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Language: en
the following is a conversation with
Sean Carroll he's a theoretical
physicist at Caltech specializing in
quantum mechanics gravity and cosmology
he's the author of several popular books
one on the arrow of time called from
eternity to here one on the Higgs boson
called particle at the end of the
universe and one on science of
philosophy called the big picture on the
origins of life meaning in the universe
itself he has an upcoming book on
quantum mechanics that you can pre-order
now called something deeply hidden he
writes one of my favorite blogs and his
website preposterous universe com I
recommend clicking on the greatest-hits
link that lists accessible interesting
posts on the arrow of time dark matter
dark energy the Big Bang general
relativity string theory quantum
mechanics and the big meta questions
about the philosophy of science
God ethics politics academia and much
much more finally and perhaps most
famously he's the host of a podcast
called mindscape that you should
subscribe to and support on patreon
along with the Joe Rogan experience Sam
Harris is making sense and Dan Carlin's
hardcore history sean's mindscape
podcast is one of my favorite ways to
learn new ideas or explore different
perspectives and ideas that I thought I
understood it was truly an honor to meet
and spend a couple hours with Sean it's
a bit heartbreaking to say that for the
first time ever the audio recorder for
this podcast died in the middle of our
conversation there are technical reasons
for this having to do with phantom power
that I now understand and will avoid it
took me one hour to notice and fix the
problem so much like the universal 60
percent dark energy roughly the same
amount in this conversation was lost
except in the memories of the two people
involved and in my notes I'm sure we'll
talk again and continue this
conversation on this podcast or on
Shawn's and of course I look forward to
it
this is the artificial intelligence
podcast if you enjoy it subscribe on
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simply connect with me on Twitter at Lex
Friedman and now here's my conversation
with Sean Carroll what do you think is
more interesting and impactful
understanding how the universe works at
a fundamental level or understanding how
the human mind works you know of course
this is a crazy meaningless unanswerable
question in some sense because they're
both very interesting and there's no
absolute scale of interestingness that
we can rate them on there's the glib
answers that says the human brain is
part of the universe right and therefore
under saying the universe is more
fundamental than understanding the human
brain but do you really believe that
once we understand the fundamental way
the universe works at the particle level
the forces we would be able to
understand how the mind works no
certainly not we cannot understand how
ice cream works just from understanding
how particles work right so a big
believer in emergence I'm a big believer
that there are different ways of talking
about the world beyond just the most
fundamental microscopic one you know
when we talk about tables and chairs and
planets and people we're not talking the
language of particle physics and
cosmology so but understanding the
universe you didn't say just at the most
fundamental level right so understanding
the universe at all levels is part of
that I do think you have to be a little
bit more fair to the question there
probably are general principles of
complexity biology information
processing memory knowledge creativity
that go beyond just the human brain
right and and maybe one could count
understanding those as part of
understanding the universe the human
brain as far as we know is the most
complex thing in the universe so there's
it's certainly absurd to think that by
understanding the fundamental laws of
particle physics you get any direct
insight on how the brain works but then
there's this step from the fundamentals
of particle physics to information
processing yeah a lot of physicists and
philosophers maybe a little bit
carelessly take when they talk about
artificial intelligence do you think of
the universe
as a kind of a computational device know
to be like the honest answer there is no
there's a sense in which the universe
processes information clearly there's a
sense in which the universe is like a
computer clearly but in some sense I
think I tried to say this once on my
blog and no one agreed with me but the
universe is more like a computation than
a computer because the universe happens
once a computer is a general-purpose
machine right if you can ask it
different questions even a pocket
calculator right and it's set up to
answer certain kinds of questions the
universe isn't that so information
processing happens in the universe but
it's not what the universe is because I
know your MIT colleagues that Lloyd
feels very differently about this well
you're thinking of the universe it's a
closed system I am so what makes a
computer more like a like a PC like a
computing machine is that there's a
human that everyone comes up to it and
moves the mouse around yeah so input
gives it input gives it input and your
and that's why you're saying is just a
computation a deterministic thing that's
just unrolling but the immense
complexity of it is nevertheless like
processing there's a state and then it
changes with good rule with rules and
there's a sense for a lot of people that
if the brain operates the human brain
operates within that world then it's
simply just a small subset of that and
so there's no reason we can't build
arbitrarily great intelligences yeah do
you think of intelligence in this way
intelligence is tricky I don't have a
definition of it offhand so I remember
this panel discussion that I saw on
YouTube I wasn't there but Seth Lloyd
was on the panel and so was Martin Rees
the famous astrophysicist and Seth gave
his shtick for why the universe is a
computer and explained this and and and
Martin we said so what is not a computer
that's a good question I'm not sure
because if you have a sufficiently broad
definition of what a computer is then
everything is right and the simile or
the analogy gains
force when it excludes some things you
know is the moon going around the earth
performing a computation I can come up
with definitions in which the answer is
yes but it's not a very useful
computation I think that it's absolutely
helpful to think about the universe in
certain situations certain contexts as
an information processing device I am
even guilty of writing a paper called
quantum circuit cosmology where we
modeled the whole universe as a quantum
circuit as a circuit as a circuit yeah
and what you bits kind of with new bits
basically right yeah so in cube it's
becoming more and more entangled so what
do you want to do want to digress a
little bit this is kind of fun so here's
a mystery about the universe that is so
deep and profound that nobody talks
about it space expands right and we talk
about in a certain region of space a
certain number of degrees of freedom a
certain number of ways that the quantum
fields and the particles in that region
can arrange themselves that that number
of degrees of freedom in a region of
space is arguably finite we actually
don't know how many there are but
there's a very good argument it says
it's a finite number so as the universe
expands and space gets bigger
are there more degrees of freedom if
it's an infinite number it doesn't
really matter infinity times two is
still infinity but if it's a finite
number then there's more space so
there's more degrees of freedom so where
did they come from that would mean the
universe is not a closed system there's
more degrees of freedom popping into
existence so what we suggested was that
there are more degrees of freedom and
it's not that they're not there to start
but they're not entangled to start so
the universe that you and I know of zien
over the three dimensions around us that
we see we said those are the entangled
degrees of freedom making up space-time
and as the universe expands there's a
whole bunch of qubits in their in their
zero State that become entangled with
the rest of space-time through the
action of these quantum circuits so what
does it mean that there's now more
degrees of freedom as they become more
integral yeah so this is the universe
expands that's right so there's more and
more degrees of freedom they're
entangled that are
playing part playing the role a part of
the entangled space-time structure so
the basic the underlying philosophy is
that space-time itself arises from the
entanglement of some fundamental quantum
degrees of freedom Wow okay so at which
point is most of the the the
entanglement happening are we talking
about close to the bing bang are we
talking about throughout the the time
right yeah so the idea is that at the
Big Bang
almost all the degrees of freedom that
the universe could have were there but
they were unentangled with anything else
and that's a reflection of the fact that
the Big Bang had a low entropy it was
very simple very small place and as
space expands more and more degrees of
freedom become entangled with the rest
of the world well I have to ask John
Carroll what do you think of the thought
experiment from Nick Bostrom that we're
living in a simulation so I think let me
contextualize that a little bit more I
think people don't actually take this
thought experiments I think it's quite
interesting it's not very useful but
it's quite interesting from the
perspective of AI a lot of the learning
that can be done usually happens in
simulation from artificial examples and
so it's a constructive question to ask
how difficult is our real world to
simulate right which is kind of a dual
part of for living in a simulation and
somebody built that simulation now how
if you were to try to do it yourself how
hard would it be so obviously we could
be living a simulation if you just want
the physical possibility then I
completely agree that it's physically
possible I don't think that we actually
are so take this one piece of data into
consideration you know we we live in a
big universe okay there's two trillion
galaxies in our observable universe with
200 billion stars in each galaxy etc it
would seem to be a waste of resources to
have a universe that big going on just
to do a simulation so in other words I
want to be a good Bayesian I want to ask
under this hypothesis what do I expect
to see so the first thing I would say is
I wouldn't expect to see a universe that
was that big
okay the second thing is I wouldn't
expect the resolution of the universe to
be as good as it is so it's always
possible that if they're superhuman
simulators only have finite resources
that they don't render the entire
universe right that that the part that
is out there that two trillion galaxies
isn't actually being simulated fully
okay but then the obvious extrapolation
of that is that only I am being
simulated fully like the rest of you are
just part not non-player characters
right I'm the only thing that is real
the rest of you are just chatbots
beyond this wall I see the wall but
there is literally nothing on the other
side of the wall that is sort of the
Bayesian prediction that's what it would
be like to do an efficient simulation of
me
so like none of that seems quite
realistic there's that I don't see I
hear the argument that it's just
possible and easy to simulate lots of
things I don't see any evidence from
what we know about our universe that we
look like a simulated universe now maybe
you could say well we don't know what it
would look like but that's just
abandoning your Bayesian
responsibilities like your your job is
to say under this theory here's what you
would expect to see yes certainly if you
think about simulation is a thing that's
like a video game where only a small
subset is being rendered but say the
entire all of the laws of physics it the
entire closed system of the
quote-unquote universe mm-hmm it had a
creator yeah it's always possible all
right so that's not useful to think
about when you're thinking about physics
the way Nick Bostrom phrases it if is if
it's possible to simulate a universe
eventually we'll do it right you could
use that by the way for a lot of things
well yeah but I guess the question is
how hard is it to create a universe I
wrote a little blog post about this and
maybe maybe I'm missing something but
there's an argument that says not only
that it might be possible to simulate a
universe but probably if you imagine
that you actually attribute
consciousness and agency to the little
things that we're simulating to our
little artificial beings
there's probably a lot more of them than
there are ordinary organic beings in the
universe or there will be in the future
right so there's an argument that not
only is being a simulation possible it's
probable because in the space of all
living consciousness is most of them are
being simulated right most of them are
not at the top level I think that
argument must be wrong because it
follows from that argument that you know
if we're simulated but we can also
simulate other things well but if we can
simulate other things they can simulate
other things right
if we give them enough power and
resolution and ultimately we'll reach a
bottom because the laws of physics in
our universe have a bottom or made of
atoms and so forth
so there will be the cheapest possible
simulations and if you believe the
original argument you should conclude
that we should be in the cheapest
possible simulation because that's where
most people are but we don't look like
that doesn't look at all like we're at
the edge of resolution you know there
were 16-bit you know things but it's it
seems much easier to make much lower
level things that then we are so and
also I questioned the whole approach to
the anthropic principle that says we are
typical observers in the universe I
think that that's not actually I think
that there's a lot of selection that we
can do that we're typically in things we
already know but not typical within all
the universe so do you think there's
intelligent life however you would like
to define intelligent life out there in
the universe my guess is that there is
not intelligent life in the observable
universe other than us simply on the
basis of the the fact that the likely
number of other intelligent species in
the observable universe there's two
likely numbers zero or billions and if
there had been billions we would have
noticed already - for there to be
literally like a small number like you
know Star Trek there's you know a dozen
intelligent civilizations in our galaxy
but not a billion that that's weird that
that's sort of bizarre to me it's easy
for me to imagine that there are zero
others because there's just a big
bottleneck to making multicellular life
or
logical life or whatever it's very hard
for me to imagine that there's a whole
bunch out there that have somehow
remained hidden from us the question I'd
like to ask is what would intelligent
life look like the what I mean by that
question in a war that's going is what
if intelligent life is just fundamental
it's in some very big ways different
than our the one that has on earth that
there's all kinds of intelligent life
that operates in different scales of
both size and temporal right that's a
great possibility because I think we
should be humble about what intelligence
is what life is we don't even agree on
what life is much less what intelligent
life is right so that that's an argument
for humility saying there could be
intelligent life of a very different
character right like you could imagine
that dolphins are intelligent but never
invent space travel because they live in
the ocean and they don't have thumbs
right so they never invent technology
you never events melting maybe the
universe is full of intelligent species
that just don't make technology right
that that's compatible with the data I
think and and I think maybe maybe what
you're pointing at is even more out
there versions of intelligence you know
intelligence in inter molecular clouds
or on the surface of a neutron star or
in between the galaxies and giant things
where the equivalent of a heartbeat is
100 million years on the one hand yes we
should be very open-minded about those
things on the other hand we all all of
us share the same laws of physics there
might be something about the laws of
physics even though we don't currently
know exactly what that thing would be
that makes meters and years the right
length and time scales for intelligent
life maybe not but you know we're made
of atoms atoms have a certain size we
orbit stars or stars have a certain
lifetime it's not impossible to me that
there's a sweet spot for intelligent
life that we find ourselves in so I'm
hoping mine didn't either way I won't
mind either being humble and there's all
sorts of different kinds of life or no
there's a reason we just don't know it
yet why life like ours is the kind of
life that's out there yeah I'm of two
minds too but I often wonder if our
brains is just designed to quite
obviously to operate and see the world
in the unnies timescales and we're
almost blind and and the tools we've
created for detecting things are blind
yeah to the kind of observation needed
to see intelligent life or other skills
well I'm totally open to that but so
here's another argument I would make you
know we have looked for intelligent life
but we've looked at for it in the
dumbest way we can rise by turning radio
telescopes to the sky and why in the
world would a super advanced
civilization randomly beam out radio
signals wastefully in all directions
into the universe that just doesn't make
any sense
especially because in order to think
that you would actually contact another
civilization you would have to do it
forever you have to keep doing it for
millions of years that sounds like a
waste of resources if you thought that
there were other solar systems with
planets around them where maybe
intelligent life didn't yet exist but
might someday you wouldn't try to talk
to it with radio waves she would send a
spacecraft out there and you would park
it around there and it would be like
from our point of view be like 2001 or
there's an you know an monolith monolith
so there could be an artifact in fact
the other way works also right there
could be artifacts in our solar system
that are have been put there by other
technologically advanced civilizations
and that's how we will eventually
contact them and we have just haven't
explored the solar system well enough
yet to find them the reason why we don't
think about that is because we're young
and impatient right like it would take
more than my lifetime to actually send
something to another star system and
wait for it and then come back so but if
if we start thinking on hundreds of
thousands of years or million year
timescales that's clearly the right
thing to do
are you excited by the thing that Elon
Musk says don't pay sex in general space
but the idea of space exploration even
though your or your species is young and
impatient ya know I do think that space
travel is crucially important long term
even to other star systems and I think
that many people overestimate the
difficulty because they say look if you
travel 1% the speed of light to another
star system will be dead before we get
there right and I think that it's much
easier and therefore when they write
their science fiction stories they
imagine we feel fast from the speed of
light because otherwise they are too
impatient right we're not gonna go
faster than the speed of light but we
could easily imagine that the human
lifespan gets extended to thousands of
years and once you do that then the
stars are much closer effectively right
and what's a hundred year trip right so
I think that that's gonna be the future
the far future not not my lifetime once
again but baby steps and unless your
lifetime gets extended well it's in a
race against time right a friend of mine
who actually thinks about these things
said you know you and I are gonna die
but I don't know about our grandchildren
that's right that's it I don't know for
predicting the future is hard but that's
at least a plausible scenario and so ya
know I think that as we discussed
earlier there are threats to the earth
known and unknown right having spread
humanity and biology elsewhere is a
really important long-term goal what
kind of questions can science not
currently answer but might soon when you
think about the problems and the
mysteries before us hmm that may be
within reach of science I think an
obvious one is the origin of life we
don't know how that happened there's a
difficulty in knowing how it happened
historically actually you know literally
on earth but starting life from non-life
is something I kind of think we're close
to right we really think so how like how
difficult is it to start lie - well I
I've talked to people including on the
podcast about this you know life
requires three things life as we know it
so there's a difference with life which
who knows what it is
and life as we know it which we can talk
about with some intelligence so life as
we know it requires compartmentalization
you need like a little membrane around
your cell metabolism you take in food
and eat it and let that make you do
things and then replication okay so you
need to have some information about
you are that you passed down through to
future generations in the lab
compartmentalization seems pretty easy
not hard to make lipid bilayers that
come into a little cellular walls pretty
easily metabolism and replication are
hard but replication we're close to
people have made RNA like molecules in
the lab that I think the state of the
art is they're not able to make one
molecule that reproduces itself but
they're able to make two molecules that
reproduce each other yeah so that's okay
that's pretty close metabolism is hard
to believe it or not even though it's
sort of the most obvious thing but you
want some sort of controlled metabolism
and the actual cellular machinery in our
bodies is quite complicated it's hard to
see it just popping into existence all
by itself probably took a while but it's
we're making progress and in fact I
don't think we're spending nearly enough
money on it if I were the NSF I would
flood this area with money because it
would change our view of the world if we
could actually make life in the lab and
understand how it was made originally
here on earth and I'm sure have some
ripple effects that help cure disease
and so on I mean that just that ending
so synthetic biology is a wonderful big
frontier where we're making cells the
right now the best way to do that is to
borrow heavily from existing biology
right where craig Venter several years
ago created an artificial cell but all
he did was not all he did it was a
tremendous accomplishment but all he did
was take out the DNA from a cell and put
in an entirely new DNA and let it boot
up and go hmm what about the leap to
creating intelligent life on Earth yeah
however again we define intelligence of
course but let's just even say Homo
sapiens the the modern the modern
intelligence in our human brain you have
a sense of what's involved in that leap
and how big of a leap that is so AI
would count in this or you really want
life you want a really organism in some
sense AI would count okay I yeah of
course of course AI would come but well
let's say artificial consciousness right
so I do not think we are on the
threshold of creating artificial
consciousness I think it's possible
I'm not again very educated about how
close we are but my impression is not
that we're really close because we
understand how little how little we
understand of consciousness and what it
is so if we don't have any idea what it
is it's hard to imagine we're on the
threshold of making it ourselves
but it's doable it's possible I don't
see any obstacles in principle so yeah I
would hold out some interest in that
happening eventually I think in general
consciousness I think we'll be just
surprised how easy consciousness is once
we create intelligence you know I think
consciousness is the thing that that's
just something we all fake
well good no actually I like this idea
that in fact consciousness is way less
mysterious than we think yeah because
we're all at every time at every moment
less conscious than we think we are
right we can fool things and I think
that plus the idea that you not only
have artificial intelligent systems but
you put them in a body right give them a
robot body that will help the faking a
lot yeah I think I think creating
consciousness in our artificial
consciousness is as simple as asking a
Roomba to say I'm conscious and refusing
to be talked out of it could be it could
be and I mean I'm almost being silly but
that's what we do yeah that's what we do
with each other this is the kind of that
consciousness is also a social construct
and a lot of our ideas of intelligence
is a social construct and so reaching
that bar involves something that's
beyond that's not necessarily involve
the fundamental understanding of how you
go from electrons to neurons to
cognition no I actually I think that is
a really good point and in fact what it
suggests is you know so yeah you
referred to Kate Kate darling who I had
on the podcast and who does these
experiments with very simple robots but
they look like animals and they can look
like they're experiencing pain and we
human beings react very negatively to
these little robots looking like they're
experiencing pain and what you want to
say is yeah but they're just robots it's
not really pain
he's just some electrons going around
but then you realize you know you and I
are just electrons going around and
that's what pain is also and so what I
what I would have an easy time imagining
is that there is a spectrum between
these simple robots that Kate works with
and a human being where there are things
that sort of by some strict definition
touring test level thing are not
conscious but nevertheless walk and talk
like they're conscious and it could be
that the future is I mean
Siri is close right and so it might be
the future has a lot more agents like
that and in fact rather than some day
going aha we have consciousness will
just creep up on it with more and more
accurate reflections of what we expect
and in the future maybe the present for
example we haven't met before and you're
made basically assuming that I'm human
as it's a high probability at this time
because the yeah but in the future there
might be question marks on that right
yeah no absolutely
certainly videos are almost to the point
where you shouldn't trust them already
photos you can't trust right videos is
easier to trust but we're getting worse
that yeah we're getting better at faking
them Yeah right getting better
yeah so physical embodied people what's
what's so hard about faking that so this
is very depressing this conversation
right so to me is excited you're doing
it so exciting to you but it's a
sobering thought we're very bad right
yet imagining what the next 50 years are
gonna be like when we're in the middle
of a phase transition as who you are
right now yeah and I in general I'm not
blind to all the threats yeah I am
excited by the power of technology to
solve to protect us against the threats
as they evolve I'm not as much as Steven
Pinker optimistic about the world but in
everything I've seen all the brilliant
people in the world that I've met are
good people so the army of the good in
terms of the development of technology
is large okay you're way more optimistic
than I am I think that goodness and
badness are equally distributed among
intelligent and unintelligent people I
don't see much of a correlation there
interesting
neither of us have proof yeah exactly is
yeah
again that pinions are freeze right nor
definitions of good and evil we come
without definitions or with without data
opinions so what kind of questions
concerns not currently answer may never
be able to answer in your view well the
obvious one is what is good and bad you
know I know what is right and wrong I
think that there are questions that you
know science tells us what happens what
the world is and what it does it doesn't
say what the world should do or what we
should do because we're part of the
world but we are part of the world and
we have the ability to feel like
something's right something's wrong and
to make a very long story very short I
think that the idea of moral philosophy
is systematizing our intuitions of what
is right what is wrong and science might
be able to predict ahead of time what we
will do but it won't ever be able to
judge whether we should have done it or
not so you know you're kind of unique in
terms of scientists listen it doesn't
have to do with podcast but even just
reaching out I think you referred to as
sort of an doing interdisciplinary
science so you reach out and talk to
people that are outside of your
discipline which I always hope that's
what science was for in fact I was a
little disillusioned when I realized
that academia is very siloed yeah and so
the question is how well at your own
level how do you prepare for these
conversations how do you think about
these conversations how do you open your
mind enough to have these conversations
and it may be a little bit broader
how can you advise other scientists to
have these kinds of conversations not at
the podcast so the fact that you're
doing a podcast is awesome other people
don't hear them yeah but it's also good
to have it without mics right in general
it's a good question but a tough one to
answer I think about you know a guy
knows a personal trainer and he was
asked on a podcast how do we you know
psych ourselves up to do a workout how
do we make that discipline to go and
work out he's like why you asking me
like I can't stop working out like I
don't need to psych myself up so and
likewise you know he asked me like how
do you get to like have inner discipline
conversations and all sorts of different
things all sorts of different people and
like that's that's what makes me go
right like that's I couldn't stop doing
that I did that long before any of them
were recorded in fact a lot of the
motivation for starting recording it was
making sure I would read all these books
that I had purchased right like all
these books I wanted to read not enough
time to read them and now if I have
motivation because I'm gonna you know
interview Pat Churchland I'm gonna
finally read her for her book you know
and it's absolutely true that academia
is extraordinarily siloed right we don't
talk to people we rarely do and in fact
when we do is punished you know like the
people who do it successfully generally
first became very successful within
their little silo you have discipline
and only then did they start expanding
out if you're a young person you know I
I have graduate students I try to be
very very candid with them about this
that it's you know most graduate
students are to not become faculty
members right it's a it's a tough road
and so live the life you want to live
but do it with your eyes open about what
it does to your job chances and the more
broad you are and the less time you
spend hyper specializing in your field
the lower your job chances are that's
just an academic reality it's terrible I
don't like it yeah but it's a reality
and for some people that's fine like
there's plenty of people who are
wonderful scientists who have zero
interest in branching out and talking to
things to anyone outside their field but
it is disillusioning to me some of the
you know romantic notion I had the
intellectual academic life is belied by
the reality of it the idea that we
should reach out beyond our discipline
and that is a positive good is just so
rare in universities that it may as well
not exist at all but that said even
though you're saying you're doing it
like the personal trainer because you
just can't help it you're also an
inspiration to others like I could speak
for myself you know I also have a career
I'm thinking about right now and without
your podcast I may
not have been doing this at all right so
it makes me realize that these kinds of
conversations is kind of what science is
about in many ways what the reason we
write papers this exchange of ideas is
it's much harder to do interdisciplinary
papers I would say yeah that's right and
conversations are easier so
conversations is a beginning and in the
field of AI that's in - it's it's
obvious that we should think outside of
pure computer vision competitions and a
particular data sets which should think
about the broader impact of how this can
be you know you know the reaching out
the physics the psychology to
neuroscience and having these
conversations so that you're an
inspiration and so well thank you never
sweet but never know how the world
changes I mean the the fact that this
stuff is out there and I've a huge
number of people come up to me a grad
students really loving the podcast
inspired by it and they will probably
have that there'll be ripple effects
when they become faculty and so on so we
can end on a balance between pessimism
and optimism and Shawn thank you so much
for talking it was awesome no Lex thank
you very much for this conversation was
great
you