Interview

with Freeman Dyson

Interviewer : Masataka Fukugita

Freeman Dyson visited the Kavli IPMU at Kashiwa
from 15th to 19th of April, 2014, and at Kamioka
from 20th to 22nd. Masataka Fukugita organizeda special Q&A session with Freeman Dyson on 17thof April for 4 hours. This document excerpts thissession, supplemented by an additional interview
on 18th and another Q&A session held at Kamioka
on 22nd.

22

Fukugita: You wereeducated at theWinchester College. Would
you tell us about thislegendary college?
Dyson: Winchester
College was founded 650
years ago by William of
Wykeham, a Bishop of
the Catholic Church andan advisor to the King.
William of Wykeham wasa capable administrator.
He founded 6 foundations,
including New College
in Oxford. Students
are allowed to enter
Winchester College atage 12 after a tough, very
competitive competition.

Freeman Dyson was educatedfrom 12 to 17 years of age at
Winchester College, a famous
elite high school of England. Hethen went to the mathematics
department of Cambridge University,where he was supervised by Abram
Samoilovitch Besicovitch. Afterwards
he worked for the Royal Air Force,
while WWII was raging. A year
after the war ended he returned toCambridge, and gradually switchedto theoretical physics. He then went
to Cornell University and worked
under Hans Bethe. He visited theInstitute for Advanced Study in 1948,
where his great work for QED wascompleted. Quantum field theory
we learn today is the formulation
thanks to Dyson. His work serves as
the best example of a mathematicalmind clearing up the mess of physics
to create a beautiful theory. He
was appointed as a professor atCornell University in 1951, and theninvited as a professor in the Schoolof Mathematics of the Institute forAdvanced Study in Princeton in 1953,
where he served as a professor (nowas a professor emeritus) for 60 years.
He has just passed 90 years of age,but still actively engaged in science.
During his long research life hehas worked on an amazing variety
of subjects, often two or more
subjects at the same time. Startingwith number theory, the subjects heworked on include:
Quantum electrodynamics –foundations of quantum field theory;
Statistical mechanics and solidstate physics;
Random matrices;
Stability of matter;
Adaptive optics;
Nuclear engineering, nuclear
power as space propulsion;
Model for the origin of life;
Time variation of the physicalconstants;
Carbon dioxide problem,
and also some others.
Now he is working on gametheory, prisonerʼs dilemma, besides
graviton detection, which waspresented in his colloquia on the
16th of April at Kashiwa and on the
21st at Kamioka.

Kavli IPMU News No. 26 June 2014

The exam is for ten
subjects, including Latin
and Greek. There were
two for mathematics, one
pure math and the otherapplied math. The exam
also includes a modern
language. My father was ateacher at this college, so
I was already familiar with
it as a college brat fromthe age of 3. The numberof students is 70, 15 eachyear, boys only. This has
not been changed until
now. The college is still
flourishing the same way
as in the old days. I still visit
it frequently.
The graduates are notnecessarily academic; somebecome bankers and somego to government offices.
England is a very classdivided society, commercial
middle class for businesspeople and academic
middle class including
university and government
people, and there is anantagonism between
them. We, the academic
middle class, consideredourselves the top students
in the school and looked
down on the others. That
tradition was intact, until
Margaret Thatcher took
her revenge, putting thecommercial middle classfirmly in power.
We lived in the samebuilding originally built in
the 14th century. It has
thick walls, cool in summer
and warm in winter. It is
comfortable to live there,
not much need for heatingor cooling. Education iscarried on in a very freestyle. In the top form wewere in class only for
7 hours a week. So we
found ample time to learn
whatever we wanted.
Fukugita: Have you
decided to be amathematician fromthe time of Winchester
College?
Dyson: No. I was muchyounger. Mathematics
was born in me. I loved
numbers and very muchenjoyed calculating fromthe time I was around3 years old. This is thesame as with musicians
who start playing piano
at age 3. It is the samefor mathematics. I knewthat mathematics waswhat I can do best. I was
already determined to bea mathematician when I
entered the College at age
12.
In the college I foundCours dʼAnalyse by
Camille Jordan in thelibrary. It consists of 3 fatvolumes, containing thewhole of 19th century
mathematics. It is a classic
work, written around 1900
and used in École Normale
in France as a text book.
It was a miracle that thisbook was in the library.
Interview

Masataka Fukugita is professor
at the Kavli IPMU. He served as aprincipal investigator at IPMU from
October 2007 to March 2012. He is
also a part-time member of Schoolof Natural Science of the Institutefor Advanced Study in Princeton
since 1988. So, he has got alongwith Freeman Dyson over 25 years.

23

My fellow classmate James
Lighthill, who became afamous mathematician,discovered this book in thelibrary, and we both readand talked about it.
G.H. Hardy was
already an old man in
Cambridge and the most
famous mathematician
in England. He had been
at Winchester College asa boy 40 years earlier. In
his autobiography CoursdʼAnalyse appears, andI strongly suspect that
it was he who brought
this book to Winchester
College. I cannot imagine
anybody else bringing
it. Unfortunately, I neverasked him about this.
Fukugita: Then you went
to Cambridge?
Dyson: In 1941 I came to
Cambridge. I entered themathematics department.
Mathematics andphysics were separate
departments. Physics wasthen still called Natural
Philosophy. Mathematics
was considered by thephysicists to be a French
disease.
It was in the middle of
the war. There were very
few students in the class.
The others were fighting
the war. Lectures were
given by Hardy, John
E. Littlewood, Abram
Samoilovitch Besicovitch,
but students were only
a few. We did not sit inclass-rooms but sat aroundsmall tables with a few
students and one teacher.

24

It was a very lucky time to
be a student.
I was a student of
Besicovitch, expert on
measure theory. He camefrom Russia, spoke English
with a very strong Russian
accent. Besicovitch gaveme problems to work on. I
liked the Russian language,
so we spoke in Russian.
We often went for longwalks in Cambridge, andwhile doing so were notallowed to speak English.
I was influenced by the
Besicovitch style: it isarchitecture. Besicovitch
had the ability to build
beautiful structures from
simple components,
which were used in hismathematical proofs. I
have used the same style
for my calculations inphysics.
After Rutherford diedin 1937 physics was at alow ebb in Cambridge. In
physics, the only professor
was Dirac. Dirac did notinteract with anybody.
Eddington was also there,
he was an astronomer.
We did not count him as aphysicist.
At the time I was there,
Lawrence Bragg was incharge of the physics
department. He succeeded
Rutherford. Bragg said:
Rutherford was the best
physicist in the world and
I am not: so we should
do something else . It
was amazing wisdom. He
made a quite astonishingdecision, not to do physics

but to do two new subjects
instead: molecular biology
and radio astronomy.
Martin Ryle brought
military radar equipment
and started receiving
signals from the sky. For
radio-astronomy, English
weather doesnʼt matter,
whether it is cloudy orraining. He immediately
made great discoveries.
In the molecular biology
group Max Perutz andJohn Kendrew became
leaders. Both wereenormously successful andCambridge became theworld leader in both thetwo subjects introduced by
Bragg.
After two years at
Cambridge, I worked
for the Royal Air Force(1943-1945). It was agrim time of the war. I
was a civilian scientist
at the headquarters of
RAF Bomber Command,collecting information
about the strategic
bombing of Germany.
After the bombing ofGermany stopped in April
1945, we still had a huge
bomber force. I would
have flown to Okinawa,in order to bomb Japan
from there, but the war
ended in August; so we
did not need to bomb
any more. It was a great
relief. We did not needto kill more people. We
were very grateful to theatomic bombs for ending
the war. At that time
everybody thought that

Kavli IPMU News No. 26 June 2014

this was the cause of theJapanese surrender, andso we were told. I recently
read the book by historian
Hasegawa who claims thatthe real reason for thesurrender of Japan was
not the atomic bombs but
the invasion of the Soviet
army from the north. Japan
could not defend against
Russians from the northand Americans from thesouth. So the Japanesegenerals thought that it
was better to surrender toAmericans, while keeping
Russians out, using theatomic bomb as an excuse
for their dishonorable
surrender. Now I agreewith Hasegawa and wish
that we had not dropped
the bomb on Hiroshima.
The bomb was not asimportant as we believed.
Fukugita: Cambridgeis the great place formathematical physics, with
Newton, Maxwell andDirac. You were following
in their footsteps. Why is
Cambridge so successful?
Dyson: The image ispresented to school
children that each country
is good at one special
thing: music in Germany,
painting in France, and in
England it is science. This
provokes gifted young
children in England to go
to Cambridge and become
scientists. The tendency
was enhanced by the
famous Tripos exams in
Cambridge.
Fukugita: What did bringyou from mathematics tophysics?
Dyson: We saw thenews on the day when
Hiroshima was bombed:
it did not say Hiroshima
was attackedʼ, but said
New force of nature
harnessedʼ. It meant thatnew science had emerged.
I did not want to use thebomb, but wanted to use
knowledge that cameout of the bomb. Nuclear
physics became suddenlya fashionable subject, andit gave a motivation tolearn physics. Quantum
mechanics was still newand exciting. Generalrelativity was also exciting.
Many things were goingon in physics. I then started
to study Heitlerʼs book,
The Quantum Theory ofRadiation . Two years later
there was a miracle, theexperiment of Willis Lambat Columbia University
measuring the energy
levels of hydrogen atoms.
I went back to
Cambridge to study
physics. Nicholas Kemmer
was my teacher, fromwhom I learned quantum
field theory. I wanted to
go to the United States.
Geoffrey Taylor, a greathydrodynamics expert
who had worked at Los
Alamos, immediately
said that I should go toCornell, where Hans Betheand the young brightphysicists from Los Alamos
were all working. I had
no idea about Cornell,but I went to Cornell
and worked under Bethe.
When I came to Cornell in
September 1947, I knew
the Columbia experimentfinding a 1050 megacycle
shift between 2P and 2S
states of hydrogen. The
old quantum mechanics ofDirac was wrong. I knewthat Bethe had beautifully
explained it. It was exciting.
It was exactly the righttime and the right place
for me to be. Richard
Feynman was then ayoung professor at Cornell.
In early 1948
Oppenheimer received
a batch of the newJapanese journal, Progressof Theoretical Physics. He
copied it to Bethe andBethe showed it to me.
I found the Tomonaga
paper, where Tomonaga
had done everything
before we did. We also
knew the work of Hans
Kramers which appeared
a year earlier, as a paper
to be presented at the1948 Solvay Conference,
explaining the idea ofrenormalisation.
I remember, when I
visited Berkeley in 1948,
I was impressed by thechemist Melvin Calvin. He
used for the first time ashort-lived carbon radioisotope to understandphotosynthesis, howcarbon dioxide is absorbed
and converted into sugar,
by tracing the moveof carbon atoms frommolecule to moleculein a few seconds. How
chemistry was going on
second by second. It was
the first application of
nuclear physics to biology,
and since that time biology
evolved fast with the useof radioactive tracers.
Oppenheimer said thatthe application of nuclear
physics to biology was
more important than thebomb.
Fukugita: How was theInstitute in Princeton atthat time?
Dyson: When I came to
Princeton, Einstein was
there. I think it was a bad
mistake for him to cometo Princeton. When hecame he had two choices,
either Caltech or Princeton.
He chose the latter sincein Caltech he had to teach.
In Princeton he did notneed to teach, so he lost
contact with students.
As a professor in the old
German style, he had an
assistant who was his
personal slave. In my time,
Einsteinʼs last assistantwas Bruria Kaufman,
who herself is a good
physicist. Kaufman said tome that being Einsteinʼs
assistant looks very goodon a resumé but in fact
was a boring job. All she
had to do was routine
calculations.
There were many young
fellows around Einstein,doing new science in theadjoining building. Einstein
was never interested inwhat we were doing andnever spoke to us. He
never came to seminars,
never to lunch. So there
was zero communication
between him and the
young members of theInstitute. I think it was
mainly his fault, althoughpartly ours. We wereyoung and arrogant, andwe didnʼt think we hadmuch to learn from him.
Fukugita: Have you evertalked to Einstein?
Dyson: No, never!
He loved children, andcertainly got along very
well with them.
Einsteinʼs long-term
secretary Helene Dukas
was a good, able woman,
and a fierce protectorof Einsteinʼs privacy andprivate affairs. We werefriendly with her. After
Einsteinʼs death she
often came to our house.
My children adopted
her as their substitutegrandmother. One rainynight, a truck came to theInstitute, and took away
all the Einstein papers
that she had collected
and cared for. The papers
were on their way to
the Hebrew University in
Jerusalem, as Einstein had
directed in his will. A few
days after this, Helene
passed away.
Bohr often came to
the Institute. He wascompletely different fromEinstein. He was verymuch interested in newexperiments. He came toour seminars, had lunch

25

Interview

with us, and talked toyoung people. He was thenworking as a diplomat,
representing Denmarkat the United Nations in
New York, campaigning
for international control of
nuclear power and nuclear
weapons. But he kept up
his interest in new physics.
Tomonaga also came to
Princeton. I liked him verymuch. Unfortunately, hearrived in the week I left
Princeton. So I had only
a short time to talk tohim. He was an extremely
unselfish person. He
had done much of what
Schwinger and Feynman
did, five years earlier,but he never said so.
Tomonaga felt guilty as hewas not sharing the great
hardships his students
were suffering in Tokyo.
He felt bad to be in the
comfortable environmentof Princeton, so he took an

26early chance to go back toJapan.
Fukugita: How was
Wolfgang Pauli?
Dyson: Pauli left theInstitute before I came to
Princeton. He was at theInstitute all the time during
the war. He was close
to Einstein and enjoyedtalking to him. He was,however, isolated and quite
unhappy at the Institute.
He settled in Switzerland
after the war, and finally
got citizenship, which had
been refused when helived in Switzerland before
the war. He didnʼt comeback to Princeton.
I got to know him in
Switzerland in 1951. Pauli
had a big psychologicalproblem. Fortunately, it
was one of the rare times
when he was very happy,
disobeying the order ofdoctors and his wife. We
had a very good friendship.

He was in a relaxed state.
We went out to walkevery day and talked a lot
about physics. We calledat all the ice-cream places
along the way, because
his doctor had forbidden
him to eat ice-cream. He
understood all the resultsfrom on-going high energy
physics, where cosmic
ray experiments werethe cutting edge at thattime. I was working on
the convergence of theperturbation expansion inquantum electrodynamics.
Pauli maintained that
it is divergent. I tried toconvince him that theseries converges, but he
did not agree. After all, weknow now that he wascorrect. I was not unhappy,
as I could write a paperon the divergence of theseries, thanking Pauli forhis help.
Fukugita: And, Dirac?
Dyson: Dirac quite oftencame to Princeton. Hechanged his character,from a silent young man
difficult to approach, toa talkative, friendly old
man with a big sense ofhumor. Like Einstein, he
stuck to theories of his
own preference, the large
number hypothesis which
turned out not to work,and the negative metricfield theory which I neverunderstood. When he wasold, he seemed to have lost
his intuitive ability to guess
what is right or wrong. He
became more and more

Kavli IPMU News No. 26 June 2014a normal person. Much
nonsense has been written
about him. He was not an
outstandingly strange man.
He was an outstandingly
intelligent man.
Fukugita: I think Heisenbeg
did not come to Princeton?
Dyson: Heisenberg did
not visit the Institute, but
he visited Einstein once.
It is recorded in the diaryof Johanna Fantova. She
was an Austrian Jew,
whose family had beenacquainted with Einsteinin 1912 while he wasworking at the German
University in Prague. She
became a friend of Einstein
20 years later in Berlin,organising his personalcollection of books, sailinga boat with him on a lake,and 20 years later again in
Princeton. In Princeton she
took a course to qualify
for a job as a librarian,following the advice ofEinstein, and worked at
the University Library. They
sailed on Carnegie Lake.
She kept a diary which wasrecently published. From
this diary we can glimpse
Einsteinʼs life in Princeton.
In it Heisenbergʼs andBohrʼs visits to Einstein
appear. Neither of themmade a good impression.
Heisenberg was still a big
Nazi, dreaming of a greater
Germany. Bohr would notstop talking until Einstein
was totally exhausted.
Heisenberg, too, wasdevoted to his personal
theory, spinor field theory,

in his late years. He
required his assistant towork on that. The assistantthat I knew was Hans-Peter
Dürr. His career was ruinedby this work. Heisenberg
did not give up spinor field
theory until his death.
Fukugita: Have you
got any impressions ofJapanese scientists, otherthan Tomonaga, who cameto Princeton?
Dyson: Yukawa came to
Princeton, but he was notdoing physics. He came to
Princeton as a politician,perhaps as a symbol ofJapanese science. He
worked for public relations
or as a diplomat and madea public appearance at theUnited Nations. I saw him a
few times but never talked
to him about physics.
Taro Asano was a young
mathematical physicist
from Tokyo. I had invited
him to the Institute. He
had done a beautiful
piece of work on quantum
ferromagnets. He wasisolated, he was shy, he
had no friend to talk to,
and did not speak muchto colleagues. Possibly
the language was a
problem. Towards summer
he got depressed anddisappeared. After theterm ended, he drove his
car at a crazy speed up
Springdale Road, crashedhead-on with a heavy
car and killed himself. I
was very sorry for this. I
escorted his wife, Sachiko,back to Japan, carrying his

ashes. This was incidentallymy first landing in Japan,
although I didnʼt go out
from the airport.
Fukugita: This reminds meof the episode of Yutaka
Taniyama, who was invitedby André Weil to theInstitute, but committed
suicide before he cameto the Institute, and his
fiancée followed him.
Dyson: André Weil was
the most friendly person.
He would have cared for
him if he had come to
Princeton. When I visited
Chicago as a young
student, Weil took me out
for a long walk of threehours, and talked about
many things. He had areputation for being fierce,but I never saw him fierce.
Maybe he had two sides.
Fukugita: Was there any
impact from the work ofYang and Mills?
Dyson: Yang did this workwith Mills at Brookhaven insummer. At that time I was
not working on particle
physics, but on randommatrices. I think that Yangʼsmotivation was to makea gauge theory of isospin,rather than to make gauge
theories a central featureof the universe. Pauli wasat Princeton at the time. He
was very negative because
Yangʼs gauge field wasmassless. Pauli thoughtthat it had nothing to dowith nature and was notinteresting. His opinion
had a big effect on people
including Yang himself.

Fukugita: How about
contacts with legendary
mathematicians, such as
Hermann Weyl, Johann
von Neumann, Carl Siegel?
Dyson: Shortly after I cameto Princeton, Hermann
Weyl and Carl Siegel left
to Zürich and Germany,
respectively. Siegel
knew me, because I had
strengthened his theorem
about the approximationof algebraic numbers
by rationals. Hermann
Weyl somehow knew me
too, and helped to getme hired as an Instituteprofessor. Soon after I
came to the Institute as aprofessor, they had alreadygone. So I had not muchcontact with these people.
The only one I knew well
was Johann von Neumann
who stayed longer. He
was enthusiasticallyworking on the electronic
computer project. I wasmuch interested in it, but
the majority of people
at the Institute were not.
Oppenheimer was notinterested in it. I was oneof the few who tried tokeep the project alive aftervon Neumann left.
The meteorologist JuleCharney came to Princeton
and ran climate models
with von Neumannʼscomputer. When thecomputer project ended,
Charney left. This was agreat opportunity missed.
The Institute could havebeen the centre of two
new sciences, climate
studies and computerscience, in the same
way that Cambridge
became the centre ofmolecular biology andradio astronomy under
the leadership of Bragg. I
proposed that Charney be
employed as a professor
at the Institute, saving the27

Interview

computer programme, but
my efforts failed miserably.
Oppenheimer did notshow any interest.
The computer project
went briefly to Princeton
University before it was
dropped a year or so aftervon Neumann left. Twenty
years later, computerscience was centred at
MIT and IBM, and climate
science was centred in
UCLA and in Norway. I feelsorry for this. The droppingof the Institute computer
project probably delayed
the growth of the two newsciences by twenty years.
Fukugita: How about
Oppenheimer?
Dyson: Robert
Oppenheimer was acomplicated character.
With Hartland Snyder,
he did his mostimportant scientific work
understanding black holes.
They showed that every
massive object, with zerointernal pressure, will entera state of permanent freefall, as a consequence ofEinsteinʼs equations. They
predicted the existenceof black holes in any
universe obeying Einsteinʼsequations. You donʼt need
any new physics. Just
Einsteinʼs theory is goodenough. It is a wonderfulpaper. This work appearedin the 1 September 1939
issue of Physical Review.
The paper appeared ata bad time, on the daythat Hitler invaded Poland
and started World War II.

28

Nobody paid attention toit.
Einstein never believedin black holes. He not only
didnʼt believe in them, butalso wrote a paper claimingthat black holes could notexist. Oppenheimer, too,never revisited this subject.
He refused to talk about
black holes, even aftercandidate black holes werediscovered in the sky. I
tried to talk about it withhim and to explain to him
why it is interesting, but
he always changed thesubject. I did not know
why. The father and the
grandfather of the blackhole did not like their son.
I would mention two
important people of geniusthat Oppenheimer failed
to recognise. One is Fritz
Zwicky, who had many
wonderful new ideas. He
was an astronomer who
discovered dark matterand the two main types ofsupernova, and predicted
neutron stars. He is now
recognised, but had neverbeen recognised while he
was alive. Oppenheimer
never spoke to him whileboth were at Caltech.
Einstein visited Caltech,
but he wasnʼt interested
in him, and never spoke
to him. I have never met
Zwicky. The other is John
Wheeler. He is also poorly
recognised. Oppenheimer
disliked him strongly.
Unlike Zwicky, he was
not a difficult person. He
had a large number ofstudents and was very
generous to them. He gave
Feynman full credit forwork on problems that hehad suggested. He was anextreme patriot, very rightwing, a 150% American,
politically opposite to
Oppenheimer. Wheeler
was a big protagonist of
black holes. This might
possibly be the reason why
Oppenheimer did not liketo talk about black holes.
Oppenheimer disliked
talking to him. Both Zwicky
and Wheeler deserve a
better recognition.
Fukugita: What is thebiggest surprise you
experienced in yourresearch life?
Dyson: The discovery of
weak vector bosons. I
had not taken the theoryof Weinberg and Salam
seriously, and I had apersonal theory of weakinteractions. So thediscovery of the vectorbosons was a surprise tome. The discovery was sobeautiful that it made me
happy to be proved wrong.
Fukugita: What do you
think of the relation
between mathematics andphysics as a mathematicalphysicist?
Dyson: The real gap was
between pure mathematics
and applied mathematics.
Pure mathematicians
were talking a different
language. Bourbaki
was fashionable puremathematics, and I was
not very interested in it.

Kavli IPMU News No. 26 June 2014

I remember a talk about
flabby sheaves .
Somebody asked what
are flabby sheaves. The
chairman, André Weil, said
that is already a classicalterminology and we do
not need to explain it . I
never understood what itwas. I got to understandfibre bundles, but I
have not gone beyond
that. Pure mathematics
had somehow become
extremely abstract. It
did not seem to me to
be a fruitful way to go.
I preferred to stay withapplied mathematics.
There seems to be no
barrier between string
theory and mathematics.
They understand eachother. There is a big
barrier between string
theory and the rest ofphysics. A new trend isgood contact between
computer scientists andmathematicians. We now
have two professors in the
School of Mathematics
working on computerscience. One of them is
Voevodsky. He is working
on the mathematical logic
of computability.
Fukugita: How do you
think about the present
status of physics? What doyou want to encourage?
Dyson: Physics has slowed
down. 60 years ago,experiments were done in
6 months and they wereexplained in 6 weeks. Now
experiments take 20 years.
Except for high energy

physics, there is still a lot
to do. Small scale scienceis still flourishing. Particle
physics is a special case.
Even in particle physics, asmall experiment, such as
the measurement of theelectric dipole moment of
the electron by Gabrielse
at Harvard, is an example
on the frontier and has achance to find somethingnew.
Progress in astronomy
is great. Twenty years
ago, we knew only a tiny
part of the Universe, onlyout to redshift 0.2. Now
this horizon has beenenormously extended.
We can see and explore
the Universe all the way
back to the Big Bang.
Astronomy can do a lotof important science withsmall instruments, both on
the ground and in space.
Kepler is a small satellite,
but enormously successful.
The BICEP2 microwave
anisotropy experimentat the South Pole is not
expensive and is equally
successful. Politics focuses
attention on big science,and big science also getstoo much attention fromthe media. I want toencourage studies in as
wide a field as possible.
Especially in astronomy,
there are so manythings to explore. Zwicky
emphasized the advantage
of single-purpose
instruments. Kepler is abeautiful example. We canstill find others.

Fukugita: How about
particle physics?
Dyson: I have a criticalview of LHC. Every event
is complicated with anenormous backgroundof uninteresting particles.
Software must be written
specifically to pick out
what is looked for. You
can discover only what you
expected. Every discovery
is predictable. The LHC
cannot make unexpecteddiscoveries. The accelerator
still uses radio-frequency
acceleration, with theelectric voltage per unit
length the same as it was
half a century earlier.
Ordinary lasers haveelectric fields 1000 times
higher. The use of laser
fields for accelerationmust be studied. Bigger
accelerators using thesame acceleration principle
are not a good way to go.
There are several ways
we can go for particle
physics. Undergrounddetectors have a good
future. They can detect
everything that happens.
Two countries, Japanand Canada, with goodscientists and not too
much money, lead theworld in the use ofunderground detectors.
Their projects are morecost-effective than the
projects in America andEurope, which invested alarge amount of money inaccelerators. Kamiokande
is a very good experimentthat has already brought

several important results.
It is always ready to detect
something unexpected.
I strongly support thisexperiment and its
upgrade. They may wait fora long time, but they havea good chance to discoversomething unexpected.
In general, experimentalists ought to be preparedfor something unexpected
to happen. This is also true
for theorists. They should
not stick to one thing,but should think abouta variety of subjects. Ifthey get bored with one
subject, they should breakout into other subjects.
I have been doing it thisway throughout my long
research life.
String theory is beautiful.
One day it may turn out tohave something to do withnature. String theory is
now close to mathematics,
but the gap between string
theory and the rest ofphysics is very wide. String
theory does not haveenough good problems forten thousand people towork on. I am not worried
about string theory in itself,
but I am concerned with
their narrow training ofstudents. This makes them
unemployable for jobs
other than string theory.
Changing peopleʼs careers
every five years would
help to solve this problem.
Particle physics is not easy
to escape from. Escapefrom other branches ofscience is easier.

I know some people
who switched from string
theory to genomics. 95%
of genomes are not genes.
We do not understandwhat these non-coding
parts of genomes are
doing. The discoveryof Human Accelerated
Regions of genomes,
where significant changes
are seen between chimps
and humans, could
motivate the start of a
new science. We must be
flexible and ready to moveinto new sciences as they
emerge.
When I was young,I carried out hardcalculations competitively.
I was not concerned withphilosophical questions.
For me, philosophy was abranch of literature, not a
branch of science. Science
was a collection of toolsthat I used for solving
problems. When I got older,I wrote books and articles
for magazines, rather thandoing competitive science.
So my work has changed
with age.

Interview29

Climate? It takes much
too long to explain. In
short, I am skeptical
about prevailing anxieties
about climate. Oak Ridge
National Laboratory
had a very good climate
programme, started
50 years ago, before it
became fashionable.
The director was Alvin
Weinberg. He insisted that
we must understand thereal world. I worked withhim for some years. There
were a lot of biologists,
who were concerned withsoils, trees, vegetation,
microbes and all kindsof ecology. In addition
there were physicists whowanted to understandclimate. So, it was a wellbalanced programme.
For carbon dioxide in
the atmosphere, half ofthe effects are concernedwith climate and half withecology. Carbon dioxide isa powerful fertiliser. It canbe a substitute for water.
The limitation is that it is
only a small fraction of
the air, while the fractionof water vapour is usuallylarger. Suppose we open apore in a leaf and get one
carbon dioxide molecule
to go in through thepore. While the pore isopen, about 100 watermolecules come out. So
the leaf is evaporatingwater much faster than30

it is absorbing carbon
dioxide. If more carbon
dioxide is in the air, theprocess is more efficientand evaporates less water,
encouraging plant growth.
The effect of carbon
dioxide is substantial forbiology. There is a 30%
increase of CO2 in theatmosphere comparedwith the amount ahundred years ago, andit caused an increase invegetation, wild forest andalso food crops roughly
half as great, namely 15%
increase of biomass due to
30% increase of CO2. This
is not well known to the
public.
For climate, carbon
dioxide is the easy partof the problem. Thereis a huge complicatedfeedback and recyclingof carbon dioxide, but it
can be measured and isfairly well understood.
Water vapour is much
more difficult. It is moreabundant and thegreenhouse effect islarger. Evaporation ofcarbon dioxide from theocean is a minor effect.
Evaporation of water fromthe ocean is much larger
and dominates the effectof CO2. Water vapour isstrongly absorbing, butalso has a tendency tocondense into clouds.
This is why the problem isdifficult. Vegetation is also
a huge source of water
vapour, and so is coupled
to the circulation of water.
Evaporation of water iscrucial to the final effect.
That is why it is so hardto calculate. If you only
have to deal with carbon
dioxide, the problem issimple.
Carbon dioxidecauses warming of theclimate. This is a serious
concern. Unfortunately,
the United Nations set
up the committee IPCC
for studying climate.
They have written into
the definition of the
programme that theyshould look at effectsof human activity on
the climate, but are notsupposed to look at
non-human effects. The
programme is highlybiased from the beginning,
and this is what I am
fighting against: I am not
simply opposing what they
are doing. The scientists
working for the United
Nations are allowed only
to look at human causesof climate change.
Climate is a difficult
problem. Particularly,
clouds are crucial but
poorly treated. The
resolution is poor insimulations. One takes
averages over 100 km in
global climate models,
while actual clouds requirea resolution of at most 1
km vertically and 10 km
horizontally. What themodels do is not to modelclouds but to represent
average cloudiness in aregion by fudge factors.
The present state ofunderstanding of climate
is poor. I donʼt trust themodels.
I also mention that
there was the little ice
age in the 17th century,
when the sun went tosleep for 70 years. The
world suffered from a cold
climate. There is a strong
correlation between the

Kavli IPMU News No. 26 June 2014

sun and the climate. This
is totally absent in the
climate models. The sun
was active for the last 50
years, and less active inthe last 5 years. Strong
global warming lasted for
50 years, but seems tohave stopped for the lastten years. This is a clear
observational hint, but it is
not included in the climate
models.
The world averagetemperature is amisleading concept. It is
unclear what it means.
The most intense warming
happens in very cold
places, mostly at highlatitudes. There are a lot of
unknowns in the model.
It is also not clear if
local warming is bad. In
some arctic areas, local
people are happy withthe warming. They had avery hard life in the past,
relying on fishing in ahorrible climate. Warming
has made their life easier.
There are always winners
and losers when the
climate changes.
I am skeptical whether
models give good picturesof reality. The real world ismuch more complicated.
My conclusion is that I
do not believe the official
predictions of climate forthe next 100 years. The
models are good tools forunderstanding climate but
bad tools for predicting
climate. They are good forunderstanding because
they allow us to see theeffect of changing one
factor at a time. They arebad for predicting because
they leave out a large
number of factors thatmight be important.