tonight I'd like to tell you about one of the big questions in science it's a
question that goes back at least two and a half thousand years to the ancient
Greeks and it's a question that has been discussed in this room many many times
over the past 200 years but it's an important question and I think it's
important that we revisited and the question is simply this it's what are we
made of what are the fundamental building blocks of nature that you and
me and everything else in the universe and constructed that's the story I'd
like to tell me so what I'd like to do is try and give you an overview of our
current understanding I'd also like to try and give you an overview of where we
hope to go in the future of what progress we can we can hope to make in
the next few years and few decades and we're going to cover quite a lot of
ground in this talk I should I should warn you now not least because I'm going
to discuss every single thing in the universe quite literally we're going to
talk amongst other things about what's happening at the world's most powerful
particle collider this is a machine that's called the Large Hadron Collider
or the LHC for short it'll come up a lot in this talk and it's a machine which is
based underground in a place called CERN which is just tell sergeant Eva will
also talk about experiments in the last few years that look backwards in time
towards the Big Bang that give us some understanding about what was happening
in the first few fractions of a second after time itself started to exist and
on top of all this I also want to give you some idea about the theoretical
abstract ideas and even a little bit idea about the mathematics that
underlies our current understanding of of the universe because I'm a
theoretical physicist what I do is study the equations try to understand the
equations that are that govern the world we live in and so I just like to give
you a flavor of what that's about at some point I should warn you now at
some point I'm even going to show you equation okay you know that you can get
sent on training courses for this kind of this kind of thing there's a number
one rule the number one rule is never show them any equations if you show them
equations you'll just terrify them at some point in this lecture you're all
going to be terrified so just prepare yourself okay okay you know there's a
traditional way to start talks like this the traditional way is to be very
cultured and talk about with Democritus and Lucretia's said two-and-a-half
thousand years ago and the ideas that the ancient Greeks had about about atoms
but you know I I don't want to start like this we've made a lot of progress
in two-and-a-half thousand years and you know there's just better places to to
kick off a science talk so the first modern picture that we had of what the
universe is made of everything we are made of is this so I hope this is
familiar to most people here this is the periodic table of elements okay it's one
of the most iconic images in all of science what we have here are a hundred
and twenty ish different elements I should point out no less than ten of
which were discovered in this very building and which constitute or at
least in the 1800s was thought to constitute everything that existed in in
nature so it's certainly true that any material you get you can distill it down
into its component parts and you'll find that all of those component parts are
made of one of these hundred and twenty elements so it's it's a great moment in
science it's really one of the triumphs of science it's also I should add the
reason that I stopped doing chemistry in school because if you're a chemist this
is basically as good as it gets I'd you know if we're honest it's kind
of a mess right I you know everything in the universe is classified into things
on the left that go bang if you put them in water through the things on the right
which really if we're honest don't do very much at all you kind of organize
everything into this stupid shape so there's a looks a little bit like
Australia there's a big dip in the top and then and then there's these two
strips of elements that you have to put along the bottom because there's no room
for them in the middle where they belong you know it I don't know about you if if
I was asked to come up with a fundamental classification of everything
in the universe this isn't what I would have gone for are there any chemists in
the audience I'm sorry for you okay but you know I'm not alone in this sides
it's not just me that thinks this is a silly way to organize nature nature
itself thinks this is a silly way to organize nature of course we know this
isn't the fundamental this isn't the end of the story this isn't the fundamental
building blocks and the first person to realize there's that there's something
deeper than this was the Cambridge physicist called JJ Thompson so at the
end of the 1800s JJ Thompson discovered a particle that
was smaller than an atom that we now call the electron and in 1897 he
announced this in this room in fact in in this very lecture series to a stunned
audience an audience that was so stunned at least half of them didn't believe
what he was saying there was one very distinguished scientist who afterwards
told JJ Thompson he thought the whole thing was a hoax the JJ Thompson has
just been pulling their leg but of course it's it's not a hoax this isn't
the fundamental elements of nature and within 15 years of JJ Thompson's
discovery his successor in Cambridge a man called Ernest Rutherford had figured
out exactly what these atoms are made of and this is the picture that that
Rutherford came up with so we now know that each of these elements consists of
a nucleus which is tiny the metaphor that Rutherford himself used was it's
like a fly in the center of the Cathedral and then orbiting this nucleus
in I should add fairly blurry orbits are
the electrons which sort of fill out very sparsely the rest of the space so
that's a picture of these atoms subsequently we learnt that the nucleus
is not itself fundamental the nucleus contains smaller particles they're
particles that we call protons and neutrons and in the 1970s we learned
that the protons and neutrons aren't fundamental either so in the 1970s we
learned that inside each proton a neutron are three smaller particles that
we call quarks there are two different kinds of quarks
by the 1970s I'm guessing physicists didn't have a classical Greek education
and they'd kind of run out of you know classy names so we we call these quarks
the up quark and the down quark okay for no good reason it's not like the up
quark is higher than the down quark it's not like it points up and just no good
reason at all the up quark and the down quark so the proton consists of two up
quarks and a down quark and the neutron consists of two down quarks and an up
quark okay this as far as we know are the fundamental building blocks of
nature we've never discovered anything smaller
than the electron and we've never discovered anything smaller than the
quarks so we have three particles of which everything we know is made and
it's it's worth stressing it that's kind of astonishing you know it's so we sort
of take it for granted we learn this in school we don't really think about it
deeply everything we see in the world all the diversity in the natural world
you me everything around us we just the same three particles with slightly
different rearrangements repeated over and over and over again it's it's an
amazing lesson to to draw about how how the world is is put together so that
that's what we have we have an electron and and two quarks and you know these
aren't the fundamental building blocks that the Greeks had thought about and
they're certainly not the fundamental building blocks that the Victorians had
thought about but you know the spirit of the issue really
hasn't changed the spirit is exactly what democracy's said 200 2500 years ago
it's that there are like Lego bricks from which everything in the world is
constructed these Lego bricks are particles and the particles are the
electron and two quarks it's a very nice picture it's very
comforting picture is the picture we teach kids at school it's the picture we
even teach our students in undergraduates University and there's a
problem with it the problem is it's a lie it's it's a
white lie it's a white lie that we tell our children because you know we don't
want to expose them to the the difficult and horrible truth too early on it makes
it easier to learn if you believe that that these particles are the fundamental
building blocks of the universe but it's simply not true
the best theory is that we have of physics do not have underlying them the
quark particle in the two quark pot sorry the electron particle and the two
quark in fact the very best theories we have of physics
don't rely on particles at all the best theories we have tell us that the
fundamental building blocks of nature are not particles but something much
more nebulous and abstract the fundamental building blocks of nature
are fluid like substances which are spread throughout the entire universe
and ripple in strange and interesting ways okay that's the fundamental reality
in which we live these fluid like substances we have a name for we call
them fields so this is a picture of a field that this isn't the kind of field
that physicists have in mind you know that this is this is what you think a
field is if you're a farmer or if you know you're a normal person if you're a
physicist you have a very different picture in your mind when you think
about fields and I'll tell you the the general definition of a field and then
we'll go through some examples so that you get get
with us um the the physicists definition of a field is the following it's
something that as I said is spread everywhere throughout the universe it's
something that takes a particular value at every point in space and what's more
that value can change in time okay so the picture to have your mind is a field
a sarees are fluid which ripples and sways throughout the universe
now it's not a new idea it's it's not an idea that we've we've just come up with
it's an idea which dates back almost 200 years and like so many other things in
science it's an idea which originated in this very room because as I'm sure many
of you are aware this is the home of Michael Faraday and Michael Faraday
initiated this lecture series in 1825 he gave over a hundred of these Friday
evening discourses and the vast majority of these were on his own discoveries on
the experiments he did on electricity and magnetism so he he did many many
things in electricity and magnetism over many decades and in doing so he built up
an intuition for how our electric and magnetic phenomena work and the
intuition is what we now call the electric and magnetic field so what he
envisaged was that threaded everywhere throughout space were these invisible
objects called the electric and magnetic fields now you know we learn this in
school again it's something that we sort of take for granted because we learned
at an early age and we don't sort of appreciate just how big of a radical
steps this this idea of Faraday's is I want to stress it's one of the most
revolutionary abstract ideas in the history of science that these electric
and magnetic fields exist so you know let me just you're supposed to do
demonstrations in this night you know I'm I'm I'm not just a theoretical
physicist I'm a very theoretical physicist it's very hard for me to do
any kind of experiment that's going to open I'm just going to show you
something that that you know you've all seen um they're magnets okay and we all
played these games when we were kids or when we were in school you take these
magnets and you move them together and as they get closer and closer
there's there's this force that you can sort of just just feel building up that
pushes the pressure that pushes against these two magnets and you know it
doesn't matter how often you do it and it doesn't matter how many degrees you
have in physics it's it's just a little bit magical you know are you and you all
you all know this there's something just just special about about this this weird
feeling that that you get between between magnets and this was Faraday's
genius it was to appreciate that even though you can't see anything in between
even though no matter how closely you look the space between these magnets
will seem to be empty he said nonetheless there's something real there
there's something real and physical which is invisible but is building up
and that's what's responsible for the force so he called them lines of force
we now call it the magnetic field so on so this of course is it's a picture of
Michael Faraday soda picture of Michael Faraday lecturing behind this very table
here is a drawing from one of Michael Faraday's papers it was pointed out to
me earlier when you leave there's a carpet just here the carpet has this
pattern this picture just repeated on it over and over and over again and on the
bottom here is one of Michael Faraday's most famous demonstrations that he did
here so I'll just walk you through what what what Faraday did the thing on the
thing on the right there's a small coil
with a hand on it this is a battery and the battery passes
our current around this coil and in doing so there's a magnetic field that's
induced in this it's what's called a solenoid and then Faraday did did the
following thing he simply moved this small coil a through this big coil B
like this and something miraculous happened when you do that there's a
moving mag netic filled Faraday's great discovery
was induction it gives rise to a current in B which then over on this end of the
table makes a needle flicker like this so extremely simple you move a magnetic
field and it gives rise to a current which makes a needle flip flicker on the
other side of of the table this astounded audiences in the 1800's okay
because you were doing something and affecting the needle on the other end of
the table yet you never touched the needle you know it was amazing you could
you could you could make something move without ever going near it without ever
touching it we kind of jaded these days you can do the same experiment you can
pick up your cell phone you can press a few buttons you can call somebody on the
other end of the earth within with it within seconds but it's the same
principle but this was the first time it was demonstrated that the field is real
you can communicate using the field you can affect things far away using the
field without ever ever touching it so this is Michael Faraday's legacy it's
that there's not just particles in the world there's other objects that are
slightly more subtle that are called fields that are spread throughout all of
space but by the way if you ever want to really appreciate the genius of Michael
Faraday he gave this lecture in 1846 if many
lectures in 1846 but there was one in particular where he he finished 20
minutes early he ran out of things to say so he engaged in some idle
speculation for 20 minutes and Faraday suggested that these invisible electric
and magnetic fields that had postulated were quite literally the only thing
we've ever seen he suggested that it's ripples of the electric and magnetic
field which is what we call light so it took of course 50 years for people like
Maxwell and Hertz to confirm that this is indeed what light is made of but it
was Faraday's genius that a that appreciated this that there are waves in
the electric magnetic field and those waves are the light that we see around
us okay so this is Faraday's legacy but it turns out
sigh Deerfield was much more important than Faraday had realized and it took
over a hundred and fifty years for us to appreciate the importance of this feel
of these fields so what happened in these hundred and fifty years was that
there was a small revolution in science in the 1920s we realized that the world
is very very different from the common sense ideas that Newton and Galileo had
handed down to us centuries before so in the 1920s people like Heisenberg and
Schrodinger realized that on the smallest scales on the microscopic
scales the world is much more mysterious and counterintuitive than we ever really
imagined it could be this of course is the theory that we now know as quantum
mechanics so there's a lot I could I could say about quantum mechanics let
let me let me tell you one of the punch lines of quantum mechanics and one of
the punch lines is that energy isn't continuous energy in the world is always
parceled up into some little discrete lump okay that's actually what the word
quantum means quantum means discrete or or lumpy so the real fun starts when you
try and take the ideas of quantum mechanics which say that things should
be discrete and you try to combine them with Faraday's ideas of fields which
have very much continuous smooth objects which are waving and oscillating in in
space so the idea of trying to combine these two theories together is what we
call quantum field theory and here's the implication of quantum field theory the
first implication is what happens for the electric and magnetic field so
Faraday taught us and Maxwell later that waves of the electromagnetic field or
what we call light but when you apply quantum mechanics to this you find that
these light waves aren't quite as smooth and continuous as they appeared so if
you look closely at light waves you'll find that they're made of particles
they're little particles of light these are particles that we call the
photon okay the magic of this idea is that that same principle applies to
every single other particle in the universe so there is spread everywhere
throughout this room something that we call the electron field it's like a
fluid that fills this room and in fact fills the entire universe and the
ripples of this electron fluid the ripples of the waves of this fluid get
tied into little bundles of energy by the rules of quantum mechanics and those
bundles of energy are what we call the particle the electron all the electrons
that are in your body are not fundamental all the electrons that exist
in your body are waves of the same underlying field we're all connected to
each other just like you know the waves on the ocean all belong to the the same
underlying ocean the electrons in your body are the ripples of the same field
as the electrons in my body there's more than this there's also in this room two
quark fields and the ripples of these two quark fields give rise to what we
call the up quark and the down quark and the same is true for every other kind of
particle in the universe there are fields that underlie everything and what
we think of as particles aren't really particles at all they're waves of these
fields tied up into little bundles of energy so this is the legacy of Faraday
this is where Faraday's vision of fields has taken us there are no particles in
the world the basic fundamental building blocks of our universe are these fluid
like substances that we call fields all right
okay so what I want to do in the rest of this talk is tell you where that vision
takes us I want to tell you about you know what it means that we're not made
of particles where we're made of fields and I want to tell you what we can do
with that and how we can best understand the universe around us okay so here's
the first thing I'm take a box and take every single thing that exists out of
that box take all the particles out the box all the atoms out the box what
you're left with is a pure vacuum and this is what the vacuum looks like so
what you're looking at here is a computer simulation using our best
theory of physics it's something called the standard model which I'll I'll
introduce later but it's a computer simulation of absolutely nothing the
this is empty space literally empty space with nothing in it this is the
simplest thing you could possibly imagine in the universe and you can see
it so you know it's an interesting place to be an empty space you know it's not
it's not dull and boring what you're looking at here is that even
when the particles are taken out the fields still exists the field is there
but what's more the field is governed by the rules of quantum mechanics and
there's a principle in quantum mechanics which is called the Heisenberg
uncertainty principle which says you're not allowed to sit still and the field
has to obey this so even when there's nothing else there the field is
constantly bubbling and fluctuating in what's quite honestly a very complicated
way I think these are things that we call quantum vacuum fluctuations but
this is what nothingness looks like from the perspective of current theories of
okay it's worth saying that this is a computer simulation it looks a little
bit like a cartoon but it's actually quite a powerful computer simulation
that took a long time to do but these aren't just theoretical these quantum
fluctuations that are there in the pure vacuum are things that we can measure
there's something called the Casimir force the Casimir force is a force
between two metal plates that get pushed
together basically because there's more of this stuff on the outside than on the
inside and you know these are real these are things that we can measure and they
behave just as we would predict they would from from our theories so this is
nothing and this brings me to the more mathematical side of of the talk because
there's a challenge in this that this is the simplest thing we can imagine in the
entire universe and it's complicated okay it's
astonishingly complicated and it doesn't get easier than this you know if you
want to now understand not nothing but a single particle well that's much more
complicated than this and if you want to understand 10 to the 23 particles all
doing something interesting that's really really much more complicated than
this so there's a problem in it's my problem not yours in a addressing you
know this fundamental description of the universe which is that it's just hard
okay the mathematics that we use to describe quantum fields to describe
everything that we're made of in terms of quantum fields is substantially more
difficult than the maths that arises in any other area of physics or or science
it's it's genuinely difficult I can put this in in some perspective there's a
list of six open problems in mathematics they consider to be the six hardest
problems in mathematics there used to be seven but some crazy rushing ago I
solved one of them so that there's six left you in a million bucks if you can
solve any one of these problems if you know a little bit of mathematics they're
things like the Riemann hypothesis or P versus NP and they're sort of famously
difficult problems this is one of those six problems you win a million dollars
if you can understand this okay so what does it mean it doesn't mean can you
build a big computer and just demonstrate that these are there it
means can you understand from first principles by solving the equations the
patterns that emerge within these quantum fluctuations okay
it's an extraordinarily difficult problem you know it
it's writing the kind of thing I do I don't know a single person in the world
who's actually working on this problem you know that that's how hard it is we
don't really even know how to begin to start understanding these kind of ideas
in quantum field theory okay that this theme about the mathematics being being
challenging is something which which is going to come back later in the talk so
I'd like just to take a little bit of a diversion for a few minutes and give you
a sense about what we can do mathematically and what we can't do
mathematically just sort of tell you what the state of play is in terms of
our understanding these theories called quantum field theories which which
underlie our universe so there there are times where we understand extremely well
what's going on with quantum fields and that happens basically when these
fluctuations are very calm and tame when they're not wild and strong these ones
are big but when they're much more karma when the vacuum is much more like a Mill
Pond than it is like a raging storm in those cases we really think we
understand what what we're doing and to illustrate this I just want to give you
this this example so this number G is a particular property of the electron
particle and I'll quickly explain what it is the electron is a particle and it
turns out the electron spins it all bits rather like the earth orbits and it has
an axis of spin and you can change the axis of that spin and the way you change
it is you take a magnetic field like this and in the presence of a magnetic
field the electron will spin the electron will stay in one place but spin
and then the axis of spin will slowly rotate like this it's what's called
precession and the speed at which the axis of that spin processes is dictated
by this number here okay so it's it's not the most important thing in you know
the big picture however historically this has been extremely important in the
history of physics because it turns out this is
number you can measure very very accurately doing experiments and so this
number has sort of acted as a testing ground for us to see how well we
understand the theories that underlie nature and in particular quantum field
theory so let me tell you what you're looking at here but the first number is
are the result of many many decades of painstaking experiments measuring very
very precisely the this feature of the electron it's called the magnetic moment
and the second number is the result of many many decades of very tortuous
calculations sitting down with a pen and paper and trying to predict from first
principles from quantum field theory what the magnetic moment of the electron
should be and you can see it's it's simply spectacular and that there's
nothing like this anywhere else in science with an agreement between the
theoretical calculation and the experimental measurements it's sort of I
think it's it's 12 or 13 significant figures it's it's it's really
astonishing any other area of science you'll be jumping up and down for joy if
you get the first two numbers right economics not even that you know just
but but this is where we're at in particle physics on a good day when we
really understand what we're doing with it's it's substantially better than than
any other area of science twelve significant figures but this of course
I've shown it because this is our best result um there are many other results
that are nowhere near as good and the difficulty comes when those quantum
vacuum fluctuations start getting wilder and stronger so let me give you an
example it should be possible for us to sit down and calculate from first
principles the mass of the proton okay we have the equations you know
everything should be there we just need to work hard and figure out what the
mass of the proton is just by doing calculations we've been trying to do
this for about forty years now we can get it to within an accuracy of
something like three percent which which isn't bad you know
3% there but but we should be much much better you know we should be sort of
pushing these levels of of accuracy and the reason is it's very simple we know
we've got the right equation we're pretty sure we you know we're solving
the right equation it's simply that we're not smart enough to solve it okay
40 years the world's most powerful computers lots and lots of smart people
but but just you know we haven't managed to figure this out yet okay that there
are other situations that I won't tell you about where we don't even get off
the ground there are some situations where very fairly subtle reasons we're
unable to use computers to help us and we simply have no idea what we're doing
so it's a slightly strange situation we have these theories of physics they're
the best theories we've ever developed as you can see by this but at the same
time they're also the theories that we understand the least and it's to make
progress we sort of have this strange balancing act between you know
increasing our theoretical understanding and figuring out how to apply that to
the experiments that we're doing and again it's a theme I'll come back to at
the end of the end of this lecture all right so so far I've been talking in a
little bit of generality about you know what we're made of and this this is the
punchline our for the halfway point of the talk and you're all made of quantum
fields and I don't understand them at least I don't understand them as well as
I I think I should so what I want to do now is it's going to a little bit more
specific so I want to tell you exactly what quantum fields you're all made of
in fact I'll tell you exactly what quantum fields exist in the universe and
the good news is that not many of them so I'll simply tell you all of them so
we started with the periodic table this is the new periodic table and it's much
simpler you know it's much nice there are the three particles that we're all
made of there's the electron and the two quarks the up quark and the down quark
and as I've stressed the particles aren't fundamental what's really
fundamental is the field that underlies them and then it turns out there's a
fourth particle that I've not discussed so far it's
called the neutrino it's not important in what we're made of but it does play
another important role in elsewhere in the universe these neutrinos are
everywhere you've never noticed them but since I began this talk something like
10 to the 14 of them have streamed through the body of each and every one
of you as many coming from above from outer space as actually coming from
below because they stream all the way through the earth and then and then keep
going they're not very sociable they don't
interact so this is every what everything is made of these are the four
particles that form the bedrock of our universe except then something rather
strange happened for a reason that we do not understand at all
Nature has chosen to take these four particles and reproduce them twice over
so this is actually the list of all the fields that make up particles in our
universe so what are we looking at here this is the electron it turns out there
are two other particles which behave in every way exactly the same as the
electron except they're heavier we call them the muon which has a mass of
something like 200 times the electron and the tail particle which is 3,000
times heavier than the electron okay why are they there we have no idea at all
it's one of the mysteries of the universe
this also are two more neutrinos so there are three neutrinos in total and
the two quarks that we first knew about and now joined by four others that we
call the strange quark and the charmed quark and then by the time we got here
we really ran out of any kind of inspiration for for naming and we call
them the bottom quark and and the top quark okay so I should stress we
understand things very very well going this way we understand why they come in
a group of four we understand why they have the properties that they do we
don't understand it at all going this way we don't know why this three of
these rather than two of them or seventeen of them or that that's that's
a mystery but this is everything this is everything in the universe
everything you're made of is is these three at the top there and it's only
when you go to more exotic situations like particle colliders that we need the
others on the bottom but every single thing we've ever seen can be made out of
these twelve particles twelve fields these twelve fields interact with each
other and they interact through four different forces two of these are
extremely familiar the force of gravity and the force of electromagnetism but
there's also two other forces which operate only on small scales of a
nucleus so there's something called the strong nuclear force which holds the
quarks together inside protons and neutrons and there's something called
the weak nuclear force which is responsible for radioactive decay and
among other things for making the Sun shine again each of these forces is
associated to a field so Faraday taught us about the electromagnetic field but
there's a field associated to this which is called the gluon field and a field
associated to this which is called the W and Z bosons field there's also a field
associated to gravity and this was really Einstein's great insights into
the world the field associated to gravity turns out to be space and time
itself so if you've never heard that before that was the world's shortest
introduction to general relativity I'm not gonna say anything else about it
I'll just let you figure that one out for yourself okay so this is this is the
universe we live in there are twelve fields that give matter of call the
matter fields and four other fields that are the forces and the world we live in
is these combination of the sixteen fields all interacting together in in
interesting ways so this is what you should think of the universe as life
it's filled with these fields fluid like substances twelve matter four forces one
of the matter fields starts to oscillate and ripple say the electron field starts
to wave up and down because there's electrons there that will kick off one
of the other fields it will kick off say the electromagnetic field which in turn
will also oscillate and ripple there'll be light
is emitted so that'll oscillate river at some point it'll start interacting with
the quark field which in turn will oscillate and ripple and the picture we
end up with is this harmonious dance between all these fields interlocking
each other swaying moving this way and that way that's the picture that we have
of the fundamental laws of physics we have a theory which underlies all this
it is to produce simply the pinnacle of science it's the greatest theory we've
ever come up with we've given it the most astonishingly rubbish name you've
ever heard we call it the standard model okay when you hear the name the standard
model it sounds tedious and Monday it should really be replaced for the
greatest theory in the history of human civilization okay that that's that
that's we're looking at okay so this is everything except it's not quite I've
actually just missed out one field there's one extra thing we know about
which became quite famous in in in recent years it was a field that was
first suggested in the nineteen sixties by a Scottish physicist called Peter
Higgs and it was by the 1970s it had become an integral part of the way we
thought about the universe but for the longest time we didn't have direct
experimental evidence that this existed where direct experimental evidence means
we make this Higgs field Ripple so we see a particle that's associated to it
and this changed this changed famously our four years ago at the LHC these are
the two experiments at the LHC that discovered it that they're sort of the
size of cathedrals and just packed full of electronics they're astonishing
things this is called Atlas this is called CMS the the Higgs particle
doesn't last for long the Higgs particle lasts about 10 to the minus 22 seconds
so it's not like you know you see it and you get to take a picture of it and put
it on Instagram you it's a little more subtle so this is the data and this
little bump here is is how we know that this Higgs particle existed this is a
picture of Peter Higgs being found
so this was the final building block you know it was important it was a really
big deal and it was important for two reasons and the first is that this is
what's responsible for what we call mass in the universe so the properties of all
the particles things like electric charge and mass are really a statement
about how their fields interact with other fields so the property that we
call electric charge of an electron is a statement about how the electron field
interacts with the electromagnetic field and the property of its mass is the
statement about how it interacts with the Higgs field so understanding this
was really the was needed so that we understand the meaning of mass in the
universe so it was a big deal the other reason that it was a big deal is this
was the final piece of a jigsaw we had this theory that we called the standard
model we've had it since the 1970s this was the final thing that we needed to
discover to be sure that this theory is is correct and the astonishing thing is
this particle was predicted in the nineteen sixties fifty years we've been
waiting we finally created it in CERN it behaves in exactly the way that we
thought it would absolutely perfectly behaves as we predicted using these
theories okay um this is gonna be the scary part of the talk you know I've
been telling you about this theory and I've been I've been waving my hands or
pretending that I'm a field let me tell you what the theory really is we just
show you what we do this is the equation for the standard model of physics I
don't expect you to understand it not least because they're a part of this
equation that no one on the planet understands but nonetheless I want to
show it to you for the following reason this equation correctly predicts the
result of every single experiment we've ever done in science everything is
contained in in this equation this is really the pinnacle of the reductionist
approach to science it'sit's all here so you know I'll admit it's not the
simplest equation in the world but it's not the most complicated either you can
put it on a t-shirt if you want in fact if you go to CERN you can buy a t-shirt
with with this equation on it let me just give you a sense of what what we're
looking at the first term here was written down by Albert Einstein and
describes gravity what that means is that if you can solve this tiny little
part of the equation just this swoop excuse me just this R you can for
example predict how fast an Apple falls from a tree or the fact that the orbits
of the planet around the Sun form ellipses or you can predict what happens
when two enormous black holes collide into each other and form a new black
hole sending out gravitational waves across the universe or in fact you can
predict how the entire universe itself expands all of this comes from solving
this little part of the equation the next term in the equation was
written down by James Clerk Maxwell and it tells you everything about
electromagnetism so all the experiment experiments that Faraday spent a
lifetime doing in this this building in fact all the experiments over many
centuries from Coulomb to Faraday to Hertz to modern developments of lasers
everything in this tiny little part of of the equation so there's some power in
in these equations this is the equation that governs the strong nuclear force
the weak nuclear force this is an equation that was first written down by
a British physicist called Paul Dirac it it describes the matter describes those
twelve particles that make up the matter astonishingly each of them obeys exactly
the same equation these are the equations of Peter Higgs and this is an
equation that tells you how the matter interacts with with the Higgs particle
so everything is is in here it's really an astonishing achievement this is our
current limit of knowledge we've never done an experiment that cannot be
explained by this equation and we've never found a way in which this equation
stops working so this is the best thing that we currently have okay it's the
best thing that we currently have however we want to do better
because we know for sure that there's stuff out there that is not explained by
this and the reason we know is that although this explain to every single
experiment we've ever done here on earth if we look out into the sky there's
extra stuff which is still a mystery so if we look out into space there are for
example invisible particles out there in fact there's many more invisible
particles than there are visible particles we call them dark matter but
we can't see them obviously because they're invisible but we can see their
effects we can see their effects on the way galaxies rotate or the way they bend
light around galaxies they're out there we don't know what they are there's even
more mysterious things there's something called dark energy which is spread
throughout all of space it's also some kind of field although not one we
understand that's causing everything in the universe to repel everything else
other things we know that are early in the first few seconds earlier than that
the first few fractions of a second after the Big Bang the universe
underwent a very rapid phase of expansion that we call inflation we know
it happened but it's not explained by that equation that I I just showed you
so these are the kind of things that we're going to have to understand if
we're going to move forward and decide what the next laws of physics are that
go beyond the standard model I could tell you I could spend hours talking
about either of any of these I'm going to focus just on the last one I'm gonna
tell you a little bit about about inflation so the universe is 13.8
billion years old and we understand fairly well well we don't understand at
all how it started we don't understand what kicked it all off at time T equals
zero but we understand fairly well what happened after it started and we know in
particular that for the first the first 380,000 years of the universe it was
filled with a fireball and we know this for sure because we've seen the fireball
fact we've seen it and we've taken a photograph of it this is called the
cosmic microwave background radiation but a much better name for it is the
fireball that filled the universe when it was much younger okay the fireball
cools down it's light has been streaming through the universe for 13.8 billion
years but we can see it we can take this photograph of it and we can sort of
understand very well what was happening in these these first few moments of the
universe and you can see it it looks literally like a fireball there there's
red bits that are hotter there's blue bits that are colder and by studying
this flickering that you can see in this picture we get a lot of information
about what was going on back 13.8 billion years ago when the universe was
a baby one of the main questions we want to ask is what caused the flickering in
the fireball and we have an answer to this we have an answer which which I
think is one of the most astonishing things in in all of science it turns out
that although the universe lanser allow the fireball lasted for 380,000 years
whatever caused this flickering could not have taken place during the vast
majority of that time whatever caused the flickering in this fireball actually
took place in the first few very fractions of a second after the Big Bang
and what it was was the following so when the universe was very very young
there was this when the universe was very very young soon after the Big Bang
there were no particles but there were quantum fields because the quantum
fields were everywhere and there were these quantum vacuum fluctuations and
what happened was the universe expanded very very quickly and it caught these
quantum fluctuations in the act so the quantum fluctuations were stretched
across the entire sky where they became frozen and it's these vacuum
fluctuations here which are the ripples that you see in the fireball so it's an
astonishing story that the quantum vacuum fluctuations were taking place 10
to the minus 30 seconds after the Big Bang
they were absolutely microscopic and now we see them stretched across the entire
universe stretch 20 billion light-years across the sky that's what you're seeing
here and yet you do the calculations for this and it matches perfectly what you
see here so this is another of the great triumphs of quantum field theory but it
leaves lots of questions are the most important one is which field are we
seeing here which field is this that's imprinted on on the background radiation
and the answer is we don't know the only one of the standard model fields it has
a hope of being as the Higgs but most of us think it's not the Higgs but probably
something new but what we'd like to do moving forward into the future
is get a much better picture of this fireball in particular to get the
polarization of the light and by getting a picture of this we can understand much
better the properties of this field that was fluctuating in in the early universe
okay this looking forward is one of the best hopes that we have for going beyond
the standard model and understanding new physics in the last 10 minutes though
I'd like to bring you back down to earth sort of we've got lots of experiments
here on earth where we're also trying to do better we're we're also trying to go
beyond the standard model of physics beyond that equation to understand
what's what's new and there's many of them but the most prominent is the one
I've already mentioned it's it's the LHC so what happened was the LHC discovered
the Higgs boson in 2012 and soon afterwards it closed down for two years
it had an upgrade and last year in 2015 the LHC turned on again with twice the
energy that it had when it discovered the Higgs and the goal was twofold
the goal was firstly to understand the Higgs better which is done fantastically
and secondly to discover new physics that lies beyond the Higgs new physics
beyond the standard model so before I tell you what what it's seen
let me tell you some of the ideas we had some of our expectations and hopes for
what would happen moving forward so that this is our favorite equation again um
the idea has always been the following you know if you're a Victorian scientist
and you go back and you look at the periodic table of elements then it's
true that there's patterns in there that give a hint of the structure that lies
underneath there's numbers that repeat themselves where if you're very smart
you might start to realize that you know yes there is something deeper than just
these elements so our hope as theorists is to look at this equation and see if
maybe we can just find patterns in this equation that suggests there might be
something deeper that that lies underneath and they're there so let me
give you an example this is the equation that describes the force of electricity
and magnetism and it's almost the same as the equations which describe the
forces for the strong force and the weak nuclear force fact you can see I've just
changed letters it's a little more complicated than that but it's not it's
not much more complicated the three forces really look similar so you might
wonder well maybe there's not three forces in the universe maybe those three
forces are actually just one force and when we think there's three forces it's
because we're looking at that one force just from slightly different
perspectives maybe here's something else which is amazing these are the equations
for the 12 matter fields in the universe the neutrinos the electrons and the
quarks each of them are Bay's exactly the same equation each of them obeys the
Dirac equation so again you might wonder that well maybe there aren't twelve
different fields maybe they're all the same field and the same particle and the
fact they look differences again maybe just because we're looking at them from
slightly different perspectives maybe so are these ideas that I've been
suggesting go by the name of unification the idea that the three forces are
actually combined into one is what's called grand unification
and it's very easy it's very easy to write down a mathematical theory in
which all of these are just one force which which appears to be three from our
our perspective there are other possibilities here you might say well
this is the matter and these are the forces and the equations are different
but they're not that different because ultimately they're both just fields so
you might wonder if maybe there's some way in which the matter and the forces
are related to each other well we have a theory for that as well it's a theory
that's called supersymmetry and it's a beautiful theory it's very deep
conceptually and it sort of you know smells like it might be right finally
you might be really really bold you might say well can I just combine the
lot can I just get rid of all of these terms and just write down one single
term from which everything else emerges gravity the forces the particles the
Higgs everything well I've got something for you if you want that as well
it's called string theory so we have a possibility for a theory which contains
all of this in one simple concept and the question going forward of course is
are these right it was very easy for us theorists to have these ideas and I
should say these ideas of what's driven theoretical physics for 30 years but we
want to know are they right and we've got a way of telling they're right we do
experiments so I should say if you want to know if string theory is right we
don't have any way to test it at the moment but if you want to know if some
of these other ideas are right then that's what the LHC should be doing the
reason that we built the LHC was firstly to find the Higgs okay at work and
secondly to test these kind of ideas that we've been having to see what lies
beyond so the LHC has been running it's been running for two years it's been
running like an absolute dream it's just it's a perfect machine two years this is
what it's seen absolutely nothing all of these fantastic beautiful ideas that
we've had none of them are showing up at all and the question going forward is
what are we going to do about it you know how are we going to make
progress in understanding the slayer of physics when the LHC isn't
seeing anything in our ideas justjust don't appear to be the way that nature
works okay I should tell you often I don't have a good answer to this it's I
said my impression is that most of my community is a little bit shell-shocked
by by what happened there's certainly no consensus in the community to move
forward but I think there's three responses that the sort of various
people have had that I'd like to share with you I think all three of these
responses are reasonable up to a point the first response to the LHC not seeing
anything is the following it's um well you know you you you young
kid you're so pessimistic it's all doom and gloom with you you just you need a
little bit more patience you know I didn't see anything last year and it
didn't see anything this year but but next year it's going to see something
and if not next year it's the year after that that it's going to see something
it's it's usually my very illustrious senior colleagues that have this this
response and you know what they could easily be right it could easily be that
next year the LHC discovers something astonishing and it sets us on the path
to understanding the next layer of their of reality but it's also true that these
same people were predicting that it would have seen something by now and
it's also true that this can't keep going for much longer
if the LHC doesn't see something within say a two year time scale it seems very
very unlikely that it's going to see something moving forward it's possible
it just seems unlikely so we know we'll know I hope with all my heart that the
LHC discovers something next year or the year after but I think we have to
prepare for for the worst that that maybe it won't okay response number two
response number two which is sort of also by similar people well all our
theories are so beautiful they absolutely have to be correct and what
we really need is a bigger machine ten times bigger will do it okay again they
they might be right I don't have a good argument against it the obvious rebuttal
however is that a new machine costs ten billion dollars there's not too many
governments in the world that have 10 billion dollars to spare for us to
asked us to explore these ideas there's one the one is China and so if this
machine is going to be built at all it's going to be built by the Chinese
government I think the Chinese government would work would see it as
extremely attractive if the whole community of particle physicists and
engineers that are currently based in CERN in Geneva moved to a town that's
slightly north of Beijing I think I think there are a few that as a
political and economic gain and there's you know a real chance that they may
decide to build this machine if they do it's about 20 years for it to be built
so we're waiting slightly longer there's a third response and I should say the
third response is is kind of the camp I'm in I should mention upfront it's
speculative and it's probably not endorsed by both of most of my peers so
this is really just my personal opinion at this point this is my take on on this
this is you know this is the equation that we know is right this is sort of
the bedrock of our our understanding but although we know it's right there's an
awful lot in this equation that we haven't understood there's an awful lot
to me that's still mysterious in this equation so although this equation look
like there were suggestions of unification maybe they're just red
herrings and maybe if we just work harder and trying to understand this
equation more we'll find that there are other patterns that emerge so my
response is I think that maybe we should just go back to the drawing board and
start to challenge some of the assumptions and paradigms that we've
been holding for for the past 30 years so I should admit I feel quite energized
actually by the lack of results for the LHC you know I sort of it feels good to
me that everyone was was wrong you know it's when we're wrong that we start to
make make progress so I sort of feel quite happy by this about this and think
that you know there's a very real chance that we could just you know start
thinking about different ideas I should say that you know there are hints in
here there are hints to me about you know mathematical patterns that we
haven't explored that there's hints this about connections to other areas of
science things like condensed matter physics which is the science of how
materials work or quantum information science which is the attempt to build a
quantum computer all of these fantastic subjects have have new ideas which sort
of feed in to the kind of questions that that we're asking here so I'm quite
optimistic that moving forward we can make progress
maybe not the progress that we thought we'd make a few years ago but just just
something new so that's the punchline of my talk the punchline is that this is
the single greatest equation that we've ever written down but I hope that
someday we can give you something better thank you for your attention
there's nothing discreet about the Schrodinger equation the Schrodinger
equation is is something you know to do with a smooth field like like wave
function the discreteness is something which emerges when you solve the
Schrodinger equation so it's not built into the heart of nature
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