[PROFILE] Steven Chu - Nobel Laureate in Physics
- Steven Chu Autobiography
My father, Ju Chin Chu, came to the United States in 1943 to
continue his education at the Massachusetts Institute of Technology
in chemical engineering, and two years later, my mother, Ching Chen
Li, joined him to study economics. A generation earlier, my mother's
grandfather earned his advanced degrees in civil engineering at
Cornell while his brother studied physics under Perrin at the
Sorbonne before they returned to China. However, when my parents
married in 1945, China was in turmoil and the possibility of
returning grew increasingly remote, and they decided to begin their
family in the United States. My brothers and I were born as part of
a typical nomadic academic career: my older brother was born in 1946
while my father was finishing at MIT, I was born in St. Louis in
1948 while my father taught at Washington University, and my younger
brother completed the family in Queens shortly after my father took
a position as a professor at the Brooklyn Polytechnic Institute.
In 1950, we settled in Garden City, New York, a bedroom community
within commuting distance of Brooklyn Polytechnic. There were only
two other Chinese families in this town of 25,000, but to our
parents, the determining factor was the quality of the public school
system. Education in my family was not merely emphasized, it was our
raison d'être. Virtually all of our aunts and uncles had Ph.D.'s in
science or engineering, and it was taken for granted that the next
generation of Chu's were to follow the family tradition. When the
dust had settled, my two brothers and four cousins collected three
MDs, four Ph.D.s and a law degree. I could manage only a single
In this family of accomplished scholars, I was to become the
academic black sheep. I performed adequately at school, but in
comparison to my older brother, who set the record for the highest
cumulative average for our high school, my performance was decidedly
mediocre. I studied, but not in a particularly efficient manner.
Occasionally, I would focus on a particular school project and
become obsessed with, what seemed to my mother, to be trivial
details instead of apportioning the time I spent on school work in a
more efficient way.
I approached the bulk of my schoolwork as a chore rather than an
intellectual adventure. The tedium was relieved by a few courses
that seem to be qualitatively different. Geometry was the first
exciting course I remember. Instead of memorizing facts, we were
asked to think in clear, logical steps. Beginning from a few
intuitive postulates, far reaching consequences could be derived,
and I took immediately to the sport of proving theorems. I also
fondly remember several of my English courses where the assigned
reading often led to binges where I read many books by the same
Despite the importance of education in our family, my life was not
completely centered around school work or recreational reading. In
the summer after kindergarten, a friend introduced me to the joys of
building plastic model airplanes and warships. By the fourth grade,
I graduated to an erector set and spent many happy hours
constructing devices of unknown purpose where the main design
criterion was to maximize the number of moving parts and overall
size. The living room rug was frequently littered with hundreds of
metal "girders" and tiny nuts and bolts surrounding half-finished
structures. An understanding mother allowed me to keep the projects
going for days on end. As I grew older, my interests expanded to
playing with chemistry: a friend and I experimented with homemade
rockets, in part funded by money my parents gave me for lunch at
school. One summer, we turned our hobby into a business as we tested
our neighbors' soil for acidity and missing nutrients.
I also developed an interest in sports, and played in informal games
at a nearby school yard where the neighborhood children met to play
touch football, baseball, basketball and occasionally, ice hockey.
In the eighth grade, I taught myself tennis by reading a book, and
in the following year, I joined the school team as a "second string"
substitute, a position I held for the next three years. I also
taught myself how to pole vault using bamboo poles obtained from the
local carpet store. I was soon able to clear 8 feet, but was not
good enough to make the track team.
In my senior year, I took advanced placement physics and calculus.
These two courses were taught with the same spirit as my earlier
geometry course. Instead of a long list of formulas to memorize, we
were presented with a few basic ideas or a set of very natural
assumptions. I was also blessed by two talented and dedicated
My physics teacher, Thomas Miner was particularly gifted. To this
day, I remember how he introduced the subject of physics. He told us
we were going to learn how to deal with very simple questions such
as how a body falls due to the acceleration of gravity. Through a
combination of conjecture and observations, ideas could be cast into
a theory that can be tested by experiments. The small set of
questions that physics could address might seem trivial compared to
humanistic concerns. Despite the modest goals of physics, knowledge
gained in this way would become collected wisdom through the
ultimate arbitrator - experiment.
In addition to an incredibly clear and precise introduction to the
subject, Mr. Miner also encouraged ambitious laboratory projects.
For the better part of my last semester at Garden City High, I
constructed a physical pendulum and used it to make a "precision"
measurement of gravity. The years of experience building things
taught me skills that were directly applicable to the construction
of the pendulum. Ironically, twenty five years later, I was to
develop a refined version of this measurement using laser cooled
atoms in an atomic fountain interferometer.
I applied to a number of colleges in the fall of my senior year, but
because of my relatively lackluster A-average in high school, I was
rejected by the Ivy League schools, but was accepted at Rochester.
By comparison, my older brother was attending Princeton, two cousins
were in Harvard and a third was at Bryn Mawr. My younger brother
seemed to have escaped the family pressure to excel in school by
going to college without earning a high school diploma and by
avoiding a career in science. (He nevertheless got a Ph.D. at the
age of 21 followed by a law degree from Harvard and is now a
managing partner of a major law firm.) As I prepared to go to
college, I consoled myself that I would be an anonymous student, out
of the shadow of my illustrious family.
The Rochester and Berkeley Years
At Rochester, I came with the same emotions as many of the entering
freshman: everything was new, exciting and a bit overwhelming, but
at least nobody had heard of my brothers and cousins. I enrolled in
a two-year, introductory physics sequence that used The Feynman
Lectures in Physics as the textbook. The Lectures were mesmerizing
and inspirational. Feynman made physics seem so beautiful and his
love of the subject is shown through each page. Learning to do the
problem sets was another matter, and it was only years later that I
began to appreciate what a magician he was at getting answers.
In my sophomore year, I became increasingly interested in
mathematics and declared a major in both mathematics and physics. My
math professors were particularly good, especially relative to the
physics instructor I had that year. If it were not for the Feynman
Lectures, I would have almost assuredly left physics. The pull
towards mathematics was partly social: as a lowly undergraduate
student, several math professors adopted me and I was invited to
several faculty parties.
The obvious compromise between mathematics and physics was to become
a theoretical physicist. My heroes were Newton, Maxwell, Einstein,
up to the contemporary giants such as Feynman, Gell-Man, Yang and
Lee. My courses did not stress the importance of the experimental
contributions, and I was led to believe that the "smartest" students
became theorists while the remainder were relegated to experimental
grunts. Sadly, I had forgotten Mr. Miner's first important lesson in
Hoping to become a theoretical physicist, I applied to Berkeley,
Stanford, Stony Brook (Yang was there!) and Princeton. I chose to go
to Berkeley and entered in the fall of 1970. At that time, the
number of available jobs in physics was shrinking and prospects were
especially difficult for budding young theorists. I recall the
faculty admonishing us about the perils of theoretical physics:
unless we were going to be as good as Feynman, we would be better
off in experimental physics. To the best of my knowledge, this
warning had no effect on either me or my fellow students.
After I passed the qualifying exam, I was recruited by Eugene
Commins. I admired his breadth of knowledge and his teaching ability
but did not yet learn of his uncanny ability to bring out the best
in all of his students. He was ending a series of beta decay
experiments and was casting around for a new direction of research.
He was getting interested in astrophysics at the time and asked me
to think about proto-star formation of a closely coupled binary
pair. I had spent the summer between Rochester and Berkeley at the
National Radio Astronomy Observatory trying to determine the
deceleration of the universe with high red-shift radio source
galaxies and was drawn to astrophysics. However, in the next two
months, I avoided working on the theoretical problem he gave me and
instead played in the lab.
One of my "play-experiments" was motivated by my interest in
classical music. I noticed that one could hear out-of-tune notes
played in a very fast run by a violinist. A simple estimate
suggested that the frequency accuracy, times the duration of the
note,did not satisfy the uncertainty relationship. In order to test
the frequency sensitivity of the ear, I connected an audio
oscillator to a linear gate so that a tone burst of varying duration
could be produced. I then asked my fellow graduate students to match
the frequency of an arbitrarily chosen tone by adjusting the knob of
another audio oscillator until the notes sounded the same. Students
with the best musical ears could identify the center frequency of a
tone burst that eventually sounded like a "click" with an accuracy
By this time it was becoming obvious (even to me) that I would be
much happier as an experimentalist and I told my advisor. He agreed
and started me on a beta-decay experiment looking for "second-class
currents", but after a year of building, we abandoned it to measure
the Lamb shift in high-Z hydrogen-like ions. In 1974, Claude and
Marie Bouchiat published their proposal to look for parity non-
conserving effects in atomic transitions. The unified theory of weak
and electromagnetic interactions suggested by Weinberg, Salam and
Glashow postulated a neutral mediator of the weak force in addition
to the known charged forces. Such an interaction would manifest
itself as a very slight asymmetry in the absorption of left and
right circularly polarized light in a magnetic dipole transition.
Gene was always drawn to work that probed the most fundamental
aspects of physics, and we were excited by the prospect that a table-
top experiment could say something decisive about high energy
physics. The experiment needed a state-of-the-art laser and my
advisor knew nothing about lasers. I brashly told him not to worry;
I would build it and we would be up and running in no time.
This work was tremendously exciting and the world was definitely
watching us. Steven Weinberg would call my advisor every few months,
hoping to hear news of a parity violating effect. Dave Jackson, a
high energy theorist, and I would sometimes meet at the university
swimming pool. During several of these encounters, he squinted at me
and tersely asked, "Got a number yet?" The unspoken message
was, "How dare you swim when there is important work to be done!"
Midway into the experiment, I told my advisor that I had suffered
enough as a graduate student so he elevated me to post-doc status.
Two years later, we and three graduate students published our first
results. Unfortunately, we were scooped: a few months earlier, a
beautiful high energy experiment at the Stanford Linear Collider had
seen convincing evidence of neutral weak interactions between
electrons and quarks. Nevertheless, I was offered a job as assistant
professor at Berkeley in the spring of 1978.
I had spent all of my graduate and postdoctoral days at Berkeley and
the faculty was concerned about inbreeding. As a solution, they
hired me but also would permit me to take an immediate leave of
absence before starting my own group at Berkeley. I loved Berkeley,
but realized that I had a narrow view of science and saw this as a
wonderful opportunity to broaden myself.
A Random Walk in Science at Bell Labs
I joined Bell Laboratories in the fall of 1978. I was one of roughly
two dozen brash, young scientists that were hired within a two year
period. We felt like the "Chosen Ones", with no obligation to do
anything except the research we loved best. The joy and excitement
of doing science permeated the halls. The cramped labs and office
cubicles forced us to interact with each other and follow each
others' progress. The animated discussions were common during and
after seminars and at lunch and continued on the tennis courts and
at parties. The atmosphere was too electric to abandon, and I never
returned to Berkeley. To this day I feel guilty about it, but I
think that the faculty understood my decision and have forgiven me.
Bell Labs management supplied us with funding, shielded us from
extraneous bureaucracy, and urged us not to be satisfied with doing
merely "good science." My department head, Peter Eisenberger, told
me to spend my first six months in the library and talk to people
before deciding what to do. A year later during a performance
review, he chided me not to be content with anything less
than "starting a new field". I responded that I would be more than
happy to do that, but needed a hint as to what new field he had in
I spent the first year at Bell writing a paper reviewing the current
status of x-ray microscopy and started an experiment on energy
transfer in ruby with Hyatt Gibbs and Sam McCall. I also began
planning the experiment on the optical spectroscopy of positronium.
Positronium, an atom made up of an electron and its anti-particle,
was considered the most basic of all atoms, and a precise
measurement of its energy levels was a long standing goal ever since
the atom was discovered in 1950. The problem was that the atoms
would annihilate into gamma rays after only 140x10-9 seconds, and it
was impossible to produce enough of them at any given time. When I
started the experiment, there were 12 published attempts to observe
the optical fluorescence of the atom. People only publish failures
if they have spent enough time and money so their funding agencies
demand something in return.
My management thought I was ruining my career by trying an
impossible experiment. After two years of no results, they strongly
suggested that I abandon my quest. But I was stubborn and I had a
secret weapon: his name is Allen Mills. Our strengths complemented
each other beautifully, but in the end, he helped me solve the laser
and metrology problems while I helped him with his positrons. We
finally managed to observe a signal working with only ~4 atoms per
laser pulse! Two years later and with 20 atoms per pulse, we refined
our methods and obtained one of the most accurate measurements of
quantum electrodynamic corrections to an atomic system.
In the fall of 1983, I became head of the Quantum Electronics
Research Department and moved to another branch of Bell Labs at
Holmdel, New Jersey. By then my research interests had broadened,
and I was using picosecond laser techniques to look at excitons as a
potential system for observing metal-insulator transitions and
Anderson localization. With this apparatus, I accidentally
discovered a counter-intuitive pulse-propagation effect. I was also
planning to enter surface science by constructing a novel electron
spectrometer based on threshold ionization of atoms that could
potentially increase the energy resolution by more than an order of
While designing the electron spectrometer, I began talking
informally with Art Ashkin, a colleague at Holmdel. Art had a dream
to trap atoms with light, but the management stopped the work four
years ago. An important experiment had demonstrated the dipole
force, but the experimenters had reached an impasse. Over the next
few months, I began to realize the way to hold onto atoms with light
was to first get them very cold. Laser cooling was going to make
possible all of Art Ashkin's dreams plus a lot more. I promptly
dropped most of my other experiments and with Leo Holberg, my new
post-doc, and my technician, Alex Cable, began our laser cooling
experiment. This brings me to the beginning of our work in laser
cooling and trapping of atoms and the subject of my Nobel Lecture.
Stanford and the future
Life at Bell Labs, like Mary Poppins, was "practically perfect in
every way". However, in 1987, I decided to leave my cozy ivory
tower. Ted Hänsch had left Stanford to become co-director of the Max
Planck Institute for Quantum Optics and I was recruited to replace
him. Within a few months, I also received offers from Berkeley and
Harvard, and I thought the offers were as good as they were ever
going to be. My management at Bell Labs was successful in keeping me
at Bell Labs for 9 years, but I wanted to be like my mentor, Gene
Commins, and the urge to spawn scientific progeny was growing
Ted Geballe, a distinguished colleague of mine at Stanford who also
went from Berkeley to Bell to Stanford years earlier, described our
motives: "The best part of working at a university is the students.
They come in fresh, enthusiastic, open to ideas, unscarred by the
battles of life. They don't realize it, but they're the recipients
of the best our society can offer. If a mind is ever free to be
creative, that's the time. They come in believing textbooks are
authoritative but eventually they figure out that textbooks and
professors don't know everything, and then they start to think on
their own. Then, I begin learning from them."
My students at Stanford have been extraordinary, and I have learned
much from them. Much of my most important work such as fleshing out
the details of polarization gradient cooling, the demonstration of
the atomic fountain clock, and the development of atom
interferometers and a new method of laser cooling based on Raman
pulses was done at Stanford with my students as collaborators.
While still continuing in laser cooling and trapping of atoms, I
have recently ventured into polymer physics and biology. In 1986,
Ashkin showed that the first optical atom trap demonstrated at Bell
Labs also worked on tiny glass spheres embedded in water. A year
after I came to Stanford, I set about to manipulate individual DNA
molecules with the so-called "optical tweezers" by attaching micron-
sized polystyrene spheres to the ends of the molecule. My idea was
to use two optical tweezers introduced into an optical microscope to
grab the plastic handles glued to the ends of the molecule. Steve
Kron, an M.D./Ph.D. student in the medical school, introduced me to
molecular biology in the evenings. By 1990, we could see an image of
a single, fluorescently labeled DNA molecule in real time as we
stretched it out in water. My students improved upon our first
attempts after they discovered our initial protocol demanded luck as
a major ingredient. Using our new ability to simultaneously
visualize and manipulate individual molecules of DNA, my group began
to answer polymer dynamics questions that have persisted for
decades. Even more thrilling, we discovered something new in the
last year: identical molecules in the same initial state will choose
several distinct pathways to a new equilibrium state.
This "molecular individualism" was never anticipated in previous
polymer dynamics theories or simulations.
I have been at Stanford for ten and a half years. The constant
demands of my department and university and the ever increasing work
needed to obtain funding have stolen much of my precious thinking
time, and I sometimes yearn for the halcyon days of Bell Labs. Then,
I think of the work my students and post-docs have done with me at
Stanford and how we have grown together during this time.
Welcome to a Conversation with History. I'm Harry Kreisler of the
Institute of International Studies. Our guest today is Steven Chu,
who is a Nobel Laureate in Physics and Geballe Professor of Physics
at Stanford. He is the 2004 Hitchcock Lecturer on the Berkeley
Steven, welcome to Conversations.
Where were you born and raised?
I was born in St. Louis. Not raised there; I only spent a few years
there. My parents then moved to Long Island. I was raised in suburb
of New York City, Garden City.
Looking back, how do you think your parents shaped your thinking
about the world and about science?
Oh, that's a tough call, because most of how they shaped -- how
parents, all parents, shape people -- is very under the table.
You're not really aware of it. I was aware of many things, though.
My parents came from China. They were students. They came here as
graduate students to go to MIT. Like many Chinese in higher
education, they had a reverence for education. They communicated
very clearly to me and my two brothers that one of the high things
you could aspire to be is a scholar, just for the scholarship's
sake, not so much as a stepping stone to some other job. That was
communicated very well. While we were young, they would always
say, "Read." They didn't care that much what we read, as long as we
read. And that, again, was something that helped.
You didn't necessarily take to school like a fish to water; I read a
short biography. You were a good student when you got interested, I
guess, is the way to summarize it.
Well, you have to normalize this to what was happening in my
[family]. I had an older brother who was an excellent student. He
was two years older than me. We were in a school in Garden City. It
was a very good public school, an excellent public school, and he
went through this public school setting the highest cumulative
average in the record of the school.
So I followed along two years later and the teachers would say, "Oh,
you're Gilbert's brother. We expect you to do just as well." That
was hard to really live up to. While he was setting records, I was
kind of coming from behind. I was an A-minus student, and by my
family's standards, this was appalling. He was very good. He was
very structured and he would study the things he was supposed to
study. And he was fundamentally a very good student.
I would get very interested in one thing and let something else lay
[aside]. It wasn't really until I went to college where they didn't
hear of my older brother that I was able to [come into my own].
But in high school you were turned on to science? How did that come
There were two things. One is I had a fantastic physics teacher as a
In high school?
In high school. And then the same teacher as a senior in high
school. This is someone who is naturally recognized. He was winning
prizes for being an outstanding science teacher.
And his name was?
I had two excellent mathematics teachers -- one in ninth grade, in
geometry, and then a calculus teacher in the twelfth grade. And
there, the mathematics was different than the other mathematics.
[In] the other type of mathematics you learn how to do algebra and
trigonometry and things like that. In those two subjects, it was
mostly about logic and thinking, and putting together logical
arguments. It was very different.
The physics and the logic/mathematics courses, I got very excited
You also, early on, liked to build things and do experiments, and
litter your mother's living room with projects. Tell us a little
about that and how that ultimately contributes to what you've become.
I don't know what it was, but since I was very young I loved
building things. I loved building things with my hands. I would be
given for Christmas a model set of airplanes or boats and things,
and I loved to put them together. I would ask my parents for things
like Erector Sets; these are little pieces of metal and screws.
Unlike Lego blocks, you actually have to screw something together,
it wasn't all pre-designed to make a boat or something like that. I
loved doing those things.
In that respect, it was somewhat different than my two brothers. In
many respects, my brothers and I are very similar, but in that
respect, I seemed to love mechanical things in a way that was
certainly nurtured by my parents, in that they said, "Okay, he wants
to do these things. We'll buy toys like that for him." But my other
two brothers didn't seem to like that.
Now, it turns out that working with your hands and building things
gives you a spatial intuition that turned out to be invaluable once
I became a scientist. I could see things in my head very clearly and
rotate them around. This idea of picturing things geometrically has
always been a part of my thinking. The layperson doesn't think of
that in terms of physicists; they think in terms of mathematical
equations. I only discovered later that most physicists do that.
So you went on to college, and you were freed of your brother, so to
speak, as a model to emulate. Where did you do your undergraduate
I went to the University of Rochester. I applied for the Ivys; they
didn't accept me. The University of Rochester was wonderful because
it was an excellent school, and, as I said, my brother was an
unknown; I could be my own person. I started working very hard in a
regular way, still, but in a very directed way. What's wonderful
about college is that beyond a few required courses, you can take
what you are interested in.
There was another thing that happened in college that I wasn't
really thinking of, and that is, as I studied more mathematics it
actually affected my writing. My writing became more linear in its
thinking, and you could definitely see logic in the writing that I
didn't have when I was in high school or grade school. In my
humanities courses the professors were [saying], "This is a coherent
paragraph." I wasn't really thinking about that, but it was almost a
magical transition from the mathematics I was studying.
Being a Scientist
Why is it that the public understanding of science doesn't proceed
at a higher pace? Is it because there are not enough scientists who
are doing the writing?
That's a difficult question. As I give more public talks, as I get
exposed to these issues more and more, I think that there are two
things: One is, unfortunately, there is a public fear of science,
especially physics. They think, "Oh, my gosh, physics ... it's hard.
It has math in it. It's going to be very difficult for me to
understand what's really going on." That, I think, is something that
might have happened in grade school or high school.
If you didn't have the right teacher ...
Yes. And the trouble with learning physical science and mathematics
is, once you slip behind a little bit, and you just didn't get this
concept, or it's not quite firm in your mind about this mathematical
thing that you have to know, well then, next week you're on to
something else. But they really expect you to know something about
last week. And so that's one of the issues.
The other issue is that the ideas are complex. Now, if you step back
and if you spend some serious time thinking about it, the kernel of
the ideas are clearly not complex. The essence of an idea is what we
try to work with most. As a professor with my graduate students, we
would read a paper and look at the paper and say, "What's the
essence of the idea? What's something new? Forget about the
equations. Forget about the complicated argument and try to identify
the kernel of the idea." That can be communicated, but it takes
You did your graduate work here at Berkeley. So in a way, you're
coming back to deliver the Hitchcock Lectures.
What contribution did your Berkeley education make overall? I'm sure
you could go through a long list. Who was your mentor here?
My mentor was Eugene Commins. He was a wonderful professor. He has a
history of having many graduate students who have gone on and done
wonderful thing. He's revered as a classroom teacher as well, and,
also, in the way he does things, the way he goes about life. In
every respect that I can think of he was a mentor, not only in terms
of the science but how you handle yourself in situations and in the
He had one remarkable quality that I wish I could copy, and that is,
he made all of his students feel special, and that they could do
something. He got all of us to live up to the highest we could do,
without saying, "You must do this," or without making us feel
pressured or guilty, or something like that. He would work side by
side with us, often late into the night, as a colleague more than as
a professor. That was a remarkable experience to grow up in that
The other thing I learned here is to try to think of things to do
that would be important in science. There are many things you can
study in science; some focus on big questions. Try to identify the
correct questions. It was not only my advisor but the Berkeley
professors around here at that time; there were six or seven Nobel
Laureates in the physics department who were active, and you could
watch they way they approached problems. This would come out not in
a formal lecture or something, but in casual conversations when
they're maybe giving a colloquium -- how they approach it, and how
they thought about it. This enters in a very subconscious way. That
is probably why there are so many distinguish graduates in Berkeley.
Help us understand what the prerequisites are for doing science
well. If a student or students were to watch this, what should they
know about this way of life and what they need to bring to it --
training and so on?
The first thing is, they have to be interested in it. They have to
be genuinely interested. They have to have curiosity. Science is
really about describing the way the universe works in one aspect or
another in all branches of science -- how a life form works, how
this works, how that works. You're really trying to understand
what's around you. You have to have a natural curiosity for that.
In certain types of science, there might be prerequisites. In
physics, you should have some mathematical ability. Otherwise, I
think it would be very hard. But beyond those prerequisites that a
lot of people do have, you need to have, first, this curiosity, a
driven curiosity. You want to know the answer. With that curiosity
comes a certain doggedness, because there are going to be setbacks,
you're going to be discouraged. Things aren't going to work. You're
going to have trouble understanding them. Things are going to be
hard to understand, especially the first time. Science doesn't come
naturally to people.
I had the hardest time in my first few years as a
freshman/sophomore, and also in high school, understanding physics
in a really deep sense. I could do well in exams, but to get it
inside your stomach and to say, "Okay, I have a real feel for it";
it took a while to develop that intuition. But there were other
drivers for that. It seemed like a beautiful way of understanding
But I'll go back to the other thing -- this doggedness, this
saying, "I'm not going to quit. I really want to find out." It
enters in other walks of life. If you think of an athlete who wants
to become a good athlete, well, there's going to be a lot of
training involved. Sometimes you don't feel like getting up early in
the morning or staying late in the afternoon and spending the hours
That turns out to be one of the most important things that separate
[students] in graduate school. At graduate school at Stanford, you
have some of the best students in the world, who you can see are
going to go on and become world-class scientists, and who are very
smart and are going to be good. But the thing that really
differentiates [among them] is this passion to find out what the
answer is: "I'm not going to quit." After those prerequisites, the
thing that separates the people who are going to excel from people
who are good and not, is that internal drive.
In a joking "aside" yesterday in your lecture you said that in
science, once you announce something, first, everybody tells you
you're wrong; then they tell you it's trivial; and then that you are
not the first to discover it. It emphasizes what you just said, that
there has to be an inner drive. But also it suggests an element of
courage, that you're going to stand up to people and say, "This is
what I think," and then keep on going even if you're proven wrong.
And then try to adjust what your experiment has shown.
That's right. When you make something that's unexpected, and it's a
little bit out of people's expectations, they're first going to
reject it. And, actually, that's one of the strengths of science.
You have to say, "No, it's not [just] because I said it is"; you're
going to have to convince them. And by convincing them, it's really
through discussion and additional experiments, because in the end
the experiment is going to be the final arbitrator. There's no high
priest or priestess of science that says, "You're right; you're
wrong." You go back and you do more experiments. So the reaction, if
you're a little bit off center or a lot off center, is, "No, that's
preposterous. You've got to be wrong." The more outlandish you are,
the more unexpected the finding, the more you're going to get that
Now. in the end, after one understands what's going on -- and it
goes back to understanding the science -- then you say, "No, no, no,
it's all right. Yes, we could have foreseen that." That's where it
becomes trivial. It's sort of, "Well, sure." It wasn't trivial at
the beginning, but after you see it, then it becomes easy. But
that's actually a mark of really understanding something, to then
say, "Of course."
The final one is, "You're not the first to discover this." That is
also true. There are always precursors. There's always someone
before you who had a glimmer of this and a glimmer of that. Science
is based upon a lot of rediscovery.
But going back to your point, namely you're going to be rebuffed and
oftentimes rejected, and it's not a personal issue. You've just got
to stand up to it and go back; now, you could be wrong, but you're
going to go back and convince yourself you're right. The rule I tell
myself and my students is, we have to be our worst critics, and once
we convince ourselves that we're right, then we should have no
problem convincing everybody else we're right. Good scientists are
their own worst critics. They're always trying to prove themselves
wrong, which is hard, because sometimes you've got an idea and you
think you're right and you have to force yourself [to ask], "Where
are the weak points of this argument, or the weak points of my
One of the points that came out in your lecture for me, a non-
scientist, was the importance of collaboration, not only with your
own students but with other scientists, and even other scientists
who are in subgroups within physics, but even beyond that, to
scientists in other fields of science, that those sets of
communications working together are important to push this process
Yes. That's another misconception that many people have about
scientists, or doing science and learning science. The misconception
is you go to school, you take classes, you study -- years and years
of study. You learn everything there is to know in a certain sub-
field, a very narrow sub-field, and then you do work in that area.
That is the form, but it's rarely taken. It's especially not true
the way I do it.
Maybe it goes back to my high school days, when I was not such a
good student. In actual fact, if one wants to go into a new area
beyond your school days, you can pick up a classic textbook and
begin to read, and begin to read in the literature; but it's not as
much fun. When I was going into biology maybe a dozen years ago, I
did try that. I picked up a big, fat tome called Biochemistry, a
classic textbook. I started reading; it was 1,500 pages. I got to
page 150, and I was deciding, "Well, it's beginning to slip out of
my head as fast as it's going in now." I reached a "steady state!"
So I said, "Well, this isn't going to work." So I would look around,
and I had some [knowledge] from reading newspapers and magazines
such as Science, Science Times, The New York Times, Scientific
American, things of that nature. I had an interest in these
biological problems, and I would pick something that I was
interested in. But, of course, since I wasn't an expert in biology,
I didn't know, "Is this a stupid question? Is this a deep question?
What?" I would say, "Well, I think I can do something here and I
have some interest." So I'd trot over to the biology department or
medical school and say, "Is this something we're studying? I think I
want to do this." And they would tell me sometimes, "No, no, it's
silly," or "It's been done before." Or sometimes they'd say, "This
is a central problem in biology." That rarely happened.
But what happened is then I would start to collaborate with these
people who spent their career in this specialty, and who grew up in
this culture. They would say, "You should read this article, and
that article, and that article." We would talk, and it was wonderful
to learn that way. So you could sort of leapfrog over the years of
school. Now to be sure, I'm not pretending I have as broad or deep
as knowledge of that. But you start with a little, thin sliver of a
particular problem, and you start to build knowledge around that
thin sliver. By the time you've done the experiment and you're
starting to write the paper, you better have some knowledge of
what's around, because you won't even get to publish in the paper if
you haven't referenced the right people or the precursors before
you. But it's learning in that way.
Then you go back to the books, but now you use the index. You
say, "I want to learn about this." So now I've begun to teach my
students -- many of my students are physicists wanting to go into
biology. I say, "Okay, we'll use the index. This is the problem. Why
don't you look here, read these five pages in this book, and these
ten pages here, and these fifteen pages here." By the time you read
this review article, within a month, you're reading the primary
In biology, without the three years of courses. Within a few months
to a few years, you're beginning to get a feel for it. It's very
important that you get this feel, because you have to ask the right
questions. One of the most important things that a scientist does is
ask a question that's important and that has a chance of being
solved. You can ask important questions like, "How does a brain
work?" but that's not sufficient. You have to pick a part of that
question where you can make you a contribution, a serious
contribution, and something that others would be interested in.
Working at Bell Labs and at the University
Before we talk about your research (and in a way that I can
understand, and maybe the public, too) in your career there was a
period when you went to the Bell Labs. I want to understand how that
contributes to your research, and understand exactly what the
difference is between being in a place like Bell Labs versus being
in a physics department at Berkeley or Stanford.
Well, the reason I went to Bell Labs, I was here as a graduate
student at Berkeley and I was a post-doctoral fellow here. After two
years of that they actually made me a faculty member in the Physics
Department. But this was a bit unusual, because I had spent eight
years at Berkeley, and I was essentially toilet-trained here, and
had a very narrow vision of science. What a department really wants
is to bring in people from different [scientific] cultures. But they
decided they wanted me as a professor. It was a beautiful place, so
But then they did something very unusual. They said, "You can start
your group and go about your business. Or, because you spend so much
time here and this was your only real experience, you also have an
opportunity to go somewhere else for a year or two." I
thought, "Well, that's wonderful. I have a job at the best physics
department in the world, and so I'll go off and spend some time and
broaden myself." So I decided to go to Bell Telephone Laboratories
which, at the time, was one of the premier research industrial labs.
When most people think of industrial labs, they think of, "Oh,
you're making better widgets. You're making something that's going
to be good for the phone system." Now, ultimately, that's true. But
at Bell Labs in that time -- this is in 1978 -- allowed a small
fraction of us -- fifty, sixty, eighty -- to do whatever we wanted;
really to do whatever we wanted.
So I joined Bell Laboratories. My department head said, "Steve, you
can do whatever you want. It doesn't even have to be physics. All we
ask is that you don't go to a high-energy accelerator and do high-
energy physics, because that would be hard on the stockholders." (My
thesis project, and when I was working as a post-doc, addressed a
high-energy physics problem.) He said, "And by the way, don't do
anything immediately. Spend six months. Talk to the people around
the labs, and just keep an open mind." This was a devastating
experience for me, because of the freedom to do whatever you want
and being told, "Don't do what you think you want to do now, but
explore." So I spent some time exploring and thinking. And there, I
really felt pressure, because he would say, "We expect great things
out of you." I didn't want to hear that. It's much nicer to have a
little problem to work on; it's very cozy.
But it did have a real influence on me, because it got me in that
mode of going and talking to people outside of my field. When I
finally started doing things at Bell Laboratories ... and I started,
first, in an area that was in condensed matter physics that I knew
nothing about, but using techniques in my old field, atomic physics
and laser physics. But it got me into the mode of, "I've got this
crazy idea." I'd go to some colleague in Bell Laboratories and
say, "How does this sound?" And they would tell me, "No, this is the
stupidest thing I've heard," or "Yeah, maybe you have something
there." It set the tone for what I've done for the rest of my life --
collaborating with people, especially outside my local expertise.
It was a wonderful experience.
I also should say, in the years I was there, '78 to '87 -- there was
an economic slump in the mid-seventies; Bell Labs just started
hiring people -- and there were a group of us, maybe a few dozen,
two or three dozen, and we all were young, energetic, bright-eyed,
bushy-tailed. We were all being put in this position: "Do something
important. Here are the resources of American Telephone and
Telegraph System. We expect you to do something wonderful." We were
there at night. We were there on the weekends. We knew what each
other's cars looked like, so we knew who was in there, let's say, on
a Saturday or Sunday. We would party together. [Looking back,] I
think either five or six of us [later] got Nobel Prizes. Over a
dozen are in the National Academy of Sciences. It's like this: we
all were growing up together. And we had these really wonderful
senior scientists there as well.
It was a remarkable period of time. Everything was exciting, and
something would come along that was not in my field, and I would
say, "Wow, this is really interesting." We'd go in, we'd discuss it.
People would jump fields, or jump areas. There was this feeling of
the excitement of the science, that even though we were doing this,
it was all right to move and do that. You wouldn't be considered a
failure because you gave up this, because something else even more
exciting came along, either from your own laboratory or from a
colleague's lab, or from the outside world.
So freedom in the best sense, but in an environment where it could
lead to new levels of understanding.
A positively electric atmosphere. You'd go in the lunchrooms and
over lunch ... everybody went there around noontime. You'd sit in
these big round tables and, "Okay, what's new?" People would leave;
other people would come. You would be sitting there chatting,
socializing, but talking a lot about science. A lot of ideas were
invented on those lunchroom tables. And so there, again, it was
something where there was this real community.
It was pretty magical. People who are close to science and
especially in the areas that Bell Labs was touching knew that there
was something magical going on at the time.
How can we distinguish that experience from, say, being at Berkeley
in the Physics Department, or being at Stanford? Was it just a
question of there being enough resources to bring all these people
together to create this magical moment?
No, there were other things. For example, in a university, like
Berkeley or Stanford, you're a professor, you have students. Part of
your job is to teach undergraduates; part of your job is to teach
graduate students. You teach graduate students by developing with
them their own projects. A lot of energy and time is spent nurturing
students. Because of that, your first duty is to look towards your
In Bell Laboratories we didn't have groups. The biggest you could
have would be a technician and a post-doc, and usually not both. If
you wanted to do something that required more than one or two
people, you would have to work with other people. That builds
collaboration into the system. And because no one had an empire,
even a mini-empire -- in the basic science areas of Bell you're one
and two or three -- you have a lot of time. You're not taking care
of people. You have a technician or a post-doc, and so it's a very
We are trying to do something like that at Stanford, in a
multidisciplinary way. We're bringing people interested in biology,
physics, chemistry, and computer science, centered around biological
problems, where people from very many disciplines will come and have
their own genres of what to do. One of the things is to limit the
size of your groups. In the university, let's say you're a synthetic
chemist; you can have groups of forty. And with a group of forty
people, you're not going to have much time to interact with
colleagues. You're not going to have much time to explore elsewhere.
So [we've] limited the size of the group to fifteen, which is still
very large. You couldn't limit it to three, because there are very
few professors that have [only] two or three graduate students in
something related to the biological sciences. There are typically
more. So the structure is slightly different. It's not clear how
much you can create the structure we had at Bell Laboratories,
because you have these other responsibilities and duties.
Nobel Research in Physics
Before we talk about this new link that you're working on between
physics and biology, let's talk a little about your research that
led to the Nobel Prize. Give us a sense of how you came upon that
problem set and what you, in fact, did. It's related to atoms,
lasers, cooling, and so on.
[It began when] I was at Bell Laboratories. There are two main
branches of Bell Laboratories. The main research branch was in
Murray Hill, New Jersey. In 1983, a director [at the other branch]
in Holmdel asked if I would become a department head in his division
in Holmdel. The director, by the way, is Charles Shank, who's [now]
the director of LBL. He said, "Well, Steve, why don't you consider
coming down and starting a new department which would be a basic
science department here?" Holmdel had excellent laser science and
laser engineering, and a lot of the great things that have come out
of optical communication were spawned at Bell Labs in Holmdel and
Murray Hill. I said, "That sounds like a great job." So I went down
and started this department, and started hiring people, and also
inherited some very talented people. Actually, two of them are here,
also: Daniel Chemla for a brief moment was in my department, now a
division leader at LBL; and Jeff Bokor, who's a professor in
Electrical Engineering, was also in this department.
There was another really wonderful scientist there named Arthur
Ashkin, an older department head. I started talking to him casually,
in the hallways. He had this dream: "Wouldn't it be nice if you can
hold on to an atom with light?" He had tried to pursue this dream in
the early seventies, in the mid seventies, but it wasn't really
working. They did some very key experiments demonstrating the
fundamental forces, but it wasn't looking like they were getting
closer to really holding on to atoms with light. Finally the
management told Ashkin, "It doesn't look like it's going to work;
you've got to move on to other things." But then I came on board,
and I was this new, young person who he could corrupt.
"You go do this."
I started thinking, "Okay, this sounds pretty interesting," and I
started having a look at it. I started doing a lot of calculations.
It was getting to be bad, and I was thinking, "I can see why you
quit." I didn't tell him that, but I was thinking to myself, "It's
not looking good."
There's a few "eureka" moments you're going to have in science.
Mostly they're gradual eurekas, which I can come back to later. But
there was this time.
It was not looking good at all; I would try it this way, that way.
It's all on paper -- not looking good. And finally, there was a big
snowstorm in New Jersey. They said over the P.A. system the forecast
looked very bad. There's going to be nine inches or something; the
lab is going to be closed, you should all go home. Now, I live very,
very close to the lab, so I said, "Oh, heck." Everybody left, and it
was very quiet. It was one of those beautiful things where you can
see the snow falling down and everything's turning fluffy white, and
maybe it was appropriate [to think about cooling an atom] because it
I found you can do an end-run. The [conventional wisdom] was first,
you hold onto an atom; then you get it cold; and then you can do
what you want with it. I said, "Well, what if you reversed it? What
if you cooled down the atom first? Don't hold onto it, but maybe in
the process of cooling it down, it's going to hang around for enough
time that you can have a chance of grabbing onto it." And so [after]
a little calculation I said, "Holy smokes. This looks like it's
going to work."
And then I said, "Well, I want to refine the calculations." So then
there's the gradual "eureka." I wanted to refine the calculation. So
you're surrounding this atom with light, and it looks like it's
getting very cold, to the point where your feeble little trap that
was going to hold the atom could work. But it needed to hang around
for a while. So I started to say, "Okay, tomorrow I'll come in and
I'll start to write a program to predict how long it will hang
around." I start to write the program. Luckily, I'm not that good at
writing programs -- I'm good until about three lines -- because if I
was really good at writing programs, I wouldn't have thought about
it at all and just written the program. So I get to three lines of
code and said, "I've seen this problem before. Einstein solved it."
Good old Albert.
What he did is, he looked at a dust particle in the fluid; he was
studying Brownian motion. Here's this dust particle being battered
from all sides by atoms and molecules. He said, "If I take this
particle and I move it, there's a viscous drag in the fluid, and
that slows it down. The reason it's being battered around is because
of random imbalances between pressure from the left and pressure
from the right." What I wanted to calculate was how this particle
would wander around, because the previous day, I'd shown it had this
viscous drag on it. and that you do have these fluctuations. I was
going to write a computer program to say, "Okay, step to the right,
step to the left, and balance all the forces," but I thought, "No, I
can use this solution. I know where it is. It's in an elementary
textbook, an undergraduate textbook. It's the 'random walk' in a
Brownian motion medium. You just plug in those numbers, and voila,
you get ... wow, it's hanging around for a long time, because it's a
And so I got very excited. I went to my boss, Chuck Shank, and
said, "Look, Chuck, I know you're not keen on this, after years of
research, but this is so simple it has a shot at working. You can
get it cold, you can hold onto it, and we can go from there." He
thought about that and he said, "Well, okay, you've earned the right
to do something crazy, but don't try to recruit someone else." So I
said, "Okay, okay, just my post-doc and my technician. " Because if
you're onto something really big, you want to bring in your friends
and say, "We want to go fast; we want to do this and ... "
So we puttered along for a few months, going like the blazes. I
talked to Art about it, and he went, "Hmm, hmm, okay. It's not the
way I dreamed it. Okay, that sounds promising." After a few months,
it began to look like it was going to work, really going to work.
And I said, "Come on, join in, and it's going to be a lot of fun."
As I indicated in my lecture, it worked much better than anybody
What are the implications of what you discovered in a layman's way
Once you get an atom very cold ... and cold is really the average
speed that an atom moves. The atoms in this room are moving at
speeds of supersonic jet planes. In fact, that's why the speed of
sound is what it is. It's just determined by the speed of molecules.
Once you get an atom really cold, so it's moving as fast as an ant
walks, a fraction of an inch per second, then very, very weak forces
can push them around, and you can do what you want with them -- for
example, using electric or magnetic fields, or light. You can hold
them, you can push them around, you can do things that you simply
cannot do when they're whizzing around like supersonic jet airplanes.
The ability to hold onto and control and manipulate these atoms
means, for example, you can toss them up; they can turn around due
to gravity in a vacuum can where there are no other atoms around,
and you can make better atom clocks. You can make what are called,
atom interferometers. You quantum-mechanically split the atom apart,
so one part of the atom is the quantum wave going to one region in
space; the other part is the quantum wave going to another region of
space. That atom interferometer can be used to measure acceleration
or gravity or rotations with very high accuracy -- in fact, in terms
of acceleration or gravity, better than any other way of doing it.
And in terms of rotations, certainly better than any commercial or
even laboratory grade laser gyroscope.
So all of a sudden, you can measure changes in gravity so accurately
that it's going to become competitive with the current ways of
measuring changes in gravity, which is useful in all exploration.
You can probably put it on an airplane or a helicopter. And with
global positioning satellites to tell you the height and changes in
distance, and inertial sensing systems, and something that measures
change of gravity over distances on a scaled meter, it opens up the
opportunity to do map gravity drains and pockets of oil, diamonds,
things of that nature, minerals, on a very fast-moving platform like
a slow-moving plane or helicopter. So there are real practical
implications. Already the world is on the atomic clock standard,
defined by so-called atomic fallons of atoms.
The atom interferometer was totally unexpected. It just popped out.
People, even the researchers in the field, [find it] hard to think
about what you can do with it, even if you force yourself, until you
have it in hand, and you can then begin to see the abilities of this
new method or technique. It's only after we had it ... and then not
only me, my group, but the world in general. No one was talking
about any of the applications that came out until we actually had it
and we saw how powerful it was, and then began to appreciate it. You
can force yourself to think of what might come about, and you can
write down a few things, but you're going to get only a small
fraction of them. That's the wonderful thing about science.
And actually, it harkens back for me to what you had said about your
high school experience, in a funny way, that learning to look at
something and think logically about it, and "Wow!" you're taking it
to a new level. Not that you were doing Nobel Laureate a work in
high school, but some of the elements are there in this work.
Yes, I think that is true. But it's also just letting something
happen. This is one of the things I did learn at Berkeley, and I
watched great scientists here. Many of them were doing something
that, in hindsight, looked very natural. They would say, "Here's an
emerging technology. With this emerging technology, can I ride piggy-
back on it? Can I use this technology to turn it backwards and do
some new science?" Normally, you would think, "Oh, basic new science
discovery; turns into a technology; you make a better widget." But
what I appreciated when I was a graduate student here was that
that's all true, but you can also take that technology, turn it
around, and you can use it. A good example is radar. During World
War II, the U.S. and Great Britain, especially, developed microwave
engineering methods to have microwaves transmitters that allowed
radar, so that we can measure and see things far away. The scientist
who helped develop that radar, and other scientists who could see
the power of that technology, seized on that shortly after World War
II. A string of Nobel Prizes came out of people who used this new
technology to do great science. Charlie Townes here [at Berkeley] is
a prime example of that. His knowledge of microwave science --
during the war he was working on microwaves.
At Bell Labs, too
At Bell Labs, that's right. After the war, he said, "I want to do
microwave spectroscopy, because here's a new tool." We now control
of short-wave multi radiation. And he became one of the leaders in
microwave spectroscopy; wrote a classic book with his brother-in-
law, Arthur Schawlow, and then invented an idea of stimulating the
emission of microwaves called the maser. The extrapolation of those
ideas from microwaves to optical wavelengths led to the laser.
That's one example of using technology -- first, building on
technology during the war, saying this is a wonderful way, a new
scientific tool; use it to do science. Then wanting to improve the
tool to get to show the wavelengths, and voila, you had the laser. I
saw this over and over again. When Charlie came to Berkeley, he
wanted to use his knowledge in lasers and microwaves to do
astronomy. So, again, he was going to ride the technology. And I was
looking around and saying, "Yes!"
Now, he's a brilliant scientist, but the lesson I learned was you
don't even have to be brilliant if you're the first to look at
something with a new tool. So I said, "Okay, what are the new
tools?" When I was graduate student there was something called a
tunable dye laser. I told my advisor, "This is a wonderful thing.
It's only a few years old. This is a tool that we should be using,
now let's go figure out some science to do with it." Luckily, there
turned out to be some very fundamental physics questions you can
address using this tool.
It's the fundamental physics that drove [Townes]. From my side, yes,
I was drawn to the fundamental physics, but also "Let's use a new
thing to do it." If you use an old tool to tackle a problem, you've
really got to be smarter than the rest of the folks, because
everybody has this tool. If you're the first to look at something
new, it's like discovering your world. You just look around and
everything you see is going to be new.
Bringing Physics to Biology
Bring us now to where you're moving, because you are going into
biology; you already touched on that earlier. You are bringing
physics to the table of biology, so to speak. Tell us a little about
what you're seeing. You quoted Yogi Berra yesterday about that; that
it's amazing what you can see when you look ...
Well, Yogi is one of my heroes. He's the great American philosopher
of the twentieth century. One of the things he said is, "You can see
a lot by watching." He said other wonderful things like, "If you
come to a fork in the road, take it." Or, "We may be lost, but we're
making great time." And many, many other things.
But, anyway, my entrée into biology was exactly what I was telling
you about. I was working on atoms -- cooling atoms, holding onto
atoms with light. I said, "Well, the same technology can be tweaked
a little bit, and we can maybe hold onto individual molecules with
light if you play some tricks. What could you do with these
individual molecules?" Naturally, I thought about biology: "Let's
first try to hold onto a piece of DNA." It's strictly a
technological thing, and that worked. Then I had some ideas of
looking at enzymes, proteins walking up and down the DNA and seeing
what you could do in biology. But first we glued little plastic
spheres to the end of this big DNA molecule -- so big that it's
length was something like 15, 20 microns, which could easily be seen
in an optical microscope. Now, you can't really see a piece of DNA,
because sideways it's only 20 angstroms, and it's not resolved by an
optical microscope. But you do a trick, you put little dye
molecules, florescent molecules; think of it as a string of
Christmas tree lights. You can't really see the string; it's too
thin. But you see the light coming from that. It shines very nicely
in an optical microscope, and you can move it around. So the first
thing we did was, "Okay, let's stretch it out. Wow, it's stretched
out. Well, let's see if we can break it." So we stretched and
stretched it harder and harder, and we couldn't break it. It's very
strong along that dimension, which is good because it holds your
family jewels. You don't really want to break it that way.
In the end what happened, it pulled out the optical tweezers, which
were these plastic handles we'd glued onto the ends of the DNA. And
it sprang back like a rubber band. It just went "boink" and crumpled
back up. I said, "Holy smokes! It looks like a rubber band. Why does
it look like a rubber band?" And the reason it looks like a rubber
band is because when a molecule is straight, it's in a very unlikely
state. If it were up to its own devices, it's being battered around
by water molecules, it wants to do some random coil geometry. That's
a much more likely state. So the reason it springs back has nothing
to do with chemical bonds and forces pulling it back; it has to do
with whether it's more likely to be found in some random coil or
straight. It's the same reason if you push all the molecules of the
air into a corner of the room and let go of them. They don't even
have to bounce on each other. They would say, "Where would I likely
be?" Well, equally likely anywhere in this room. And so the pressure
evens out very quickly. That's why it would spring back like a
I said, "Well now, I can do this on a single molecule." What things
could you do there? Well, you can understand polymers. Polymers are
long, skinny molecules. You can look at it one at a time. So it was
a back-door entrée into polymer physics, and we did that for a half-
dozen years. Finally I started getting back into biology be<br/><br/>(Message over 64 KB, truncated)