of low toward high entropy. And indeed, we see that
phenomenon playing out right along the
cosmological timeline. But one thing that I
stress within that rubric is that the increase
in entropy does not demand or require
or entail that there is the usual intuitive idea of
degradation, of withering away, of falling apart
because you can have an overall increase in disorder
while, at the same time, having local pockets
of order emerge within that particular vector. And that's the
vital reason why we have structure in the universe. You can have pockets
of order forming within the overall
tendency toward disorder. So that's, if you will,
organizational theme number one. Organizational theme number
two, as you note, is evolution. And I think most of us, when
we encountered evolution for the first time,
certainly when I did, we were taught it
within the framework that Darwin and Wallace
gave it to the world, which is in the evolution of species. And in that setting,
we understand, well, how it is that a given
collection of lifeforms can fan out to a very broad,
larger collection of lifeforms through the properties of
mutation and natural selection. But that already
assumes life exists. So what I describe in
the book is a perspective on natural selection
and evolution that has been developed in
more recent times, where it can take place right at the
level of atoms and molecules. So I describe a certain
kind of chemical combat-- not species combat,
but chemical combat-- in which molecules learn
the trick of replication, and those molecules that
replicate faster, more stable, more efficiently
are the ones that will grab more of the natural
resources in the environment, and therefore their
molecular form will dominate the demographics. And then molecular mutations,
where the copying mechanism is imperfect, can yield
other molecules, which may be better or
worse, but those who are better at
replication will, of course, now dominate from
that point forward. So in a sense,
you have evolution is building up structure,
entropy, at some level, is assisting it
when it's creating local pockets of order,
but in the far future, as the narrative
describes, ultimately works in tension with evolution,
degrading structure as we head to the
very far future. SPEAKER 1: That tension
was so fascinating to me because when you're thinking
about it intuitively, you think of the two
principles as being in somewhat of an opposition to each
other, that entropy is just this progression
towards disorder, like how are we evolving these
complex structures of life. But it was really fascinating to
think about it in terms of life is basically a side effect of
the way that entropy unfolds with being countered by
gravitational forces, et cetera. BRIAN GREENE: Yeah. I mean, so there's two
points in that question. The latter is that, without
the force of gravity, there'd be no structure at all. So in the Big Bang,
particles, energy is all moving in an outward direction. And if it was simply the kind
of entropy and second law of thermodynamics
unfolding that we teach in a standard
undergraduate course, where we, for instance, talk
about molecules in a room, those molecules in
a room will simply spread out and fill the room. And if that was what was
happening in the cosmos, the particles in the
Big Bang would simply fill out and spread throughout
the entirety of space, and there would be no
structures that would exist. It's the force of gravity which
radically changes that story. And of course, in an
undergraduate course, we rarely talk
about gravity when we're teaching thermodynamics
and statistical mechanics. But gravity, of course,
has the tendency to pull things together. And because of that,
you can actually reach higher entropy states
by not letting the particles simply fan out, but
rather having some of them come together and yield
structures, like stars, in the process squeezing
out the entropy potential within that matter by
generating heat and light that travels outward. So you get a pocket of order
and an overall increase of entropy in the environment. And we, in some sense,
are just like stars. We are collections of
particles that come together, allowing the entropy
potential of matter to be increased by
virtue of the fact that we've taken raw material
from the environment, we burn it up, we give off
heat to the environment, we keep our entropy low by
virtue of injecting entropy into the environment. So you're right, we're
kind of a sideshow that the universe
leverages to have matter reach its entropic potential. SPEAKER 1: In talking about
the emergence of life, you had this really great
succinct foreword quote about the emergence of life,
"life is physics orchestrated," which really stuck with me. So that's just four words. You've talked about
this a little bit. Can you elaborate a bit more? BRIAN GREENE: Yeah, you
know, we are special, life is special in
some ways, right? We can think, we can feel,
we can react in various ways to the environment. But one of the
beauties of thinking about life and consciousness
within the cosmological unfolding is that we see
deep continuities, right? Just as a star is a collection
of particles that is fully governed by the ironclad
laws of physics, we each are collections
of particles that are fully governed by the
ironclad laws of physics, too. Now, our organization
is more exquisite compared to the organization,
say, in a tabletop, or even in a star. And that allows us
to realize behaviors that are unavailable to
the table or to the star. And that certainly is welcome. That's a good thing. But the bottom-line
message is we are all bags of
particles governed by the laws of physics. And this was a statement
that I made on "The Late Show with Stephen Colbert." It just sort of came out
in a heated conversation, to which he responded hey,
that's a great pickup line. And it is, actually. You should try it out. But that's what I mean by
life is physics orchestrated. We are physics
that is manifested in a highly coordinated manner. And that's really the only
distinguishing characteristic of us compared to the
inanimate objects in the world. SPEAKER 1: So related to that,
what I found fascinating also is, given all the
mysteries of the universe that we've already solved
about how Earth came to be, the solar
system came to be, one of the biggest mysteries
that seems like we're still working out is how a big
bag of particles governed by the law of physics
achieves consciousness and self-awareness like you
were talking about earlier. BRIAN GREENE: Yeah. SPEAKER 1: Do you have thoughts
on how that study is going, and what might be some of
the answers to that question? BRIAN GREENE: Well,
it's the big mystery that nobody has answered as yet. And there are many theories
that are out there. In the book, I
describe those that I find the most compelling, or the
most radical, perhaps, as well. The big question, the so-called
hard problem of consciousness, as articulated by
David Chalmers, is, how could it be
that a collection of mindless, thoughtless
particles like electrons, quarks, and protons
can somehow come together and, in their
aggregate, turn on the lights? How can those particles moving
inside a gloppy gray structure inside of our heads
somehow create the sensations, the
responses, the thoughts that you and I
and everybody else have every moment
of their lives? Where in the world
does that come from if the
ingredients themselves show no evidence of
having any such qualities? Now, one answer to that
question-- and in fact, it comes from David
Chalmers, and others, as well-- is maybe the
particles do have consciousness. You look at that,
you're like, really? Are you going to really put
forward an idea like that? And that's the extent that
some people are led to through beating on
this problem and not being able to make any
progress, or any progress that feels like it's heading
in the direction that will answer the question. So could it be that
electrons and quarks have some proto-conscious
quality, and only by virtue of putting
a lot of them together do you get sort of macroscopic
consciousness, the thing that you and I can recognize
happening inside of our heads? Now, I am not one who is
moved by that perspective. I should say, if it were true,
I think it would be thrilling. I'd love it to be
the fact that we've long since missed that electrons
are thoughtful entities. How spectacular would that be? But I don't see any reason
to go to that extent. In fact, the model
that I think is worth thinking about is
the conversations that were happening in
the 1800s about life, even in the early 1900s. You can say the same thing. How can a collection
of lifeless particles somehow come together and
switch on and become animate? How in the world could
that be possible? And in the old days, the
view was it is not possible. You have to inject
something else on top of the particles, some
vital life force, vitalism. Nobody talks like that anymore. And the reason is because, as
we've gotten better and better at understanding the
structure of life, most people to think about it
have come to the conclusion that it's just particles
and the laws of physics, and chemistry and biology, but
that all reduces to physics, and that's all that you need. And I think that, at
some point the future-- I don't know, 50,
100, 1,000 years, whatever-- we will come
to a similar realization about consciousness,
and we'll look back and smile at how, in the
20th and 21st century, we injected so much mystery
into this quality of the world, when, in reality, it was nothing
more than particles and laws. And look, once you guys develop
a truly conscious AI system-- I don't know how you
prove that, but once you do develop that, I think that
will also be a moment where we're like, yeah, you
organize things correctly, the thing starts
to think and feel. That's just what matter does. SPEAKER 1: One thing that
your book touches on a lot is that there's this companion
philosophical question that goes along with that. You know, as bags of
particles that are entirely governed by physical laws,
how do we have consciousness, but also how do we have
any sort of free will? BRIAN GREENE: Well, we don't. SPEAKER 1: Right. BRIAN GREENE: That's
the end of that. I say that flippantly, but
I really do believe that, as you see in the book. However, there are so
many different definitions of what free will is that you
have to take a statement like that, I would say,
with a grain of salt, or you really have to
plumb it very carefully to understand the kind of free
will that I'm talking about. I'm talking about the
freest kind of free will. I think that's what most of
us intuitively imagine when we think that we have free will. We imagine that we are
the ultimate autonomous authors of our actions. Right? We can think about the world,
we can be affected by the world, but ultimately, when
we act, that action is originating within us. We are not mathematical
beings whose strings are pulled by physical law. And that just is incoherent. We are collections of particles
fully governed by physical law, and every thought that we
have, every action that we take is nothing but those
particles playing out the dictates of the mathematical
equations, the physical laws. So that version of
free will-- and I think it's the intuitive
one-- seems to me to be completely incoherent. Now, what happens when
philosophers and scientists think about these ideas, you can
go in a variety of directions with that sort of realization. And the direction that I go is a
longstanding and well-respected approach called compatiblism,
which is basically finding a new kind of
freedom that you argue, and as I argue in the book, is
as valuable as the old version that isn't true, and
in that way plays the role of a
substitute for the thing that we lost when we recognized
that traditional free will is gone. And as I describe in
the book, my view-- it's not a view that others
haven't articulated in one form or another-- is simply that what
makes us special is not that we can transcend physical
and mathematical law-- we can't-- but rather,
because we are so ordered and so well-choreographed, we
can execute a spectacular range of behaviors that are
unavailable to most objects in the world. And I mean, right here,
even sitting here right now, I just articulated a
thought through a sentence. And I take a step back,
and I'm like, yeah, my particles just did
a reasonably good job of saying what my
other particles were trying to articulate. And I sit back, and I'm
like, thank you, particles, for doing that, or
thank you, physical law, for allowing my
particles to do that. And in that way, I
actually feel a degree of gratification for the fact
that my particles did something that I'm happy with. And when my particles do
things that I'm not happy with, I similarly feel a
degree of remorse. But that's what's going on. And all of it comes
from physical law. SPEAKER 1: What you
touch on in the book as sort of a corollary
to that is it certainly feels like we have free will,
and maybe that's what really matters, that we can
have this conversation, and it doesn't feel like
I'm being ventriloquized to have this conversation. It feels like these
are my actual thoughts. BRIAN GREENE: Yeah,
yeah, no doubt there is some evolutionary
advantage to these collections of particles having the
sensation that they are in control of their actions. Presumably, beings that
have that sensation may be able to navigate the
ancestral environment better than collections
of particles that did not have that sensation. And so it's deeply ingrained
in everything that we do and everything that we think. But you have to bear in
mind that evolution did not equip us to understand the
true nature of the world. Evolution equipped us
in order to survive. And those are two radically
different propositions. So you need to bang really
hard on qualities of the world that you hold true to make
sure that you haven't been led to that perspective
by the survival value that it had over the
course of 100,000 generations in the past. And in fact, you
can even go further. You know, take
quantum mechanics. I think none of us-- at least I don't,
I'd be interested if someone felt
differently-- none of us have quantum mechanical
intuition in our bones. If I pick up an
object and I throw it to anybody who's out
there in the audience, they'll know how
to put their hand and catch it because we have
Newtonian physics in our bones. You don't have to calculate
trajectories to figure out where to put your hand. But if I were to fire
electrons at you, you'd have to do the quantum
mechanical calculation because you would not know
where to put your hand to get the highest probability
of capturing the electron. Why is that the case? 100,000 generations
of our forebears, those who had Newtonian
intuitions survived. Those of our forebears who sat
down on the African savanna and said, let me think about
Schrodinger's equation, they got eaten. So they did not propagate that
genetic tendency into the gene pool, and therefore, it takes
this kind of concerted effort to go beyond what
we are programmed to do in order to figure out
other qualities of the world. And I think a similar
thing applies to free will. We think we have it, we have
the sensation of having it, but that's all that it is-- a sensation. SPEAKER 1: Talking about
survival and evolution in the central
section of the book, you also have a really
interesting discussion of human areas of inquiry, like
religion and the arts, that don't necessarily have
direct connections to our survival of getting
food, reproducing, et cetera. There's some really
interesting discussions about potential evolutionary
antecedents to those areas. And I was curious your
thoughts about why we write poetry, why
we perform music, why we have monotheistic
beliefs, et cetera. BRIAN GREENE: Well, there are
a lot of interesting questions in there. And as you note, there
is a long-standing and continued discussion
or debate about the degree to which these
kinds of behaviors may have been seeded by the same
kind of seeding that gives us Newtonian physics intuition. Could it be the case
that we tell stories-- I mean, what happens? We leverage language early on
in the history of our species. We learn how to communicate. And do we take that
capacity and immediately translate it into
communicating information from one member of the
species to another? Well, that's part of
what we do, but we spend a whole lot of
time-- there's evidence going back thousands
of years, of course-- we spend a whole lot of
time getting together and exchanging
fictional accounts that both members
of the conversation know have nothing to do
with the external world, and yet we feel compelled
to listen to these stories, to repeat these stories,
to modify these stories, to pass these stories on. Why in the world do we do that? What a waste of
time, it seems like. Wouldn't it be better that
we sharpen a few more spears or gather more fruit
and nuts, rather than sitting around
and talking nonsense to each other about things that
never happen in the real world? Now, you could say
maybe it's just an artifact of
having a big brain. A brain gets big enough,
that's a good thing from an evolutionary
perspective, but maybe a side effect
of having a big brain is a brain that
just never shuts up. It never stops telling
stories because it just can't get enough of
that kind of activity. But others have suggested
that maybe there is an evolutionary basis
of this, in the sense that, by telling
stories to each other, we kind of fire up a flight
simulator of engagement with the world, where
we are able to have a whole variety of
experiences that are safe but allow us to imagine
how we might respond if we encountered those kinds of
experiences in the real world. So maybe those of our
forebears who exchanged stories in this manner
were the ones that were better able
to respond quickly, nimbly, and effectively when
unexpected things happened in the world because they had
this body of fictional accounts that they, in some
sense, could draw upon, and in that way guide their
behavior going forward. And there's a whole analogous
version to that kind of story, highly controversial
story, that applies to other activities, the
ones that you mentioned, religion and
creative expression. Like why would we spend
time chiseling figurines? Why did we spend time
painting cave walls? I mean, you look at some of the
caves that have been painted, and for one of our forebears
to have to travel sometimes kilometers in darkness
through underground waterways to find various surfaces
on which they would paint various kinds of
beings that didn't even exist in the real world,
perhaps, why in the world would they do it? It's the same kind of
question with storytelling. And again, a whole variety
of potential evolutionary perspectives have
been put forward. Maybe it allowed groups
to cohere more fully than they would otherwise. So in competition with
other groups out there in a hunter-gatherer
past, maybe those are the ones who triumphed. Or perhaps creative
expression is just the brain's way of firing
up its innovative qualities. It can sharpen its own
ingenuity by taking things in the real world
and rearranging them in distinct patterns, or by just
firing up and examining things that have nothing to
do with the real world but nevertheless allow
creative juices to flow. So those are the kinds of things
that evolutionary psychologists have explored. And I integrate these
kinds of explanations within the context of the book
because, as we started out early on, when you see
entropy and you see evolution as these entwined braids that
take us from the Big Bang through the formation
of stars and planets to the emergence of life, to
the emergence of consciousness, do these principles
continue to guide what happens as we go forward when
you've got self-aware beings now part of the equation? SPEAKER 1: What was
really interesting for me, a recurring theme
throughout the book is that our narratives
happen at different levels of abstraction. BRIAN GREENE: Yeah. SPEAKER 1: So you can sort
of drill all the way down, reductionist-wise, to
the quantum level, where it's just all
about probabilities of locations of particles. And as humans, those sorts
of narratives of the world are not especially
compelling, if we're just-- it's like a
bunch of particles here, a bunch of particles
there, et cetera. You can move up a level
to the Newtonian level, and talk about motion and
momentum and all those aspects of physics. And what I found
fascinating about looking at it from that
perspective is that, as you go up the levels
of abstraction, that's where you can fit in
things like the arts and religion, et cetera. What are these narratives
that mean something to us, and how do we-- an ongoing process of how
we understand the world. BRIAN GREENE: Yeah,
no, I think that really is a central theme of what
I describe in the book because, in order
to have the fullest understanding of the
world, the universe, you need to use the
kinds of descriptions, the kinds of stories
that are most relevant to the
kinds of questions that you happen to be asking. So look, I mean, if
you're interested in the basic ingredients
and the fundamental laws, then certainly the
reductionist account that physics has provided is
the one that you should use. But if you're
interested in life, you don't really want to go
down to the level of molecules and atoms because you want to
deal with the aggregates that allow us to more fully
examine what life is. It's very hard to
see life at the level of an individual electron. You need to synthesize
your reductionist account to have a fuller
story of what life is at the level of
chemistry and biology. And then, as you describe,
I go further than that because the
richest accounts allow us to go up
in scale and think at the level of psychology,
the level of neuroscience, which gives us some insight
into why conscious beings do the things that we do. And when you get
to religion and you get to storytelling
and mythmaking and creative expression,
these kinds of accounts are more closely aligned
with how we intuitively think about the
world, and it's really through this nested
layering of the stories that you gain the most
full tapestry of what it means to be human. The thing that I would
emphasize is that, even though these
stories are each told in a different language,
and even though these stories are relevant for a different
class of questions, a point that I
stress in the book is that the stories need
to be mutually compatible. And oftentimes, that doesn't
have a great deal of purchase, but it does on certain
kinds of questions, such as the free will question. So you can say, well, free
will is just something that happens at the human level. You don't need to talk
about what's happening down the reductionist level. And that is an
incoherent statement, as far as I'm
concerned, if you're talking about the
kind of free will that I was
articulating early on, because that notion
of free will has tentacles that reach right down
to the reductionist account. And to say that
you have free will and you don't need to talk
about the stuff down here is cutting out the
very thing that informs the answer
to the question whether we have free will. So it's a mutual
compatibility of stories that give us insight into
different layers of reality. And as you build them up,
you have the fullest account. SPEAKER 1: So spoiler
alert for those who haven't read the
book yet, there's a bit of a downer in
the end, as the book ends by narrating what
the demise of the universe is going to look like. So can you give us some
insights as to what it's going to look like
when the world ends? BRIAN GREENE: Yeah,
you know, it's interesting that you
describe it as a downer. And I understand where
you're coming from. There was an article
just published in "Time" magazine today, I was
reading it this morning, and it sort of starts
off the first paragraph being how bleak it all
is in the far future. But I think, as you realize from
going to the end of the book, I would not interpret
it that way. SPEAKER 1: Yeah. BRIAN GREENE: But I'm happy to
lay out some of the milestones in the far future
of the universe, just to get a feel for why
it might appear to be dark. And the way I do
that in the book is I make use of a
metaphor that I think is useful for grasping the
incredibly long time scales that you need to
consider in order to really fill out that story. I imagine, and I ask
you to imagine with me, that the Empire State
Building is our metaphor. And each floor of the
Empire State Building, imagine, represents a
duration 10 times that of the previous floor. So I'm using a spatial
metaphor to talk about time in the far future. And in this scheme, everything
from the Big Bang until today extends from the ground floor
to just above the 10th floor. 10 to the 10 years, 10 billion
years since the Big Bang. And from here, we
just go exponentially far into the future. I'll take you through
a couple of the floors. By floor 11, we
find that the sun will swell to over 200
times its current size, swallowing up the inner
planets, possibly the Earth. By floor 12, the
distant galaxies will rush away faster
than the speed of light, leaving us floating
in a sea of darkness. By floor 14, most stars will
use up their nuclear fuel and will fade to black. By floor 19, the Earth, if it
wasn't swallowed up by the sun back on floor 11, it will
now spiral into the dead sun because it loses energy through
gravitational radiation. By floor 30, most
stars and most galaxies will fall into the galaxy's
central black hole. By floor 38, protons,
the very heart of matter, will likely
disintegrate, meaning that all complex matter
by that point goes away. By floor 50, if there are
any cogitating beings left in the world, which is hard to
imagine, as matter falls apart, but let's just, for
argument's sake, imagine that there's
some thinking being that still exists out
there in the cosmos, that being will think its final
thought by the 50th floor because it will burn up in its
own entropic waste generated by the very process
of thought itself. Between floors 68 and
the peak, black holes, which will be the only
things that are still hanging around in a
bath the particles, they will evaporate
through Hawking radiation, leaving us floating in an
endless sea of particles wafting through an ever
colder, ever larger universe. That's it. Now, that's where
the bleakness-- SPEAKER 1: Yes, that's
the downer part, yeah. BRIAN GREENE: [? --no ?]
[? doubt ?] [? comes ?] [? from. ?] But you know, here's
a different way of thinking about it, which is there has
been a tendency throughout human history to imagine that
there is some external purpose, some external meaning, and
all we need to do is go out and find it or carefully listen,
and the universe will provide us with those sorts of answers. And this kind of-- look, that could be true,
but there's very little or no evidence for that. And this kind of narrative
from the beginning to the end, I think, makes it
quite clear that there is no ultimate purpose,
there is no ultimate meaning. We are the product of the
purposeless, mindless laws of physics playing
out from the Big Bang until today and on
to the far future. But having said that,
think about the fact that we are here by
virtue of the fact that a whole collection
of quantum processes, stretching back to the Bang, a
virtually infinite collection of quantum processes,
each of which could have turned out
that way instead of this, turned out in just the right
way to allow us to exist, which means that,
against spectacular odds, we somehow are here. And it's not just
that we're here. We are organized, as we
discussed, in the right way, that through what I like
to describe as a flitting burst of activity we
can create beauty, we can illuminate mystery,
we can experience wonder. And to me, that gives that
deep sense of gratification that really almost borders
on reverence for the fact that we are here and
can do these things. And in a world that is
deeply distressing at times, incomprehensible in various
ways, shocking in other ways, to me, that kind of
reverence injects something that is vital and valuable. And to me, in the
current environment, something that I think adds
an incredibly deep layer of satisfaction in an
otherwise distressing world. SPEAKER 1: My favorite
section of the book at the end was talking about all
the wacky things that will happen as matter
disintegrates, et cetera. Just with quantum probabilities
and the vast expanses of time, eventually weird
things will happen. Maybe bobbleheads
will materialize in deep space, et cetera. My favorite was the discussion
of the Boltzmann brains. BRIAN GREENE: Yeah, Boltzmann
brain is a very curious idea, and it is a relevant idea well
beyond the peak of the Empire State Building. So you can say I sort
of took you from today up to the hundredth
floor, if you will, of the Empire State Building. But is that truly it? And what you recognize
is that the combination of virtually unlimited
time, together with the probabilistic
nature of the quantum laws, yields a very
potent combination. Because if quantum
mechanics says that something can happen,
even with an incredibly small probability, if
you wait long enough, you're virtually assured
that that unlikely event will, at some point, happen. And when it comes to
the nature of thought, the most probable, although
incredibly unlikely, event that the universe
allows to happen is that those particles that
I mentioned that are floating through the void, every
so often, a couple of them can smash into each
other and stick together, or through the energy
of their collision create a new particle. And every so often, a
third particle can come in. Sometimes they'll fall apart,
but sometimes it will happen. Again, if you wait
long enough, one of the processes
that can happen is particles can just
randomly come together to yield a brain, a brain that
can be imprinted by virtue of the particle arrangement
with the very thoughts that you or I currently possess. So imagine that my
brain, which is just a collection of particles
in a certain configuration, is reproduced in the far
future out there in the void. Well, that brain
floating out there, perhaps, would think that
it's at Google having this conversation right now,
but it's completely confused because it just came together
through the random motion of particles. Now, you have to wait a very
long time for this to happen. One of the estimates
that I give in the book is the exponential Empire
State Building took us up to 10 to the 100 years, a familiar
number for everybody here, but the length of
scales that you'd have to deal with for Boltzmann
brains is 10 to the 10 to the 68, a double exponential. But if you've got
unlimited time, who cares how long it's going to take? There's nobody
sitting around saying, when is that brain going
to form in the void? There's no other brain
waiting for it to happen. So this is a curious idea. Physicists typically find
it a very disturbing idea. Not because it's weird, right? We're all happy
with weird stuff. What's really disturbing about
it is, if you ask yourself, or if I ask you, perhaps, where
did your brain come from-- I know it sounds
kind of personal, but I don't mean it in sort of-- I'm not trying to intrude
on your personal space, but I think most
of us would give an account that would say, look,
I was born, and my parents, they were born,
and you'd sort of trail it all the way
back, perhaps even go back to the Big Bang. And that's an interesting story. But here's the thing-- the number of brains
that can be created in that conventional
manner is relatively small compared to the number of
brains that can form in the void if you're waiting
for an effectively infinite amount of time. So if you ask yourself, by
sheer dint of probabilities, are you one of those
brains that formed in that very rare process
which started at the Big Bang and yielded the brain in the
manner that you've described, or is it more likely that you're
one of those brains that's floating in the void. And since there's so many
more of those compared to the conventional
approach, the odds would suggest that
it's more likely that you are a brain floating
in the void who just told a very quaint and beautiful story
about starting at the Big Bang and being born in the
traditional human manner, but a story that's
completely false. And the disturbing quality
of that conclusion is-- take my brain. Imagine it's now actually
formed in the void. That brain thinks it understands
the laws of physics, quantum mechanics and
general relativity, because that brain seems to
remember having taken quantum mechanics and general
relativity, across the water, over there at Harvard,
and seems to recall looking at all the data
that confirm those theories, but all that's fake. All of it's false
because the brain just came together right now. So that brain now can't
trust anything at all. So [INAUDIBLE] skeptical
nightmare that happens. The brain can't even
trust the very reasoning that led us to conclude
that the brain should form. So you've undercut
all rationality when you allow these Boltzmann
brains into the story. So we physicists tend
to use this possibility as a diagnostic tool,
that if our theories allow for this to happen, we have
to find some means of dealing with that conclusion or
modifying the equation so it can't happen in order that we
don't ruin rationality itself. SPEAKER 1: I
appreciated that there were some reassurances in
that section of the book that the likelihood of us
actually being Boltzmann brains right now is still
relatively low. There is a chance that
Boltzmann brains might not form. BRIAN GREENE: And those
are the kinds of theories that people develop. They try to develop theories
where perhaps the universe ends before there's enough time
for a Boltzmann brain to form. So you find physicists
who start to be excited about the
demise of the universe because now you have a more
self-consistent story that you can tell if the timescales
don't reach, say, 10 to the 10 to the 68
years into the future. That's only one way
that people have tried to deal with
this conclusion, but it certainly
suggests the extent to which people are
willing to go in order to avoid the problem. SPEAKER 1: I think
it's a good time to open it up for questions. AUDIENCE: So you mentioned that
your compatibilist perspective about basically coming up
with a more reduced but still basically mapping to human
intuition what freedom means, would a conscious AI with full
self-knowledge of its own code and memory be able to
have any kind of free will under that perspective? BRIAN GREENE: Well,
again, if you're using the definition of free
will that I'm describing, the answer would be yes
because, if it was sufficiently sophisticated, it would
have a broad range of behavioral responses that
it could execute in response to various stimuli
that it encountered in the external environment. And that, to me, is the
freedom of relevance when we're talking
about us humans, and therefore,
presumably, can be generalized to any
other structure that has that capability. The point is it's not
freedom from the tyranny of mathematical
laws, it's freedom from restrained
behavioral responses that has long constrained
the inanimate world. So if you can take
the inanimate world and allow its behavioral
responses to blossom, then you're in exactly
the same situation. And that entity,
by this definition, would have free will. AUDIENCE: But if it has
perfect self-knowledge, it can see the code paths
that led to any action. So you could say that,
given a certain input, it's completely deterministic in
a way that completely cuts out quantum anything. BRIAN GREENE: So you will
note that, in my remarks, I never used the
word deterministic, I never used the
word indeterministic, and, in our discussion
of free will, I never invoked
quantum mechanics. Why? It's irrelevant. What do I mean by that? Well, often people say,
in a classical world, then it's fully determined,
and clearly there's no such thing as
free will, right? You tell me the positions
of the particles now, you tell me their
velocities, and then you just turn the
Newtonian crank, and that will fully determine
what happens in the future. Clearly, no room for a
volitional being to intercede in that progression. Then people come along and say,
but with quantum mechanics, all of a sudden there's a window
opening because, now, it's not fully determined,
only the probabilities of one or another
outcome are determined. And they try to slip
free will in there. But let's think about it. If you have an indeterministic,
probabilistic set of laws, then you have random outcomes
governed by the measures of quantum probabilities. Is a random outcome
somehow a place where you're going
to put human freedom? I don't think so. When we have an intuition
about free will, we're not imagining someone's
flipping a coin back there, and that's how our actions
are being determined. And if that's what's going
on, I don't feel any better than I do in the classical
description of the world. So deterministic
and indeterministic is a complete red herring. It is irrelevant to
the conversation. What matters is, is the
progression of the world governed by laws? Is there a lawful
progression, regardless of what those laws are? And if the answer
to that question is yes, then the
kind of free will that I was talking about at
the outset does not exist. And so it doesn't
matter the system. We are that AI system
that you're talking about. That we happen to be flesh
and blood, who cares? We're exactly the
same situation. And if I could look internally
and fully understand the workings of
my brain, my code, it wouldn't change the
conversation one single bit. AUDIENCE: Have you
heard of angled worlds? BRIAN GREENE: Angled? AUDIENCE: Mangled. BRIAN GREENE: Mangled. I don't think I have. AUDIENCE: It's a theory
in quantum mechanics where basically, when two
probabilities get sufficiently small, they interfere with
and destroy each other. And this is one of the
theories I was wondering if you'd heard about about
addressing why Boltzmann brains might not happen. BRIAN GREENE: I'm
not familiar enough to give a coherent answer
to that particular approach, but again, much as we
were describing before, people have invoked a whole
variety of different techniques to try to argue that
the kinds of processes that would yield a Boltzmann
brain will never be realized. None of them, at the
moment, have sort of caught fire and
convinced the community that this is no longer an issue
that needs to be thought about. So it's very much
an ongoing question. AUDIENCE: Jumping back a little
bit to the discussion of where things like storytelling
and art-making came from, it seems like there's a tendency
in these discussions of where did these things come from
to talk about them in terms of or's. Maybe humans tell stories
because this, or maybe-- are there any
frameworks that you know of that take these ideas-- obviously, it might
not be an or or it may not be an inclusive or. It might be an inclusive or. Are there any
frameworks that talk about looking at these
things in conjunction, like whether the probabilities
are higher if, you know, telling stories gets you
this and this and this? BRIAN GREENE: Right. You know, there are a
variety of different voices that chime in on a
question of that sort. Some have a very anti sort of
adaptionist perspective, which basically says anybody who
tries to invoke survival value to these
kinds of behaviors is overstepping the bounds
of evolutionary ideas, and telling just so
stories that try to give us some semblance of
coherence for the behaviors that we see human
beings engage in. And many of those folks would
say that's a big mistake. It's a big mistake. One should simply recognize that
evolution and natural selection have their place, but if you
try to push those ideas further to truly gain an understanding
of all of human behavior, you're just pushing
it into a domain where it no longer applies. So you have to be very careful. And I think the most
thoughtful of researchers and practitioners try
to maintain that care. And I think that's where a
lot of those or's come from, because look, it's pretty
hard to do experiments to, say, rerun the
evolutionary unfolding, to really see why it was that
individual X did Y or seeded that behavior into
the gene pool. And so I think the
best that you can do is to make arguments
that seem convincing. And one of the traditional
arguments of this sort is-- and the most familiar, I'd say,
it's often used as the gold standard, if you will-- why is it that we
have a tendency to like sweet foods
and fat foods? Answer, those of our forebears
in the ancient environment who stocked up on
fruits and nuts were the ones that could
survive when times turned lean, and therefore that predilection
for those kinds of foodstuffs was seeded into the
future gene pool. So we go and we have
Haagen-Dazs or we have [INAUDIBLE] whatever. And it's no longer viewed
as a health promoter, but the link to our evolutionary
past seems quite convincing. To make that same
kind of argument about religious affiliation,
the telling of stories, creative expression
is much, much harder. So for instance, Steve Pinker,
one of the world's leading thinkers in this kind
of domain, his view is that music-making
and most art-making he does not consider to
have an evolutionary basis. In fact, he famously calls
them cheesecakes of the mind. They're foodstuffs of no value
that leverage or parasite, if you will, on ancient
qualities that did have adaptive value. If we were sonically attuned in
the ancient environment, then we'd understand our
environment better. If you could hear a footstep
or if you could hear some lion or leopard, if you were really
attuned sonically to the world, then presumably you
had some survival value associated with that. And he views music
as something that leaps beyond the adaptive
value of that sonic sensitivity to kind of just push our
pleasure buttons in a way that has no adaptive value
whatsoever, just like eating cheesecake
has no adaptive value in the modern world. And there are some who agree
with that, some who don't. I, however, find
it quite convincing to think about the role
of these activities in developing and
sparking and nurturing the innovation,
the ingenuity that allowed us to create
the things that allow us to be in this room right here. So I'm not particularly
convinced by his perspective, although I totally get it. And that's where, again, one
of these big or's comes from. So at the end of the
day, one thinks carefully about these arguments and comes
to some intuitive understanding of which way of
thinking about the world seems to be most convincing. And it's very hard
to nail it down. I mean, I come
from a world where you make your case
by calculating, say, the electron's magnetic
moment to 10 decimal places, then you compare it decimal by
decimal to the observations. That world is not
one that's easily extended to the
kinds of questions that we're talking about now. SPEAKER 1: We have an
online question, as well. "How much do we know about what
our primitive ancestors, say 100,000 years ago, thought
about the meaning of existence, and when did we start
thinking that way?" BRIAN GREENE: Yeah, so it's
sort of a similar version of the question that we just
had, which is not much, right? I mean, all of recorded
history goes back, you know, whatever,
5,000, 6,000 years, right? And the beautiful way of
thinking about the past, the cosmic calendar that
Carl Sagan introduced, where you imagine that all of
cosmic history from the Bang until today is in a
single calendar year-- the Big Bang happening on
January 1st-- you ask yourself when did modern humans
appear, well, we appeared at 11:40 PM on
New Year's Eve, right? And you ask yourself, where
did recorded history start? Well, that happened at
10 seconds to midnight. So if you want to go further
back, it's very hard. And therefore, you're
led to speculate or you're led to try to
imagine a pre-recorded history that naturally, seamlessly
melds into the history that we know about. You say things
like, look, if we, as a species, or some
members of our species, wrote the epic of
Gilgamesh from 3,500 BC, well, if in those early
days we were spending time in chiseling into
cuneiform tablets some story about a demi-god who
was out there trying to find immortality, you have to imagine
that we were also telling stories way before
that, even though they were in an oral tradition
that wasn't recorded. Does that seem reasonable? It seems reasonable to me. It's hard for me to imagine
that we started to chisel and it's, OK, now the first
story, we've never had practice telling stories before. So that's the kind of
reasoning that's used, but it's very hard to give the
kind of convincing explanation that we're familiar
with, like I was saying, from, say, fundamental physics. AUDIENCE: I noticed
the title of your book is "Until the End of Time." And I'm wondering,
since entropy basically contributes to the
direction of time, do we reach a state
of maximal entropy where particles just don't
interact with each other, and does time cease or does it
fluctuate back and forwards? BRIAN GREENE: Yeah, so
it's a great question. And one has to
really bear in mind that the second law
of thermodynamics, this increase of entropy, is not
a law in the conventional sense of the law. What do I mean by that? What I mean is the second
law of thermodynamics should really be called
the second tendency of thermodynamics, the second
overwhelming likelihood of thermodynamics, because it's
a probabilistic statement that says it's overwhelmingly likely
that, if particles are seeded out to the world, they will
evolve in a manner that increases their entropy. But that tendency can
be violated, right? I mean, if I take a
handful of 100 pennies and I throw them on
the floor, we all know that it's highly
likely that it'll be roughly 50 heads or 50
tails in that grouping. We also know, however unlikely,
that it could turn out that they're all heads. We wouldn't want to bet on it. We wouldn't want
to hold our breath waiting for it to happen. But that move toward order, that
move toward low entropy is not, in some sense, in violation
of the laws of physics, it's just highly unlikely. And similarly, the move
toward order in the universe is just an unlikely
move, it's not one that the laws of
physics prevent. So even if we do
reach this state that looks like maximal entropy of
particles filling the void, much as we're talking about
with the Boltzmann brains, those particles can,
like the pennies, they can do the analog
of landing all heads. If we wait long enough, the
pennies will land all heads. If we wait long enough, some
structure, however unlikely, however much it violates the
second law of thermodynamics, will happen. So you never reach a
state of ultimate stasis where absolutely
nothing can happen. You reach a state
where it's increasingly unlikely for things
to happen, where the timescales for
those unlikely things gets longer and longer. SPEAKER 1: So we have
one more online question that relates to stuff we
were talking about earlier with mutual compatibility. "Scientific advances
tend to contradict traditional explanations. What new sources of ultimate
meaning have arisen? For example, human
space colonization, efforts towards artificial
superintelligence, or the simulation hypothesis." BRIAN GREENE: Yeah, so
it's not obvious to me that scientific advances
tend to contradict traditional explanations. Some scientific advances do,
but a great many scientific advances confirm
our intuition, it's just our intuition is built
up on a particular scale, and the advances that are
relevant to that scale will confirm them. When we go beyond
those scales, we find things that are
quite unfamiliar. So I think of the
various possibilities that the questioner
asked, the simulation hypothesis I think is perhaps
the most radical of all, which is, again, familiar to you
guys here, the possibility that we're in some
futuristic supercomputer run by some kid in a
futuristic garage, and all that's happening
here is we are playing out the programming that that kid
in the garage has set in motion. Now, again, do I consider
that a likely scenario? I don't. I find it a useful
scenario to think about because it is a version
of reality in which there is a version of a god. That kid is the god,
created this world. But it's not supernatural. That kid is governed
by the laws of physics at that higher level of reality. And that would be a version
that would be completely compatible with accounts of the
world that imagine that there's some intelligence that guides
the cosmological unfolding. Nick Bostrom at Oxford makes
a very interesting argument along the lines of the Boltzmann
brain argument that I gave before, which is it is
very difficult to create a real universe, it's hard
to spark a new Big Bang, but it might, in
the far future-- or maybe now, if we're
in that simulation-- it may be very easy to
create simulated worlds. You know, just fire them up one
after another after another. So if I ask you, are we
in the real universe that came from the real
Big Bang or are we in the simulated universe
where there was a simulated Big Bang, again, if you're willing
to just go with the odds, there are many more simulated
worlds compared to real ones, and therefore, if
you throw a dart you're more likely to
hit a simulated world than a real one, and
therefore, perhaps it's more likely that we are right
now in a simulated world. Again, do I buy that? Not in a deep way, but I find
it a very interesting argument to think about. In fact, people
have written papers, how should you behave
if you think that we are in a simulated world? And if you guys think about
this for half a second, I think you'll come to
the same answer that was in this paper, which is
that kid doesn't want to waste CPU on someone who's boring. No wallflowers, right? They get eliminated
from the reality. So you better be
pretty damn interesting if you want to continue
existing in the simulation. AUDIENCE: Again, going back to
this interesting idea of why do we do art and storytelling,
I liked your idea of evolution and entropy in interplay. When we do art,
when we make music, aren't we creating
a bunch of entropy that, if we didn't do it, we
would create less entropy? BRIAN GREENE: Through
any action at all, the answer is absolutely yes. And that gives us
a nice, uniform way of thinking about
all of activity, whether it's activity of a
lifeform or activity of a star. It all fits into that overall
progression [INAUDIBLE] the unlikely possibility
of entropy going down that, over long timescales,
we believe will happen. So from that perspective,
you don't gain much insight into the kinds of behaviors that
you were making reference to. But if you then use
the other strand of the explanatory chain,
if you then use evolution, and if you buy into not,
say, the Steven Pinker argument, but if you
buy into the possibility that these behaviors
go all the way back-- I mean, there is example of
rudimentary musical instruments go back 60,000 years, right? So if you imagine that it was
these kinds of activities that really distinguished
our creative capacities, then you start to have a
coherent account that you can at least begin to develop. I mean, one way of
saying it is this. If there were a
humanoid race, say on this planet of
Vulcan-like beings-- and I don't mean that
derogatory to the Vulcans, I've all due respect
for them, but what I mean by that is beings that
were completely rational, only spend their
time on things that will enhance their own
survival in the most obvious, flat-footed
way of getting more food or having better
shelter, and you have those beings in
competition with beings more like ourselves,
who waste time making archaeological instruments
that we then can find or painting cave walls
or telling stories, I suspect that it's these more
irrational beings that win out against the more rational ones, because it's only through
those kinds of behaviors that you come upon
striking new insights that allow for innovation. And it's that
willingness to waste time, it's that
willingness to allow the creative juices of flow
freely that, ultimately, I think, allowed us to be the
dominant species in the world. AUDIENCE: So you
don't think there'd be a lot of difference
in the entropy created by us versus the Vulcans. BRIAN GREENE: Yeah, from
an entropic standpoint, there wouldn't be much of a
difference because, if you de-focus your eyes-- and sometimes I do this-- if you de-focus your eyes and
you look around this room, and all you see are
collections of particles banging into each
other, fully guided by mathematical equations,
whether those particles are telling stories, creating
art, or just sort of sitting around watching television,
it doesn't make any difference to that de-focused
view of the world. And that's the
reductionist account. It's a correct account. It's not a particularly
useful account for understanding the kinds of
questions that you were asking. And it's a kind of
leveler, in that sense. And if you then want to
go beyond that leveling, you have to refocus
your eyes and really focus on what actually those
collections of particles are doing. SPEAKER 1: Thanks so much,
everyone, for coming. BRIAN GREENE: Thank you. [APPLAUSE]
