[MUSIC PLAYING]
BROWN: It's a pleasure
to welcome everyone
to MIT on this bright
and glorious morning.
I'm Bob Brown, the
provost of MIT,
and I'm standing in for
President Charles Vest, who
happens to be traveling.
He, Chuck, would very
much love to be here.
During his time
as president, this
will be the only Nobel
laureate that we've
received that he does
not introduce personally.
It's a glorious day
for American science,
for MIT, and for the
Department of Physics
with the awarding of the
Nobel Prize in physics
to Professor Frank Wilczek.
I'm going to let Marc Kastner,
the department head in physics,
make the formal introduction.
Mark?
KASTNER: Thanks, Bob.
Before I begin, I'd like to
introduce two other physics
Nobel laureates who are here--
Jerry Friedman and
Wolfgang Ketterle.
[APPLAUSE]
Jerry shared the prize
with the late Henry
Kendall, another faculty member
in our department, in 1990.
And when I introduced Wolfgang
to the department colloquium
after his Nobel Prize
was announced in 2000,
I pointed out that we
had had five Nobel Prize
winners in the physics
department in 25 years.
And I thought that once every
five years was pretty good,
but the faculty should
really work a little harder.
[LAUGHTER]
And here you see
they come through.
[LAUGHTER]
Frank Wilczek is, as Bob
Jaffe says, a luminary.
He is one of the great
minds of modern physics.
In 1972, when Frank
began his research
on quantum
chromodynamics, the theory
of the strong interactions,
we knew there were quarks.
And we knew it because of the
experiments of Jerry Friedman
and Henry Kendall.
And a lot was known,
but the pieces
of what held these
quarks together,
the strong interaction,
were fragmented.
There was no way of
putting it together.
The work that Frank did with
David Gross and Politzer
put things together in a
way which allowed physics
to move forward.
And it is one of the
great cornerstones
of our understanding
of modern physics.
Frank came here from
Princeton about the time
of the millennium.
And it really began a new
century for MIT physics.
It gives me great pleasure
to introduce him to you.
[APPLAUSE]
WILCZEK: Thank you.
[APPLAUSE]
Thank you.
[APPLAUSE]
All right.
That's enough, that's enough.
OK.
An occasion like this I think
is, first of all, an occasion
to give thanks.
And I have a lot of
people I want to thank.
I want to thank my
parents who were
first-generation Americans.
My grandparents emigrated
under difficult circumstances
around the time of World
War I. And my parents
grew up in very
difficult circumstances
in the Depression,
but worked very
hard to get themselves
educated and then
to support my education.
And I was very pleased
to be able to call them
this morning with this news.
I also want to thank
the United States for--
[LAUGHTER]
--supplying the
system of education
which did so well by me.
I'm a public school
guy all the way
and a beneficiary of the
excellent public schools
of New York City in the 1950s.
And I think it's very important
that the country continue--
or recover-- the excellence in
its education that it's had.
I also got excellent
instruction at Chicago
before coming to Princeton,
where after that it
gets famous.
[LAUGHTER]
I also want to thank
my wife, Betsy.
It was the time I was
meeting and courting
Betsy that I did this
work, and I don't think
that's entirely a coincidence.
[LAUGHTER]
We're still together,
and she's here,
and I thank her very much.
Although they didn't have
much to do with this work,
I'd also like to
thank my daughter
for making life a lot
of fun and enabling
me to keep happy and productive,
I think, at a reasonable level
ever since.
More seriously,
I'd like to thank
the community of
physicists, I guess
represented by Jerry
Friedman here especially,
the community of
physicists who really
laid the foundation
of insight and facts
that we were able to leverage
into a fundamental theory
of the strong interaction.
And our input definitely
was important--
I don't want to be
too modest about this.
[LAUGHTER]
--but it absolutely was
not from out of thin air.
It was rooted in hard
experimental work
and theoretical insights from
a large number of communities.
We stood on the
shoulders of giants,
but also on the shoulders of
a lot of only reasonably tall
people, a very large number of
average height people, and even
a few dwarfs were important.
Finally, I'd like
to thank nature
for being so kind
as to really become
simple and understandable
at short distances.
Our work is really a
vindication of the whole idea
that it is possible to
understand nature precisely
and mathematically by
studying the fundamentals that
go on at short distances
and high energies
and building up from there.
So I'd like to thank mother
nature for her good taste--
[LAUGHTER]
--in choice of principles, and
symmetries, and rationality.
So I don't know what
I'm supposed to do now.
[LAUGHTER]
So maybe I'll just
say a few words
about what's up on the board,
which is representative,
and then take questions.
So starting over here--
BROWN: Can you grab
the microphone right
up front, the wireless?
[INAUDIBLE]
WILCZEK: This one?
BROWN: No, no.
WILCZEK: Oh, in here.
Oh, that.
OK.
So--
BROWN: It's on.
WILCZEK: --this this was the
result of the calculation that
came from calculating
processes in space and time
where gluons interact
with other gluons
and modify the distribution
of colored charge.
Or they can also go through
intermediate quarks.
And there are a number of
different kinds of processes.
I won't go through
the details, nor--
[LAUGHTER]
--give you a quiz on this.
But the result of
this calculation
was a formula for
how the coupling
of the strong
interaction changes
as a function of energy.
And what we found is that as a
result of quantum fluctuations
and rearrangements of
color fields in the vacuum,
in empty space--
what you call the
vacuum, in empty space--
the effect of a charge at
higher and higher energies--
or equivalently, at shorter
and shorter distances--
gets weaker and weaker.
This is what's called
asymptotic freedom.
And because the its effect
gets weaker and weaker,
the particles behave more
and more as if they were free
of any interactions, as the
energies get larger and larger
or the distances get
smaller and smaller.
That's why it's called freedom.
It's also simplicity,
because it means
that the complications
due to the interactions
become less and less severe or
less and less necessary to take
into account as you go into
higher energies or shorter
distances.
So that was the formula from
pen and paper calculations.
And the original calculations--
because they had
many cross-checks
and they involved
techniques that
were pioneering at the time--
really filled notebooks.
Nowadays, that
calculation is often
assigned as an exercise in
quantum field theory classes.
It's still difficult to do
in less than a page or two,
but that was the
core calculation.
From that calculation it was
a relatively straightforward--
but not trivial--
exercise to derive
experimental consequences.
In a variety of
different experiments,
which I'll be happy to
explain if someone asks,
one can check whether
this predicted behavior
of the effective
charge getting weaker
and weaker at high energies and
short distances in fact occurs.
And most gratifyingly--
well, this is, of course,
entirely manufactured data, but
gives the spirit of the actual
curve, which I didn't bring in--
our prediction for how the
strength of the coupling
should vary as a
function of energy
has been vindicated now by
many thousands of measurements
and literally hundreds of
different kinds of experiments.
And so I still find it a miracle
to think that the calculations
and concepts that on the one
hand you scribble on paper
match the results that are
measured in accelerators with
these gigantic magnets and
detection apparatus' that seem
to come from an entirely
different universe of discourse
and concepts.
And yet, one maps onto the other
with this amazing accuracy.
And then I'll display
one more thing.
So this all has to
do with the behavior
of the so-called strong
interaction, which
is responsible for building
up protons and neutrons out
of quarks and for the
interactions of protons
and neutrons that are
responsible for building up
atomic nuclei and
holding them together
and responsible for our mass.
So if you think
you're overweight,
you have me to blame--
[LAUGHTER]
--mostly.
This one is one of
the theoretical uses
of this insight.
We would like to
construct, as much as
possible, a unified description
of the different forces
of nature.
But when we go out
and measure, we
find that several of
the different forces
don't seem to want to be unified
in that they appear to have
very different strengths.
So here, alpha-3 is the inverse
strong coupling constant--
alpha-S is the same as alpha-3--
this coupling constant
that describes the strength
of the strong interaction.
Here its inverse,
so it increases
as the energy increases.
And instead of getting a
curve, because I plotted it
with a logarithm, it gives
more or less a straight line.
But the details don't matter.
The point is that the
coupling constant changes
as a function of the energy.
And likewise, the
coupling constant
for the weak interactions
and for the electromagnetic
interactions change depending
on the energy or distance
at which you measure them.
And likewise, even the
gravitational interaction.
And so you can see if
the dream of unification
at short distances
can really be achieved
by extending and extrapolating
this kind of calculation
to other interactions
and to higher energies.
And miracle of
miracles, it works--
well, more or less.
[LAUGHTER]
It works quantitatively
in detail,
doing justice to the
accuracy of the experiments.
I should say, before
getting carried away,
but what's actually measured
is what's in this oval here.
And the rest is extrapolation.
And those of you who
know about logarithms
will know that to
get a logarithm
to change by a factor of 10 is
a very enormous extrapolation.
So that's the sort of thing
we're talking about here.
We're going from a 100
GeV in energy to 10
to the 18th GeV in energy to
make this extrapolation-- so,
far beyond what we've measured.
But because of the
success of the theory,
we have some confidence
that it makes sense to do.
And when you do
it in full detail,
you find that it
more or less works
with the particles we know.
However, if you really wanted
to get it to work accurately,
you'd have to up
the ante and include
something that is called
low-energy supersymmetry.
Now, low-energy
supersymmetry is something
that has consequences.
It's something
that has to show up
at the next great
accelerator, the Large Hadron
Collider at CERN.
So we're actually
making predictions
for the near future.
We can be shot down or not.
I'm not going to give
back my Nobel Prize--
[LAUGHTER]
--if it doesn't work.
On the other hand, I'll be in
the market for a second one--
[LAUGHTER]
[APPLAUSE]
But this is an example of how we
build on insights from the past
to makes predictions
for the future.
And it's a very exciting future
indeed for this kind of work.
So with that, I'll
take questions.
KASTNER: Before questions,
let me take this opportunity
to introduce one more of
our department's Nobel Prize
winners, Sam Ting.
[APPLAUSE]
Sam was actually our
first physics Nobel
Prize at MIT in 1976.
And all the ones
before this year
were in experimental
physics, so this
is a breakthrough year for us.
This is our first prize
in theoretical physics.
BROWN: Be glad to
take questions.
MODERATOR: [INAUDIBLE]
phone [? mob. ?]
Ask the phone if they
have any questions.
BROWN: People on the phone,
do you have any questions?
REPORTER: Hi, yes.
My name is [INAUDIBLE].
I'm from the Washington Post.
WILCZEK: Hello.
REPORTER: I wonder if you could
describe your collaboration
with your two
colleagues, where it took
place and the circumstances.
WILCZEK: Yeah.
Well my collaboration was
with David Gross only.
David Gross was an
assistant professor
when we began the work.
He got promoted to associate
professor somewhere in there.
And he was my thesis advisor.
And we worked very
intensely together.
David Politzer was a
graduate student at Harvard.
And we learned of
his work really
only after both groups had
found their main results.
We learned of his work
through Sidney Coleman,
who was a brilliant physicist,
David Politzer's thesis
advisor.
David Politzer was at Harvard
and Sidney was on leave
from Harvard to Princeton.
And Sidney realized that we
were working on related things.
So we knew of each other's
existence at an early stage
and remained in
friendly competition
by having occasional
communications.
AUDIENCE: What does it mean
for you to have won this prize?
WILCZEK: Makes me very happy.
[LAUGHTER]
It also makes me relieved.
I'd be lying if I said
it came as a shock.
The theory I've
thought for a long time
was very, very important.
The data in favor of it has been
clear for at least 20 years.
And so every year at this
time for the past 20 years
or so, I've had an unpleasant
week and a sleepless night.
[LAUGHTER]
I'm very pleased that
that's all over with.
[LAUGHTER]
[APPLAUSE]
But more seriously, I think
it's very welcome recognition
for an endeavor--
understanding the fundamental
interactions of nature
and understanding them in a
precise mathematical way--
that is one of the crowning
glories of our culture.
It's one of the
things that people
will think about
1,000 years from now,
if there are still people,
or their robotic descendants,
or whatever.
But it's one of the
real gems of our culture
that you can understand
nature in this way,
and then when you do you
find very beautiful things.
And I hope to pay back in the
sense of using this recognition
to feed some of it back
into the field as a whole
and make sure that it keeps
supported and keeps vigorous.
BROWN: Yes, in the back.
AUDIENCE: I was wondering if
you could in layman's terms
describe this theory of
the strong interaction,
because you kept
referencing back to that.
WILCZEK: Right.
AUDIENCE: And I need to have
that building block for me to--
WILCZEK: OK, so what is
the strong interaction.
When people in the
1930s started to get
a reasonably mature
understanding of what
atomic nuclei
were, they realized
that atomic nuclei can be
thought of as built up out
of protons and neutrons, but
that the interaction that
held them together between
protons and neutrons
had to be a fundamentally
new interaction.
The interactions that
were known at the time--
electromagnetism and
gravity-- were not
sufficient to hold
atomic nuclei together.
So this became the problem
of the strong interaction--
what is it that holds
atomic nuclei together.
That's not an easy
thing to investigate,
because nuclei are
very, very small.
And so the experiments were
at first relatively crude.
They consisted in throwing
different particles together
at high energies and
seeing what came out.
And people hoped, I
suppose, that what came out
would be simple building blocks
and that you would understand
the protons and neutrons-- or
maybe the protons and neutrons
themselves would be
deflected by a ways,
then that would tell you
what their interactions were.
But what happened instead was
that when the particles were
smacked together you found
whole new worlds of phenomena,
that there were many,
many unstable particles
besides protons and neutrons.
They have funny names like pi
mesons, rho mesons, lambda,
[? sigma. ?] A lot of them
are just Greek letters.
But anyway, though in a
way similar properties
to protons and neutrons, they
had very powerful interactions.
You could turn protons
into lambda particles,
but then you could also turn
lambda particles into protons.
So they seem to be more or
less on the same footing.
And understanding that
whole complex of phenomena
became what's called the problem
of the strong interaction.
And it got completely
out of hand by the 1960s.
There were hundreds of
particles, no real rhyme
or reason to why there were
so many or the patterns.
Then primarily
Murray Gell-Mann--
but with a lot of
help from others--
started to see patterns
in this and found
that he could understand the
observed kinds of particles
by postulating that
they were made out
of other things, quarks,
that had somewhat simpler
properties.
So some things were
made out of three quarks
and other things were made out
of a quark and an antiquark--
those are baryons and mesons.
And those were the
strongly-interacting particles.
There was no real understanding
of what a quark was other
than it was some kind
of mysterious thing
that you could build
other things out of.
Part of the mystery was
that individual quarks
were never discovered.
They can't exist in isolation.
And so this was clearly a
provisional understanding.
Then, well, skipping a lot of
very interesting complications
and very deep
insights, certainly one
of the next great milestones
was when Friedman, Kendall,
and Taylor, and
their collaborators
did the very smart thing of
using a microscope to study
inside of protons and neutrons.
Of course this is not
the kind of microscope
you buy at a hardware store.
It's a microscope that
involves very, very high energy
electrons and a lot of
interpretation of what you see.
But using that, they were able
to probe inside the proton
and show that--
with some clever
interpretation-- what
you were seeing was
something like quarks,
and furthermore that the quarks
inside the proton at very
short distances were interacting
with each other surprisingly
weakly when they
got close together.
So that posed the
problem for us--
how can you get a
consistent description
of entities, that is consistent
with the basic principles
of quantum mechanics
and special relativity,
that interact very
weakly at short distances
but powerfully at
long distances,
because we know quarks can't
separate from each other.
And that at first seemed
to be a contradiction,
because in most consistent
realizations of quantum
mechanics and special
relativity charge tends
to build up a long distances--
I'm sorry, charge tends to get
shielded at long distances,
so the effect of
coupling gets smaller
at long distances, which is
the opposite of what we wanted.
That's the ordinary behavior of
matter in dielectrics or things
you learn about in ordinary
undergraduate physics.
But what we found,
somewhat to our amazement--
I think more to David's
amazement than to mine,
because I didn't know as much--
[LAUGHTER]
--we found a unique
kind of theory,
the so-called
non-abelian gauge theory,
a theory with very remarkable
mathematical properties
and high amounts of symmetry,
that had the opposite property,
that instead of
charges canceling
themselves and shielding
at large distances
they anti-screened.
So the charge would
grow at long distances,
get smaller at small distances.
So a very small seed
charge and weak interaction
could build up to a
strong interaction.
And those theories
were so rare, theories
that had that kind of
behavior were so rare,
that with only a few broad
hints from experiment
and implementing
that requirement
we were led to a unique theory
of what the strong interaction
had to be.
And that's what's now called
QCD, or Quantum Chromodynamics.
So part of that was
introducing in addition
to the quarks what are
called gluons, colored gluons
with specific properties.
So along the way we
discovered gluons
and showed that the
interactions really
simplified at short distances.
