The message I want to convey to
the students here is that with a good education, dedication and hard work, you
can accomplish things well beyond your hopes and have a future that can even
exceed your dreams. I was such a young person many years ago and I would like to
tell you how this came about for me. To do this, I should tell you a little
about my background and how I chose physics as a career, a career that gave me
the opportunity to probe the wonders of nature. I would also like to describe
some of my efforts to uncover natureís secrets. I do this not because I consider
myself so important as an individual. Rather, I do this because my career
demonstrates how any student can work toward a productive and satisfying career
in science, or in any other field. I also hope that some of the lessons I
learned along the way may be useful to you.
I was born in the city of
Chicago, in the United States. My parents were immigrants from Russia. My father
came to the United States in 1913 and my mother arrived in the United States in
1914 on one of the last voyages of the Lusitania, which was sunk during World
War 1. My parents had little formal education, except for courses in English
after they arrived in the United States. But they were self taught and had wide
I grew up in difficult times.
When I consider the kind of environment in which I grew up, I think it would
have been totally inconceivable to anybody who knew me that someday I would be
awarded the Nobel Prize. I was raised in a poor neighborhood in the west side of
Chicago. The public schools were inadequate and there were bad influences on the
streets. It was the Great Depression and my parents had severe financial
problems. I received my primary and secondary education in Chicago. As a child,
I liked to draw and paint. In high school, I entered a special art program,
which allowed me to draw and paint a few hours a day; and my ambition was to
become an artist.
While I always had some interest
in science, I only developed a strong interest in physics when I was in my
fourth year in high school. This came about as a result of my reading a short
book entitled Relativity, by Albert Einstein.
You might wonder what attracted
me to this book. Of course, Einstein was greatly admired by my parents, as he
was by people throughout the world. I had read a little about relativity and
what I read fascinated me. I thought that this book might give me some
understanding of the mysteries of how meter sticks shrink and clocks slow down
when they move fast Ė things that I had read about in popular articles. I read
the book carefully and tried my best to understand these matters; but in the
end, I really didnít understand the basic concepts of special relativity. This
only made me more curious and more determined to try to understand these
perplexing ideas. It was clear to me that I would have to study physics to
really understand the theory of Relativity.
This book opened new vistas for
me and deepened my curiosity about the physical world. When I completed high
school, I received a scholarship to the museum school of the Art Institute of
Chicago. My art teacher strongly encouraged me to accept this scholarship.
However, I decided to continue my formal education and sought admission to the
University of Chicago because of its excellent reputation and because Enrico
Fermi taught there. Enrico Fermi was one of the greatest physicists of the 20th
I spent my first two years at the
University in a highly innovative and intellectually stimulating liberal arts
program. I am happy that I had that exposure to the liberal arts because they
opened the world to me in many areas that have given me great satisfaction
throughout my life. I entered the Physics Department in 1950.
The Physics Department was a very
exciting place. I had a wonderful education, but I found it very difficult. My
high school background in mathematics and physics was inadequate, and at times I
had to struggle. Sometimes, I wondered if I had made the right choice. But I
refused to be discouraged because I truly loved what I was studying. I worked
with great dedication and passed all of my exams.
When I was ready to start my
doctoral research, I decided to ask Fermi whether he would supervise my
research. While I wasnít optimistic about him accepting me as one of his
students, I thought I had nothing to lose by asking him. I certainly could
accept being turned down by such a great man. So I went to ask him; and to my
great surprise, he said yes immediately. I was overjoyed. This taught me an
important lesson. Be willing to risk failure. Reach high even if you think you
donít have a chance. You might succeed! Being supervised by Fermi was a
remarkably stimulating experience that shaped the way I think about physics.
After I received my PhD, I
continued working in Fermiís laboratory, which had been taken over by an
outstanding young faculty member, Val Telegdi, after Fermiís tragic death in
1954. At about that time there were some puzzling observations of the decay of a
newly discovered particle that were causing much controversy and speculation in
the particle physics community. In a bold paper, two young physicists, T. D. Lee
and C. N. Yang proposed that this apparent paradox was due to the
non-conservation of parity in the weak interactions and suggested some
experimental tests of this hypothesis. The so-called weak force is one of the
four basic forces of nature and is responsible for igniting energy production in
the sun and also for radioactivity. And Parity is a quantum mechanical concept.
Its conservation is equivalent to the idea that a physical system should behave
in the same way when observed in a mirror.
While most of the community
considered the conservation of parity to be a sacred principle, Professor
Telegdi asked me to join him in making a measurement to test the bold hypothesis
of Lee and Yang, who had been students at the University of Chicago. Most of the
others in our lab thought that this was a waste of time. I remember giving a
seminar at our Institute on the measurements we were going to make. After the
seminar, a distinguished older member of the faculty came up to me and said that
I had given a nice talk, but that I should realize that we were not going to
As it turned out, we were one of
the first three groups that demonstrated the non-conservation of parity in the
weak interactions; and as result of these experiments, a new theory of the weak
interactions was developed. Lee and Yang were awarded Nobel Prizes in 1957 for
their work. The lesson that I learned from this is that one should be willing to
test new ideas, even if they are rejected by others. Progress in science only
comes about when old theories give way to new ideas.
1960, I was hired as a faculty
member in the Physics Department of the Massachusetts Institute of Technology.
In 1963, Henry Kendall and I started a collaboration with Richard Taylor and
other physicists from the Stanford Linear Accelerator Center and the California
Institute of Technology to design and construct electron scattering facilities
for a physics program at a two mile long, 20 Billion electron-volt, electron
linear accelerator that was being constructed at Stanford University, called
SLAC. We soon set up a small MIT group at SLAC and for extended periods of time
one of us was always there.
From 1967 to about 1975 the MIT and SLAC groups carried out a series of
measurements of inelastic electron scattering from the proton and neutron that
provided the first direct experimental evidence that the proton and neutron are
made up of quarks. This work confirmed the quark model and provided the
experimental foundations for Quantum Chromodynamics, the theory of the so-called
strong force. It was a very exciting time for me.
It was for this work that Henry
Kendall, Richard Taylor and I were awarded the Nobel Prize in Physics in1990.
What a surprise and joy that was! It was a magical week in Stockholm filled with
the kind of grandeur and excitement that I had never had experienced before.
There were talks, press conferences, receptions, gala parties, and sumptuous
banquets, one of which was held in the royal palace. But the most stunning event
was the ceremony in which the Nobel Prizes were presented to us by the King of
Sweden. It was held in a beautiful concert hall, bedecked in flowers, with an
audience of a couple of thousand men and women in formal wear and evening gowns.
Between the presentations of the awards, there were interludes of beautiful
music. It is a memory that my family and I will always cherish. But sometimes I
wonder to myself how was it possible that this really happened to me.
When we started this experiment
for which we so honored, many physicists told us that it was a waste of time. In
fact, members of our collaboration who had participated in the design and
construction of the apparatus dropped out of the experiment because they wanted
to do something more productive. Let me now tell you about this work.
But to start, I should put this
work in the context of what is known about matter. Looking at the top of the
first slide, we see just ordinary matter, consisting of atoms and molecules.
Everything here is made up of such matter, this table, us and everything around
us. If we increase the magnification a 100 million times, we see the atom. The
atom consists of electrons going around a positively charged small object in the
center called the nucleus. This picture was proposed by a Japanese physicist,
Hantaro Nagaoka in 1904. It was confirmed in 1911 by Rutherford in a famous
series of experiments using the scattering of alpha particles. If we now
increase the magnification another 100,000 times, we see the nucleus which is
composed of neutrons and protons. That picture started unfolding in 1919, when
Rutherford identified the proton as the nucleus of the hydrogen atom, and
culminated with the discovery of neutrons in 1932 by Chadwick. If we increase
the magnification further, we see that the proton and neutron are composed of
other particles called quarks. That story started unfolding in 1968 and goes on
to the present. Thatís the story I want to tell you. *
The beginning of this story was
the discovery of a new kind of particle called the pi meson or pion. The
existence of this new particle was theoretically predicted by a Japanese
physicist, Professor Hideki Yukawa, in 1935. Physicists started searching for
this new particle because the theory was very compelling. In 1947, it was
discovered; and Professor Yukawa was awarded the Nobel Prize in Physics in 1949
for this outstanding theoretical work. When the pion was discovered, there was
great elation in the physics community because there was a feeling that there
was some understanding of the subatomic world. But this elation was short lived
because enormous complexity soon developed in this field. *
By 1960 a large number of
different particles had been discovered, and it was unclear how these various
particles were related to one another. These newly discovered particles were the
result of new and higher energy accelerators and new types of particle
In 1961 a classification scheme
was developed for these many newly discovered particles. It was like the
periodic table of the elements except that it was for particles. This
classification scheme not only provided an order for these newly discovered
particles, but it also predicted the existence of particles that not had yet
been discovered. And all of these particles predicted by this scheme were later
discovered. But the question arose: Why is this classification scheme so
In 1964, two physicists
independently proposed quarks as the building blocks of particles, because they
found that quarks could be the basis of this classification scheme. Initially,
the quark model had three types of quarks: the UP quark, the DOWN quark and the
STRANGE quark. But quarks had a very peculiar property that was very surprising
and troubling. They all have fractional charge, and no particle in nature has
ever been found with a fractional charge. The UP quark has a charge +2/3, the
DOWN quark is -1/3 and the STRANGE quark is -1/3. *
Now the proton, you see is made
up of 2 UP quarks and a DOWN quark, giving the proton a charge +1 and the
neutron is made up 2 DOWN quarks and an UP quark, giving a charge 0. You see
that is basically how the proton and neutron are constructed in this theory. *
What do physicists do to find out
if something is real? They will look for it. Well, there were many attempts to
find these quarks. But not a quark was found. To many physicists this was not
surprising. Fractional charges were considered to be a really strange and
unacceptable concept, and the general point of view in 1966 was that quarks were
most likely just mathematical representations - useful but not real.
So most physicists at that time
did not think that quarks existed. There were, however, a few physicists who
would not give up the quark model, and they persisted in making calculations of
applications of the quark model. But few physicists paid attention to them.*
In 1966, there was an important
development in this story. The Stanford Linear Accelerator at SLAC was completed
and brought into operation. This is a very long high energy linear accelerator
for accelerating electrons. Inelastic electron-proton scattering experiments
started in 1967 and continued until 1974 by an MIT-SLAC collaboration, which
included Henry Kendall, Richard Taylor, and myself along with other physicists.
Conceptually this was a very simple experiment. You would shoot electrons at
protons. Electrons would scatter off and many other particles would be produced.
You would only detect and measure the electrons and this provided the first
direct evidence for quarks. Let me explain how, because the scientific
methodology is really quite simple. I will explain it by an analogy. *
I give you a fish bowl with a
certain number of fish in it and put it in a dark room. I ask you: Tell me how
many fish are in the bowl ? I also ask that you not put your hand in the fish
bowl. But I do give you a flashlight. Well, what you would do is turn on the
flashlight and look, right? You would see how many fish there are in the
fishbowl. That would be the sensible thing to do.
Well, you see, the experiment was
basically the same idea. Instead of having a light beam, you have an electron
beam. Instead of using your eyes, you use particle detectors. Instead of having
a brain to reconstruct the images, you do that with a computer, programmed by
human intelligence. And, of course, instead of looking for fish inside the
fishbowl, you are looking for what is inside the proton. So itís basically that
idea. You are looking inside the proton with the equivalent of a very powerful
electron microscope. The effective magnification that this experiment provided
was a factor of 60 billion times greater that that of an ordinary microscope.
This is the picture of the
Stanford Linear Accelerator. Itís two miles long and you can see thereís a road
going over it. The electrons are bent into three beam lines. These are the two
experimental halls. The experiment was done in the larger of the two halls. The
electron beam is bent and it enters this hall that houses the experimental
apparatus. The linear accelerator delivered an electron beam of 20 billion
electron volts, which was a very high energy in those days.*
Here is a picture of the magnetic
spectrometers used to measure the energy of the scattered electrons. The larger
of the two is the 20 billion electron volt spectrometer. It was 50 meters long
and weighed 3000 tons. The other one could measure up to 8 billion electron
volts and it was 25 meters long. The beam comes in from the left, and hits the
target at the pivot in front of the spectrometers. The spectrometers can move on
the rails that run around the pivot. These were the biggest instruments in
physics at that time. *
Now what are the characteristics
of scattering that you would expect on the basis of the quark model as compared
to that from a proton whose electric charge is smeared out, which was the model
of the proton at that time? In a certain sense, this is really the crux of the
matter from a physical point of view. If you had the old model, in which the
charge was quite diffuse you would expect the electron to come in and not be
deviated too much because the charge is smeared out and thereís nothing hard
inside to really scatter it in a hard collision. The incoming electron comes in
and goes through the proton without too much deviation. This is shown in the
upper image. But if you have constituents inside the proton, then occasionally
an electron comes in and scatters with a large angle from one of the
constituents, as you can see in the lower image.
So, an excessive amount of large
angle scattering would imply much smaller objects inside the proton.
Consequently, by looking at the scattering probability distribution you can
determine what is inside the proton, and this is how the experiment was
analyzed. I want to show you what was found.
Here in this slide, we show the
probability distributions of scattering from the experiment as compared to that
expected from old model of the proton. The top curves here are the measurements.
The rapidly falling curve is the type of distribution you would expect from the
old model of the proton. And you see the difference, as much as a factor of a
thousand between what the old model would have predicted in scattering
probability and what the experiment produced. Basically what these measurements
showed was that an unexpectedly large amount of large angle scattering was
observed. Now, the experimenters went on to try to analyze and reconstruct the
images, in terms of what was measured.
How big were the objects inside?
The results indicated that they were point-like. They were smaller than could be
measured with the resolution of the system. But this was a very strange point of
view. It was so different from what was thought at the time that we were
reluctant to discuss it publicly.
So using these instruments, we
found that both the proton and neutron were composed of point-like constituents.
We called them point-like because they are so small we were not able to measure
their size. We were also not able to determine if they had the correct
Fractional charge was a much more
difficult problem; and to really resolve that problem another type of scattering
had to be brought into the picture. Neutrino scattering had to help provide the
First of all, what are neutrinos?
Neutrinos basically are particles that are almost ghost-like. They have a very
small amount of mass, they have no charge and they barely interact. Neutrinos
interact so weakly that a 100 billion volt neutrino, has on the average to go
through 4 million kilometers of iron before it scatters once.
How do determine the charges of
the constituents? You can find out about the charges of the constituents by
making comparisons of electron and neutrino scattering from the proton and
neutron. Comparisons of our electron scattering results and neutrino scattering
measurements from CERN, a laboratory in Switzerland, demonstrated without a
doubt that the quark model was correct. And physicists who strongly doubted the
existence of quarks finally had to accept their existence.*
One question remains - what is
the size of the quark? Well, the size of the quark is still smaller than we can
measure. So we say itís point-like.
We donít necessarily believe that
itís a point, but as far as our tools of measurement can go, we only see points.
The upper limit of its size from current measurements is exceedingly small. If
we take a carbon atom, which is much, much smaller than a virus, and expanded it
to the size of the earth, a quark would be less than a half of centimeter in
comparison. And thatís the upper limit of its size. But even if we canít measure
their size, I hope that you are convinced that you are made up of quarks and
that your quarks are very well held together. *
You might wonder what lessons I
have learned about life during my career? Here are some of the things that I
Dream and work hard and your
highest aspirations may come true. When you choose your career, go into a field
that you truly love. Only when you have a deep interest and passion in a field
can you make the commitment that is necessary to accomplish something important.
What drew me into physics was a sense of awe about the wonders of nature and a
deep curiosity about how nature works.
When I was a student and
throughout my career I have worked hard, but I have never felt that I was
working hard because I love physics so much. I feel that I have one of the best
jobs in the world. I get paid for trying to solve puzzles of my choice and
teaching a subject that I love.
My profession is a source of
great pleasure. When I develop an insight into a problem that has been puzzling
me, I experience a great sense of joy. And making a discovery brings even a
greater joy. Just think, in making a discovery, you may be the first person in
the history of humankind to observe or understand the secret of nature that you
have just uncovered.
I have also learned in my career
that to accomplish something important you often have to take risks in pursuing
your ideas and goals, even if others discourage you from doing so. You must have
the courage of your convictions. I would never have received a Nobel Prize
without going against the well intentioned advice from respected people in my
I would now like to conclude with
some general remarks about the importance of science and technology. What we
have learned from science has profoundly shaped the way we view our place in the
universe. It has provided us with some understanding of how the universe works
from the basic building blocks of the subatomic world to the outer reaches of
the cosmos. And evolutionary biology has given us an understanding of our place
in the natural order of life.
But science also has an immense
impact on how we live. The world is changing very rapidly, driven to a large
extent by science and technology. The development of humankind has been strongly
linked to the innovations arising from human creativity, from the earliest crude
tools to the modern technological society of today. In the modern era, science
and technology have provided innovations that have enhanced our standard of
living, improved our health and driven the economies of nations. But science and
technology must be used by society with wisdom and humanity. The great
theoretical physicist Victor Weisskopf, said ď Society is based on two pillars,
knowledge and compassion. Compassion without knowledge is ineffective. And
knowledge without compassion is inhumane.Ē
You, students here, are receiving
an education that will provide a strong foundation for your futures. Remember, a
good education is something on which you can build on throughout your life and
which can provide you with a satisfying career.
All of you will have much to
offer your nation and the world. Your help is needed to create a bright future,
a future based on both knowledge and compassion. I have great confidence that
you are well up to the task. So do all that you can do to fulfill your
potential, and your accomplishments and your future may even exceed your dreams.
Jerome I. Friedman (MIT)