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

Hello, YouTubers. The World Science Festival is looking for enthusiastic translation ambassadors for its YouTube translation project. All you need is a Google account to get started. Here is a link to Loose Ends: String Theory and the Quest for the Ultimate Theory so you can see how it works: http://www.youtube.com/timedtext_video?ref=share&v=YSWd21z2qqE All you need to do is type along with the video and save when done. Here is another link to check out the full list of programs that you can contribute to. http://www.youtube.com/timedtext_cs_panel?c=UCShHFwKyhcDo3g7hr4f1R8A&tab=2 At the WSF we want to to cultivate a world informed by science and inspired by its wonder. With your contributions you can introduce science to a whole new world.

35:02 voile string vibrates in the wire ,

in which medium the string in string theory vibrates?

44:35 ????? please explain.

i know parallel universes exists.

57:22 nooooooooooooo noooooo nooooooooooooooooo..

I dont know much about astrophysics so this question might sound stupid.

If the earth puts the moon in orbit, if the sun puts the solar system in orbit, if the blackhole puts all the stars and planets in orbit. Do you think that the galaxy in orbiting something bigger on a large scale that cannot be measured?

And is it possible there is something putting the universe itself in an orbit?

Sorry if I sound stupid. Big fan of your lectures and videos by the way 😊

The universe is a hair theory

String theory brought you unscientific extrapolations and sensationalistic BS that is still out there in the public.

24:20

The first dude talking to Brian Greene is just annoying. And physicists should NEVER use words like "intuition". It is a philosophical error that has no place alongside reason and reality, the epistemology and metaphysics of all science

Brian Greene is extremely important in regard to get rid of all the bullshit people consume on a daily basis. He knows stuff, he knows how to think and he knows how to deliver what he thinks to people who are dumber than him, so they can follow his thoughts. Imagine a guy like Brian in politics. That would've been a step closer to a world that we actually can enjoy being in.

Ok guys I think we are all amateur scientist at heart even if that's not our field of expertise. Most ppl like to think & figure out things on their own & I think A LOT lol! A lot about the universe & how I THINK! when we're looking thru our telescopes back in time we are not just seeing what the universe looked like back in time but ALSO how fast it MOVED back in time. So when its said the universe is moving faster & faster away from us maybe what they should be saying is how fast the universe was moving back then. If the presumption or theory is the Big Bang in fact it certainly should have been moving faster back then which is what we should be observing & not just how fast it was moving away from us but also how fast WE were moving away from the Big Bang itself. In any case I'm still working out the math! lol