Kind: captions
Language: en
the following is a conversation with
brian greene theoretical physicist at
columbia and author of many amazing
books on physics including his latest
until the end of time mind matter and
our search for meaning in an evolving
universe
this is the lex friedman podcast to
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in the description and now here's my
conversation with brian green
in your most recent book until the end
of time you quote bertrand russell from
a debate he had about god in 1948
he says quote
so far as scientific evidence goes the
universe has crawled by slow stages to
somewhat pitiful result
on this earth and is going to crawl by
still more pitiful stages to a condition
of universal death
if this is to be taken as evidence of
purpose i can only say that the purpose
is one that does not appeal to me i see
no reason therefore to believe in any
sort of god
that's quite a depressing statement as
you say this is a bleak outlook on our
universe and the emergence of human
consciousness so let me ask
what is the more hopeful perspective to
take on the story
well i think the more hopeful
perspective is to more fully
understand
what was driving bertrand russell to
this perspective
and then to see it within
a broader context
and really that's in some sense what
what my book until the end the time is
all about but
in brief i would say that there's a lot
of truth to what bertrand russell was
saying there when you look at the second
law of thermodynamics which is the
underlying scientific idea that's
driving this notion that everything's
going to wither decay fall apart yeah
that's true second law of thermodynamics
establishes that
disorder entropy in aggregate is always
on the rise and that is indeed
interpretable as disintegration and
destruction over sufficiently long time
scales but my view is when you recognize
how special that makes us
that we are these exquisitely ordered
configurations of particles that only
will last for a blink of an eye in
cosmological time like terms the fact
that we're here and we can do what we do
to me
that's just
really something that inspires gratitude
and wonder
and and a sense of of deep
purpose by virtue of being these unique
collections of entities that happen to
rise up look around and try to figure
out where we are and what the heck we
should do with our time
so it's not that i would disagree with
burch and russell
in terms of the
basic
physics and the basic unfolding but i
think it's really a matter of the slant
that you take on what it means for us
so maybe
we'll skip around a bit but let me ask
the biggest possible question then you
said purpose so what's the meaning of it
all then
is uh is there a meaning to life that we
can
take from this
from this brief
emergence of complexity that arises from
simple things and then goes into
a heat death that is once again returns
to simple things as the march of the
second law the thermodynamics goes on i
think there is but i don't think it's a
universal answer
and so i think throughout
the ages there has been
a kind of quest for
some
final way of articulating meaning and
purpose whether it's god
whether it's love whether it's
companionship i mean many people put
forward different ways of
taking this question on
and there is no one right answer when
you recognize deeply
that the universe doesn't care there is
nothing out there
that is the final answer it's not as
though we need a more powerful telescope
and somehow if we can look deeply into
the universe all will become clear in
fact the deeper we've looked both
literally and metaphorically
into the universe and into the structure
of reality the more it's become clear
that we are just a momentary byproduct
of
laws of physics that don't have any
emotional
content they don't have any intrinsic
sense of meaning or purpose
and when you recognize that you realize
that searching for the universal for
this kind of
a question
is a fool's errand every individual has
the capacity to make their own meaning
to set their own purpose and that's not
some platitude that is what we are
because there is no fundamental answer
it's what you make of it and however
much that may sound like a hallmark card
this really is the deep lesson of
physics and science more generally over
the past few hundred years well there's
some level where you can objectively say
that whatever we've got going on here is
kind of peculiar
it's kind of um
special in in in in terms of complexity
and maybe you can even begin
to measure it and like come up with
metrics where
whatever we got going on on earth these
like uh
interesting hierarchical complexities
that form
more and more sophisticated biological
system that seems kind of unique when
you look at the entire universe
the um
the observable part that we can see with
our tools i mean
so i have to ask as you described in
your book once again
uh schroedinger wrote the book what is
life based on the few lectures he gave
in 1944
so let me ask
the fundamental question here
what is
life this particular thing we got going
on here this pocket of complexity that
emerged from such simple things yeah
it's a tough question i asked that
question even to richard dawkins
once
and i already have my preconceived
notion which he pretty much confirmed
which is
if one could give an answer to that
question that allowed you to sort of
draw a line in the sand
between the not living and the living
then perhaps we would have the insight
that we yearn for and trying to say what
is so special about life but the fact of
the matter is it's a continuum there's a
continuum from the things that we would
typically call non-living inanimate to
the things that we obviously call
adamant and full of the currents of life
somewhere in there
it is a question of the complexity of
the structure the ability of the
structure to
take in raw material from the
environment and process it through a
metabolism that allows the structure to
extract energy and to release entropy to
the wider environment
somewhere in those collections of
biological processes is the
necessity or the necessary ingredients
and processes for life but
drawing that line in the sand is not
something that we're able to do but i
would agree with you
it's deeply
peculiar
it may in fact be unique
but it may not it could be that
the universe is such that under fairly
typical conditions a star
that's
a well-ordered source of low entropy
energy that's what the sun is together
with a planet being bathed by that low
entropy energy together with a surface
that has enough of the
raw constituents that we recognize are
fairly commonplace result of supernova
explosions where star
spews forth the result of the nuclear
furnace that is the core of a star it
could be
that all you need are those fairly
commonplace conditions
and maybe life naturally forms like the
james webb space telescope right is
going up hopefully in december and one
of the one of the goals of that mission
is to look at atmospheres around distant
planets and perhaps come to some sense
of how special or not
life or leaf life as we know it is in
the universe
which part of the story of life
let's stick to earth for a second do you
think is the uh is the hardest if you
were like uh
a betting man like which part is the
hardest to uh make happen is it the
origin of life again we haven't drawn
the line of worth
as you say uh the line between a rock
and a rabbit
um
that part is it uh complex organisms
like multicellular organisms
is it uh
crawling out of the ocean where the fish
somehow figured out how to crawl around
is it then the
uh us homo sapiens
as we like to think of ourselves special
and intelligent
uh or is it somewhere in between as you
also talk about
again very hard to know at which point
this consciousness yeah
emerge like if you if you were to sort
of took us
a survey and made bets
about other earth-like planets in the
universe where do you think they get
stuck the most well i would certainly
see if we're going to go all the way to
conscious beings like ourselves i would
put it at the onset of consciousness
which again
i think is a continuum i don't think it
is something that you can draw the line
in the sand but there are obvious
circumstances there are obvious
creatures such as ourselves where we do
recognize a certain kind of
self-reflective conscious awareness
and if we think about what
it would require for a system of living
beings to acquire consciousness
i think that's probably the hardest part
because look
take earth
and recognize that it weren't for you
know some singular event 65 million
years ago where this large rock slams
into planet earth and wipes out the
dinosaurs maybe the dinosaurs would
still rule the planet and
they may well have not developed the
kind of conscious awareness that we have
so
for billions of years on this planet
there was life
that didn't have the kind of conscious
awareness that we have and it was an
accidental event in astrophysical
history that allowed a mammalian species
like us to ultimately be the end product
and so yeah i could imagine there's a
lot of life out there
but perhaps none of it's
wondering what's the meaning of life or
trying to make sense of it
just going about its business of
survival which of course is the dominant
activity that life on this planet has
practice we are a rare exception to that
and i really appreciate that you lean
into some of these unanswerable
questions to me today but the
so you think about consciousness
not as like a phase shift the binary
zero one you think uh
it was a continuum that humans somehow
are maybe some of the most conscious
beings on earth
so you're so
i mean people will dispute that
yes i mean whoa and it's a very hard
argument people will dispute that rocks
probably will stay quiet on the matter
maybe not right for the moment they're
waiting for their opportunity but but
but i i i agree that um look even when
you and i look at each other i
am not fully convinced
that you're a conscious being right i
mean i think that you are on to me i
mean your behavior is such that that's
the best explanation for what's going on
but of course we're all in the position
of only having direct awareness of our
own conscious
being and therefore when it comes to
other creatures in the world we're in a
similar state of ignorance regarding
what's actually happening inside of
their head if they have a head and so
it's hard to know
how singular we are but i would say
based on the best available data and the
best explanations we can make yeah there
is something special about us i don't
think that there are fish walking around
and you know
coming up with you know existentialism i
don't know that there are you know dogs
walking around who've developed an
understanding the general theory of
relativity i mean maybe we're wrong but
that seems the best explanation
what do you think is more special
intelligence or consciousness
i think consciousness and i think that
there's a
deep connection between these ideas they
are distinct but they're deeply
connected but
look i mean to me and to of course many
philosophers actually coined a name for
this the heart problem of consciousness
you know david chalmers and others
as a physicist i look at the world and i
see
it's particles governed by physical law
we can name
them you know we've got
electrons we've got quarks that come in
various flavors and so forth we have a
list of ingredients that science has
revealed
and we have a list of laws that
seemingly govern those ingredients and
and nowhere in there is there even a
hint
that when you put
those particles together in the right
way
an inner world should turn on and it's
not only that there's no hint
it's insane i mean it's ridiculous
how could it be
that a thoughtless
passionless emotionless
particle
when grouped together with compatriots
somehow can yield something so deeply
foreign to the nature of the ingredients
themselves so so answering that question
i think is among the deepest and most
difficult questions that we face
do you
think
it is in fact a really hard
problem
or
is it possible
i think you mentioned your book that
it's just like almost like a side effect
it's an emergent thing that's like oh
it's nice it's like a nice little
feature
yeah well i mean when people use the
phrase hard problem i mean they mean in
a somewhat technical sense that
it's trying to explain something
that
seems fundamentally unavailable to third
party objective
analysis
right i'm the only one that can get
inside my head and i can tell you a lot
about what's happening inside my head
right now it's reflected in what i'm
saying and you can try to deduce things
about what's going on inside my head but
you don't have access to it in the way
that i do and so it seems like a
fundamentally different kind of problem
from the ones that we have successfully
dealt with over the course of centuries
in science where we look at the motion
of the moon everybody can look everybody
can measure it we look at you know the
properties of hydrogen when you shine
lasers on everybody can look at the data
and understand it and so it seems like a
fundamentally different problem and in
that sense it seems like it is hard
relative to the others but
i do think ultimately that the
explanation will be as you recount i
think that a hundred years from now or
maybe it's a thousand it's hard to
predict the time scale for
developments but i think we'll get to a
place where we'll look back and kind of
smile
at
those folks in the 20th century and
before 21st century and before who
thought consciousness was so incredibly
mysterious when the reality of it is
it's just a thing that happens when
particles come together and and however
mysterious that feels right now
i think for instance when we start to
build conscious systems you know things
that you know you're more familiar with
than i am when we start to build these
artificial systems and those systems
report to us
i'm feeling sad
i'm feeling anxious yeah there's a world
going on inside here i think the mystery
of consciousness will just begin to
evaporate well that's
first of all beautifully put and i agree
with you completely just the way you
said it it'll begin to evaporate
i have built quite a few robots and have
had them do emotion
emotional type things and it's immediate
that exactly what you're saying this
kind of mystery of consciousness starts
to evaporate that
the
kind of need to truly understand to
solve the hard problem of consciousness
like disappears because
well
i don't really care
if i understand what can solve the hard
problem of consciousness that thing sure
as heck looks conscious you know i feel
like that way when i interact with a dog
i don't need to
solve the problem of consciousness to to
be able to interact
and richly
enjoy the experience with this other
living being obviously same thing with
other humans i don't need to fully
understand it and there's some aspect
maybe this is a little bit too
engineering focused but there's some
aspect in which it feels like
consciousness is just a
nice trick
to help us communicate with each other
it sounds ridiculous to say but
sort of uh
the ability to experience the world is
very useful in a subjective sense it's
very useful to put yourself in that
world and to be able to describe the
experience to others yeah it could be
just the social and the emerge obviously
animals the sort of more primitive
animals might experience consciousness
in some more primitive way
but this kind of rich
subjective experience that we think
about as humans i think it's probably
deeply coupled like language and poetry
yeah that resonates with my view as well
i mean there's a
scientist maybe you've spoken to michael
graziano from princeton yeah he um
he's developed ideas of consciousness
that look i don't think they solve the
problem but i think they do illuminate
it in an interesting way where basically
we
are not aware
of all the underlying physiochemical
processes that make our brains and our
inner worlds tick the way they do
and because of that dissociation between
sensation and the physics of it and the
chemistry of it and the biology of it it
feels like our minds and our inner
worlds are just untethered like floating
somewhere in this gray matter inside of
our heads
and the way i like to think of it is
like look you know if um if if if you're
in a dark room right and and i had
glow-in-the-dark paint on my fingers so
all you saw was my fingers dancing
around there'd be something mysterious
how how could those fingers be doing
that and then you turn a light you
realize oh there's this arm underlying
it and that's the deep physical
connection explains it all and i think
that's what we're missing the deep
physical connection between what's
happening up here and what is
responsible for it in a physical
chemical biological way and so to me
that at least gives me some
understanding of why consciousness feels
so mysterious because we are suppressing
all of the underlying
science that ultimately is responsible
for it and one day we will reveal that
more fully and i think that will help us
tether this experience to something
quite tangible in the world i wonder
if the mystery
is uh
an important component of enjoying
something
so once once we know how this thing
works
maybe we uh
will no longer enjoy
like this conversation we'll seek other
sources of enjoyment but
there's uh this is again from an
engineering perspective i wonder if the
mystery
is is an important component well you
know there's have you ever seen
there's this beautiful interview that
richard feynman did
you know great nobel laureate physicist
responsible for a lot of our
understanding of quantum mechanics
quantum fields and so forth and he
was in a conversation with an
interviewer where he noted that some
people feel like once the mystery is
gone once science explains something
it
the beauty goes away you know the wonder
if it goes away and he was
emphasizing in his response to that he's
like no that's not the right way of
thinking about he says look when i look
at a rose
he says yeah i can still
deeply enjoy the aroma the color the
texture he says but what i can do that
you can't if you're not a physicist i
can look more deeply and understand
where the red comes from where the aroma
comes from where the structure comes
from he says that only
augments
my wonder it only augments my experience
it doesn't flatten it or take away from
it so
yeah well i sort of take that as a bit
of a
of a motto in some sense that that there
is a wonder that comes from a kind of
ignorance and i don't mean that in a
derogatory sense but just from not
knowing so there is a wonder that comes
from mystery there's another kind of
wonder that comes from knowing
and and and deep knowing and i think
that kind of wonder has its own
special character that in some ways can
be more gratifying
i hope he's right i hope you're right
and but there's also i remember he
he said something about like an
like science is an onion or something
like that you can peel back you can keep
it keep peeling back i mean there is
also
when you understand something there's
always a sense that there's more mystery
to understand
like you never get to the bottom of the
mystery but i think it's also different
than you know
i don't think you can analogize say to a
magician right the magician you know
does some trick you learn how it sounds
like oh my god that was that's
ridiculous when you find but but nature
is perhaps the best magician if you want
to try to make the analogy there because
when you peel things back and you
understand
how it is that things have color and you
have electrons
dancing from one orbital to another
emitting photons at very particular
wavelengths that are described by these
beautiful equations of quantum
electrodynamics part of which that
feynman developed
it gives you a greater sense
of awe when the curtain is pulled back
than what happens in other circumstances
where it does flatten it completely yeah
it's very possible then say in physics
that we arrive at a theory of everything
that unifies the laws of physics and has
a very strong understanding of the
fabric of reality even like from the
very for the big bang to today
it's possible that
that understanding is only going to
elevate our appreciation of this whole
thing yeah i think it will i think it
will i think it has it has so far
but the other side of it which you which
you emphasize is
it's not like science somehow
reaches an end right there are certain
categories of questions that do reach an
end i think we one day we'll close the
book on nature's ingredients and the
fundamental laws now that can't prove
that maybe it goes on forever smaller
and smaller maybe they're deeper and
deeper laws but i i don't think so i
think that there's going to be a
collection of ingredients in a
collection of basic laws that chapter
will close
but
it's one chapter now we take that
knowledge and we try to understand how
the world builds the structures that it
does you know from planets to people to
black holes
to the possibility of other universes
and every step of the way
the collection of questions that we
don't know the answer to only blossoms
and so
there's a there's a deep
sense of gratification from
understanding certain quantities of the
world but i would say that if you take a
ratio
of what we understand to the things that
we know that we don't yet understand
that ratio keeps getting smaller and
smaller because the things that we know
that we don't understand grows larger
and larger
do you have a hope that we solve that
theory of everything puzzle
in the next few decades so there's been
a bunch of attempts from string theory
to all kinds of attempts of trying to
solve quantum gravity or basically come
up with a theory for quantum gravity
there's a lot of uh complexities to this
one for experimental validation
you have to observe effects that are
very difficult to uh measure
so you have to build like that's like an
engineering challenge
and then there's the theory challenge
which is like
it seems very difficult to connect the
laws of gravity to quantum mechanics do
you have a hope or are we
hopelessly stuck well i have to have to
have a hope i mean it's
in some sense but i devote at least part
of my
professional life toward trying to make
progress on i'm glad you use the phrase
quantum gravity
i'm not a great fan of the theory of
everything phrase because
it does make other scientists feel like
if they're not working on this what are
they working on man's like you know
there's not much left when you're
talking about theory of everything
biology is just small d yeah right
exactly
yeah so so it is really trying to put
gravity and quantum mechanics together
and uh since i was a college kid i was
uh deeply fascinated with gravity
and as i learned quantum mechanics the
the notion of physicists being stumped
and trying to blend them together how
could one not get fired up about maybe
contributing something to that journey
and so we've been on this you know i've
been on this for 30 years since i was a
student we we have made progress
we do have ideas you mentioned strength
theory is one possible scenario it's not
stuck string theory is a vibrant field
of research that is making incredible
progress
but we've not
made progress on this issue of
experimental verification validation
which as you know it is a vital part of
the story so i would have hoped that by
now we would have made contact with
observation if you would have
interviewed me back in the 80s when i
was you know a wild bright-eyed kid
trying to make headway working 18 hours
a day on this sort of stuff i would have
said yeah by by 2021 yeah we're gonna
know whether it's right or wrong we'll
make contact i would have said look
there may be certain mathematical
puzzles that we've got to work out but
we'll know enough to make contact with
experiment that has not happened
on the other hand if you would have
interviewed me back then and asked me
will we be able to talk about
detailed qualities of black holes and
understand them at the uh the level of
detail that we actually i i would have
said no i i don't think that we're going
to be able to do that will we have a
an exact formulation of strength here in
certain circumstances no i don't think
we're going to have that and yet we do
so it's just to say you don't know where
the progress is going to happen but yes
i do hold out hope that
maybe before i move on
to wherever i don't think there is an
after but i i would love before i
leave this earth to to know the answer
but
you know science and the universe it's
not about
pleasing any individual it is what it is
and so we just press onward and we'll
see where it goes so in terms of string
theory
if i just look from an outsider's
perspective currently at the theoretical
physics community string theory is the
theory was as a theory has been very
popular for for a few decades but has
recently fallen out of favor or at least
there's been like
you know it became more popular to kind
of
ask the question
is string theory really the answer
where do you fall on this like how do
you make sense of this puzzle why do you
think it has fallen out of favor yeah so
i don't i would actually challenge the
statement that's fallen out of favor
i would say that
any
field of research when it's new and it's
the the bright shiny bicycle that no one
has yet seen on that block yeah it's
going to attract attention
and
the news outlets are going to cover it
and students are going to flock to it
sure but as a as a field matures it does
shed those qualities because it's no
longer as novel as it was when it was
first introduced 30 or 40 years ago
but you need to judge it by a different
standard you need to judge it by
is it making progress on foundational
issues deepening our understanding of
the subject and by that measure string
theory
is is is scoring very high
now at the same time you also need to
judge whether it makes contact with
experiment as we discussed before too
and on that measure we're still
challenged so
i would say that
many strengthers myself included
are are very sober about the theory it
it has the tremendous progress that it
had 30 40 years ago that hasn't gone
away but we've become
better equipped at assessing
the long journey ahead and that was
something that we weren't particularly
good at back say in the 80s look when i
was just starting out in the field
there was a sense of
physics is about to end
string theory is about to be the be-all
and end-all final unified theory and
that will bring this chapter to a close
now i have to say i think it was more
the younger physicists who were saying
that some of the more seasoned even if
they were pro-string theory at the time
i don't know if they were rolling their
eyes but they knew yeah that was going
to be a long long journey i think people
like you know john schwartz one of the
founders of string theory michael green
no relation to me founders of the theory
edward whitton you know one of the main
people driving the theory back then and
today
i think they knew that we were in for a
long haul
and and that's the nature of science
quick hits that resolve everything few
and far between
and so if you were in
for
the
quick
solution to the big questions of the
world then you would have been
disappointed and i think there were
people who were disappointed and moved
on and work on other subjects if we were
in in the way that einstein was in
for a lifetime of investigation to try
to see
where
what the answers to the deep questions
would be then i think string theory has
been a rich source of material that has
kept
so many people deeply engaged in moving
the frontier forward there's a few
qualities about string theory which are
weird
i mean a lot of physics is just weird
and beautiful so let me ask the question
what do you as most beautiful about
string theory well but what attracted me
to the theory at the outset
beyond its putting gravity and quantum
mechanics together which i think is um
it's true claim to fame at least on
paper it's able to do that
what attracted me to here was the fact
that it requires extra dimensions of
space
and this was an idea that intrigued me
in a very deep way even before i really
understood what it meant
i somehow
had i mean talk about sort of the
emotional part of consciousness and the
cognitive part in some perhaps you call
it strange in some strange emotional way
i was enamored with einstein's general
relativity the idea of curved space and
time before i really knew what it meant
it just spoke to me i don't know how
else to say it
and then
when i subsequently learned that people
had thought about more dimensions of
space than we can see and how those
extra dimensions would
be vital to a deep understanding of the
things that we do see in this world four
five six dimensions might explain why
there are certain forces and particles
and how they behave
to me this was like amazing utterly
amazing and then when i learned that
strength theory embraced all these ideas
embraced the general theory of
relativity embraced quantum mechanics
embraced the possibility of extra
dimensions
then i was then i was hooked and so when
i was a graduate student
we would just spend hours
we i mean a couple of other graduate
students and myself who had a have sort
of worked really well together at oxford
in england we would we would work these
enormous numbers of hours a day trying
to understand the shapes of these extra
dimensions the geometry of them what
those geometrical shapes for the extra
dimensions would imply for things that
we see in the world around us
and it was a it was a heady heady time
and and that kind of excitement has sort
of filtered through over the decades but
i'd say
that's really
the the
part of the theory that i think really
hooked me most wrongly
how are we supposed to think about those
extra dimensions i was supposed to
imagine actual physical reality or
is this more in the space of mathematics
that allows you to
sort of come up with tricks to describe
the four-dimensional reality that we
more directly perceive
no one really knows the answer of course
but if i take the most straightforward
approach to string theory you really are
imagining that these dimensions
are there they're real i mean just as
you would
say that the three space dimensions
around us you know left right back forth
up down
yeah we they're real they're here we are
immersed within those dimensions
these other dimensions are
as real as these with the one difference
being their shape and their size
differs from the shape and size of the
dimensions that we have direct access to
through through human experience
and
one approach imagines that these extra
dimensions are tightly coiled up
curled up crushed together if you will
into a beautiful geometrical form
that's all around us
but just too small for us to detect with
our eyes too small for us to detect even
with the most powerful equipment that we
have nevertheless according to the
mathematics the size and the shape of
those extra dimensions leaves an imprint
in the world that we do have access to
so one of the ways that we have hoped
yet to achieve to make contact with
experimental physics is to see a
signature of those extra dimensions in
places like the large hadron collider in
geneva switzerland
and it hasn't happened yet doesn't mean
it won't happen
but that would be
a stunning moment in the history of the
species if data that we acquired in
these dimensions
gives us kind of incontrovertible
evidence
that these dimensions are not the only
dimensions i mean how
mind-blowing would would that be so with
a large header and collider it would be
something in the movement of the
particles or
also the gravitational waves potentially
be a place where you can detect signs of
multiple dimensions like with something
called ligo but much more accurate in
principle all of these can work so one
of the experiments that we had high
hopes for but by high hopes i'm actually
exaggerating one of the experiments that
we
imagined might in the best of all
circumstances yield some insight we
weren't with baited breath waiting for
the result we knew it was a long shot
when you slam protons together at very
high speed as a large hadron collider if
there are these extra dimensions and if
they have the right
form and that's a hypothesis that may
not be correct but when the proteins
collide they can create debris energetic
debris that can in some sense leave our
dimensions and insert itself into the
other dimensions and the way you'd
recognize that is
there'd be more energy before the
collision than after the collision
because the debris would have taken
energy away from the place where our
detectors can detect it so that's that's
one real concrete way that you could
find evidence for extra dimensions but
yeah since extra dimensions are of space
and gravity is something that
exists within in fact is associated with
the shape of space
gravitational waves in principle can
provide a kind of you know cat scan of
of the extra dimensions if you had
sufficient control over
those processes we don't yet but perhaps
one day we will
does it make you sad
a little bit or maybe looking out into
the future you mentioned edwin
that no nobel prizes have been given yet
related to string theory do you think
they will be do you think you have to
have experimental validation or can a
nobel prize be given which i don't think
has been given for quite a long time
for uh
purely sort of theoretical contributions
yeah it certainly as a matter of
historical precedent has been the case
that those who win the prize
have
established investigated
illuminated a demonstrably real quality
of the world
so
gravitational waves the prize was
awarded after they were detected not not
the mathematics of it but the actual
detection of it you know the higgs
particle
you know it was an idea that came from
the 1960s peter higgs and others in fact
and it wasn't until
on july 4th when the announcement came
that this protocol had been detected the
large hadron collider that people viewed
it as eligible for the nobel prize the
idea was there the math was there but
you needed to
confirm it indeed the prize ultimately
was awarded so i'm not surprised
in fact i would have been surprised if a
nobel prize had been awarded in the
arena of string theory because it's far
too
speculative right now it's far too
hypothetical in fact
i am sympathetic to the view
that it really shouldn't be called
string theory it degrades the word
theory
because theory in science of course
means the best available explanation for
the things that we observe in the world
the things that we measure in
experiments about the world
and string theory does not do that at
least not yet so it really should be
the string hypothesis right we're at an
earlier stage of development
and that's not the kind of thing that
nobel prizes should be awarded for
what do you think about the critics out
there peter white he's from colombia too
i think sabine hafenstadter
is that a healthy thing or should we
sort of focus on sort of the optimism of
of these hypotheses yeah
it's actually a good way that you frame
it
because
i'm always
somewhat repelled
by
views of the world
that start from the negative
try to cut down an idea try to say
that's the wrong way of thinking about
things and so on i'm
much more drawn maybe because i'm an
optimist i don't know i'm much more
drawn to those who go out into the world
with new ideas yeah and and don't try to
cut down one idea but rather present
another one that might be better
and so you make the first idea maybe
strengthy irrelevant because you've come
up with the
better approach to the world
so do i think it's healthy look i think
having a wide
range of
views and perspectives is generally a
healthy thing
i think it's good to have
arguments within a subject in order that
you stay fresh and you stay focused on
the things
that matter but in the end of the day i
think it's a more
vital contribution to give us something
new rather than to criticize something
that's there yeah i'm totally with you
um but it could be just the nature of
being an optimist i and also just a
a love of engineering it's there's it it
helps nobody by criticizing
the uh the rocket that somebody else
built just build a
bigger cheaper better rocket
exactly yeah and that seems to be how uh
human civilization can progress
effectively
we we've uh mentioned the second law of
thermodynamics i got to ask you about
time
yeah and
do you do you think of time as emergent
or fundamental to our universe i like to
think of it as emergent
i don't
have a solid reason for that perspective
i have a lot of hints of reasons that
some of which come out of string theory
and quantum gravity that perhaps would
be worth talking about
but what i would say is
time is
the most familiar quality of experience
because there's nothing that takes place
that doesn't take place within an
interval of time and yet at the same
time
it is perhaps the most mysterious
quality of the world so it's a wonderful
confluence of the familiar and the
deeply mysterious all in one little
package
if you were to ask me what is time
i don't i don't really know i don't
think anybody does i i can say
what time gives us
it allows us the language for talking
about change
it allows us to envision the events of
the universe being spread out in this
temporal timeline and in that way
allows us to see the patterns that
unfold within time i mean time allows us
the structure and the organization to
think about things in that kind of a
progression but
what actually is it
i i don't really know and that's so
strange because
we can measure it
right i mean there are laboratories in
the world that measure this thing called
time to spectacular precision
but you know if you go up to the folks
and say like
what is it that you're actually
measuring
i don't know that they can really
articulate the kind of answer that you
would expect
from those who are engineering a device
that can measure something called time
to that level of precision
so it's a very curious combination
what do you make of the one-way
feeling of causality like is causality
a thing or is that too just a human
story
that we put on top of this emerging
phenomena of time i don't know
um i can give you my my guess and my
intuition about it
i do think that at the macroscopic level
if we're talking about sort of the human
experience of time i do think at the
macroscopic level there is a fundamental
notion of causality that does emerge
from a starting point that may not have
causality built in so i certainly would
allow that at the deepest
description of reality when we finally
have that on the table
we may not see causality directly at
that fundamental level but i do believe
that we will understand how to go from
that fundamental level to a world where
at the macroscopic level there is this
notion of a causes b
a notion that einstein deeply embraced
in his special theory of relativity
where he showed that time has qualities
that we wouldn't expect based on
experience you and i if we move relative
to each other our clocks
tick off time at different rate and our
clocks is just a means of measuring this
thing called time so this is really time
that we're talking about time for you
and time for me are different if we're
in relative motion he then shows in the
general theory of relativity that if
we're experiencing different gravity
different gravitational fields or
actually more precisely different
gravitational potentials
time will elapse for us at different
rates these are things that are
astoundingly strange that give rise to a
scientific notion of time travel okay so
this is this is how far einstein took us
in
wiping away the old understanding of
time and injecting a new understanding
of its qualities so so there's so much
about time that's counterintuitive
but i do not think that we're ever going
to wipe away causality at the
macroscopic at the microscope i mean
there's so many interesting things at
the macroscopic level that may only
exist at the microscopic level yeah like
we already talked about consciousness
that that very well could be one of the
things you mentioned time travel so
um
i mean according to einstein
and
in general
what
types of travel do you think our
physical universe allows well certainly
allows
time travel to the future and i'm not
talking about the silly thing that you
and i are now going into the future
second by second second i'm talking
about really the diversion that you see
in hollywood at least in terms of its
net effect whereby
an individual
can follow an einsteinian
strategy
and
propel themselves
into the future in some sense more
quickly so if if i wanted to see what's
happening on planet earth 1 million
years from now
einstein tells me how to get 1 million
years from now build a ship i got to
turn to guys you know who know how to
build stuff i can't do it like you build
a ship that can go out into the universe
near the speed of light
turn around and come back let's say it's
a six month journey out a six month
journey back and einstein tells me how
fast i need to travel how close to the
speed of light i need to go so that when
i step out of my ship
it will now be one million years into
the future on
planet earth
and this is not
a controversial statement right this is
not something where there's differences
of opinion in the scientific community
any scientist who knows anything about
what einstein taught us agrees with what
i just said it's it's commonplace it's
bread and butter physics and so that
kind of travel to the future is
absolutely allowed by the laws of
physics there are engineering challenges
they're they're technological challenges
close to the speed of light yeah yeah
and they're they're even biological
challenges right they're g-forces that
you're going to experience you know so
there's all sorts of stuff embedded in
this but those
i will call the details and those
details
notwithstanding
the universe allows this kind of travel
to the future and if i could pause real
quick
you could also
at the macro level
with biology extend the human lifespan
to do a kind of
travel forward in time
if you expand how long we live yeah
that's a way to from a perspective of an
observer a conscious observer that is a
human being
you're essentially traveling forward in
time by allowing yourself to live long
enough to see the thing yes so that's in
the space of biology
uh what about traveling back in time
yeah that's the um
that is a natural next question
especially if you uh if you're doing if
you're going on one of these journeys is
it a one-way journey yeah can you can
you come back
and
the physics community doesn't speak with
a unified voice on this as yet but i
would say that the dominant perspective
is that you cannot get back
now having said that there are proposals
that serious people have written papers
on
regarding hypothetical ways in which you
could travel to the past and
we've seen some of these again hollywood
loves to take the most sexy ideas of
physics and build narratives around them
this idea of a wormhole like jody foster
and contact went through a wormhole
deep space nine star i'm sure there are
many other examples where these ideas
that i've probably never even seen
but with wormholes there's at least a
proposal of how you could take a
wormhole tunnel through space-time
manipulate the openings of the wormhole
in such a way that the openings are no
longer synchronous they are out of sync
relative to each other which would mean
one's ahead and one's behind which means
if you go through one direction you
travel to the future if you go back you
travel to the past
now
we don't know if there are wormholes
possible according to einstein correct
they are possible according to einstein
but even einstein was very quick to say
just because my math allows for
something doesn't mean it's real and he
famously didn't even believe in black
holes yeah didn't believe in the big
bang right and yet the big the the black
hole issue has really been settled now
we have
radio telescopic photographs of the
black hole in m87 who's in newspapers
around the world just a couple of years
ago so
so it's just to say that just because
it's in einstein's math um it doesn't
mean it's real but yes it is the case
that wormholes are allowed by einstein's
equations and in principle
you can imagine you know putting
electric charges on the openings of the
wormhole allowing you to toe them around
in a manner that could yield this
temporal asymmetry between them maybe
you toe one of the mouths to the edge of
a black hole in principle you can do
this slowing down the passage of time
near that black hole and then when you
bring it back it will be well out of
sync with the other opening and
therefore could be a significant
temporal gap between one and the other
but people have studied this in more
detail questioned could you ever keep a
wormhole open assuming it does exist
could you ever travel through a wormhole
or would there be a requirement of some
kind of exotic matter to prop it open
that perhaps doesn't exist so
there are many many issues that people
have raised and i would say that the
general sentiment
is that it's unlikely
that this kind of scenario is going to
survive our deeper understanding of
physics when we finally have it but that
doesn't mean that the door is closed so
maybe it's a
a small possibility that this could one
day be ready that's such an interesting
way to put it
it will not this kind of scenario will
not survive deep understanding of
physics
it's an interesting way to put it
because
it makes you wonder what kind of
scenarios
will be created by our deeper
understanding of physics maybe
uh
sorry to go crazy for a second but if
you have like the pan psychosome idea
that
consciousness permeates all matter maybe
traveling in that whatever laws of
physics the consciousness operates under
something like that in that view of the
universe if we somehow are able to
understand that part maybe traveling is
super easy yeah
it does not follow the constraints of
the speed of light
something like this yeah so
look i have i have a definite
degree of um
sympathy with the possibility
that consciousness might be more than
what we described earlier is just the
byproduct of mindless particles you just
made the rock happy
exactly you know so so
it isn't the approach that
feels to me the the most likely but i i
see the logic
if you've got the puzzle how do mindless
particles build mind one resolution
might be the particles are not mindless
the particles have some kind of
proto-conscious quality so there's
there's something appealing about that
straightforward solution to the puzzle
and if that's the case if we do live in
a pan-psychist world where there's a
degree of consciousness residing in
everything in the world around us then
yes i do think some
interesting possibilities might emerge
where maybe there's a way of communing
with physical reality
in a in a deeper way than we have so far
i mean we as human beings a vital part
of our existence is human to human
communication contact we live in social
groups and that's what it's allowed us
to get to the place where we've gotten
imagine
that we have long missed that there's
other consciousness out there and some
kind of relationship or communion with
that larger conscious possibility would
take us to a different place now do i do
i buy into this yet i don't i don't see
any evidence for it
but do i have an open mind and allow for
the possibility in the future yeah i do
so if that's not the case and you have
these
simple particles that at the macro level
emerges some interesting stuff like
consciousness another thing you write
about in the until the end of time book
is the the thing that seems to emerge at
the macro level is the feeling
like uh that like there's a free will
like we decide to do stuff and you have
a really interesting take here
which is
no there's not a free will i'm just
going to speak for you and then you
should correct me no there's not a free
will
but there is
an experience of freedom yeah
yeah
which i i really love so where does the
experience
where does freedom come from if we don't
have any kind of physics based free will
yeah and and so the idea
follows naturally from all that we've
been talking about let's make the
assumption
that all there is in the physical
universe is stuff governed by laws we
may not have those laws may may not know
what the fundamental stuff is yet
but everything we know in science points
in the direction that it's physical
stuff governed by universal laws
and
that being the case or that being the
assumption then you come to a particular
collection of those ingredients called a
human being and that human being has
particles that are fully governed by
physical law
and when you then recognize that every
thought that we have every action that
we undertake is just the motion of
particles when i'm thinking thoughts
right now of course at this level of
description it is the motion of
particles cascading down various neurons
inside of my head and so on and every
single one of those motions collectively
and individually is fully governed by
these laws that we perhaps don't have
yet but we imagine one day we will that
leaves no opportunity for any kind of
freedom to break free from the
constraint of physical law and that is
the end of the story
so the traditional intuitive notion of
free will that we're the ultimate
authors of our actions that we were the
buck stops that there is no antecedent
that is the cause for our decided to go
left or right choose vanilla or
chocolate live or die
that intuitive sensation does not have a
basis in our understanding of the
physical world so that's the end of the
free will of the traditional sort but
then your question is
what about this other kind of freedom i
talk about and the other kind of freedom
if you focus on it intently i think
is actually the true version of freedom
that we feel and that freedom is this
you look at inanimate objects in the
world rocks bottles of water whatever
they have a very limited behavioral
repertoire why
their internal organization is too
coarse for them to do very much right
you have to you try to have a
conversation with a glass of water you
send sound waves it doesn't do much it
may vibrate a little bit but the
repertoire of responses are incredibly
limited
the difference between us and a rock or
a bottle of water is that our inner
organization by virtue of eons of
evolution by natural selection is so
refined so spectacularly ordered that we
have a huge repertoire of behaviors that
are finely attuned to stimuli from the
external world you ask me a question
that's a stimulus and all of a sudden
these particle processes go into action
and this
is the result this answer that i'm
giving you so the freedom that we have
is not from the control of physical law
the freedom that we have is from the
constrained behavior that has long since
governed inanimate objects we are
liberated from the limited behavioral
repertoire of rocks and bottles of water
to have this broad spectrum of responses
do we pick them we do not do we freely
choose them we do not
but yet we have them and we can marvel
at those behaviors and that's the
freedom that we have the complexity and
the breadth of that repertoire is is
where the freedom is is there something
to be said about
emergence
i don't know if you
know i've looked at much about objects
that
i seem to uh
love way more than anyone else which is
cellular
yeah like game of life type of stuff
there you know from simple things
emerges
beautiful complexities
and so that's that repertoire
it's like it seems
if you have enough stuff
just beautiful complexity emerges that
sure as heck to our human eyes looks
like there's consciousness there there's
free will there's little objects moving
about and making decisions i mean all of
that you can say it's
anthropomorphization but
it sure as heck feels
like their organisms making decisions
um what what is that that emergence
thing is is that
within the realm of physics to
understand is it uh
is it within the realm of poetry where
because what is that like complex
systems emergencies what is that will
that ever be understood by science so
here's here's the way that i think about
it so there are
clearly qualities of the world that
emerge on macroscopic scales
our sense of beauty wonder consciousness
all these kinds of qualities
do i feel that they ultimately are
explainable from the laws of physics i
do
there is nothing that's not ultimately
ultimately explainable with the laws of
physics from this physicalist
perspective which is what i take
so
you got the particles you got the laws
and you have things that emerge from the
choreographed motions of those particles
but is that the best language for
talking about these emergent qualities
usually not
if i was to
take something even more mundane like a
baseball flying through the air if i was
to describe it in terms of the quarks
and the electrons i'd give you this
mountain of data with you know 10 to the
28 particles and all of their
coordinates in space as a function of
time i hand you this mountain of data to
be like i don't know what this is
and then if you really were clever and
looking oh it's a baseball just
described in the in the least economical
way possible it is much more useful
and insightful to talk about the
baseball flying through the air
similarly there are things at the
macroscopic level like human experience
and human emotion and human action and
the sensation of free will that we
undeniably all have even if it itself
doesn't have a basis in our
understanding of the physical world it's
useful to talk about things in this very
human
language and so yes it's vital to talk
about things in the poetic language of
human experience but do not lose sight
of the fact and some people do they say
oh it's just an emerging phenomenon
don't lose sight of the fact that
emergent phenomena are emerging
from this deeper understanding that
comes from the reductionist account of
physical law and there's a lot of
insight to come from that such as
the freedom that you thought that you
had the freedom of will that you thought
you had it doesn't have a basis in that
reductionist account so it's not real
so speaking of the poetry of human
experience you mentioned the images of
the black holes how did it make you feel
a few years ago when that first image
came out it's truly amazing
a sense of
well i guess the feeling was
both amazing and and there's a little
sense of um
jealousy is not quite the right word
but a sense of
longing yeah i think that's a better
word because
here's a subject that started with
einstein back in 1915 writes down the
equations of the general theory of
relativity
and then there are
scores of individuals over the decades
you know starting with people like carl
schwarzschild who analyze the equation
see the possibility of black holes
people develop these ideas john wheeler
all these greats of physics
it's still a hypothetical subject it
gets closer to reality through
observations of the center of our galaxy
stars whipping around in a manner that
could only really be explained by there
being a black hole in the center of our
galaxy but it was still indirect
to actually have a direct image
that you can look at
what a beautiful arc narrative arc from
the theoretical to the absolutely
established and that's what we hope will
happen with other areas for instance
string theory right i mean holy
mathematical subject at the outset and
still pretty much a holy mathematical
subject today
yeah do we long
for that image where we can look at it
and say
string it's real i mean you know i mean
how thrilling how thrilling to be part
of that journey to be part of that that
step that moves things from the abstract
to the concrete
yeah uh so like the image of the dna the
early images of the dna for example uh
but there is something especially so the
problem with strings
is they're tiny so it's harder to take a
picture i in in the following sense when
you think of a black hole i mean you
have a swirl of i guess what is i i
don't even know it's dust to go whatever
light creeding onto the uh event horizon
and then there's darkness yeah center
and you you just imagine so that picture
in particular i guess is of a gigantic
black hole so you just i mean it's 10
million billion billions of times the
mass of the sun yeah so it's both
exciting and terrifying i mean i don't i
don't know where you fall on the
spectrum i think
it's exciting at first like the longer i
think about it every time i think about
it the more terrifying it becomes so it
always starts exciting
and then it goes to terrifying and both
are
feelings very human feelings that i
appreciate
it's like terrified aw
somehow it's still beautiful that's a
good way of saying it i think i kind of
share that that reaction because there
is a way in which
when you work on this subject like all
the time
i teach it i teach about black holes
write the equations on the blackboard
the ideas
reside
in a very cognitive
i don't know mathematical portion of the
brain or at least for me and it's only
when you like sit down and it's quiet
and you start to contemplate wait wait
wait wait this is just like a
mathematical game
there are these monsters out there now i
don't not in it in a sense of i fear for
my life but it's
a sense of
how extraordinary is this universe and
so it is breathtaking how powerful
nature is yeah how stupendously powerful
nature is
um
and so there is
a deep
sense of humility that i think this
instills if you really allow the ideas
to sink in
well i have to ask about the most
stupendously powerful thing to have ever
happened in our universe which is the
big bang yeah
what's up with the big bang
so we can i mean with gravitational
waves the hope is when you have
more and more accurate measurements of
the gravitational waves you can crawl
back further and further back in time
towards the big bang
do you ever hope that we'll be able to
understand
the
the early spark that created
our universe yeah
you know that and the deep
interior of a black hole i think the the
biggest mysteries that we hope
the melding of quantum mechanics and
gravity will reveal will illuminate and
you know what question could be
more captivating than why is there
something rather than nothing right why
is there a universe at all
and will the theories that we're
developing take us
to an answer to that i don't know
even if we truly knew what the big bang
is that's a big question it's own right
one would still be left with the
question well okay
so you've explained the process by which
a tiny nugget of a
universe a kind of nugget of space-time
can undergo some kind of growth to yield
the world around us but
presumably in that explanation you're
going to involve mathematics
and some ingredients like quantum fields
or or matter or energy or something
where did that stuff
come from you know can we get to that
level of explanation i don't know but it
is remarkable
that
if you ask what happened
a millionth of a second after the big
bang
it's not really that controversial
any longer right even though there's a
lot of argument in the field and it's
very heated right now i should say
regarding what is the right theory of
the big bang what is the right theory of
early universe cosmology where i mean
early much earlier than a millionth of a
second a lot of dissent a lot of
uh
heated arguments about that no pun
intended yeah right exactly um but but
but you go like a millionth of a second
after that yeah and and we're on pretty
firm ground isn't that amazing right
yeah to understand you know what
happened from that point forward
but to go back is is is controversial so
there is this theory called inflationary
cosmology
which i would say has been the dominant
paradigm
since uh early 1980s so what does that
mean roughly 40 years now it's been the
dominant cosmological paradigm and it
makes use of a curious feature of
einstein's general theory of relativity
his fear of gravity where einstein shows
us mathematically that gravity can not
only be attractive you know the kind of
gravity that we're used to things pull
together but it can also be repulsive
and that fact is then leveraged by
people like alan guth and and andre
linday and at the time paul steinhardt
and andres albrecht and others to say
okay if we had a little nugget in the
earlier universe which was
filled with the stuff that yields this
repulsive gravity well that would have
blown everything apart it would cause
everything to swell
beautiful explanation for what the bang
in the big bang was and then people
mathematically analyze the consequences
of this idea and they make predictions
for tiny temperature differences across
the night sky that in principle could be
measured
you send up balloons you set up
satellites with very refined
thermometers
and they measured the temperature of the
night sky and the statistical
distribution of the temperature
differences agrees with the mathematical
predictions yeah
i mean
it's amazing you just sort of have to
stand in awe
of this insight so you think
aha the theory has been established but
scientists are
an incredibly skeptical
bunch
and some scientists including one of the
people who helped develop the theory at
the outset paul steinhardt
comes along and says well yeah it's done
this theory's done pretty well so far
but there are aspects of this theory
that are making me lose confidence for
instance this theory seems to suggest
that there might be other universes
like how do you make sense of a theory
that suggests other universes or or
there are others who come along and say
this theory seems to um
talk about
length scales that are minuscule even by
the so-called plank length the sort of
shortest length that we can imagine
making sense of in a theory of quantum
gravity how do you make sense of that
and so and so they develop a list of of
things that they consider to be chinks
in the inflationary cosmological
theories armor and they develop other
ideas which they claim
yield the same predictions as inflation
and cosmology for those temperature
differences across space but don't
suffer from these problems and then the
inflationary cosmology folks say no no
no hang on you know your theories
suffers from different problems and so
the arguments goes it's a healthy debate
talk about real debates and science
so when you ask what's up with the big
bang
i don't know right now um if you would
have asked me five years ago
maybe even less than that three or four
years ago i've said look
inflation on cosmology has some issues
but the package of explanations it
provides is so potent
and the issues that beset it are
seemingly solvable to me
that i would imagine it's going to in
the end win out
i would still say that today but i
wouldn't say it as loudly i wouldn't say
it as confidently i think it's worth
thinking about alternate ideas and it
could be the case that the paradigm at
some point shifts
does dark matter and dark energy fit
into the
shifting of the explanations for those
yeah certainly so so dark energy has uh
in in the inflationary theory
is kind of a big mystery
so
dark energy is the
observational
realization in the last 20 years that
not only is the universe expanding it's
expanding ever more quickly
something is still pushing things
outward and the explanation is that
there's like a residual version of the
repulsive gravity from the early
universe but it's such a strange number
when you write that amount of dark
energy using the relevant units in the
theory of quantum gravity it's a decimal
point followed by like 120 zeros and
then a one
we're not used to those kinds of numbers
in physics we're used to
a half
one
pi
e square to two those are the kinds of
fundamental numbers that emerge in our
explanations of the world and we look at
this bizarre number decimal point all
these zeros and one we say
something's wrong there like where would
that number
have come from now there are people who
suggest resolution to it so it's not
like we're totally in the dark on it but
those people like paul steinhardt who
have alternate cosmological theories
cyclic cosmologies as they call it claim
that they have a more natural
explanation of the dark energy that it
naturally feeds into a cyclical process
that
is their cosmological paradigm so yeah
if the
cosmology should change it's conceivable
our view of dark energy may change from
deeply mysterious to deeply integrate it
into a different paradigm that is
possible i think it's roger penrose that
think that information can bleed through
from before the big bang to the after
the big bang yeah is that uh is the big
bang uh
like a full erasure of the hard drive or
is there some information that could
bleed through yeah i mean so sir roger
is among the most creative thinkers of
the last 100 years rightly
won the nobel prize for his insights
into singularities in space time that
we know to afflict our mathematical
solutions of black holes in the big bang
and so forth and um
he has an enormously fertile imagination
and and i mean that in the most positive
sense and um so he has put forward this
idea this conformal cyclic cosmology i
think is the uh the official title
although i could be getting that wrong
i can't say that i've studied it i have
seen
lectures on it i don't find it
convincing as yet it feels
like it's being
built
to find a solution as opposed to sort of
more naturally emerging
maybe roger would say otherwise and i
don't mean to in any way
cast aspersions on the work it's vital
and interesting and people are thinking
about it i don't consider it as close a
competitor
to say the inflationary theory as for
instance the stuff that paul steinhardt
has put forward but
again you've got you got to keep an open
mind in this in this business when
there's so much that we don't yet
understand i mean it is wild to think
that information can survive something
like that just like
it is wild to imagine that information
could escape a black hole for example or
it just seems like
by construction these things are
supposed to not
bleed out anything but one of the
challenges in all these theories is when
we talk about a singularity has this
really sexy term the singularity yeah
but a singularity is is in more ordinary
language
a physical system where the mathematics
breaks down
it's nonsensical it's like taking one
divided by zero you put that into a
calculator and it says e error right it
does not make sense doesn't compute and
and so it's very hard
to
make
definitive statements about things like
the big bang or about black holes until
we cure the mathematical singularities
and there are some who claim that in
certain regimes the singularities have
been cured i don't by any means think
that there's consensus on these ideas so
when one talks about information sort of
bleeding through the big bang you've
really got to make sure that the
equations have no singularity you talk
about cyclic cosmology you've got to
make sure that the equations don't have
any singularities as you go from say one
cycle to the next now some of the
proponents of these theories claim that
they have resolved these issues i i
don't think that there's a general sense
that that is the case as yet but it
could be that look i life is so short
that i i haven't had the time to deeply
delve into all the mathematical
intricacies of all the ideas that have
been put forward if i did that i'd never
do anything else
but that that's what the issue is and of
course it's just math there may be holes
there may be uh
there may be gaps in our our
understanding in the way we're modeling
physical variables well that's the point
in fact when you said i was about to
jump in and say modeling but you got
there first and it's exactly the right
point you're talking about the universe
here
right and the
how do you how do you talk about the
universe with a straight face
mathematically and the way you do it is
you you simplify
you throw away those characteristics of
the universe that you don't think are
vital to a full understanding and so
we're going to get to a point people are
starting to where we've got to go beyond
those simplifications
and so cosmology has for a long time
modeled the universe in the most
simplest terms homogeneous isotropic
it has just a few parameters that
describe it the average density of mass
and energy and so forth we have to go
beyond those simplifications and that
will require
putting these things on computers we're
not going to be able to do calculations
there so much as
astrophysics has gone beyond many
simplifications to now give really
detailed simulations of star systems and
galaxies and so forth we're going to
have to do that with cosmology and
people are starting to do that today
yeah i've seen some interesting work on
uh simulation
most simulation cosmology by the way is
just awesome but
you know just like simulation of the
early formation of our solar system to
understand
how the like the ore cloud and just
i don't know the the whole of it the how
earth came to be yeah
like how jupiter just
protects us protects us and then there's
like weird like
moons and
volcanoes and
and like modeling all of that the
formation of all that
uh is fascinating yeah because that
naturally is the question of how does
life emerge and these kinds of rocks
how does a rock become a rabbit yeah
uh but
speaking of models uh there's an
equation called the drake equation
we were talking about life
have to ask when you're at the highest
level first when you look out there
how many alien civilizations do you
think are out there
zero one or many
so
if you say
civilization i
would bring my number way down
it could be zero
if you talk about life
i think it could be many
as we were saying before i think the
move from life
to consciousness the kinds of beings
that would build what we would recognize
as a civilization
that may be extraordinarily
rare i hope it's not you know as a kid i
love star trek i i just love the idea
that we would be part of some
universal community where look
experience on planet earth suggests it
doesn't always go so well when groups
who are separated try to come together
and and live in some larger collective
but again as an optimist
how amazing would it be to converse with
an alien civilization and and learn what
they've figured out about physics and
cosmology and and compare notes and and
and learn from each other in in some
some wonderful way i i love that idea
but if you ask me the likelihood of it
i i would err on saying
it may be so improbable
that the conditions conspire to allow
life to move to this place of of
consciousness that it might be rare
it might be oversimplifying things but
just observing the power of the
evolutionary process
i tend to believe
and like you read
different theories of how we went
uh
how homo sapiens evolved
it seems like the evolutionary process
naturally leads to
to
homo sapiens
or creatures like that or much better
than that so to me the
there's several scary scenarios so
okay the positive scenario is life
itself is really difficult so that
origin of life is difficult that's
exciting for many reasons
because
we might be able to prove that wrong
easily in the near term by finding life
elsewhere sure
the scary thing to me is if uh
life is easy
and there's plenty of conscious
intelligent civilizations out there and
we have not
obviously made contact which means with
intelligence and consciousness comes
responsibility and
ultimately
destruction
so with power comes great responsibility
and then we end up destroying ourselves
that's the
uh the scariest the the positive i guess
version is that
maybe we're being watched
uh sort of like
there's a transition
to where you don't want to ruin
uh the primitive villages out there and
so there's a protective layer around us
yeah they're they're watching
so where where do you and these possible
explanations to the fermi paradox why
haven't we contacted aliens
do you land on well
i think the most straightforward
explanation is that there aren't any
now
there are many other explanations too so
i you can't be dogmatic about things
that are just sort of gut feel
but
you know one of my favorite
twilight zone episodes i don't ever saw
this one where
this alien civilization finally comes to
planet earth and gives us this book that
they really want us to to have and to
hold and it's in this foreign you know
language you don't understand the
cryptographers they desperately try to
decipher it as humans are going to visit
this other alien planet and they're all
sending back postcards how wonderful it
is and so forth and they they finally
decipher the title it's to serve man and
everyone's so thrilled oh they're here
to service it all makes sense and then
just as one of the final cryptographers
is going on to the alien ship
his his helper runs and says i've
deciphered the rest of the book to serve
man it's a cookbook you know so
you know
so yeah is that is that a
possibility sure you know and and so
could they be watching us and just sort
of waiting for us to uh get to a mature
enough
level
i don't know it strikes me well you know
i think it'd be better to have this
conversation after the james webb
telescope i mean i do think that
um if we look at the atmospheres
of many planets i mean there's now an
estimate now that there's on order of
one planet per star on average so we've
long known that you know the galaxy
hundreds of billions of stars numbers of
galaxies hundreds of billions of
galaxies so we're talking about hundreds
of billions of hundreds of billions of
planets i'm like you know and if we
start to survey some of these planets
and one after the other after the other
we just sort of find
no evidence for
any of the biological markers it could
be of course maybe life takes a
radically different form it'd be hard to
know that but i think you know that
would at least give us some insight on
the life question but i just don't see
how we get insight on the civilization
or consciousness question without you
know the direct connection and and it
strikes me that if consciousness is
ubiquitous
let's say life is i'm willing to grant
that if consciousness is also ubiquitous
then i don't understand why
they haven't been here or why there
hasn't been separate because presumably
they should be much further ahead of us
how unlikely would it be that we're like
of all consciousness in the universe
we're the most advanced that would be
such a special
place for human beings that it's hard
for me to grant that as a likely
possibility rather i think we're kind of
running the mill
and there are many who are far more
advanced than us and i don't think that
they
would expend the energy to hide
themselves
so i don't think they care enough and so
i see that's actually what i i believe
that there's uh a very large number of
civilizations that are far more advanced
than us
but my sense is the humans are
exceptionally limited both in our direct
sensory capabilities and our physics
our tools
of sensing that just like with the
string theory and the multiple
dimensions we're just not
like it's like i honestly believe there
could be stuff in front of our nose that
we're just not seeing
what because we're too dumb too
uh too much hubris
and i mean it's a bunch of stuff and too
ignorant as a
to the
fabric of reality all of those things
yeah we're young
yeah in terms of intelligence but i
guess what i'd say is like i'm on board
with all of that as a real possibility
but then
it does strike me that
we are sufficiently
able to observe
the unit look we can look back to
you know
a fraction of the duration
from here to just a fraction is left
that we are unable to see um so however
young we are
we have been able to sort of pierce the
universe and it just strikes me that
there would be some signature but maybe
maybe that that's coming but but look
having said that i do
look i i i certainly note the fact that
it's rare that i stoop down
while walking in manhattan and sort of
dig up some ants in the bushes on the
side of the street and talk to the ants
right because it's just not interesting
to me so if we're like the ants on the
cosmological landscape then yeah i can
imagine that the super advanced aliens
would be like
like whoever you know but but i feel
like we're sufficiently advanced that
there should be some signal signature of
that but maybe it's coming i think the
deeper fundamental problem between us
and the ants is that we don't have a
common language it's not it's not the
interest it's that we don't even have a
common language
and so the the alien civilizations don't
even know how to communicate like we
humans have
convinced ourselves we're special
because we developed the language you
talked about you talk about the
importance of language to intelligence
but it makes you wonder like how very
niche is that
like club that we've
like tried we've created of language and
linguistic type of systems that are very
specific to our particular kinds of
brains and we share ideas together are
all super excited that we can understand
the universe because we came up with
some notation yeah and math i wonder if
there's some
totally other kinds of language that
communicates on a different time scale
with different very different mechanisms
in a space of information that just is
not it's everything everything is lost
in translation yeah and it could well be
it's a look i mean i think part of the
reason i go toward the possibility
of the soul intelligence
is there's a certain kind of romantic
appeal
to looking out in the cosmos and it's
just quiet and it's just eternal silence
there's some there's something that
appeals to me at an emotional level that
way but yeah i mean um nobody
nobody knows and uh it's certainly um
conceivable
that we're there's just a radical
mismatch between the kinds of things
that we are able to observe and
sensitive to
versus the kinds of structures that
permeate the universe in a manner that
simply we're unable to detect well if we
are alone
that is exciting in
one of the ways it's exciting is um
that it's up to us to become to expand
out into the universe
to um permeate
consciousness out into the universe
so that's where space exploration comes
in let me ask you as somebody who's a
screen theorist a physicist
do you think space exploration a
colonizing space is a physics or an
engineering problem what would you say
yeah i think it's fundamentally an
engineering problem if
we're not trying to do
things like
build wormholes the way they did say an
interstellar to get to a different place
or trying to travel near the speed of
light so that we would actually be able
to traverse interstellar distances i
mean without that
our colonization will happen in a very
very slow
rate right um
but one of the beauties of relativity is
if you do travel near the speed of light
you you can actually go arbitrarily far
in a human lifetime people say how's
that possible you can't go billions of
light years well you can actually
because as you can do this bleed of
light the way in which space and time
change allows you to go in principle
arbitrarily far that's that's very
exciting but if we put that physics side
of the issue
in the manipulation space and time to
the side yeah i think it's a deep
engineering problem you know how
do you terraform other planets i mean uh
how do you
go beyond our local neighborhood say
without you know using the ideas of
relativity so i think it's all quite
exciting and i think the idea is you
know using solar sails that you know
people have developed and
uh you know trying to take that first
step to mars i think that's a vital and
valuable step to take but yeah i think
these are fundamentally engineering
challenges or extending the human
lifespan through biology research or um
maybe reducing what it means to be a
human being into information and
uploading certain parts of it maybe not
all the full resolution of a human life
but maybe the essential things
like the dna and be able to reconstruct
that human being
but
you know i have to ask about mars
you know
do you find
the
the dream of humans stepping on mars
stepping foot first but also colonizing
mars
um
one that's worth us fighting for yeah
usually so i mean i think what we have
long
been not always in the best way
is a species of explorers
in the literal sense of
traveling from
one part of the world to another or in
the more metaphorical sense of trying to
travel through our minds to the quantum
realm or back to the big bang or to the
center of black holes so i think that's
fundamentally part of of the human
spirit so i do think that's a vital part
of
our heritage brought forward into its
next incarnation that's who we are
do you think there'll be a day
in the future where
a human being is born on mars
and has to
learn about his or her
human origins on earth like they'll have
to read in the book
yeah i don't think it'll be a book at
that stage it'll probably just be
uploaded into the head or something or
you know imprinted into the dna and then
they just sort of sense it but yeah i
think there's there's well look the the
issue you raised before is the vital one
is it the case that any sufficiently
advanced civilization destroys itself
is that sort of a a commonplace quality
i mean that's the other potential answer
to the fermi paradox uh why aren't they
here because by the time they got to the
technological development where they
could travel here they blew themselves
up they destroyed themselves and that's
a you know you know an unfortunate but
you know
not a hard to imagine possibility based
on things that have happened here
on planet earth but but putting that to
the side i think it um you know that's
the big obstacle but putting it to the
side we will resolve the engineering
challenges and and you know i should
probably um modify my answer from before
when you said is it engineering or
physics it's really both right so so we
will surmount the engineering challenges
and that will then make the physics
challenges relevant it'll make it
relevant to figure out how to travel
near the speed of light it'll make it
relevant to learn how to manipulate the
shape of space-time and so forth so
so i think it's a multi-stage process
where it is engineering and ultimately
physics and if we stick around long
enough those are the kinds of challenges
i think that we're ultimately going to
surmount and then the physics side is
figuring out how to harness energy
enough to travel outside the solar
system which seems like a heck of a
difficult journey but even mars itself
of um
i don't know maybe because i i was born
in the soviet union and was
born with the
you know looking up at the stars and
that dream of like the highest of human
achievement his ability to fly out there
to you know to join the stars
i i really like the idea of going to
mars of and not just stepping foot on
mars and it wasn't until
maybe um
misinformed but for me personally
uh it wasn't until elon musk
started talking about the colonization
of mars
did i realize like
we humans can actually do that
and the first of all the importance
of somebody saying that we can do these
seemingly impossible things
is um immeasurable because uh you know
the fact that he he placed that into my
mind
and into the minds of millions of others
maybe hundreds of millions maybe
billions of others young kids today i
mean that that's going to make it a
reality i for some reason i'm deeply
excited
even though my work isn't ai
that echoes all of this i'm excited by
the idea that somebody would be born
as we were saying on mars
and sort of look up and be able to see
with the telescope earth and say that's
where i came from
i don't know that
that idea scale to other planets to
other solar systems yeah that's really
exciting hugely exciting i i think
you're absolutely right i mean the vital
thing
is to dream
right i mean
and it sound hackney but it is so
important
for for young kids for the next
generation to to think about the things
that are seemingly impossible i mean
that's what makes them possible and this
is one which is concrete enough
i mean this is something that's going to
happen soon in terms of actually going
to mars
and then the next step of establishing
some
presence some semi-permanent or
permanent presence this is this is not
something that's gonna wait to the 25th
century i mean this is something that's
going to happen relatively soon
so i mean it could well be in your
lifetime unlikely mind but possibly in
your lifetime that that kid will be born
and and and have the experience that
that you describe so yeah it's
spectacularly exciting
and i actually i would love to go on
mars and one of the early
you would yeah what if it's one way i
was i'm happy really wow yeah and i'm
i'm single if there's ladies out there
that want to start that family
let's go let's go out to mars no i think
uh see i have to tell you something you
spoke about terror
thinking about like black holes
if i actually think about going to mars
and being on mars
and put myself in there fully
that's terror inducing
the idea of to be
in this foreign world where you can't
come back where you've made this this
choice that can't be reversed or you
know at some point it may be but but in
that guys
that to me carries a deep sense of
terror hmm
you know i i feel that sense of terror
every time kerouac jack carrack talked
about this and on the road is you know
when you leave a place if you're honest
about it
like life is short
and when you leave a place you move to a
new place and you think of all the
friends maybe family you're leaving
behind as you drive over the hill
that that really is goodbye
like we sometimes don't think of it that
way when we're moving but that really is
goodbye to that life to the person you
were to all the people maybe if it's
close friends you'll see them maybe 10
15 more times in your life and that's it
yeah and you're saying goodbye to all of
that and so in the same way i i see it
as way more dramatic when you're flying
away from earth and it's like it's
goodbye
to dunkin donuts and starbucks and
it's goodbye to whatever i don't know
why i picked those but some all the
things that are special to earth
it's goodbye but that's that's life i i
suppose
more what excites me about that kind of
journey
is it's a distinct contemplation of your
mortality acceptance of your mortality
you're saying
just like when you take on any difficult
journey it's accepting
that you're going to die one day
and might as well do
something truly exciting yes i mean i
will you know i'm with you on that i uh
i'm a
strong believer that
deep underneath human motivation is
this this terror of our own mortality
you know there's this wonderful book
that had a great influence in me called
the denial of death
by ernest becker
and
when you
are aware
of the ways in which
our mortality influences our behaviors
it really does add a different slant a
different kind of color to the
interpretation of human behavior
yeah it's funny um that that book had a
big influence on me as well is that
right right
and terror management theory and and
i
again from an engineering perspective i
don't know how many people that book
influenced
because i talk to people about the fear
of death and it doesn't seem to be
that fundamental to their experience
and i don't think on the surface is
fundamental to my experience but it
seems like an awfully in terms of we
talk about models and strength theory
and theories in terms of theories of
this macro experience of human life it
seems like a heck of a good theory
that the fear of death is that the kind
of is the warm at the core yeah well i
mean and the terror management theories
that you make reference to i mean
the
this is a group of you know
psychologists social psychologists who
devise these very
clever experiments real world
experiments with real people
where you can directly measure the
hidden influence
of the recognition of our own
mortality i mean they've done these
experiments where they have group of
people a group of people b
and the only difference between the two
groups is that group b they somehow
reminded them in some subtle way of
their own mortality sometimes it's
nothing more than interviewing them
with a funeral home across the street
you know an influence is there but it's
but it's subtle you don't even think you
take note of and they can find
measurable
effects
that differentiate the two groups to a
high degree of statistical significance
and how they respond to certain
challenges or certain kinds of questions
that shows a direct influence of the
reminder
of their own mortality and i've read a
number of these studies and they are
really convincing and so yeah i would
say that the reason why so many people
would say that
yeah fear of mortality it's not front
and center in my world view
yeah i don't really think about it much
doesn't really matter too much the
reason why they're able to say that is
because this thing called culture
has emerged over the course of the last
10 000 years and part of the role of
culture is to give us a means of not
thinking about our mortality all the
time of not living in terror of the
inevitable end which faces us all so
it's completely understandable that
that's the response because that's what
culture is at least in part four it's at
least possible
that uh the fear of death the terror of
your mortality is the creative force
that created all of the things around us
at this human civilization
and i think about from an engineering
perspective
this is where i lose all of my robotics
colleagues is i feel like
if you want to create intelligence you
have to also
engineer in some kind of
echoes of this kind of fear of uh and
not you know fear is such a complicated
word but
it's kind of like a scarcity
a scarcity of time a scarcity of
resources
that creates a kind of anxiety like
deadlines get you to do stuff yeah and
there's something almost fundamental to
that in terms of uh
human experience yeah well that's an
interesting thought so you're basically
in order to
create
a kind of
structure that mirrors what we call
consciousness yes you'd better have that
structure
confront the same kinds of issues and
terrorism
that we do consciousness and suffering
only makes sense in the context of death
if you want to i feel like
if you want to fit into human society
if you if you're a robot if you want to
fit into human society you better have
the same kind of existential dread
the same kind of fear of mortality
otherwise you're not going to fit in
[Laughter]
it might be it might be wild but it's at
least like we're talking about all the
theories that
are at least worth consideration i think
that's a really powerful one and
definitely one has uh resonated with me
and um
definitely seems to capture something
beautifully
like real about the human condition
and i i wonder it's of course sucks to
think that we need death
to appreciate life
but
that just may be the way it is well it's
interesting if this robotic or
artificially intelligent system
understands the world and understands
the second law of thermodynamics and
entropy
even in artificial intelligence will
realize that
even if its parts are really robust
ultimately it will
disintegrate yeah i mean so the time
scales may be different but in a way
when you think about it doesn't matter
once you know that you are mortal in the
sense that you are not eternal the time
scale hardly matters
because
it's it's either the whole thing or not
because on the scales of eternity any
finite duration however large is
effectively zero
on the scales of eternity and so maybe
it won't be so hard for an artificial
system to feel that sense of mortality
because it will recognize the underlying
physical laws and recognize its own
finitude
and then it'll be us and robots drinking
beers looking up at the stars and just
uh
you
know uh having a good laugh in awe of
the whole thing yeah
i think that's a pretty good way to end
it talking about the fear of death we
started
talking about the meaning of life and
ended on the fear of death brian it's
just an incredible conversation pleasure
thank you
i really really enjoyed it it's been a
long time coming i'm a huge fan of your
work a huge fan of your writing thanks
for talking about thank you
thanks for listening to this
conversation with brian green to support
this podcast please check out our
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and now let me leave you with some words
from bill bryson
physics is really nothing more than a
search for ultimate simplicity but so
far all we have is a kind of elegant
messiness
thank you for listening and hope to see
you next time
you