For more than a century physicists have
tried to find a unified theory a single
mathematical framework capable of
describing all of nature's forces Albert
Einstein who unified space and time and
a special and general theories of
relativity pursued this goal for over 30
years
never succeeding today scientists are
continuing the quest seeking to combine
general relativity describing the
universe on large scale stars and
galaxies with quantum mechanics
describing the universe unsub atomic
scales each of these two theories works
amazingly well in its own domain but put
them together like in the dense center
of a black hole and the math falls apart
in the 1970s scientists came upon a
potential solution but from an
unexpected starting point studies of
nuclear processes in that era we were
trying to understand the strong nuclear
force it's just the force that holds the
nucleus of the atom
together and that was a complete mystery
how to do it in trying to solve that
mystery physicists were led to a
promising equation that seemed to
describe vibrating strings that would
hold together atomic constituents but
within just a few years a different
theory proved to be the right solution
for understanding the strong nuclear
force and so strings no longer seemed
necessary almost all of these several
hundred people stopped working on string
theory at that time and only a handful
of diehards continued to pursue them the
few of us who continued working on
string theory felt that the mathematics
was so beautiful and compelling that
this theory had to be good for something
much like Einstein who spent long
periods working on ideas outside the
mainstream Schwarz and his colleague
Joelle Sherk continued to explore string
theory we realized what string theory
was good for and that was as a quantum
theory of gravity at that point I was
convinced that this is what I've been
working on to the rest of
career Schwarz was proposing that
string theory which had failed as a
theory of the strong nuclear force was
actually the solution to one of the
biggest problems in all of physics
uniting gravity and quantum mechanics
when Schwarz excitedly announced this
prospect few people paid any attention
the field just wasn't ready so Schwartz
and a new convert Michael Greene spent
years developing the theory mostly on
their own
then in 1984 they achieved a
breakthrough showing that the
mathematics of string theory deftly
avoided potentially lethal technical
issues and this time the community of
physicists heard them
Princeton between the University and the
Institute for Advanced Study you had
almost half the experts in the world who
were working on related topics and I am
told that at that point almost all of
them dropped what they were doing and
became string theorists as string theory
rapidly progressed there was a sense
that research was but a few years away
from uncovering the final and unified
theory of physics more than 30 years
later the goal of a fully unified and
thoroughly tested theory has yet to be
achieved but enthusiasm remains high
string theory has come closer than any
other attempt to go beyond known physics
and tackled the grand challenge of
unification but the question remains is
string theory and elegant mathematical
chimera or our string theorist rapidly
approaching the realization of
einstein's dream
welcome to tonight's program which is
focusing upon a really ancient project
the project as we described in that
little segment project of unification
and you can really trace the human urge
to try to unify our understanding going
all the way back I mean Democritus long
time ago imagined that reality amounted
to atoms and the void that's all that
there was Galileo spoke about the book
of nature being written by God in the
language of mathematics that would be
the unifying framework describing things
all in terms of the symbols that we use
to articulate mathematical equations and
as in that little piece and as well as
many of you no doubt know Albert
Einstein spent 30 years trying to unify
our understanding of the laws of physics
but ultimately came up empty-handed and
what we're going to discuss here tonight
is the next chapter of that story a
story that is ongoing and we're going to
break down the discussion into three
conversations which very roughly
speaking will cover the past the present
and the future of unification there will
be overlaps so that way of thinking
about things is not completely accurate
but that's the general progression of
the evening so let's get right down to
it and we have a number of guests who
are leaders in the field and thinking
about these kinds of ideas and the first
guest this evening is a professor of
natural philosophy physics and astronomy
at Dartmouth College is a fellow of the
American Physical Society
and winner of the 2019 Templeton Prize
please welcome Marcelo gleiser so
Marcelo thank you for being here today
and you know when we talk about
unification we know that throughout
history there have been many steps and
route to the approach that some of us
have been pursuing in fact you pursued
at one point as well string theory and
we have a little road map that we can
bring up on the screen which kind of
shows some of the key steps now
obviously there's a lot on this and
we're not going to be able to cover it
all but what I'd like to do in our
conversation is sort of start at the
bottom left-hand side which many people
view as the first step in the modern
program of unification which is putting
electricity and magnetism together so
can you take us a little bit through
that history maybe going back to Faraday
and Maxwell and what happened sure so
we're talking about early 1800s and
people had some experience of
electricity by having shocks whenever
they you know had a very dry environment
and they were touched like a doorknob or
something and they knew about magnetism
since well for a long time but at least
in 1601 the court physician of Elizabeth
the first called William Gilbert he
wrote a book about magnetism and he
realized that the earth was a giant
magnet and that's how compasses work you
know the basically aligning with the
north magnetic pole and so these two
things were considered to be very
different and until Michael Faraday
started to make some experiments and and
actually even before him Hans Christian
Oersted in Copenhagen he realized that
if you had an electric current going
through a wire a magnet would move and
so there was this and it was sort of an
accidental discovery had a bunch of
stuff on the table or doing
demonstrations and then he figure that
out so clearly there was a connection
between the two and it took Michael
Faraday's brilliance you know to develop
this and he realized that it wasn't just
an electric current that could
effect magnetic compasses but it was
actually magnetism
just like the picture is showing up
there that he realized that if you move
a magnet you can't create an electric
current as well so there was clearly a
connection between the two and he
started to visualize this and this was
also very useful for us with the notion
of a field you know that basically the
presence of these sources of magnetism
of electricity they they spread around
space and this spreading around space is
how say a charge will fill the presence
of another charge through this field
right and then later on came Maxwell
maybe a couple of decades later and he
then elaborated these connections
between electricity and magnetism
showing that you actually have a set of
four equations right the ones that you
see on a t-shirt right you have and God
said four equations and there was light
because what Maxwell did was he wrote
the equations of how changes in
electricity magnetism because of
different sources or even in empty space
propagated and he realized the
propagation was at the speed of light so
clearly the way light should be
interpreted is actually as a moving
electromagnetic field in space and hence
the unification of the two now those
those four equations that are on
t-shirts that perhaps it's worth noting
his formulation was a little more
complicated so you know as we mature in
our understanding in the field of
science and this will be a theme
actually throughout tonight we get
better and better and finding ways of
streamlining combining unifying in a
sense even in the mathematical notation
so today we have these four equations
but back then it was kind of a mess fact
you if you really use special relativity
which we'll talk about soon you can
actually write all of them in one
equation yeah it's beautiful right
exactly so why don't we turn to that so
this is our first unification
electricity and magnetism this deep
unexpected connection Maxwell codifies
it mathematically in the electromagnetic
equations that we all teach the
undergraduates and physics around the
world
Einstein perhaps is rightly credited
with the next step in the
toward unity by recognizing an
unexpected link between space and time
say can you sort of take us you already
mentioned light so the speed of light
being constant is a vital part of that
story as well so when you take us
through that though so I still realize
that there were some inconsistencies
with the formulation of Maxwell's
equations and and nobody could figure
out exactly what was going on one of the
big mysteries in in the 19th century was
that you know as we know from intuition
every wave propagates in a medium right
so if you throw a rock on water you know
the energy of the rock is gonna hit the
water you're gonna see the waves
propagating on water Here I am talking
to you that means you have sound waves
growing through the air if there is no
air there's no sound no explosions in
outer space so every way seems to need a
medium to propagate so the question then
became okay so at does light propagate
right there was a important question
because you can see Stars which means
the medium should be transparent right
and it can't have any viscosity because
otherwise the planets would slow down
and fall into the Sun so he had a
transparent no friction no weight
clearly and he had to be somewhat rigid
actually quite rigid but to propagate
waves at that kind of speed so it's kind
of like a magical thing which people
call the ether right and for many many
years Maxwell try to create models of
the ether to kind of make sense of all
this and in 1887 there was a very famous
experiment actually by American
physicist Michelson Morley where they
actually were going to show how the
eater interferes with the propagation of
electromagnetic waves and they couldn't
find it so there was like a mystery for
a while how is that even possible all
right and only 1905 Einstein came up
with his way new way of thinking so he
creates the special theory of relativity
he's 26 years old and he comes up with
two essential postulates one of them
very reasonable known way before from
the time of Galileo that the laws of
physics should be the same for everybody
at least everybody moving with with with
constant speed relative to
an order makes sense otherwise how could
you actually have laws of nature if they
change when people moved around and the
second one which is a really amazing one
is that the speed of light should always
be the same for any observer
irrespective of how the source is moving
right and with these two things he
showed that you could actually that the
the speed of light and the way we make
measurements of distances in space and
of moments in time a duration in time
were affected and that's where you have
the very strange idea of time dilation
you know time moves slower if your clock
is moving and space contraction where
little you know a rod for example or you
if you're moving close to speed of light
you're kind of shrinking the direction
of the motion so schematically it's as
if space and time as we see here are
kind of adjusting themselves in order to
keep this other thing the speed of light
from change and keeping it constant at
you know whatever units you like this
one is miles per hour but this constancy
of the speed of light winds up
establishing an unexpected unity between
space and time they need to work
together in order to keep the speed of
light constant so that's sort of the
second big moment in the modern route to
a unified understanding of nature now
after the special theory of relativity
mentioned that's 1905 Einstein is 26
years old he could have stopped there
right I mean that that's the kind of
achievement that many of us would say
you know there's not much left for me to
do but frying Stein he was just getting
started right so the next step is he
goes further and brings the force of
gravity into the story so it just tell
us a little bit about the next ten years
and this further unification of space
time and gravity so it did take about
ten years for a chance to really get to
the end of the story but his first
intuitions were not much later after
1905 he said he had the Hat his happiest
thought right which was the idea that if
somebody is kind of dramatic if
somebody's falling from a roof dog that
person won't feel
his or her own weight right so you're
sort of this idea of weightlessness they
were falling through space and you feel
weightless that is was his intuition and
you know all this because living in New
York you go up and down elevators all
the time and you know when you're going
down an elevator from a high-rise very
fast you feel lighter right now if
televator just Falls you feel weightless
so I just and realized that to talk
about motion they had acceleration in it
you also had to talk about gravity so as
he tried to expand his theory of special
relativity special here's just was about
motions at constant speed to motions
with acceleration he realized that that
new theory had to be a theory that
included gravity as well and that's a
beautiful thing because as he goes to
formulate the theory which we would say
it's perhaps the most beautiful theory
in physics the biased of course you know
because that's what we do right that
theory was a theory that related gravity
not to this kind of mysterious action at
a distance
which was what Newton did he in a sense
did a unification of the laws of gravity
on earth and in space as well but it was
a theory that describe gravity as the
curvature of space and also the its
effects time and how time flows if you
have a very strong mass you know that to
do that so that was his next big step so
he realized that and of course we should
also mention the connection between mass
and energy there is a byproduct of all
this so in 1905 there was a second paper
on speciality which is the famous equals
MC square paper right in which there is
a deep connection between mass and
energy and that mass had the property of
affecting the geometry of space and
because of that there is a change in the
motion say of planets around the Sun
which can be explained by this by this
beautiful theory so we now have this
part of the the map fairly set now
in 1919 70s or so there was another
important moment that we don't really
have time to go through but it's quite
analogous to what Maxwell did putting
electricity and magnetism together and
that
the electroweak theory which puts
together another force of nature which
is the weak nuclear force together with
the electromagnetic force they also
proved to be different aspects of a
single ingredient called the electroweak
force so we get to this point by say
roughly 1980 now we could stop here
right we have gravity in the story we've
got electricity magnetism weak nuclear
force and so forth but we want to
continue to move toward unity as best as
we can
now the next steps however go beyond
what we have experimentally tested so so
the question is what do we do so we can
give a sense of the equations behind
this which is not a bad thing to show
because it helps to motivate us to go
further so so what are we looking at
right from one equation to this that's
not good right yeah so this is
essentially what summarizes what we call
the standard model of particle physics
which basically is a description of all
12 particles that we have measured in
the laboratory especially like at the
Large Hadron Collider at CERN and before
that a formula these huge machines that
can actually find these particles of
nature so there are 12 of those and then
there's also the Higgs which is a
particle responsible for giving mass to
all the other particles and basically
this is the state of the art in a sense
that we can actually measure and feel
comfortable somewhat about what we know
and this describes essentially three
fundamental forces gravity I'll forget
it gravity is not even there right so
this is not about gravity this is about
electromagnetism and the weak and strong
nuclear forces so the weak nuclear force
very quickly is the one responsible for
radioactive decay for their activity for
having you know how the Sun powers
itself in a sense and the strong nuclear
force is one that keeps say the atomic
nucleus together and I have a bunch of
protons they're all positive they should
be running away from one another but
they're glued together
by the strong force who also keeps the
quarks which are the fundamental
particles you see here inside of protons
and neutrons okay so this is it
one thing about the electroweak
unification though is that it is not as
perfect as we would like it to be
because the way we think about these
forces that every force has a what we
call it a coupling constant but
basically a measurement of how strong
that force is innocent so gravity has
the G for neutrons constant right
electromagnetism has Eve for the
electric charge and it turns out that
the electroweak unification does not
have a single coupling constants to
connect the two it's still describing
the two forces somewhat differently they
seem to review similar behaviors at very
high energies which is the the
inspiration we can actually show the
rest of the road map but the road map
from here unlike this equation which is
experimentally tested as we go further
these steps are not experimentally
confirmed in fact we can even go further
and show the rest of the map and
basically everything that's above Row 3
is hypothetical and we have been
developing the mathematics behind these
next steps in the road toward unity for
three decades if not longer so the deep
question that we face and I posed to
Marcello without having the experiments
without having the observations without
having the data that will allow us to go
above the third row where we do have
experiments and data that confirms
everything where does that leave us and
you have very specific views on whether
we're perhaps doing the right thing and
pushing forward with a purely
mathematical motivation to go further
right so a little bit of history is that
I in 84 I was doing my PhD at King's
College and with when Schwarz talked
about his and Greene you know talking
about that discoveries in the string
theory I'm like wow this is it
no you got to work on this it's
beautiful it's at the time the idea was
that you'd really find a unification of
the four known forces of nature which is
something we should talk about at some
point four known forces of nature is
very important so I jumped into this and
and tried hard like you did and a bunch
of other people in our generation you
know try to to make sense of all of this
and and the program was very sound in
the sense that behind our expectation of
trying to find this unified formulation
there were very concrete predictions
right I mean so in order for these
string theories to work you had to
impose a new symmetry of nature called
supersymmetry and supersymmetry had a
very specific prediction which is
basically to every particle of the
standard model the twelve particles I
talked about there should be a mirror
world so to speak of supersymmetric
particles so the electron has a
supersymmetric is called this electron
the photon the particle of light a
photino and so on and hopefully with big
machines you should be able to find them
right that was the big expectation of
the time so you big bigger and bigger
machines and one of the goals of the
Large Hadron Collider in Switzerland was
not just to find the Higgs which
beautifully was done in 2012 but to also
find the lightest of all supersymmetric
particles and and it hasn't it's not
there at least we haven't found it yet
right and and so that rules out some
versions of supersymmetric theories and
then the question is what do you do as a
theoretical physicist at this point
right that you basically spend decades
of your life working and of course we're
going to have another guess here there
is a real expert on this you spend
decades of your life working on this
thing and you know you're placing a bet
on this and it's not coming through so
what are you supposed to do at this
point right so do you say I'm sorry I
was wrong and you move on to other
things well it turns out that
supersymmetric
theories they're so flexible in their
formulation that you can always kind of
change the parameters in ways where the
particles that you were supposed to find
are so massive that you could not find
in the head-on Collider which basically
means is a theory that in principle
cannot be killed right because it could
I mean you say look I haven't found it
no problem when we have a accelerator
which is a hundred times bigger you'll
find it and then you can always to a
certain extent drill this up and create
more and more complicated models right
and I don't think there is anything
wrong with that because there's what I
would call it creative perplexity right
now related to this because clearly we
want this beautiful Platonic dream of
simplification of nature to be true but
at the end of the day nature is the
ultimate guide you know we have to
listen to nature because that's the
whole goal of physics is to explain what
the world is like not what the world is
like you'd like it to be and and so this
is a very interesting time for us right
now because things that we thought were
going to be definitely discovered are
not quite being discovered and the
moment now is a little complicated and
and it's a very important moment because
what we decide to do now is going to
impact the field of particle physics for
decades to come because these
accelerators are very complicated
machines and it takes decades of
planning and a lot of money to make them
work now you have a particular
philosophical orientation in terms of
human knowledge more generally and I
think you even have a slide that you
that you gave us that summarizes that
perspective so just take us through your
view on the program to sort of try to
find the deep fundamental laws that will
describe all physical phenomenon versus
your view of how knowledge progresses
right so this is actually the title of a
book of mine called the island of
knowledge and it's basically a metaphor
for how we humans understand the world
around us so the idea is
simple if everything that we know about
the world fits in an island right as we
know more about the world and about
ourselves and about a place in the
universe this island grows and as every
good Island you know it's surrounded by
an ocean and I call mine the ocean of
the unknown so science in a sense is an
exploration of what we don't know right
that's the whole point we are expanding
our views we're expanding of tools of
exploration I call them reality
amplifiers in our telescopes or particle
detectors in ways that we can see more
that we could see in the past so that is
how we advance right so as the island
grows into this ocean of the unknown the
paradox of knowledge though is the fact
that the boundary between what is known
and what is don't what is not known
grows so that means that as you learn
more about the nature of reality
you're become equipped to ask questions
that you couldn't have asked before
because you had no idea simple example
of that the telescope so before Galileo
built a telescope you know in 60 well it
wasn't his first wasn't the first
telescope but he said it was he was
smart and then he sold it to all the you
know the nobility of Venice made money
etc but so he he builds his telescope he
looks at the sky and he sees things that
no one had ever seen before right and
that was a profound change in our
worldview and with many implications you
know religious implications social
implications for softer implications
because of this expansion of knowledge
and because of this new machine he was
able to ask questions about the world
about the universe that no one could
have asked before right and so to me
this is very much how science advances
it's through this expansion into the
unknown that allow us to begin to ask
new questions for example we couldn't
have asked anything about supersymmetry
before we had the idea of supersymmetry
and now we're looking for it and we
don't find it let's assume we could find
it and then this whole new way of
thinking about the world is
is going to happen because of this new
theory now having said that presumably
you do agree that there are chapters
inside the book of knowledge that can be
fully written they open up other areas
but it's conceivable that we will have
the theory that describes all of the
fundamental forces describing all the
fundamental particles of matter how they
combine and the kinds of behaviors that
aggregates can play out maybe something
that is beyond our ability to ever fully
articulate like I don't think a
fundamental theory will ever for
instance be able to predict the the
kinds of socks the color sucks that I
have on I don't even know what I've got
but I've got black right now right so
it's just unlikely that we'll be able to
undertake those kinds of calculations
but what about the fundamental theory
that's on our map toward unity is that
something that you think fits into the
unknowable or is that something that you
imagine could be no right so so that's a
great question so I think in terms of
what philosophers like to call the map
and the territory
okay and the idea is that we are map
makers that's what we do our theories
are maps of what we see of the world
right the territory if you were to
there's a famous short story by jorge
luis borges about the map makers that
wanted to make a very perfect map and
every time they improved the map the map
became bigger and bigger and bigger
until they had the map as big as the
country and that was the best map they
could ever have and clear was a useless
map right because maps are descriptions
of what we can see and so the point is
that our theories are maps of reality
guided by what we can eventually measure
right and given that our machines our
technologies can never give us a
complete picture of reality there is
always a higher energy scale until you
get to the Planck scale and we are very
far from that that is really very
dangerous I think to assume that the
four forces of nature that we know now
are the only forces of nature
exist so what I would like to point is
that the best that we can do is to
construct a unified theory of the known
forces of nature but to make a statement
that that is the ultimate theory of how
the funnel is to me really unjustified
by the way we do science right but
typically of course I think most
physicists have the attitude that all
theories are provisional they're the
best description that we have at a given
moment of the physics that we have
access to but you know we all know that
even Einstein's equations will be
modified as we try to understand the
universe in more extreme realms than his
equations were developed to explain so
let me finish up with one one question
because we only have a couple minutes
before I need to move on to the next
participant tonight it's kind of a big
one but maybe I have a quick thought on
if it's too big just telling me hey I
don't want to talk about that we can
just end it right there but when we talk
about complete theories some I'm often
asked what do you think about girdle's
incompleteness theorem and what does
that imply for this program girl of
course famously wrote down a theorem a
long time ago that basically said that
if you have a system with axioms that
are sufficiently rich to be able to
describe things like arithmetic that
either the system will be inconsistent
or if it's not inconsistent there will
be true statements within that system
that you'll never be able to establish
to be true within the system itself does
that have any bearing in your mind on
the program of searching for the deep
fundamental laws of physics I think it
is in a sense because it's kind of like
the Russian dolls right I mean so to
bypass the giggles incompleteness
theorems you have to create a bigger
system that encompasses that one right
but then of course that bigger system is
going to have the same problem and then
a bigger system and on a bigger system
and the problem is that we just the idea
of completeness of knowledge is is is a
very dangerous one and I think it'll
prove that in mathematics
and the notion that in physics because
we do need to validate empirically what
we're doing it becomes even more
complicated because we depend on
technology on machine and so I'm very
happy with the notion that we can't know
everything there is to know at the level
of fundamental particles because that's
what's going to keep us working harder
to move on and on and to me is the
process this quest for knowledge that
really matters not so much the unpredict
and gives us something to do going
forward exactly yeah ok Mia in the
second part of the conversation we're
going to turn specifically to string
theory proper and try to get a sense of
how far we've gone in connecting it to
the physics of the real world imagine I
have a beautiful tree that's filled with
oranges and I asked myself what is the
orange made of how do I answer that
question well I want to look deeply
inside the orange so I magnify it and I
magnify it again and if I keep on doing
it
deep inside sooner or later I begin to
see molecules come into view but
molecules are not the end of the story
because the molecules I can enlarge them
and if I make them big enough deep
inside I begin to see atoms atoms are
not the end of the story too because we
have electrons zooming around the
nucleus deep inside mostly empty space
in the atom but deep inside we see the
nucleus so if I grab that and magnify it
I see that the nucleus is itself made of
particles neutrons and protons and if I
grab one of the neutrons and magnify it
I find yet further particles little tiny
quarks inside now that is where the
conventional ideas stop
string theory comes along and suggests
that inside these particles there is
something else so if I take a little
quark and I magnify it conventional idea
says there's nothing inside but string
theory says I'll find a little tiny
filament a little filament of energy a
little string like filament and just
like the string on a violin I pluck it
and it vibrates creates a little musical
note that I can hear the little strings
in string theory when they vibrate they
don't produce musical notes they produce
the particles themselves so what quark
is nothing but a string vibrating in one
pattern an electron is nothing but a
string vibrating in a different pattern
a neutrino nothing but a string
vibrating and a different pattern still
so if I take all of this back together I
have my ordinary orange and if these
ideas are right they are speculative but
if they are right deep inside the orange
or any other piece of matter there's
nothing but a dancing vibrating cosmic
symphony of strings that's the basic
idea of string theory how far we've gone
toward establishing or refuting that
this idea actually describes the world
around us and for that discussion I'm
pleased to bring out our next guest he
was recently elected to the National
Academy of Sciences and is currently
writing a book on the big questions
confronting particle physicists and
cosmologists please welcome Michael dine
so Michael thanks thanks so much for
joining us and you know we had this map
of unification that we can bring back up
where we see at the top this proposed
idea of superstring theory also called
m-theory maybe we'll get to that in the
course of our conversation but the the
key question is is that step of the
story something that we can justify
through experiment and observation I
mean the mathematics is beautiful John
Schwarz spoke about it in the opening
that it puts gravity and quantum
mechanics together the left-hand side we
understand well quantum mechanically the
right-hand side is problematic quantum
account your string theory puts that all
together so it's a beautiful compelling
structure and the question is aligning
it with experiment now in the previous
conversation with Marcela we spoke about
supersymmetry which is the super super
string and that for a long time was held
out as the smoking gun that we were
going to prove the super symmetric
quality of the universe so first of all
when we talk about supersymmetry what
does it mean for the spectrum of
particles the stuff that should be out
there well I suppose back up in the in
you wrote these equations or we
presented these equations for the
standard model and they look really ugly
yeah okay they're not really ugly
they're really rather beautiful so the
so the theory is biskits ocularly
successful until recently we were
missing one piece which was this Higgs
particle and there was a lot of
speculation about what that might be and
now that's been found and and it acts
sort of just like it's supposed to right
so so so we had this this kind of very
pretty story and the thing that sort of
excited a lot of the interest in string
theory and certainly part of your career
and certainly mine was the and East
rominger who we'll hear from next is
that string theory seems to be able to
produce this standard model at least in
rough outline right in a very remarkable
way so so so that's partly why I didn't
want to bias this that way but your
beautiful Theory comes out
right when all sake comes out vertically
you mean like the vibrations of the
stream the kinds of particles that we
see on the left they bring in a very
remarkable way yeah and and so that part
is is really quite pretty now there had
been before string theory came along
there were reasons to think they might
that that might be they're mostly
connected with puzzles are related to
the higgs particle and a lot of us
thought who worked on this at the time
thought maybe this idea was a little
contrived and then a long came string
theory and among the things string
theory did was oh there was okay me not
these particles next extra things yes
these Morton these additional vibrations
were were there and I certainly was I
actually should say I was sort of
dragged kicking in streams
screaming into the subject of string
theory because I've read all your papers
I thought you were a gung ho and duty I
was initially I was part of part of this
generation that viewed string theory is
kind of passe this thing as you saw in
John Schwartz's argument and yeah and
there was a period where I would talk
particularly the ed Witten
and I would say how are you gonna solve
this problem and you would say you
scratch his head and they say I don't
know and then he would come back two
days later and say by the way so so it's
my do I have a solution yes yeah right
yes so so I got quite nervous and in
particularly this fact that a lot of
these features of supersymmetry were
there that we had speculated on was got
me quite excited right and I thought I
think in the spirit of things you said
that there were weeks away and I better
get to work so but sweetly but I should
say that it's sort of understood in fact
supersymmetry is a little too much of a
crutch in string theory the only string
theories who really understand well have
exact supersymmetry so all these other
particles would be there there were in
addition to the electron which they in
addition to the electron which is which
which is so familiar to us there would
be this thing just like that except just
a little bit different on this electron
and it's not there it's now so back in
back in the eighties when I started to
work on string theory all the somewhat
more established scientists such as
yourselves gave the impression that this
was the next frontier of particle
physics we're building this big machine
in Geneva and it's gonna find these
particles and that I mean tell us where
we stand on that program so the truth is
there were reasons to be skeptical about
this program you tell me for a while I
actually if you listen to me carefully
as the low post as many of my friends
some of whom you were having in other
parts of being you would have heard me
say that but but but but what we're now
in the situation that we have the the
Large Hadron Collider at CERN which has
now been running well for almost a
decade has has this that has both
established the cigs party really
established the standard model with
exquisite precision has allowed us to do
all kinds of things both experimentally
and theoretically which I wouldn't
imagine we could do it's a number of
years ago okay but one things that has
done is is said I think as Marcello said
that if supersymmetry is there the
particles are heavier than we guessed
and Marcello described the theory as
rather elastic in a way it inside its
elastic but it gets uglier as the masses
of these particles get to reach of the
large right so so to be specific for
example the the what we know about the
Higgs suggests that the now suggests
that the supersymmetric particles if
they're there are are out of reach of
the LHC and out of reach of a lot of the
things that we currently contemplate so
so so it's so it's it's a trouble it's
an idea in some tension in some trouble
yeah I mean I should I should say I
don't know I I recently did a sort of a
quick
just curious on the fraction of the
papers that I've written in my career
that assumed that supersymmetry is
correct and it's a significant fraction
it could be as much as 90% of the work
that I've done so there's a certain kind
of discomfort associated with the lack
of finding these part do you share that
discomfort or I don't know if it's 90%
of my papers it's in it's a it's a it's
a it's a number and yes I share I share
I share this discomfort I think will
come but I think will come shortly to
some of the or a little bit to some of
the reasons why perhaps some of our D
ideas about where supersymmetry should
be you have a certain amount of hubris
yep and so let's change your slightly
there and talk about another key quality
of string theory that is really quite
iconoclastic that that it requires that
the universe have more than three
dimensions of space this is sort of one
of the other strange features and
because just sort of you know in a
cityscape like here you can consider the
dimensions to be up down back forth
left-right and if you zoom in according
to the ideas of string theory you go
small enough you're gonna find extra
dimensions of space usually imagine that
they're curled up really small in order
that they evade direct detection as we
look around the world around us and
strings are imagined to be so small that
they vibrate within these tiny curled up
dimensions of space so depending on the
formulation of the theory there could be
six or seven of these extra dimensions
we understand that distinction quite
well the question is is it a matter of
simply hiding away these extra
dimensions that are sort of a weird
mathematical feature of the theory or is
there a way that we might indirectly
find evidence that these extra
dimensions are actually out there could
they be the smoking gun there there well
there are various ways to think about
this question I mean I often when I talk
to students or lecture about this say
the real problem
so first you get kind of dizzy when
somebody introduces you to this idea and
the next problem is they say how hard it
is to if they're curled up to actually
see any evidence so and there had been
speculations on the possibility there
actually some of these extra dimensions
or would be large yeah sort of
millimeters even size so as you could
imagine sort of probing them with
tweezers and people subsequently have
done experiments and ruled out these
kind of very what people call large very
large extra dimensions there is still a
chance on my own embedding is against it
that we will we could find evidence that
we will not know so I would bet against
but there is the possible but I want to
say there is the possibility and
certainly people consider it and people
in doing experiments consider what might
be the evidence in trying to exclude or
place limits on these possibilities but
but as you say it also seems I am I
strongly suspect that well not we may
not know the whole picture that that
extra dimensions do play some role will
play some role in some larger
understanding of the laws of nature now
one of the things that excited me about
this subject we sort of talked a little
historically back when these ideas were
first really being developed back in the
1980s the precise shape of the extra
dimensions sort of played the role of a
kind of DNA of the string theory
universe because the shape of the extra
dimensions would affect how the strings
vibrate and as you saw in the little
opening video how the strings vibrate
determines the properties of the
corresponding particle so the thought
back in the 80s was if you understood
the precise shape of the extra
dimensions you might actually be able to
calculate those numbers in that crazy
formula that we showed before that had
within it you probably couldn't see it
the mass of the electron the mass of the
quarks the mass the neutrinos the mass
of the Higgs that all of that might be
embodied by the geometry of these extra
dimensions a unity if you will of all
those numbers inside the geometry the
shape of these extra dimensions that
program presumably was something that
was appealing to you in that era as well
one of the problems of course is there's
not just one shape we're showing one
shape over here
I mean tell us what happened in the
eighties and nineties for the you're
actually more of an expert on this than
I am but the but but there really and
Andy as well there there has been a
proliferation pot of sorry it should
perhaps back up and yes a basically we
don't really understand string we
understand string theories sort of we
don't really understand this it that
well we can't write the equations as
nicely as Maxwell wrote dis equations
but we know we sort of know when we
found a solution of the equations right
and we thought we had just a few at
first and some of them looked like you
and yourself worked on examples which
looked like they had lots of features of
the standard model but there has been a
proliferation so then now I don't know
what the right way to characterize it
but ordered many orders of magnitude of
of known solutions as many as many
different shapes may differ from
different features so so we're not I
personally am NOT an optimist that one
could find the one right I I view this
as a problem that one will have two more
probe at least for the moment in a sort
of statistical fashion asking what's
characteristic what's generic as opposed
to trying to find this specific standard
model if you will find those generic
features here by alright japes
so my fantasy for example is explaining
you know these we're coming back to
supersymmetry yeah a kind of question
like might be among these is it typical
that the scale of supersymmetry breaking
that the the splittings between these
particles in their masses is that
something you should see if the LHC is
it something that is somewhat larger
scale could you figure that out right
and there's so many could you to sort of
do some statistics of these and figure
it out now now one other sort of
astounding development in the late 1990s
was the discovery that the expansion of
the universe is actually speeding out or
accelerating and and that was an
unexpected I thinked about certainly for
me I presumably for you as well we
thought that the expansion will be
slowing down over time gravity tends to
pull things back together but yet it's
going faster and faster to explain that
we needed to introduce this idea of dark
energy that yields this repulsive push
the weird thing is the amount of dark
energy is a bizarre number right it's a
starts with a decimal point has a huge
number of zeros after it and you know
there's a sort of convenient feel for it
right here so this number trying to make
sense of this observed number indirectly
some people of other approaches what has
this done to the program of trying to
connect string theory to the observable
world so let me go back to supersymmetry
first and you kind of explain what the
tension was I did try before and why I
why I claimed I was at least cautious
okay
and so you've drawn here something I
didn't count the zeros but I'm guessing
you about 120 years there are 120 zeroes
so supersymmetry was proposed to explain
a similar problem where they're about 32
zeros yeah okay so 120 is a lot more
than 32 and it is in many ways a more
fundamental problem and we don't have
really good ideas we have an idea which
we'll talk about to perhaps understand
this none of us are totally in love with
it and it's different than the idea of
supersymmetry so this is something we
already we knew even before this was
discovered that that there was some
tension here significant tension here
and it's gotten just worse with this
with this understanding and discovery
any other idea presumably referring to
is the multiverse idea yeah so once you
sort of take us through the thinking so
you've already sort of alluded to it
here that the we we have this
proliferation of solutions of the string
equations actually I should perhaps back
up
and say that the multiverse was proposed
before string theory in a sense it was a
formula this was proposed by Stephen
Weinberg who who basically predicted the
dark energy so he basically said a way
you might understand the dark energy is
to imagine that there are actually if
you like many universes with different
values of this crazy number most of
which are big I think you have a slide
it shows most of which are don't have so
many zeroes yeah but but there's just so
many that a few of them have these zeros
and if you're some kind of star trekky
kind of figure I think you know
exploring is these many universes
somehow once in a while you'll find one
with this very small number and what's
special about these ones with small
numbers he pointed out is only those
will have stars planets things were
people or intelligent beings are less
intelligent being soon be yeah and this
so this this idea gives a lot of gives
pause but it also successfully really
predicted the amount of dark energy
that's observed so string theory looks
like it might provide a setting for this
idea this multiverse it has the
potential we're not sure it's also
actually related to our lack of
understanding of how supersymmetry is
broken
yes Turing theory but there's the
possibility that string theory works
this way the idea is that you could have
all these different universes with
different shapes for the extra
dimensions giving rise to different
amounts of dark and different values of
all those coupling constants of all
those numbers in the sly and now some
people look at a solution like that
quizzically and they say look you guys
have all these problems you don't have a
unique shape for the extra dimensions
you don't have a unique universe and in
order to leverage those problems you
imagine that maybe all these universes
are out there and that we're just 1 in
this grand collection and aren't you
guys just giving up or even worse
papering over the problems that your
theories have we have you respond to
this I remember a talk that David gross
noticed string theorists cave where he
kept repeating Churchill's lines yes
never never never
yes
and and there's a question of whether
it's giving up so my own personal
attitude and now I'm not I'm not
speaking of a great movement or
something
is that a way we might deal with this is
to understand the statistics of of these
many states so I think for those of us
who now live in a world of big data and
so on you could imagine you know you
somehow sample all these and you have
some idea what's typical you're right
and there's a one proach one one view
one aspect of this which is related to
things that you worked on as well is
related to the fact that most of these
many universes aren't stable they're
sort of like unstable elements they
would decay after a fall apart quickly
yeah fall apart and quickly and we want
to stick around for you know at least 15
billion years or so and these would fall
apart typically in fractions of seconds
okay so you could ask what might account
for what what among as you sample these
which are the stable ones and it turns
out interesting enough the stable ones
are tend to be the super symmetric ones
so this doesn't quite predict
supersymmetry at the LHC but this is a
in the class of things we might hope to
address right but there are I should say
there are many people who reject this
whole way of thinking entirely so you
know we're getting toward the end of our
of our time here and and I wanted to
just ask you the file I don't know if
this is a personal question role but if
we go back to your frame of mind in say
the 1980s when there was this incredible
excitement about supersymmetry string
theory super gravity unification if you
were to project forward from the
mid-1980s to 2019 how have we done we
the good questions first so so I would
say that we actually a little bit as our
focus has changed yeah in some ways
I think in fairness to myself again III
there's something called the tyneside
burg problem which is which basically
deals with some of the problems we faced
and and and I think we've come further
to addressing it than we actually have I
might have guessed so but we also have I
think this is something that Marcello
said we've also sharpened our questions
okay so in ways that perhaps aren't even
on these slides we understand the dark
energy has now given us a sharp set of
questions the dark matter which I don't
think has figured so much in our
discussion yeah how's also and again in
a qualitative way string theory gives us
some handles on these questions as well
so I am I'm keeping busy I am I think
there are lots of interesting questions
I think some things are hard I mean I
think the fact that you know everyone
just to pause and say that the fact that
the Higgs particle is there and actually
acts you know it's not something I would
have really expected it's really a very
remarkable comes out of attention
mathematics and Naturals really so so so
looking looking forward final question
imagine that in the next 20 years we
don't find supersymmetry either at the
LSE maybe we have a new Collider it
doesn't find any evidence for
supersymmetry we don't find the dark
matter so we don't have that as an input
to our story we we sort of don't have
any connection to observable
experimental physics what do you think
happens to the program of unification
the program of supersymmetry and in that
situation I think it goes on but I think
I am my own thing now I'm being I am
being personal here I think well first
of all of course in 20 years I'm older
than you
in 20 years I will be you know it won't
matter but but the but i but i think i
think it will go on but i think it will
it will be a narrower field and it will
be I mean I think
you know there will be quiet there is
always a question of what are both what
we do theoretically and also what's
feasible and affordable to do
experimentally right now and these will
be these will be serious issues right
right great talking to you Michael thank
you for your insights on these issues
Michael dying everybody
all right so the final section of the
program we're going to turn to an
approach to gain insight into some of
these questions it's coming from a
somewhat different angle from the study
of black holes sort of extreme form of
gravity and for that conversation we are
pleased to have and astrologer he has
numerous awards including the Dirac
Medal and the breakthrough prize in
fundamental physics and it's work has
shed light on the black hole information
paradox discovered by Stephen Hawking
please welcome Andy Fromm
so great to see you Andy and you know in
this third part of this conversation on
the search for unity the path toward
realizing Einsteins dream and a more
modern version and Einstein even thought
about it we're gonna turn to the study
of black holes and before we get into
the details of that subject I mean just
quickly tell us I think most everybody
here is familiar but you know what is a
black hole and moreover what was
Einstein's view about black holes was
the into this possibility comes out of
his equations yeah so if you're on the
surface of the earth and you want to get
into outer space you have to jump at 11
kilometers a second on the moon it's a
little easier if you jump at 7
kilometers a second you can go on
forever scape the gravitational pull of
the moon but if you have enough mass in
one place to get away you would have to
be able to jump at the speed of light
and Einstein told us nobody can ever go
faster than the speed of light and so
nothing can escape from a region of
space-time where gravity is that strong
not even light and therefore it's called
a black hole because the black light
doesn't get out and the first solution
to Einstein's equations was in fact a
black hole
Schwarz child family solution and
Einstein encounters this solution to his
own equations yes and and what does he
what does he say
what does he think I it's it's an
incredible thing I mean the solution was
found just a few months after the field
equations in complete form exact
solution of the equations and we spent a
hundred years trying to understand it
and Einstein himself the great man 30
years later sorry
25 years later wrote a paper in which he
said black holes don't exist and it's
not because Einstein was stupid it's
because it was just there really
seeing objects and we've been trying to
understand them for a hundred years we
understand a lot about them we know they
do exist in a spectacular development
last month yes a picture of it let me
bring that picture up yep there it is
yeah
warmed all the hearts of those of us
who've been working on it for many
decades and but there's still huge
puzzles about a black hole which came up
with Stephen Hawking's work in the 70s
and those we are still very confused
about and oddly
string theory has had a lot to say about
them and string theory in the hands of
Andrew Strom mature has had a lot to say
about that and we'll get to that you
don't have to be modest I understand but
we want to get to the the incredible
insight that you and kurma baphu had
about black holes to get there can you
take us back to one particular puzzle
that was first articulated by John
Wheeler which had to do with these ideas
of entropy and black holes yeah so a
black hole is a very kind of perfect
simple object it's really kind of a hole
in space which is very perfectly
described by Einsteins solution of
Einstein equation and in that way it's
very different from for example a star
so if we take two stars of the same mass
they will differ in innumerable details
they will have different composition of
molecules the molecules would be moving
in different ways but black holes are
just every black hole of the same mass
and they also have a spin is according
to Einstein according to their equations
exactly the same and this puzzled people
and the great John Wheeler who also
invented the word black hole
describe this by saying a black hole has
no hair that is it's a featureless
object so if you have to bold people in
the room you can't distinguish them by
their hairdos if you do people with
their you could say what as a short
haircut the other one has a comb-over
whatever there's many different
distinguishing features but so stars are
like people with hundred black holes or
like bold people they're all the same
and well if you can't see very well so
he envisioned if you say threw a cup of
tea I think it's the the metaphor that
he is you take a cup of tea and you sort
of throw it into a black hole he was
worried that the the information carried
by the tea the entropy if you will the
disorder carabao the tea would have no
way of showing up inside a black hole
because like you say it has no hair and
they all look the same right so this
system was a puzzle that you could sort
of get rid of entropy by throwing it
inside a black hole and it would be gone
from the universe and his student
bekenstein began to think about this and
he gave insights that ultimately led to
your work what was his view of this
puzzle well they were very bothered so
going back to Newton and before there is
an idea which is very important to
physicists namely that there are laws of
physics and moreover we like to think
that the laws of physics govern
everything that happens if we knew all
of them and if we had perfect knowledge
and part of that is that information
should never be lost things can't just
disappear and so if you throw a cup of
coffee or a computer or your diary or
something into a black hole
according to the way that Einstein would
have described them there's no trace of
it left
it's just van
and that is antithetical to everything
that physicists would like to believe so
what do we do with that puzzle so is it
you know do we have to bite the bullet
and say that information is gone and we
just have to deal with it or what do we
do well this story got substantially
enriched due to the amazing work of
Stephen Hawking in the 70s there's a
missing piece in this discussion was the
inclusion of quantum mechanics and so
Stephen asked the question well what
happens if you have a black hole in the
real world and we know that a black hole
everything is subject to the quantum
mechanical uncertainty principle it it
allows no exceptions and so a black hole
itself is somewhat uncertain and the
location of the horizon of the black
hole the edge of it wobbles around a
little bit has some uncertainty to it
and that allows things to kind of slip
out quantum things can slip out and the
way that they slip out was described in
a kind of breathtakingly simple and
elegant paper by Hawking in the mid 70s
and I had a very precise formula maybe
we could see that formula and it it is
one of the important formulas in I would
consider one of the several most
important formulas that came out of the
20th century physics Stephen has it on
his gravestone inscribed is that true
yes and it's on the floor it was all
with all that with all the terms yes Wow
under what that cost that
yeah I think somebody else paid for
probably yeah it's all floor it's on the
floor Westminster yeah it's very
important formula we just talk a little
bit about that formula so yeah so the s
and there's is entropy we can think of
this as a formula for how many gigabytes
you can put inside a black hole and it
turns out if you want to have a
smartphone with more gigabytes the size
the the number of gigabytes you could
put into your smartphone is proportional
to the volume inside yours right put the
little chips in there you fill it up
goes like the volume this formula isn't
like that the formula for the gigabytes
that you can put in a black hole and
it's proportional to the area so it's as
if you're only allowed to put chips on
the surface of the black hole right and
that's surprising because the formula
goes against our intuition right that
that the amount of information the
amount of stuff should be proportional
to how much volume is there but it's
saying it just goes like the area right
now when we study thermodynamics and
entropy as undergraduates yeah if I
could interrupt for yeah it's a lot of
gigabytes yes all of the all of the
gigabytes in the Google data banks could
fit inside a black hole a trillionth of
a trillionth of an inch they're thought
to be the best information storage
devices you did that hard to get they
get hold of that information but maybe
her name yeah but so so it's a lot of
information but it scales in a funny way
doesn't go with the volume it goes like
the area but the point I was making
before is that when we study
thermodynamics as undergraduates
we're told that entropy
and you know it's related to information
is account if you will the different
ways of rearranging the ingredients that
make up whatever system you're studying
yes so a lot of entropy means there's a
lot of rearrangements that
macroscopically all pretty much look the
same if it's low entropy then they're
fewer such rearrangements exactly now
you mentioned before that black holes
are like the simplest thing right
there's a horizon but there's kind of
empty space inside so the puzzle still
is what are we counting right in that
formula right and you you gave insight
deep insight into that yeah so I just
just want to rephrase that that you know
according to what Einstein and Schwarz
Hilda the black holes were and wheeler
they were the simplest most featureless
object right and then according to
Hawking they were the most complex
conceivable objects with the most
structure that you you could possibly
have so this was a huge puzzle and we
didn't it sat there for decades many
people lost a lot of sleep over it we
didn't know what to do about it and then
string theory came along and had
something to say about it and that was a
surprise but maybe shouldn't have been
such a surprise you know as you
discussed earlier
string theory started out we're
scientists we're exploring the unknown
there's no road map we just explore
everything and we might find something
that we didn't expect
you know Columbus was looking for China
and he might have been disappointed when
he found America
but in retrospect it was a good thing
and so we started out with strings and
Brian was in the beginning talking about
this picture of quarks and leptons and
neutrinos being made of of strings that
picture could be right the jury is still
out but later on and and I would say
actually this this began and in a
wonderful collaboration that Brian and
Dave more exciting collaboration that
Brian and Dave Morrison and I had some
years ago in which we found that strings
way in between becoming quarks and
leptons could turn into little black
holes and then you put a lot of them
together and which I hey this is kind of
interesting they can turn into little
black holes then we started studying how
they put put them together and we could
make eventually learn how to make big
black holes out of them and we learned
in that work this was also the beginning
with bright and devorah said with other
many people it takes a village there are
many people involved in this but we
learned how string theory can pull off
this magic feat of describing an object
which at once looks like an empty hole
and a maximally complex object so in
some way that can be described with very
precise mathematics something is in both
incredibly complex and incredibly simple
when something gets very complex it
becomes simple again so with that you
gave the world really the first way of
quantitatively analyzing the
rearrangement of ingredients that have
put together in the right way
yield in the right circumstance a black
hole right so many viewed this
a kind of key moment in string theory
because while it's not predicting an
observable feature of the world that we
go out and sort of directly measure yeah
it is making contact with the
quantitative feature of the world that
was already on the books for decades and
this is the first time that there was a
way of understanding it through our into
mental theory right right so string
theory found a solution to a problem
that had been posed in a completely
different field now this solution this
trick the string theory has for
accounting for all the gigabytes in a
black hole we don't know if the trick
its to say it's the trick that is
actually used by m87 black hole m87 that
we just saw a picture of but it there
aren't we didn't know there were any
tricks now we know that there's one
trick and we're trying hard to
understand if m87 uses the same trick
that's this string theory uses so we can
extract lessons from string theory about
the real world and that's something
we're working yes so this is a this is
now as of no doubt you follow the news
this is a black hole real one that's
what 55 million light years away in
different galaxies and 87 now observed
making use of these radio telescopes
that are scattered around the globe is
it conceivable that we could use even
more precise versions of these
observations to make contact with some
quality of string theory that would be
kind of iconic to it that might actually
single it out as the unique or among the
few possible theoretical frameworks for
understanding the observations it's it's
it's possible and we're trying you know
to make a link between this picture
and the ideas in string theory and when
we did this calculation in string theory
it was a very complicated calculation a
lot of mathematics algebraic geometry
long complicated calculations at the end
we got perfect agreement so we knew that
we had done it right perfect agreement
with Hawking's formula talk perfect
agreement with Hawking's formula so you
could describe Hawking's formula as you
know you again going back to you have a
smartphone you start putting gigabyte
photos into it you put 16 of them in and
then you can't put anymore in and you
deduce that your smartphone can hold 16
gigabytes of data you don't know how it
stores the data that's what Hawking did
he deduced how much their information is
in a black hole what we did using string
theory where we have a lot of control
over the equations was pry the thing
open look at the bits count'em and show
that it showed that it showed that it
agreed now we did it in a very
complicated way and as often happens in
science you start to realize that you
can do the calculation at a shorter and
shorter and shorter way and ultimately
we realized that the key ingredient that
enabled us to do this calculation was a
special symmetry that these black holes
have called conformal symmetry and then
we realize that some black holes in
nature once that spin very very fast
have this same conformal symmetry and so
probably
we can understand the construction of
their what the chips inside it looked
like using the same ideas that we used
in string theory they haven't been able
to deduce the spin of this yet and we
are trying to understand that they will
get a better image we will understand
the form of the image better but we're
trying to see if this black hole has
that conformal symmetry that we the same
one that we used in string theory and so
we've written some there's a chance that
that will work out yep and there's a lot
of black holes out there there's you
know thousands or billions of them up
there
this this is an image with only 16
pixels I'm expecting that you know this
is the beginning of seeing black holes
well this is like not even a black and
white TV I'm I'm hoping that we will get
you know high resolution images and we
will see many black holes some of them
we know are spinning at nearly the speed
of light and and have the conformal
symmetry and so we've made some
predictions for what exactly what will
the black hole will look like the
detailed pattern of of the polarization
of the light and the shape of the image
and so on and in principle this could be
seen and it would be an interesting
right so that is our that is our
prediction of what the polarization the
light that comes from the black hole
what they did with the Alex Lobosco
Delila gates of dead cop it's what the
polarization of the light will look like
if you were looking down the barrel
action
we're looking at 15 degrees so it's
actually an even more complex pattern
yep
but there's a very definite prediction
now this is not proof of string theory
but it is it is how science works it
works in unexpected ways
and we're talking to the event horizon
team about how to best set up the
actually little telescopes to try to
look at this and yeah so so we're coming
toward the end of the discussion a
couple of the things I wanted to to
discuss with you before we conclude so
in part one we spoke to Marcelo gleiser
about the general idea of unification
and starting with Maxwell and
electromagnetism and going ultimately
towards string theory and he mentioned
this possibility that you know they're
perhaps islands of knowledge and maybe
there are limits to what we can ever
figure out in part two we spoke to Mike
dine about trying to make linkages
between the unification program and warm
you know bread and butter visit particle
physics supersymmetry things that we
might actually see it the Large Hadron
Collider and that program has yet to be
successful so one way of looking at
these sort of first two parts of the
conversation is great try but you're
sort of not really getting there in my
conversations with you across the deck
is you were one Columbia what's it would
you have said that to Columbus when it
came back we try but sorry I wanted
China
exactly exactly No so that really speaks
to your optimism which has been
completely clear to me over many decades
but but just to give a sense where do
you stand on on on your your view of
string theory is it not has it reached
what you'd hoped it would by this era is
it is it in some ways you have some ways
no and like what's your prognostication
going forward well so there's a view of
the nature of physics that perhaps
started in the beginning of the 20th
century that progress in physics was
about understanding things called
duction ISM understanding you know
molecules are made of atoms atoms are
made of electrons and protons protons
are made of quarks and then we go down
to strengths that's the reductionist
program but it's a really kind of
one-dimensional view of what science is
and the original idea which many or but
not all people had of what string theory
was good for was it was the final
resolution of the reductionist program
now we knew what everything was we found
the strings that's the end of it physics
departments around the world can shutter
their doors you know that's not how it
works you know we keep exploring we keep
finding new things strings had to be
explored we're still exploring we found
other things that we didn't expect we
found out about black holes we found out
about Holograms we learned we spawned
new fields of mathematics we you know
been used to describe superconductors
you know walk all kinds of of wonderful
things that we learned and in fact I
think that the idea that people were
excited about back in 1985 was really a
small thing you know to kind of complete
that table that you put down in the
beginning of the spectrum of particles
and then we could say okay you know this
is last year the World Science Festival
it's all it's all done now we've got you
know it you know string theory was
really the beginning and what has
happened so we didn't do that we didn't
predict new things that were going to be
measured at the Large Hadron Collider
but what has happened is so much more
exciting and than than our original
vision right
that is we've learned in the process of
trying to understand what makes up a
black hole it turns out the interesting
things were not the small things but the
big things m87 this thing you could drop
our solar system in it and not notice it
and we don't understand it right so
we've learned we've we've learned a lot
about about the big things and we've
learned things which we sadly don't have
time to go into it but about the nature
of space and time which in quantum
mechanics and we're we're getting little
hints of a radical new view of the
nature of space and time in which it
really is just an approximate concept
and emergent from something deeper I
mean that is really really more exciting
I mean it's exciting as quantum
mechanics or general relativity probably
even more so right and I think that
before we solve the puzzles that you've
heard about tonight we will have a
revolution in the way that we think
about the universe at least as profound
as what was brought on by quantum
mechanics and general relativity and I
would trade that for a slightly
lengthened list of elementary particles
any day another great point and on that
that is a spectacular and it's Rominger
conversation thank you folks
