OK, let's get this started.
Professor [? Valles ?]
is away today.
So he asked me to
stand in to say
a few words about the
Arthur Williams lectures.
So here is a page I think
I wrote 10 years ago.
The story of Arthur Olney
Williams, Jr. Arthur Olney
Williams, Jr., was a descendent
of two prominent Rhode Island
families-- the
Williams, who included
the colonialist founder, Roger
Williams, and the Olneys.
You've all heard of Olneyville.
His forebears include Stephen
Olney, Secretary of State
in the cabinet of
Grover Cleveland.
Arthur grew up in
East Providence,
graduated from East Providence
High School in the 1930s.
He entered a nationwide
contest to find
the brightest boy at America.
Unfortunately, those
were in the old days.
They weren't looking for girls.
There were statewide
examinations,
and the winner in each state
went to Menlo Park, New Jersey,
where Thomas Edison lived,
for the final competition.
The winner of that exam
was to meet with Edison
and to receive a four year
scholarship, all expense paid,
to MIT.
And that year, the
winner was Arthur.
OK, Arthur graduated from
MIT, came back to Brown,
got his Ph.D., and worked with
Bruce Lindsey on atomic wave
function calculations,
then a professor
at University of
Maine for three years
before returning to Brown
as a faculty member, where
he remained for 30 years.
In 1955, Professor
Williams became chair
overseeing the expansion
of the department.
Brown was known for its
strength in acoustics,
but Arthur was responsible in
expanding the area of research
from acoustics to
condensed metaphysics
and to particle particles.
So we all owe him thanks
for getting into frontier
areas of research.
His own research
on underwater sound
was awarded the Pioneers of
Underwater Acoustics Medal
from the Acoustic Society
of America in 1982.
In the words of one
of our own professors,
this says, "Professor Williams
took a good, very generous
interest in young
faculty, helped give them
a warm introduction to Brown.
He was a gracious host of
many, many parties at his house
that has contributed to the
cohesiveness of the department.
He was one of those faculty
who contributed more
to the university
than mere grants
and written, published papers."
Now, with that
introduction, we're
going to now bring
to the present.
And Professor Volovich will
introduce today's speaker.
[APPLAUSE]
OK, so today, we are thrilled
to welcome Professor David
Gross from the Kavli
Institute for Theoretical
Physics in Santa Barbara.
Professor Gross received his
Ph.D. from Berkeley in 1966
and then was a junior
fellow at Harvard.
After that, he
went to Princeton,
where he Higgins Professor
of Physics for 20 years
until he moved to Santa Barbara
as the Director of Kavli
Institute for
Theoretical Physics.
Professor Gross has
made numerous, very
profound contributions
to physics.
In 1973, Professor
Gross, working
with his graduate
student, Frank Wilczek,
discovered asymptotic
freedom, which
says that the closer
quarks are to each other,
the weaker the strong
interaction between them.
And as you know, when quarks
are in extreme proximity,
the nuclear force
between them is so weak
that they behave almost
as free particles.
In 2004, Professor Gross
was awarded the Nobel Prize
in Physics for his discovery
of asymptotic freedom
together with Frank
Wilczek and David Politzer.
After the discovery
of asymptotic freedom
and the emergence of
quantum thermodynamics,
Professor Gross spent
many years working
on the dynamics of gauge
theories in an attempt
to solve quantum thermodynamics.
Then, in the beginning
of 1980, Professor Gross
started to work on string
theory and, in particular,
in 1984, together with
his collaborators,
he discovered the heterotic
string which, at the time,
seemed to offer the best
possibility of explaining
the standard model
from string theory.
Since then, Professor Gross
continued to work largely
on string theory.
In addition to the Nobel
Prize, Professor Gross
won numerous awards.
It's a huge list including
the Dirac Medal, MacArthur
Fellowship,
[? the Harvey ?] Prize,
and is a member of the
National Academy of Science.
And finally and most
importantly, Professor Gross
has been a great inspiration
and an academic hero
for several generations
of young physicists.
So here's Professor Gross.
[APPLAUSE]
OK, thank you.
It's great to be back.
Dom was showing
me that I was here
20 years ago in the middle
of another snow storm.
I've got to move this
thing from this screen.
In the middle of
another snowstorm.
But aside from that, it's a
great pleasure to be back.
So I'm going to talk
today about the frontiers
of fundamental physics.
But before I get started,
I want to apologize
for limiting myself to those
areas of fundamental physics
that I'm engaged it.
More specifically,
elementary particle physics,
but discovery and understanding
of the basic building
blocks of matter and the
forces that act on them.
That's not all of
fundamental physics.
But it is that area
of physics that
is actually after the
reductionist core of matter
and forces.
Now, let me start at
the beginning with what
I regard as the first major
discovery in particle physics
and the establishment of
the experimental techniques
for studying
elementary particles.
And that was Rutherford, who
was interested in studying
the structure of the atom
which, in the early part
of the 20th century,
was totally unknown.
Electrons were known, discovered
somewhere a few years before.
But what the atom was made of
and how a positive charge that
had to be there in the
atom was distributed,
and where the mass of
the atom came from,
nobody had the vaguest idea.
Rutherford invented
experimental particle physics.
He figured, thought,
that the way
to study what was going on
inside the atom in the absence
of microscopes that
could look directly
into the atom at
that time, or even
now to a large
extent, a way to do
that would be to take alpha
particles, which he had largely
discovered and developed in
his study of radioactivity,
and bombard gold nuclei, gold
atoms, without alpha particles.
And they would scatter
through and around the atom.
And he had his graduate
students, Geiger
and Marsden-- Marsden?
Marsden, doesn't
matter, to distinguish
from your esteemed colleague--
sit in a dark room for hours
until their eyes got
accustomed to the dark.
And then, they would
observe the scintillations
that the deflected
alpha particles
made on a fluorescent screen.
And they measured how
many particles came out
at different angles,
the deflection
of the alpha
particles by the atom.
They published their results.
By the way, Rutherford--
although the idea
of the experiment
was Rutherford's,
he did not sign the big
experimental discovery
paper, or the discovery
of what turned out
to be the nucleus of
atoms, or atomic structure.
But he did submit,
and it was published
right after the experimental
paper, a theoretical paper.
Being a great physicist, he
also understood enough of E&M
to calculate for the first
time the Rutherford cross
section, where the scattering
of charged particles
often point heavy mass.
And he determined,
concluded, that all
of the mass that had
the charge of the atom
was located in a very small,
central object, of which he
placed the limit--
the size of which
was one part in 100,000
of the size of the atom.
He couldn't actually measure it,
but just placed an upper limit.
He discovered the nucleus
of atoms, and the structure
of atoms, which resembled
that of the solar system,
and within two years led to
Bohr's model of the atom.
And soon after, the quantum
mechanics and the revolution
we are still living with.
But he also discovered
the nucleus,
which was for him a point
blank center of the atom.
But more importantly
for particle physics,
for fundamental physics,
he discovered the way
to study subatomic,
sub-nuclear matter.
And we haven't really gone far
beyond that in the last 100
years.
We still, in order to
discover the nucleus,
bombard particles-- now,
colliding beams of particles.
We increase the energy.
Of course, with larger
colliders than radioactive alpha
particles, like the Large
Hadron Collider of CERN,
and the detectors
are far, far advanced
from the simple
fluorescent screens.
This is the ATLAS
detector at CERN.
But still, we employ the
technique that Feynman once
described-- if you
want to understand
how a delicate watch
is made, one way
is to take two such watches,
smash them together,
and see what comes out.
Take a picture of what comes up.
And then, look at the picture,
identify the compartments,
and try to figure out
how the watch works.
That's what Rutherford
invented in effect.
Smash alpha particles
into an atom.
See what the atom's made out of
by looking at what comes out.
Some people think this
is a pretty stupid way.
It is a stupid way
of studying watches.
We have better techniques.
But we don't have
better techniques
for elementary particles.
And that's what we do at
the Large Hadron Collider.
We smash nuclei, or we smash
protons, actually, the simplest
nuclei, together.
These large colliders
that produce billions
of electron-volts of
energy in the collision,
and we see what comes out.
And we measure it in these
enormous detectors surrounded
by these massive magnets
to try and figure out
from the rather complicated
pictures of what comes out,
identify the springs
and the cogs.
And from this,
with some analysis
and the help of
theorists, figure out
what's going on inside matter.
And it's been pretty
useful, this technique
invented by Rutherford
100 years ago.
We have, in the last
century, more or less
understood the
structure of the atom.
Of course, it's already begun
in the beginning of the century
with the invention
of quantum mechanics
and the understanding of the
structure of atoms, molecules,
matter, proteins,
people, and all that.
But the latter part of
the [INAUDIBLE] center,
we actually understood what
happens in the nucleus,
greatly magnified here.
Nucleus, we learned, is made of
neutrons and protons, nucleons.
And later, we
learned that nucleons
are made out of quarks.
And so we've identified both
the elementary constituents
of matter, we now believe
the one exception, quarks,
and there are various kinds
of quarks and electrons
and their
neutrino-like partners.
But more importantly,
perhaps, we
have understood in
great detail the forces,
all of the forces, that
act on the nucleus.
There are three
essential forces.
Electromagnetism, of course,
which covers the structure of
charged particles
within the atom.
And that effect is what
explains atoms, molecules,
and ordinary material.
And the two nuclear
forces that act only
within the nucleus, the strong
and weak nuclear forces.
And all of this is described
in a-- something called
the standard model, which was
completed already in the 1970s.
Now, the standard model
is more than a model.
I really don't like
that title, and I've
been promoting the view
that we should call it
the standard theory.
It's by far the
most comprehensive,
beautiful, and predictive
fundamental theory
that we've ever had in physics.
It's clearly a theory, because
you can put its equations,
or the principle that leads
to the equations, which
if we were in principle
to calculate with,
we could explain in
whatever precision
we desire just about every
experiment we can perform
in the laboratory or anywhere.
Might not look beautiful to
you, but give me enough time,
I could teach you
how beautiful it is.
And I could put the
equations on a t-shirt.
And this, the equations that
follow from this theory,
in most cases with
only one or two
or three input parameters--
in some cases you need up
to 19 or so-- parameters
that must be measured and not
calculated, can
explain just about
everything experimenters
have or will
measure in a reductionist test.
This theory is
unbelievably successful.
It consists, as I
said before, of a list
of the elementary
constituents of matter,
starting with the quarks, the
up and down quarks, that make up
the proton and the neutron,
and the nuclei that make up
your atoms, together with
the electron and its partner,
the neutrino.
And as we discovered
in the construction
of the standard model,
the experimenters
discovered not only
these particles
that make up ordinary matter,
but two other families
of quarks and leptons,
similar in all
respects except their masses.
They tend to be much
heavier, harder to produce,
and unstable.
Charmed and strange
quarks, and muon neutrinos,
and muon, tau neutrinos and tau
neutrinos and top and bottom
quarks.
This, we believe,
have good evidence,
exhausts the list of
elementary particles,
and certainly exhausts
the list of observed
elementary particles with one
exception that I'll come to.
And as I said, we have
understood with great detail
the three forces that act
within the atom and the nucleus.
The one missing component
here is the famous Higgs,
which you all know as
the final ingredient
necessary to describe
the properties
of the weak interaction, an
elementary scalar particle
with no spin whose existence
was finally confirmed
in the simplest form by now
four years ago-- oh, no, four
years ago?
The final nail in this
theory, confirmation
of its simplest structure.
And together, this is an
incredible achievement,
I believe, of science,
fundamental science,
which culminates to some extent
a march over 2,000 years,
since people dreamed of an
atomic structure of matter.
We see no place, really,
where the theory breaks down.
Or almost no place-- I'll be
discussing the [INAUDIBLE]
in a moment.
But in order to explain just
about every measurement we
carry out in this
room, or at the LHC,
we can use in principle
the standard model
to calculate sometimes
to the accuracy of one
part in a trillion, often to
accuracy of one part in 1,000.
Our experimental
friends are somewhat
frustrated by the
success of this theory.
We also see very few
limitations on the applicability
of this theory.
It works, as far as we can tell,
everywhere in the universe.
Stars across the galaxies obey
the laws of the standard model.
It explains the
structure of the universe
and, together with Einstein's
classical theory of general
relatively, leaves little
unexplained-- except for one
or two things I'll come to.
And as far as we can see, if
we extrapolate this theory
to very high energies or
very short distances-- which
is the same.
You need very high frequency
probes or high energy
to probe short distances.
We know of no place where the
theory necessarily breaks down
until we get to an
enormously small distance,
or high energy, called
the Planck scale.
But that range is 60
orders of magnitude.
So I regard this as a triumph
of the physical sciences,
of physics, that we can have
a theoretical structure which
yields equations who
calculate, and that
spans 60 orders of
magnitude-- perhaps.
Now, I want to explain one
feature of this standard model,
which has to do with the
nature of the forces that
act within the atom
and the nucleus.
Because one of the most
remarkable discoveries
embodied in the standard
model is the fact
that all of these
forces are at the core
the same kind of force.
They're really the same thing!
Electromagnetism is perhaps
the most familiar to you.
The strong or weak,
unless you're a particle,
quantum field
person, you probably
aren't acquainted too much with
the weak and strong forces.
You've never felt them.
And yet, they're
stronger than this force.
But the amazing thing
is that they're really,
at their core, the
same kind of force.
The difference being
that electromagnetism
is Maxwell's theory, E&M--
most of you have learned--
is a theory of one kind
of charged particle.
We call it a gauge theory.
It's a theory of fields
that transmit the force
between charged particles.
But it's a theory with one kind
of charge, the electric charge.
And we all have felt
that charge sometimes
on dry days, when we
walk perhaps around
and then touch a piece of metal.
You felt a current of
charged particles moving.
But the amazing thing is
that the weak nuclear force
responsible for radioactivity,
the strong nuclear force that
holds quarks together,
is the same kind
of theory with one difference.
In the case of the weak
force, there are two charges.
We call them flavor.
Up, down are the charges.
Or electro-neutrino
are the charges.
Two kinds of charges.
And in the case of
the strong force,
there are three
kinds of charges.
We call them colors--
red, white, and blue.
Every quark here, actually,
has three charges--
a red charge, a blue
charge, and a white charge.
That, in a sense-- that
plus quantum mechanics--
is the only difference.
I'm going to try to explain
that, a little bit of physics
here.
So electromagnetism is a
theory of charged particles.
The force is mediated by
the electromagnetic field.
These are the field
lines, you know,
and they spread out according
to Coulomb's Law or Maxwell's
equations.
They describe the force
on a test charge particle
at any point in space.
And these particle
and antiparticles
of opposite charges
attract each other, right?
So if you try to
pull them apart,
you have to do some work.
But since the force falls
off like 1 over R squared,
you can pull electrons,
say, out of the atom.
And then, you make
it run in wires
and do work and otherwise be
the basis for modern technology.
We would say that as you pull
the charged particles away
from each other,
the energy you have
to exert-- that you have
to supply-- increases.
But then, it saturates.
And that's called the
ionization energy.
So if you hit an atom
with enough energy,
electrons come out.
You ionize it.
And you've all studied
that force, I'm sure.
And it's easy to
deduce the force law
using what we call--
oh, here's an electron
and an anti-electron, a
positron, a distance, R, away.
Using one equation
which summarizes
a part of Maxwell's equations
known as Gauss's Law, which
is that you take
a sphere, and you
calculate the total flux
of the electric field
through the sphere.
You get the charge.
That's Gauss's Law.
In this case, you take a
sphere like this around one
of these charges.
The area of the sphere
is roughly R squared.
The electric field is what I
call E. So roughly speaking,
E R squared equals
Q. And then, if you
want to calculate
the work done, you'll
see that the energy, E
goes like 1 over R squared,
and the energy is the
integral of E times R.
So you get an energy
cost that decreases
1 over R and saturates.
And that's why you
can ionize atoms.
Now, let's go to the strong
force that acts of quarks.
In the theory of
the strong force,
quantum chromodynamics--
it's the same theory,
except that there are
now three charges.
Each quark comes with its color.
And this, so this
is an up quark.
Up is irrelevant here.
But red is important.
This is an anti-red quark
with the opposite red charge.
Now, if it wasn't for
quantum mechanics,
we would think that the
force between the quarks
would be also Coulomb
force, 1 over R squared.
It's the same kind of force.
And if that were
the case, then you
could pull quarks out of nuclei.
You could give enough energy
to collide them together.
With enough energy,
quarks would fly out,
just like they do out of atoms.
You could make
quarks run in wires
and have quark motors
and quark technology.
The reason you can't
do that, it turns out,
the reason you can never
pull quarks out of hadrons,
particles made out of
quarks, was the reason
it took so long to understand
the strong interactions
and why they were so mysterious.
Because one never saw the color.
It's the reason you never
feel the strong force, which
is much, much stronger than
the electromagnetic force.
You don't feel it
because the quarks,
as I will try to explain
it, can never get out
of the atom, the nucleus.
And therefore, all you notice
by remnant molecular type forces
are the forces between
colorless nuclei.
And nucleons turn
out to have no color.
So it's for the same reason
that you don't ordinarily
feel electrical forces
between two people--
because by and large, they
are neutral electrically.
Sometimes, however,
you can ionize them.
And then, you feel the force.
But you can't ionize a proton.
And that has to do with
the primary feature
of quantum mechanics, the
uncertainty principle.
Now, you all know that
the uncertainty principle
says you can't be
at the same place
with a determined velocity.
And if you have a
classical system,
like an oscillator like
this, which can move.
As you know, it
can be in what we
call its ground state, its
state of lowest energy, at rest,
and definitely here.
But that's not possible
quantum mechanically.
Heisenberg taught us that if you
imagine an oscillator like this
and you want to test or observe
that it is in its ground state
here, well, you have
to observe that.
And how do you observe?
Well, you send in
a light ray, which
consists of a photon with
something, quantized energy.
But that gives the
oscillator a kick.
The consequence, in quantum
mechanics, every oscillator,
every degree of freedom,
every quantum field,
it has some inherent quantum
oscillation, fluctuation
we say, motion, carried energy.
The strong force,
as I said, mediated
by the chromodynamic field,
lives in a quantum medium.
That quantum medium
is called the vacuum.
You might think the vacuum
is empty, but it's not.
Nothing can be empty because
if you were to probe it,
you'd set it in motion.
And that quantum vacuum
on the scale of the nuclei
is filled with these fields,
these chromodynamic fields,
that are mediating--
potentially mediating
the force between colored
and charged objects.
On the scale of these
nucleons, these fields,
which themself carry charge--
color charge, as it turns out--
are very violently fluctuating.
This is a picture of what
the vacuum looks like if you
had microscopes that
could see distances
of a millionth of a
millionth of a centimeter.
We don't, of course.
But in the theory,
we can calculate
what it might look
like if you could
see the fluctuating fields
of the chromodynamic fields.
So this is a complicated medium.
And this medium has
properties, much like water
has dielectric properties
that screen electricity.
You put a charge into
a dielectric medium,
it's reduced by dielectric
phenomenon in the medium.
The quantum vacuum is a
medium that, in this case,
turns out to squeeze these
flux lines into a tube.
Flux lines can't
disappear because they
have to end up on a charge.
But the quantum
vacuum, turns out,
squeezes the flux lines as much
as they can to form a tube.
That's the phenomenon
called asymptotic freedom
in one of its guises.
And given that, we
can now calculate
the force between points.
Again, simple, very simple
freshman physics calculation.
We just use Gauss's Law.
As I said, electricity
and magnetism QCD
are really the same thing
except for the properties
of the vacuum, the medium.
In this case, the flux lines
only go through a fixed area.
This is a tube.
You stretch a tube,
keeps the same area.
So now, Gauss's Law says
that E times this area
equals Q no matter how far
away from the quark you are.
And that means the
electric field does not
fall off with distance.
And then, you
calculate the work you
have to do to move the quarks
a distance R. It's going
to be linear in the distance.
To separate them to infinity,
ionize the proton or the meson,
would require an
infinite amount of work.
So that's a freshman physics
explanation of what we call
[INAUDIBLE].
And it was the discovery of
this phenomenon, this feature
of theories like
Maxwell's theory
but with more than
one charge that
produced the theory of
the strong interactions.
This is a picture
of actually what
happens when you solve
QCD and pull quarks apart.
See the field lines being
squeezed to form a flux field.
And that explains why
you can't pull quarks--
nobody's ever seen or will
see, unless you heat up
the universe.
Turns out you can
heat up water, right?
You heat up water,
it turns into gas.
The dielectric constant
of gas is much smaller.
It has very little effect
of the dielectric properties
of electric fields.
The same thing is
true with a vacuum.
If I were to take
this same picture,
turn up the
temperature to hundreds
of millions of degrees,
the phase of the vacuum
would change.
And the proton or mesons
like this would melt,
and the quarks would come out.
But unless we heat up
the vacuum to hundreds
of millions of degrees, you're
never going to see a quark.
There was a time in the history
of the universe where quarks
were moving around
rather freely and not
confined within hadrons.
OK, let's move to experiment.
This theory really works.
So for somebody involved
in proposing this theory,
it is an enormous pleasure
to see one's predictions get
better and better
over the years,
especially with the
LHC, where we now
have tests of the predictive
power of this theory over 12
orders of magnitude.
A million million scale.
It's fantastic.
But I must say the
most pleasing thing
for a theorist is to
be able to calculate
some thing, some property
of nature that's mysterious.
And when I was a
graduate student,
I was talking to
my friend here, who
was a student at the
same time at Berkeley,
they were discovering hadrons,
strongly directed particles
that all the time-- or it
used to be called Rad Lab,
but was then changed to the more
politically correct Lawrence
Berkeley Lab.
And all these particles
were being discovered.
They all looked like
protons and some neutrons,
but nobody could say
anything about them.
But now, with lattice QCD, where
you formulate QCD on a lattice
and then take the limit as
the lattice space goes to 0,
it has been now possibly,
with an enormous amount
of work and large scale
computing over the years
to calculate the spectrum
of the observed hadrons
to incredible accuracy.
These are [? real ?]
hadrons, mesons
made out of very heavy
quarks, up and down quarks.
Those are bottom quarks.
In principle, in QCD, if we
forget about the quark masses,
which are a very small
little collection needed
to get this accuracy, but
conceptually unimportant,
all mass ratios-- let
me give you one mass,
the mass of the proton.
All the other masses
are [INAUDIBLE].
They're pure numbers
that, with enough work,
you can calculate
within QCD to arbitrary
precision and [INAUDIBLE]
greater [INAUDIBLE].
OK, that's the standard model
and its great successes in QCD.
Physics, however, thrives
not on answered questions
and on our agreement
with experiment
but on unanswered questions and
disagreement with experiment.
And the standard model, as
magnificent an achievement
as it is, is clearly deficient
for both experimental and
theoretical reasons.
Experimentally, the
astronomers have
discovered a form of
matter that does not
fit into the standard
model called dark matter.
Neutrino masses,
that's no big deal.
That's easy and
anticipated to be cured.
But it's not known
what the details are,
nor does the standard
model tell you
what the details have to be.
There are features
of the universe
like the excess of baryons
that were here that we don't
understand how they came about.
Then, there are issues of
the grand structure which
surely must include
gravity, such as
the cosmological constant.
Theoretical point
of view, nature
so far has revealed
to us pieces of what
must be a unified whole.
Theorists are
motivated to unify.
There are unnatural features
of the standard model
and its parameters that can
not be calculated that seem
unnatural and need explanation.
There are the masses and
mixings of the quarks
which are not determined
by the standard model.
And then, there is the
ill-understood aspects
of cosmology.
Some of these, like my
favorite, supersymmetry,
hint at discoveries, new
experimental discoveries that
could be made at a machine
like the LHC, or in other ways,
but are accessible either
now, or last six months,
or the next six months.
But let me discuss
some of these issues.
One is the search
for unification.
Now, the standard
model consists,
as I showed it, of three forces
and two kinds of matter--
quarks, leptons, and
electromagnetism,
weak and strong.
The remarkable thing
is-- [INAUDIBLE]
try to briefly explain that
all these forces, at the core,
are the same kind of force.
Doesn't have to be.
There are many other forces
theorists could dream up.
These are the most beautiful,
and they're the only forces
we see, except for gravity.
Which is also, in a sense
that I can't explain,
the same kind of force.
So when you are
faced with pieces
of an overall picture
like the universe,
there are two possibilities.
They either fit
together, or they don't.
It's like the pieces
of a jigsaw puzzle.
The amazing thing is
that just the same time
the standard model
was being completed
in the middle of the 1970s,
it was understood immediately
that these pieces fit together
like pieces of a jigsaw puzzle.
And unlike a jigsaw puzzle,
sometimes you lose a piece.
And you try to put it
together, and you only
realize-- takes a lot of
work to realize somehow you
can't fit it together.
There are missing pieces.
In the standard model, there
are no obvious missing pieces.
There are these clues,
data that tells us
that something is missing.
But the structure fits together
and can be generalized easily
to a theory of the same
kind with one kind of force
and one kind of matter.
That didn't have to be the case.
It takes a little
sophistication to imagine
putting something
as familiar to you
all as electromagnetism together
with something unfamiliar
like the strong nuclear force.
How could they look the same?
They look very different.
But we can understand that.
It has to do with the fact
that physical phenomena can
look different at different
scales, symmetries
that underlie these theories can
be broken at different scales.
Might also ask why the forces
are so different in strength.
Strong nuclear forces
are much stronger
than electromagnetic forces.
That's the reason
hydrogen bonds,
fusion bonds are much stronger
than the dominant ones,
electromagnetic bonds.
Well, the strength
of the forces varies
with energy, or with distance.
That in fact was first
revealed by this phenomenon
of asymptotic freedom
where the strong force
gets weaker as you go up in
energy or down in distance.
You bring the quarks together
for high energy quark
collisions, described as if
the quarks are very weakly
interacting.
And the electromagnetic
force acts
in the opposite way--
it gets stronger if you
bring the particles together.
So it's conceivable that when
viewed with very high energy
or short distances, they unite.
And within a few years of the
standard models completion,
the extrapolation was made.
And indeed, the forces
seem to come together
at an extraordinarily
high energy.
This is a logarithmic scale.
Way beyond the present
day observation,
which is the dotted line here.
It actually happens to be
close to the point where
gravity becomes strong.
Gravity, the one force you
feel-- every day, you get up,
and you feel gravity.
But it's the weakest
force in nature.
The only reason you feel it
is because it's universal.
Everything is attractive.
There are no
anti-gravity charges.
The charge of gravity is
energy, which is positive.
So when I hold this
thing up, the whole Earth
is pulling down.
Every atom in the Earth,
10 to the 54 atoms
are pulling down
on this pointer.
And I'm exerting a little bit
of an electromagnetic force
with the chemical
reactions in my muscles.
And I'm resisting
the whole Earth.
Gravity is extremely
weak, and the only reason
that you feel it is that
there's nothing to shield it
like the other forces.
But since the charge is energy,
it grows rapidly with energy,
like quadratically.
So when you get to
the unification scale,
it's 40 orders of
magnitude stronger
than it is at the atomic scale.
And then, it competes
with the other forces.
This, to me, is the most
important clue we've learned,
a clue that I take,
and many of us,
that all the forces,
together with gravity,
are unified if we can perform
experiments at these distance
scales-- 10 to the
minus 33 centimeters,
or these energy scales, way
beyond what's manageable.
We would directly see that
all the forces are the same.
And that clue has guided
fundamental physics
of the type I'm discussing
for the last 40 years.
Now, it's just a clue.
It could be a coincidence.
And many of my friends
who, for whatever reason,
want to do something
interesting that
doesn't lead to
this conclusion are
willing to drop,
ignore this clue.
And that's their right.
And that's the nature
of this kind of physics.
We have very few such clues.
In my opinion, you have to
take them very seriously.
But it's just a clue.
Doesn't tell us how
the forces unify.
The fact that gravity is
involved is important,
but it doesn't tell us very
much about what goes on here.
Luckily, there are
some ideas, one
of them being supersymmetry.
I don't really have
time to describe it.
It is a different
kind of symmetry.
It's a hypothetical, invented,
theoretical, no direct evidence
for it symmetry of space-time.
Symmetries of
space-time have played
an enormous role in physics.
They're properties of
a good approximation
of the world around us.
They lead to conservation laws.
For example, as you
know, the laws of physics
are invariate under rotations.
I do an experiment.
Here's an experiment.
I drop this, measure how
long it took to fall.
Give it this, now I can deduce
something about gravity.
Now, I rotate my
laboratory 90 degrees,
do the same experiment.
You get the same answer, right?
You all know that.
The laws of physics are
invariate under rotations.
That's why, when I write a
paper, I don't have to say,
I did the experiment,
and my laboratory
was pointing north, or
west, doesn't matter.
I also don't have to say
when I did the experiment
or where I did the experiment
because the laws of physics
are invariate under space
or time translations.
All of these symmetries
underlie and organize
the laws of physics.
So supersymmetry is just
the fact that some of us
might hypothesize that
the laws of physics
are invariate under
rotations in superspace.
So that's supersymmetry.
But you might ask,
what is superspace?
So superspace is
the assertion that
in addition to space, x, y, z,
right, left, forward, backward,
up, down, there are
other dimensions.
But a different
kind of dimension--
dimensions you
measure with numbers
that anti-commute,
whose multiplication law
depends on the order.
So theta 1 times theta 2 is
minus theta 2 times theta 1.
There are such
numbers, believe me.
It's like square
root of minus 1 also
is a good number to work with.
Anyway, it turns out there
are very natural spaces
with dimensions,
extra dimensions,
where the measured
coordinates, measured distances
along this extra dimension with
these anti-commuting numbers.
And you can
beautifully generalize
all the physics we've ever
constructed to these bigger
superspaces.
And if you demand symmetries
under rotations, superspace,
from theta dimensions
to theta dimensions
or theta to ordinary
dimensions, you
get a gorgeous, beautiful,
powerful extension
of all the fundamental
theories we
have, like quantum
electrodynamics or quantum
chromodynamics, Einstein's
theory, everything.
But the nice thing about
this generalization
is that when applied
to fundamental physics,
it makes predictions, and it
explains certain features,
weird features, that
we don't understand
of our present knowledge,
such as dark matter, perhaps,
unification, perhaps,
and other issues.
For example, that
unification of the forces
plotted here has inverse
couplings versus energy.
It doesn't really work as
measurements and theory
are getting more precise.
The extrapolation really fails.
With this choice of
coordinates, the three forces--
this is the strong force,
this is the electromagnetic--
should meet at one point,
these straight lines.
And they don't.
But if you add
supersymmetry, simply say,
there is supersymmetry.
There is a scale of energy where
that symmetry is not apparent,
it's broken, and that scale
is about a TV, a trillion
electron volts, then
this extrapolation works
to one part in 100, to 1%,
after extrapolating over
14 orders of magnitude.
Now, that could be
regarded by some,
and is, as an important
clue for supersymmetry,
for the true symmetry of
nature, with a breaking
of that symmetry and
new particles appearing
at around a trillion
electron-volts
and unification--
or a coincidence.
Many people have been
motivated by this,
both experimental
and theoretical,
for the last 40 years.
LHC has been looking for
supersymmetric particles
for the last five
years, six years.
So far, no evidence.
But no evidence
doesn't mean absence.
This other clue, important
clue, is dark matter,
which has been discovered
by astronomers who tell us
that the galaxies
are really islands
in the middle of a
halo of dark matter,
that dark matter
constitutes most
of the matter
within the galaxies,
within clusters of galaxies.
Most of the matter
of the universe
is a form of dark matter
that doesn't radiate light,
that doesn't interact
strongly with quarks
and leptons, our kind of
matter that we're made out of.
And this is-- I regard it as an
enormous challenge to particle
physics.
Especially that astronomers
discovered this kind of matter
and we still can't produce
it in the laboratory
or detect it passing
through our laboratories,
or see any other
signal than the fact
that this matter exerts a
gravitational force on stars
and bends light around it.
But the evidence is
overwhelming that it
exists throughout the universe.
The simplest
explanation is that it's
made out of some kind of
particle, very heavy, hundreds
of GV or more,
weakly interacting
so it doesn't produce
light, it doesn't
interact with other
detectors which
are far underground
and trying to see it.
And that's a major challenge.
But one of the other attractions
of an idea like supersymmetry
was that although developed
for other reasons,
coming out of string theory
and for its elegance,
predicted naturally a candidate
for dark matter, which--
if this is the right scale--
would kind of explain
the abundance of dark
matter in the universe
and the Big Bang
theory of particle
cosmological production.
So this again, for many,
was an important clue
for supersymmetry at
a TEV, and perhaps
to be discovered along with--
or as the lightest new particle,
particularly [INAUDIBLE]
supersymmetry
is a candidate for dark matter.
But again, this agreement
of our candidate
could be a coincidence.
I stress this because
this kind of physics
is unlike many other
areas of physics
where one-- like [INAUDIBLE]
physics, for example, where one
is working directly in
contact and usually following
in the footsteps of direct
experimental observation.
This kind of stuff,
where the threshold--
the only scales we
can for sure identify
are removed from
present day observation
by many, many, many
orders of magnitude,
relies heavily on building out
from a well-defined, rigid,
and enormously successful
theoretical structure,
the standard model, and building
on the few clues we have
theoretical-- like we
should be unify with gravity
and understand quantum
gravity, and experimental, we
should explain dark matter.
We should-- we should
look for things like this.
This is a kind of event
that might be seen someday
at the LHC, like next month.
Where this is, again, a
collision, very high energy
collision, 13 TEV energy
goes into this point.
Lots of stuff is
produced and comes out
in these jet particles.
And you can just see
that a lot of stuff
is going upwards,
this way and that way.
Not much is coming downwards.
And one of the conservation
laws in physics
is the conservation of
energy and also momentum.
Newton's third law, you know?
If suddenly this moves
that way, something better
be moving that way.
So there's missing energy or
missing momentum going down.
Then, you can measure.
You can measure the properties
of what you can't see.
That's how neutrinos
are seen, by the way.
Very hard to see neutrinos
except often as missing energy.
And that could be a
signal for dark matter
that just moves
through the Earth
without interaction, or
through the detector,
or of supersymmetry,
the lightest
supersymmetric particle, which
would behave the same way.
And they might be the same.
But this is perhaps how
supersymmetry and/or
dark matter will soon be
discovered at the LHC.
Perhaps.
But I want you to remember
that when you read in the paper
that physicists at CERN have--
if they announce they've
discovered something which looks
like what theorists tell them
might be supersymmetry, what
they're really discovering
is quantum dimensions
of space-time.
It will be correct to
say then-- in fact,
it would be incorrect
not to say that we
don't live in
ordinary space-time,
but we live in super-space.
The fact that you don't have a
layer of these extra dimensions
begs the question,
how are you aware
of the ordinary dimensions?
Space-time, I'll remind
you, is a mental construct.
You don't feel space-time.
You don't see space-time.
You have, as an infant,
somehow, miraculously,
while your brain was
developing, constructed
a model of physical reality that
placed it in space and in time.
But it's only a model
constructed by biological us.
And we've already
modified that model
quite a lot with relatively,
special and general,
and we might have to modify
it with quantum dimensions.
And that's the stakes
involved at the LHC
or with this kind of physics.
Now, let me say a word about
the future of particle physics,
which always faces challenges
because it's always
pushing the frontier.
One way of describing
the future is
the picture of the optimistic
or pessimistic point of view.
Physicists, by the
way, in my experience,
oscillate from week
to week or year
to year between those
two extreme points
of view, extreme pessimism
and extreme optimism.
Just made a discovery,
or made a mistake.
The LHC hasn't
discovered anything new.
Oh!
Someday.
Extreme pessimistic
scenario is that, well,
as has so far been shown
by the LHC-- where am I?
Everything agrees with
the standard model,
even this new sector
of physics revealed
by the discovery of
the Higgs particle.
So in this pessimistic scenario,
there's nothing new, even
in the Higgs sector.
There's no signal for this, even
for extension or supersymmetry
or anything else.
All of this is
logically possible.
None of the detection of
dark matter in the sky,
underground, or at the LHC.
No indication of where the
next threshold of physics is.
So if you want to
plan ahead, you
should know what
you're looking for.
There might be no sign
even from the LHC.
Could be anywhere without
some theoretical idea
or experimental clue what to do.
Or my opinion, there's
only one thing to do,
which is to fully explore
the regions which we're just
moving into, which means
build a bigger machine.
This, of course, is
perfectly possible
since we already did it.
There's a big hole in Texas
where we already did it
before Newt Gingrich
got in power.
It's called the SSC.
So we can do it.
It does require money and will,
but I think that's possible.
And in the absence, we have
to continue as far as we can.
Anyway, I'm much more inclined
along the extremely optimistic
scenario that the Higgs
sector will turn out
to be very interesting,
this new particle
couples in ways
which can explore
new kinds of physics
in addition to just
the old kinds of physics.
Supersymmetry can show
up any day at the LHC.
And dark matter is
waiting to be detected
by one of these three methods,
this, in the next decade.
And that will give very strong
guidance for the next steps.
And there are many ideas for the
next steps, many different ways
of extending basically
Rutherford's method again
to higher energies and better
detectors, linear electron
[INAUDIBLE].
But again, with the
same conclusion.
Only exploring these
range of energies,
either in a linear collider.
You could dream of doing this
at Fermi Lab, or at CERN.
But what I find most
exciting is the entry
of a new player into
this game, namely
China, the biggest economy
in the world, if not today,
next month.
And very, therefore,
can afford to build
one collider much
cheaper per capita
than any other
collider in the world.
Here is the site where the plan
is to build a 100 TEV collider.
That still doesn't exactly
tell us what happens up here.
This energy takes us
a little bit-- varies,
but what are we doing up here?
Here, again, we
have a crucial clue.
Because this is the point where
gravity becomes important.
Quantum gravity.
And we are forced--
well, it looks
like we're forced
to think of unifying
not just the topic of nuclear
forces, but gravity as well.
And that has led to all
sorts of fascinating ideas,
like string theory.
But again, this is
just a clue that you
have to bring in quantum gravity
in your attempt to unify.
We might try to unify
it somewhere else.
But this clue says,
no, in order to unify,
we need to include gravity.
Therefore, you need to try
totally different kinds
of physics.
Ordinary quantum field
theory, standard model
doesn't work for gravity, which
has led us to string theory.
But this still might be wrong.
That's the nature of the game.
String theory started with
an attempt to understand QCD.
These mesons, flux
tubes, are fat strings.
That's how string theory
was originally described.
It's a theory of flux tubes.
And that's correct.
We now understand, after the
development of string theory,
in some sense.
It was then understood that
if you have open strings,
you can close them.
And that these closed
strings describe gravity.
So this is a discovery
within string theory
which, given that original
clue, is enormously affirmative.
Not a proof of anything, not
an experimental confirmation.
It's a theoretical
discovery, not anticipated,
that enhances your belief in
this theoretical structure.
That this kind of theory
for the first time unifies
these gauge forces that underlie
the standard model and gravity.
Open strings and closed strings.
We still are pursuing
this idea after 40 years.
And the various ideas
that it has thrown up,
like are there more than three
ordinary dimensions of space?
Because again, one of
the things that came out
not put in to string theory
was that there are more spatial
dimensions than we observe.
So the other dimensions of
space have to be curled up.
This is a kind of a
picture of a beautiful way
of curving six dimensions.
And each point in
space right here,
if we look at this point
with a good microscope that
could see Planck
scale physics, you
could see or deduce a
structure like this.
This, again, I think
although the simplest models
of so-called
compactification of string
theory, the heterotic string,
are much too simple probably
to give the standard model,
or we lack the principle.
But the idea that the
unanswered questions
of an approach like
the standard model--
like, why are the forces
like electromagnetism,
why does the matter come
in the form that it does?
What are the values
of the masses?
These are all questions that
the standard model can't answer.
They have to be put in.
But here, they just
come out of the geometry
of the compacted
five dimensions.
I always thought the
Greeks would love this.
These fundamental
questions are answered
by geometry and topology.
So I'm going to try
to end up describing
how I view the framework
of fundamental physics.
The standard model is a
quantum theory of fields.
Field theory is supreme.
We have a quantum world.
Quantum field theory
is the theory.
Of course, quantum field
theory isn't just a theory.
It's a framework.
And what we've learned
is that there is
another part of this framework.
There's something
we used to call--
or people still
call-- string theory.
I don't think string
theory is a theory, either.
It's a framework.
There are many, many
solutions or ways
of using our primitive,
still primitive understanding
of this part of the
framework to construct
consistent quantum
mechanical states.
In recent years, the
amazing thing we've learned
is that these frameworks
are really the same.
There are many fascinating
cases of physical phenomena,
some of them actually useful
in condensed matter physics,
and certainly in quantum
field theory, which are also
described by string theory, or
its low energy, long distance
approximation called gravity.
These are both part of a
big quantum field framework.
And they don't tell you
what the standard model
or standard theory is.
The standard model of a
really theory is a theory.
You can calculate numbers
and ask experimenters
to test your predictions.
That's theory.
This theory lies within
a framework which
includes strings,
field theories,
and as we're learning,
quantum gravity.
And we have absolutely no idea
the extent of this framework,
even.
Continually gets larger
and larger and richer.
And we're exploring
it's structure
in many different ways.
And we're using the fact that
it has all these different ways
of looking at it--
strings, branes,
field theories, to improve
our calculation abilities
in certain circumstances.
And especially in probing the
nature of the quantized theory
of gravity.
But what the final
framework is, we don't know.
And what picks out a theory
that we can test experimentally,
we don't know.
What we do know is
that when you start
working in this framework,
issues of space-time
and the nature of
space-time are challenged
in ways that go way beyond
imagining quantum dimensions,
from the very essence
of the way you learned
as an infant to
picture space-time
as a smooth structure, a
fixed topology, and certainly
a fixed number of dimensions.
All of these features fade.
You can tear space-time
smoothly in string theory.
You can change the
topology smoothly.
You can change the number
of dimensions smoothly.
And the way this is sometimes
put, and most of us believe,
is that space-time
should be thought
of as an emergent
phenomenon, emergent concept.
It's a crude approximation
of physical reality,
pretty good for large
distances and times.
But microscopically, or
in certain circumstances
like black holes, you're
going to have to modify what
you think of space-time.
And of course, gravity
is dynamical space-time.
Einstein taught us gravity also
can be thought of as emergent.
Emergent from what?
Well, we have examples
using these different ways
of representing physical
phenomena, sometimes
in terms of strings
and gravity, sometimes
in terms of more ordinary
quantum mechanical systems.
But there are very
special examples.
And they don't involve
usually emergent time.
And we don't really know
what the rules of physics
could possibly be if space
and time, especially,
is a truly emergent concept
that you don't start with.
How do you even
formulate the rules
of physics, which is supposed to
be about predicting the future,
if time itself is emergent?
And then, if you
watch and you want
to make predictions, which
you better be in the position
of doing eventually,
should our predictions--
what picks of this framework
a particular dynamic?
What picks the standard model
out of quantum field theory?
Well, we don't know.
We just guessed the right
quantum-- particular quantum
field theory.
And we have this big framework
of string/field field theory,
but we don't know what
picks the particular theory.
And even worse, we're now
doing quantum gravity.
We're forced to if we believe
this clue and all the hints
we have, and we
should do so anyway.
And with gravity, we have to
address the question of what
fixes the initial state.
Now, we know a lot about
the universe, the history
of the universe from close
to the beginning, inflation,
expansion, formation
of the galaxies,
accelerated expansion.
But the beginning?
We try to avoid asking such
questions always in physics.
But if you don't ask
how the universe began,
we try to answer questions
that don't depend on that.
And we can't even imagine how
could we possibly determine
the initial condition?
But we have to.
Because if a subject
of our inquiry
includes a theory of gravity
unified with the other forces,
the answer-- as
Einstein taught us--
is the history of space-time.
And the history of space-time
includes the beginning,
and the boundary if
there's a boundary, what
happens to the boundary
if there is, and the end.
So physics is always
trying to avoid this.
Good idea.
But if you have a
solution, a theory that
unifies the rest of
physics with gravity--
we're discussing
dynamical space-time,
and that dynamic
includes the beginning
and the end and the boundary.
And if your solution is
sick at the beginning
as all solutions
we've ever constructed
are-- something is wrong with
your solution or your way
of thinking, we clearly have
no idea what the rules are.
So we have a wonderful theory
of one or two particles.
But in my opinion, the
most excited questions
remain to be answered.
We have fantastic
instruments and experiments
and fantastic speculations.
And the best is yet to come.
Now, I've talked over my time.
Five more minutes to agree with,
so I don't violate my abstract.
Is that okay?
Yeah.
So I want to just briefly
address the question--
oh, oops.
[LAUGHTER]
That was if I didn't
get permission
for the five minutes.
[LAUGHTER]
So I've discussed a
bit of the journey
of learning about
fundamental physical reality.
Your question was,
how long can we
go doing this kind of physics?
Can we go on forever?
And I want to just very
briefly address three issues.
Some people, when they get
to the stage of imagining
we get unifiable
forces and gravity
and answer all these
questions, that
will be a final
theory of everything.
Is there such a thing
that can be constructed?
Well, how do we know that
we're capable of that?
And do we have
the will to go on?
So there are three issues.
One, first issue is, is there
a final theory of everything?
So I regard this as a
geometrical question,
a question about the
geometry of knowledge.
I'm going to just present
a simple geographical model
of knowledge and
ignorance, which
is more powerful and nicer
than the standard onion model.
Onion model is a model
where knowledge is an onion,
and you peel away to
get to the core, which
I find brings tears to my eye.
[LAUGHTER]
And it's not a very
good model, either,
because it doesn't
explain anything
except the pain involved.
But the way I see it, we
live in a sea of ignorance,
and we're pushing out
a region of knowledge.
So it's the opposite.
We're moving outward
instead of into the onion.
The good thing about
a model, every physics
knows, it has to explain
something you already observed
and make a prediction.
What it explains is the
fact that you, I'm sure,
all have learned, that
although as the studies go on
and history rolls on,
knowledge increases.
It increases like the volume
of this sphere of knowledge.
And a lot of that's
in the libraries.
You can get it.
That's the accumulated
knowledge of humankind increases
[? everything. ?]
What the figure
explains is something
you learn as you're a student,
sometime in your career,
the more you know, the
more you don't know.
Ignorance also increases.
The more we learn, the
more questions arise.
And that's reasonable, too,
because ignorance is really
the region at the boundaries
of knowledge and ignorance.
So out here, there are
unknowns all right.
But as Rumsfeld said,
there are unknown unknowns.
Ignorance is really known
unknowns-- the things
we're aware that we don't know.
But that increases, but
only as the surface area.
So that also explains that even
though we-- as life goes on,
you realize you know--
your ignorance increases.
Your knowledge increases.
But the ratio increases as well
because volume increases faster
than surface area.
And so you get wiser.
So this is a good model.
Then, what we'll ask--
is there a final theory
within the model?
So the question
of whether there's
a final theory, a
theory of everything,
is sort of a question-- is there
a finite amount of ignorance?
If you use up all the
ignorance, then we'll
have a theory of everything.
And this has happened before in
the exploration of the Earth.
So this is a map from the
middle ages, a European map
of the known Earth.
So everything in here
was known, has a name.
A lot of it was part
of the Roman Empire.
And this is the border
of the known universe,
sphere of knowledge.
Notice, the areas that we were
aware that we don't know about
are right at the border.
Keep going-- we don't
even put it on the map.
It's unknown unknown.
And it's pretty empty because
we haven't explored it yet.
Now, there are a lot
of explorer societies
throughout the world exploring
the Earth, making maps.
Eventually, as you know,
they went out of business
because it turned out
the Earth is round.
And sooner or later,
they started running out
of unexplored territory,
and finally you
have-- at least at the
resolution of a few miles--
our complete, final
map of the world.
Our final theory of the
world, of the geography
at some scale of the world.
So the issue is, is the
sea of ignorance compact?
Hold on.
If it's compact, like
the surface of a plane.
If it's unbounded
or infinite, then we
can go on doing science forever.
The more we learn, the
more ignorance there'll be.
And you'll go on,
and it'll never stop.
Maybe, however, like the
surface of the Earth,
it's compact and finite.
And eventually,
we'll get to a stage.
So how would you know this?
You get to a stage
where something-- there
are fewer and fewer questions,
fewer and fewer ideas
for grants, or thesis
projects for students.
That would be a sign
that you're running out
of questions, that you're
nearing a final theory.
My experience is that we're
not even close to that--
no evidence of that.
In fact, one of the things in
a theory like string theory
is we've realized
in the last four
years the more we learn
about string theory,
the more questions there are.
It's not a sign that we're
nearing the final theory.
Anyway, even if we did, it
wouldn't be the end of physics,
of course.
Although it might be the end of
reductionist physics one way.
Most of what we study in
science are the infinite variety
of phenomena that
can be put together
in a given microscopic
reductionist basis.
But it would be the end of
a certain kind of physics
if it were to
happen, which I see
no sign that we're close to.
There are likely other problems
in going on forever either way.
One is that we might
be too dumb to proceed.
Why should we, as
human beings at this
point in evolution of life
on this little planet,
assume that we are smart enough
to understand quantum gravity
or-- we certainly know
that other species are
incapable of that.
[LAUGHTER]
[INAUDIBLE]
Don't even bother with those.
So we can comprehend that
dogs cannot comprehend quantum
mechanics.
Why should we be so arrogant
to imagine that nothing
is beyond our comprehension?
With that line of thought,
we get pretty pessimistic.
Because clearly, we
shouldn't be arrogant.
Clearly, there must be things
beyond our comprehension,
that we can't even comprehend.
There are.
Or there might be.
However, I don't think
this is a danger, either.
I'm an optimist.
First of all, we
have something--
the one thing that
really differentiates us
from our other fellow species
on the Earth is language.
Or its most developed
form, mathematics.
And language, as
Chomsky has taught us,
has infinite capacity.
A newborn baby, after
somehow learning a language
just by listening
to its parents,
can utter sentences no one
has ever uttered before.
Language's infinite capacity and
mathematics's infinite capacity
have a lot of infinities.
This infinite might not
be enough to comprehend
the sequence of quantum
gravity or whatever.
But least it's infinite.
Second of all, there's
an experimental test.
If we were getting to
the point, I think,
where we were facing questions
that we were like dogs, too
dumb to understand,
to comprehend,
I think we'd begin
to notice that.
We'd begin to notice that
graduate students in physics
would take longer and
longer to get their degrees.
There's some of that, but
that has other reasons.
They'd take longer and longer.
Eventually, they would
die before they--
[LAUGHTER]
They just would never get to
the frontiers of knowledge.
That's not the case.
There still is brilliant
and knowledgeable people
who manage with this equal
effort and ease and youth
to get to the frontiers
of knowledge and expand.
So that's the experimental
side, which hasn't yet happened.
And finally, by the way,
if we ever got to the point
where we realized
we were incapable,
oh, well, we would start
tinkering with our minds
or [INAUDIBLE] with machines
or do whatever it takes.
So I'm not worried about that.
The thing that's
much more worrisome
is that we may lose the
will and the means to go on.
It's getting more expensive
to build high energy colliders
or telescopes in outer space.
And I don't know.
Here, I don't have
a clever answer.
I just have hope.
And I'll end on that
hope with this quote
from David Hilbert,
mathematician
who said on his gravestone,
"We must know, we will know."
Thank you.
[APPLAUSE]
OK, great.
We have [INAUDIBLE].
We have a science [INAUDIBLE].
[LAUGHTER]
We have time for
a few questions.
So as the procedure, if you
just go to the microphone, $300.
[LAUGHTER]
And ask your questions.
What are your thoughts for the
discovery of the [INAUDIBLE]
earlier this year
at [INAUDIBLE]?
You say you're
[INAUDIBLE], so I'm
assuming you've [INAUDIBLE].
Oh, it's hugely important.
You're right.
It's closer to three to
four or five [INAUDIBLE].
It all depends on
who you talk to.
I have a lot of hope.
Not that I have any idea
what it is or why it is.
But I just have
hope because it'll
be something new and exciting
and give us more clues.
But I listen to my colleagues.
And there's not enough to
go around at this point.
I'm proud of--
say it in public--
that the 135 GV Higgs was there
before it was announced based
on what I knew in that
experiment and my belief
in the standard model and
the simplicity of nature.
But here, I have no
theoretical clues.
And I'm not competent to judge.
OK.
Hi, Professor Gross.
So for the next high
energy collider,
how much will
[? has there been ?]--
especially among
physicists and teachers,
like [INAUDIBLE] sources.
Well, let's see.
I think the fact that
there are new plans
in large parts of the world
with enormous economies
that want to contribute,
to stimulate technology,
to advance science.
I think the wealth of the
world since the [? SSE ?]
was built 20 years ago.
The wealth of the world
has increased enormously.
So this is not an
enormous step worldwide,
if you view it that way.
So the ability
for this next step
is in the ability
and the knowledge
to do that from the
technical point of view,
and the ability of the world
to do that should be enough.
That's partly up to
scientists to convince,
to explain to
non-scientists why--
and it is possible
to put in place
from an intellectual
point of view
and a economic point of view,
and a general development
point of view.
I think that will prevail.
I'm optimistic.
In taking a view
of time, we should
say that we will thank
Professor Gross for--
[APPLAUSE]
