Home > Professor lights > Vol.06 Hitoshi MURAYAMA

Vol.06 Hitoshi MURAYAMA

Where did we come from?
Solving mysteries by
gaining wisdom from science

Hitoshi MURAYAMA

Principal Investigator and Hamamatsu Professor of the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) at the University of Tokyo Institutes for Advanced Study

In 1991, Hitoshi Murayama completed his PhD in Physics at the School of Science, the University of Tokyo. He worked as a research associate at Tohoku University and then as a postdoctoral fellow at Lawrence Berkeley National Laboratory. He then joined the Physics Department at the University of California, Berkeley, and became the MacAdams Professor of Physics (current position) after working as an associate professor and professor there. From 2007 to 2018, Professor Murayama also served as the founding director of the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) at the University of Tokyo Institutes for Advanced Study. Since 2019, he has been given the new title of “University Professor” at the University of Tokyo for his achievements.

September 17, 2020  
Affiliation, title, and other information are as of the time the article was published.

Professor Murayama, who founded the Kavli IPMU located on the Kashiwa campus of the University of Tokyo, is a particle physicist and the principal investigator on the team using the Subaru Telescope to investigate the mysteries of the universe with cutting-edge science. While pushing ahead with research activities through constant travel between the United States and Japan, he gives lectures in various places, appears on TV programs, and writes a series of articles for a national newspaper in Japan. His energetic activities span a wide range of issues. We talked to Professor Murayama to hear about his work at the forefront of science, and to find out more about the background of this amazing person with seemingly unlimited energy.

Inspiration from watching TV shows while absent from school

Professor Murayama casually comments on his childhood, including when he had asthma, while mixing in a little humor.

The many people who have come in contact with Professor Murayama describe him as friendly, having a wealth of knowledge and the surprising skill of being able to explain even difficult scientific topics in a way anyone can understand. What kind of life did he have up to now? We started out by asking him about his childhood.

“As an elementary school kid, I had terrible childhood asthma. I was absent from school for a frightening number of days throughout the school year. Two times a month, I had to get an IV drip of adrenal cortical hormones, and was told I would have a moon-shaped face, so things were really terrible,” said Professor Murayama.

But, his struggle with this illness provided an opportunity to discover a deep talent within him.

“When you take time off from school and are home during the day, you usually watch TV, right? But, for me, daytime dramas weren’t very interesting since I was still a child. So, I started watching what is now called NHK E Television, or what in the old days they called NHK Educational TV, and found some really interesting programs there.”

For example, in the math program, there was a RAKUGO, a traditional Japanese comic storytelling, explaining how “an infinite series converges,” which is a part of high school mathematics.

This amusing example went like this: “A customer went to a tofu shop to buy tofu, and after buying one block of tofu, he started to flatter the shop owner, saying, ‘Everybody says your tofu is the best-tasting tofu in all of Tokyo!’ The shop owner liked hearing this and said, ‘Oh really? Well, I’ll give you half a block tofu for saying those nice things.’ The customer then said, ‘You are really a generous person, so everybody comes here to buy tofu.’ The shop owner then said, ‘That’s great, I’ll give a half of the remaining half as a ‘Thank you!’ and …”

Professor Murayama continues the story as if he himself were the storyteller.

“This kept going with the shop owner saying, ‘Okay! Okay! A half of the remaining half! A half of the remaining half! I’ll give you everything still remaining!’ The customer, hearing this, thought: ‘Great! I’ll have enough tofu to last the rest of my life!’ And yet, when he looked in the bowl, there were only two blocks of tofu. One block was the tofu he bought initially; half of the other block of tofu was given to him by shop owner; and half of the remaining half, that is, a quarter of one block, then one-eighth of one block…. yet it all added up to only two blocks.”

Even if you keep endlessly adding to a number, you only get two. This story—“An infinite series converges”—at first sounded really difficult, but when tofu was substituted into the explanation, it became easy to understand.

He further comments, “I felt very fascinated with this and thought, ‘Wow. I never knew about this!’ That night when my father came home, I told him about the interesting TV show. He said, 'Really?’ and he bought me books on mathematics, as he was a researcher. First, I read a junior high school reference book, and then I read a senior high school reference book. After reading those books, I finally read a book for college students.”

Professor Murayama could read college level books while still in elementary school. He also says, “I got into a lot of fights”—when he occasionally went to school.

“Some things I just won’t forgive,” he says. “There was a real bully at school, and when he did something that made me angry, I really fought with him. At home I was mostly sick, and when I went to school I was mostly fighting, so I must have been a difficult child for my parents to raise,” he says with a laugh.
 

His father raised him with a scientific mindset

Later on, his father was transferred to Germany, and Professor Murayama went to the newly-built local overseas Japanese school there, where he demonstrated his character.

“One thing I still remember from the local Japanese school is my social studies teacher. One day this teacher was talking about why there are the four seasons of spring, summer, fall and winter. He explained that the earth spins on a tilted axis, so Tokyo, which is in the northern hemisphere, gets a lot of sunlight in summer. On the other hand, in winter, the earth is in a position opposite that of summer so the southern hemisphere faces more toward the sun and gets lots of sunlight. “I heard this explanation and thought, ‘Wow, so that’s how it works.’ Though still a child, I felt really impressed by all this.”

Professor Murayama, who was then a junior high student, asked the social studies teacher a question. “Well then, the equator has summer two times a year, right?”

The earth spins on a tilted axis, so during Japan’s summer solstice (midsummer) the northern hemisphere faces the sun, and in the winter solstice (midwinter), the southern hemisphere faces the sun. During the vernal equinox and fall equinox, which fall between those periods, the equator is facing straight toward the sun, so when I said, “The equator has two summers” the teacher replied, “Such a stupid thing can’t possibly happen!”

“This got me really mad. Then I did the only thing I could and went to the school library. A look at the temperature graphs for each world region showed that Nairobi in Kenya, which is close to the equator, does in fact have summer twice a year.”

When he showed that book to the teacher and said, “Look, the equator does have two summers,” the teacher said nothing at all and was speechless. “From the teacher’s point of view, I must have really been an annoying child to deal with,” says Professor Murayama.

For the boy Murayama, the idea that the equator has two summers was “a theoretical prediction verified by an observed phenomenon.” Verifying a prediction by data was really the scientific method. Following the scientific method by investigating it in the library showed that the prediction was in fact accurate. In other words, the issue of summers near the equator was solved by applying the scientific method.

How did the boy Murayama learn to apply the scientific method? “I guess, when I was a child and full of curiosity and asked things like ‘Why is it that…?’ or ‘Why does it become that way?’, my father, who was also a researcher, would always give a definite reply. If he couldn’t give an answer, then he would go buy a book providing the answer.”

Spending childhood in such a way helps create the belief that things that may first appear mysterious always have a definite explanation, so encountering a mystery makes one want to solve it.

There are many children like the boy Murayama in elementary school who are full of questions about the world around them and ask adults about the questions they have. But adults often tell children there is no time to give answers, and offer comments like, “Don’t worry about stupid things like that; go do your homework,” or “Eat your dinner first,” or “It’s time for your bath.” They use excuses like this to kill the child’s inquisitive spirit.

“That child then becomes discouraged, believes his question is worthless or that there won’t even be a reply to his question, and totally gives up asking about things,” says Professor Murayama. He continues: “But things could be a lot different if the parent says, ‘Well now, let’s think about this together or let’s investigate this’ when the child asks a question.”

Diversity is completely natural in words and culture

Professor Murayama lived in Japan through the fifth grade of elementary school and from the sixth grade through junior high school attended the local overseas Japanese school in Germany. How did he view his life in another country? 

”Living in Germany was interesting. I was also happy because it was a different environment and I was finally healthy. But besides all of that, just driving by car for a few hours brought me to another country. It was something you cannot experience in Japan.”

The Murayama family lived in Dusseldorf. The border with Holland (Netherlands) was close by, so on weekends he and his parents drove two hours by car to go shopping in Holland. At that time there was no European Union and no Euro. Crossing a country’s border meant a big difference in prices for goods, e.g., buying vegetables in Holland was much cheaper than in Germany.

As they drove from Germany toward Holland, the language also changed. “Namely, as we neared the border, the words people used changed gradually from German to a German dialect and then to the Dutch language.”

For example, the greeting “Good Morning” is “Guten Morgen” in German, but as you near the border this becomes “Yuten Morgen” and finally when you cross into Holland it becomes “Goedemorgen.” The word “Thank You” is “Danke” in German but in Dutch it is “Dank u” which is similar to the English phrase “Thank you.”
“So, words are not something precisely grouped into particular languages and the feeling I get from knowing they are connected to each other is interesting to experience. For example, when buying biscuits at a pastry shop, you will see the main ingredients such as flour and sugar listed in 10 different languages.”

Countries that link to different adjoining countries are a special feature of Europe. Various types of people are linked together in some way but have different lifestyles, and the feeling that this is totally natural is something you don’t see in Japan. What Professor Murayama experienced in Germany would affect him throughout his subsequent career.

“I don’t feel any inner resistance to going overseas. I no longer feel any inner resistance to places where I don’t know the language or to different cultures. In other words, I have a feeling that things will somehow work themselves out,” says Professor Murayama.
 

Professor Murayama played the double bass eight hours a day in college

Professor Murayama illustrating that music, mathematics and physics are all connected.
Professor Murayama illustrating that music, mathematics and physics are all connected.

Afterward, in his senior year of junior high school, the family returned to Japan. But the three years spent overseas going to junior high school were also a factor in making him feel uncomfortable with the environment in Japan—where there are hierarchical relationships and a social norm of not speaking your mind. After attending a senior high school for returnee children and then going on to college, that feeling of unease became stronger and stronger.

“The senior high school students were all returnees from abroad, so the cultural atmosphere was the same as overseas. But this also meant that entering college in Japan was my first real contact with Japanese society. Rules such as having to use polite Japanese to senior students were a real culture shock. Because of that, I didn’t go to classes much,” says Professor Murayama.

He felt that he needed some kind of substitute activity to devote himself to, and so he entered an orchestra group and played the double bass for eight hours a day. What was different from simply enjoying the music was that he was looking and listening to music from a scientific point of view.

For example, he wondered why the tone heard from a clarinet was different from that heard from a violin.

“I liked music since my senior high school days, so I often recorded the sounds from different musical instruments and viewed those sound waveforms on an oscilloscope. Doing that showed me what a big difference there was between a violin waveform and a clarinet waveform,” says Professor Murayama while showing a graph to illustrate this.

Professor Murayama performing on the double bass at Kavli IPMU
Professor Murayama performing on the double bass at Kavli IPMU

The waveform of a sound from a musical instrument is the sum of sounds oscillating at twice, thrice, and four times the speed—and so on—of the basic sound. For a violin, the waveform is the sum of all those sounds, while the sound made by the clarinet gives the impression that something is missing: in the case of a clarinet, all of the even-numbered harmonics are missing.

Also, why does the C chord create a harmony?

”Actually, this is a discovery made by Pythagoras. When searching for a harmony by playing three strings stretched at a fixed strength, a string length ratio of 4:5:6 will produce a harmony. This is the C chord.”

Pythagoras believed that the universe is composed of integers, and he attempted to describe various phenomena by way of numbers. “Pythagoras was a mystic believing in the supernatural and discovering that beautiful sounds could be created from a simple integer ratio of the C chord—that must have made him very happy,” says Professor Murayama.

Professor Murayama’s interest in great people from the past was linked to his fascination with music and, in his college days, his musical performances were said to have reached a semi-professional level. He was also called upon, along with his musical peers in college, to give performances at entrance and graduation ceremonies of high schools in Tokyo.

Encounter with elementary particle physics and setbacks

How did Professor Murayama first get involved with his specialty of elementary particle physics?

“At a seminar in my third year at college, I read for the first time a book on elementary particle physics, and found it extremely exciting. I knew from my high school days that everything around us is made up of atoms, that atoms have an atomic nucleus, and the atomic nucleus contains protons and neutrons. But this book was the first time I heard about the quarks that are in protons and neutrons, the forces acting between these quarks and their properties, and how these particles were discovered. And all of this was written like a historical novel.”

In the summer of the fourth year at college, Professor Murayama couldn’t make up his mind about whether to take a graduate school entrance exam or make a living from music. But he couldn’t shake off the appeal of digging into things to see what more he could learn. So he decided “if it’s going to be physics, then I’ll go with elementary particle physics that deal with the tiniest things.” And so, he went on to graduate school.

However, he ran into a roadblock again. In the elementary particle theory research lab he joined, nobody was researching elementary particles.
“At the time, that research was regarded as out-of-date. When I told the teacher ‘I want to study this (elementary particles),’ the teacher ridiculed me, saying, ‘Why do you still want to do that stuff now?’ So I found myself completely alone at the research lab.”

“At one time, outside lecturers were invited to hold intensive courses at our school.” One of them was one of the few researchers in Japan studying traditional elementary particle physics and he gave a lecture that met Professor Murayama’s expectations. After the lecture, the student Murayama ran up to him and asked to be taught by him. The researcher’s reply was, “Okay, I can teach you, but I will be in the UK for the next two years, so maybe I can teach you when I get back here.”

Two years later, that researcher came back to Japan, and, again, Murayama asked to be taught by him. “Yes, I remember saying I would teach you,” the researcher replied. “But teaching just one person is not very efficient, so find at least 7 students to study along with you.”

“This was a completely unpopular field of study, so I went and persuaded one person at Hiroshima University, two persons at Kyoto University, two persons at the Komaba campus of Tokyo University and two junior students to get the total of 7 persons. In this way, I finally gathered 7 people. A special course then started.”

This was March in the second year of his PhD degree course. That meant he had to complete his doctoral thesis by December that same year. The next eight months starting from April would be an important period that would decide his future success or failure.

”In those eight months, I worked and studied really hard. This was the first time I was able to study what I wanted to study. I kept trying, worked on various types of calculations, and wrote up and submitted my doctoral thesis. However, my paper was almost rejected!”

In most cases, the doctoral thesis review consists of an open process and then shifts to a closed process where the students are questioned by the examiners. Once that is finished, the students leave and the examiners start their discussion. Usually, the students pass the review almost immediately, and if they wait outside, the chief examiner comes out before even five minutes are up and offers congratulations to the student.

“However, I was told ‘Return to the research lab’ instead of waiting outside the room. In the research lab I waited five minutes, then 10 minutes, then 20 minutes but nobody came. After about 30 minutes, a teacher—instead of the chief examiner—finally came.”

Professor Murayama’s doctoral thesis was related to developing software that allowed calculating difficult reactions that had been impossible to calculate up to that time when observing reactions in elementary particle experiments. This involved actually creating software and summarizing various simulation data on a computer. However, the teachers reviewing the experimental side said, “This is not experimental data; these are just calculation results,” and the teachers reviewing the theoretical side said, “This isn’t a theory; this is just computer software.” The meeting to judge his thesis turned out to be a terrible affair.

“After all, ‘Unless you can make these types of calculations, you won’t understand the results—even if you complete the experimental work.’ And so, they apparently accepted my thesis with kindness. Maybe the thesis and contents were bad,” says Professor Murayama. This software in fact has now been used for more than 30 years all over the world. But even though it had tremendous value, almost nobody realized it at that time.

Professor Murayama found that he was unable to do the research he wanted in Japan, so a few years later, he decided to go to the United States.

UC Berkeley: A place where strange guys can win the Nobel Prize

After consulting with various people and thinking about where to go, Professor Murayama decided on UC Berkeley. Looking back on that time, he says with a laugh, “It was a sudden ray of sunshine in my life.”

Professor Murayama saw many talented people at UC Berkeley. He says, “There was a very strange person. He was also the legendary physicist and Nobel Prize winner Luis Walter Alvarez, who discovered several elementary particles. His most famous paper is the ‘Dinosaurs were killed by an asteroid impact’ theory.”

Elementary particles and dinosaurs —in the eyes of an amateur, these are not related, but Professor Luis Alvarez made the connection within his head. “The point here is that a person making elementary particle experiments must have the ability to search out and perceive reactions that rarely occur. For example, that person must have the skill to very accurately sense even minimal quantities of an element.”

Professor Luis Alvarez discovered a highly rich deposit of an element called iridium in a stratum near the Yucatan Peninsula in Mexico. Iridium is extremely rare on our planet but is contained in large quantities in meteors and asteroids coming from outer space. Professor Luis Alvarez therefore thought to himself that an asteroid was the likely source of this stratum.

When he next investigated the age of the stratum, he found it was exactly the time that the dinosaurs became extinct. That is when Professor Luis Alvarez made the connection within his head, “This asteroid is the reason why the dinosaurs became extinct.” Professor Murayama comments, “The archeologists at that time never even considered an asteroid as the reason for the dinosaurs becoming extinct. ‘A physicist came along and said something strange.’ Now his ‘Dinosaurs were killed by an asteroid impact’ has become an established theory.”

Professor Murayama describes an image of the “Big Bang,” as seen on his computer screen.
Professor Murayama describes an image of the “Big Bang,” as seen on his computer screen.

UC Berkeley is a place full of the kind of free thinkers you would never encounter in Japan. The culture there has created a mind-set where one is not bound to a particular field; rather, one is free to apply all of one’s own skills to “solving the problem because it exists” or because “it is an interesting problem to tackle.”

“In this same way, there was another person here called George Smoot, who was awarded the Nobel Prize for being the first person in the world to take a photograph of the Big Bang. Smoot was one of my colleagues at Berkeley and originally carried out research on reactions in a laboratory by using an accelerator. At one point, he suddenly stated, ‘I want to know the start of the universe.’ He then got started, aimed a telescope at outer space and took pictures,” says Professor Murayama with a laugh.

There are many eccentric persons there who were accepted as the norm. That was the spirit of UC Berkeley at the time.

“After going to UC Berkeley, I started finding it highly enjoyable. People used to judge me with comments such as, ‘Your work is out-of-date and you are a person living in an old box.’ But at UC Berkeley, I also felt a new atmosphere of ‘You don’t have to care about the box’ and ‘Anyway you are free to do whatever you want’—which really gave me a feeling of freedom.”

How are elementary particles linked to outer space?

A parking lot at UC Berkeley reserved for NL (Nobel Laureates)
A parking lot at UC Berkeley reserved for NL (Nobel Laureates)

If you walk around the UC Berkeley campus, you will see rows of parking lots for Nobel Prize winners. There are no parking lots for ordinary users on the university grounds or in the vicinity. “And that is why researchers aim for the Nobel Prize — because they want a parking space,” says Professor Murayama, half-jokingly. Being able to see from up close a Nobel Prize-winning colleague who took a photograph of the Big Bang—while doing research on elementary particles—Professor Murayama got the feeling that “elementary particle research and space research are in fact connected!”

However, how is elementary particle research related to space research?

“The universe is the largest object capable of being observed, but the extremely slight ‘fluctuation’ seen in the Big Bang photograph is due to the tiniest elementary particles capable of being observed— with our technology. Elementary particles comply with the strange laws called quantum mechanics. Quantum behavior cannot be completely predicted each time an action occurs, and there is always an element of uncertainty. This uncertainty that is stamped onto the universe takes the form of the fluctuation seen in the Big Bang.”

A quantum fluctuation in elementary particles was the seed of the universe and the source of matter and life. Infinitesimal matter such as elementary particles is what determines the fate of the universe.

“Immediately after the universe started, there was a time when the phenomenon called inflation made it expand so large as if it was torn apart. Because quantum mechanics cannot always predict what will happen each time something occurs, somewhat dense regions and somewhat sparse regions were created within this suddenly expanding universe. There was a lot of dark matter* in the dense regions that pulled in more dark matter through the force of gravity, and the gravity grew stronger and pulled in more dark matter and so on, until the dense regions considerably expanded. This then formed a star when crushed by gravity, and—eventually—a galaxy, and that’s how we were created."

The universe began with inflation, and dark matter brought up matter and life.

“Therefore, the process of inflation that generated quantum fluctuations is the ‘father’ that spread the seeds of the universe, and dark matter that fostered the seeds is the mother that gave birth to us. That’s how it is—that is our universe.”

*Dark Matter: A form of matter that is thought to have a mass but cannot be directly observed optically. The nature of dark matter is still unknown.

If the topic is merging interdisciplinary fields, then the theme is the universe!

In October 2007, Professor Murayama became the founding director of an organization then called the Institute for the Physics and Mathematics of the Universe (IPMU). He says, “I originally had no intention of becoming director. I was asked to write up some organization planning and accidentally became its director, so it all just sort of happened.”

At that time, the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) had launched projects with the goal of achieving “World’s top-level research standards,” “Creating interdisciplinary fields,” “Forming an international research environment” and “Innovating our research organizations.” The projects would be part of the World Premier International Research Center Initiative (WPI), whose goal has been to create research centers having global appeal for the world’s top-level researchers. The University of Tokyo, which has been part of this undertaking, asked for a consultation with Professor Murayama, who was then working at UC Berkeley. They explained that they were gathering researchers in the fields of theoretical physics, experimental physics, mathematics, and astronomy—and planning to create a new research lab with the above concepts in mind. And they asked him how to first go about creating the proposal planning for the initiative.

Hearing this question, what immediately sprang to Professor Murayama’s mind was an image of the roughness of the universe after the Big Bang. He told them, “The theme for this new research lab is the universe.”

”This miniscule roughness of the universe can in one way be thought of as sound. Sound travels through dense and thin locations in air and the Big Bang was the first sound in our universe. Such a sound can be described by mathematics, and how this sound became a star is physics, and the observation of this phenomenon is astronomy . . . I proposed to use this approach. Anyway, let’s just say that this new research institution links mathematics, astronomy and physics along an axis that spans the universe.”

The University of Tokyo also told Professor Murayama that they wanted him to be the director of this new institute. Professor Murayama was 42 years old at the time and the research institution budget for a 10-year period was 13 billion yen.

“I thought there was no way that this large budget would be entrusted to a young man in his forties. Moreover, I had almost no experience in working in Japan, and on top of that, I thought that Japan would not spend money on a field such as outer space—which offered no actual profit,” says Professor Murayama. He continues, “Anyhow, I wrote up the requested planning proposal, listing my name as the founding director, and submitted it, but quite honestly, I thought it would never be approved. However, the planning was in fact approved!”

One-third of the planning examiners were foreigners, from which I conjectured that they thought, “Well, the goal of this program is to change Japan, so let’s approve this plan and give it a try. The overseas examiners probably thought that it would be okay to approve at least one of these somewhat odd planning proposals,” says Professor Murayama with a laugh.

Getting Japanese researchers onto the international stage

Piazza Fujiwara is a 3rd floor space of the Kavli IPMU building where all researchers gather at 3 p.m. each day for tea time
Piazza Fujiwara is a 3rd floor space of the Kavli IPMU building where all researchers gather at 3 p.m. each day for tea time

When the planning proposal for Kavli IPMU was approved, a double-life between the US and Japan—that he had never even expected—began for Professor Murayama. “A hard part was that I no longer had the time to do my own research,” he says. On the other hand, good things were also happening that provided the opportunity to introduce Japanese researchers to the world.

Professor Murayama goes on to say, “Since I was in the US for a long time, I kept wondering why Japanese researchers were not around even though there were a lot of Japanese performing excellent research work.”

Barriers included problems with English and lack of ability to powerfully express oneself. Though they perform fascinating research, there are many Japanese researchers whose work has not been recognized in the US. “I had long thought that this was a total waste of talent and so came up with the idea of establishing a place at Kavli IPMU for an exchange between Japanese and people from overseas. It is a place like Dejima island, where Japan met the Western world,” says Professor Murayama.

More than 10 years after establishing the institute, Kavli IPMU has in fact become a reality. There, the merging of interdisciplinary fields presents an opportunity to study research from other areas—especially those that one is not familiar with—and leads to surprising discoveries.

“For example, in the field of galactic archaeology, the movement of individual stars in a galaxy is observed, and when their movement is reversed, the group of stars is actually found to come not from within the galaxy but rather to have initially come from another cluster. This proves that galaxies merge with each other and gradually develop.”

Far away galaxies are galaxies from the past and generally have small and distorted shapes. These galaxies gradually become large, round, and beautiful shapes as they repeatedly merge with each other.

“In other words, galaxies are getting old, just like us adults. Hardly any galaxies are making stars any more. Almost all of the galaxies around us were formed 10 billion years ago and are in fact aging and making few children.”

However, when old galaxies collide with each other, reactivation occurs and new stars are born in huge numbers. It is said that our galaxy will collide with the Andromeda galaxy 5 billion years from now. “That event will likely create many new stars and give us something interesting to look forward to, after 5 billion years,” says Professor Murayama.

This is the world of galactic archaeology, a field completely different from Professor Murayama’s specialty of elementary particle physics. However, the techniques applied in galactic archaeology will also play a major role in a puzzle that he is trying to solve.

“Galactic archaeologists in fact study the detailed movement of stars in the galaxy and so know at what amount of gravity the stars attract each other. Doing that allows us to know where and what amount of the invisible dark matter is present in the galaxy. Further investigation will allow us to determine whether dark matter is mutually passing through other dark matter like a phantom, or has the appropriate size to allow them to occasionally collide with each other. This has led to new efforts in applying galactic archeology to the study of dark matter.”

This could be a benefit from merging interdisciplinary fields. At Kavli IPMU as a general rule, all researchers gather for teatime at 3 p.m. each day. This may be a difficult custom for shy Japanese to get used to, but it is essential for allowing frank discussions between researchers from different fields.

Future goals and all about the photon

Professor Murayama’s tour of duty as the institute’s director ended last year.  What will be his next goal?

“What I really want to focus on right now is discovering the real nature of dark matter. Dark matter can be thought of as our ‘mother,’ so I would like to meet her. There are now many ways available to investigate dark matter, so I feel we might soon be able to grasp some real knowledge about it.”

What is the next goal, after dark matter?

He says, “I stated that the seeds planted by the initial inflation of the universe were fostered by dark matter, but if there are no atoms to serve as material, those seeds won’t grow. But when the universe was first born, there were no atoms, and when matter was created, antimatter was created along with it—and when both are left in this 1-to-1 relation, the matter and antimatter will cease to exist.” But if matter and antimatter cancel each other out, then the universe should be empty. Which leads one to ask: why are we living and breathing here now? Professor Murayama says:

“I believe that slightly disrupting the balance between matter and antimatter leaves a very small asymmetry and the remaining asymmetry is us. Well, then, how was this asymmetry created? That brings us to expectations for the neutrino. Research is progressing on using gravitational waves to investigate the mechanism that generates the asymmetry between matter and antimatter. Up until now, these things were thought to be absolutely unrelated; but now, there is a general feeling that these are possibly somehow connected.”

While trying to unlock a mystery, a connection is gradually starting to appear little by little, something like the relation between dinosaurs and elementary particles, and this awakens our endless curiosity.

Lastly, we would like to ask about the photon, which is one of the elementary particles—and the theme of this webpage. What can you tell us about photons?
“Well, the image I have of them is that they are white, small particles that turn round and round. They also give us a great deal of information.”
So, what kind of a role do they play?

“Well, say there is a galaxy some billions of light years away from us. Photons from that galaxy scatter in all directions. These photons travel for some billions of years and some of them even somehow make it to our planet. And that alone is a miracle in itself.”

“Thanks to these photons, we can view the state of faraway galaxies. In fact, taking a close look reveals various colors, and analyzing the makeup of those colors shows where, how many, and what elements there are—and how they behave and move. So these photons give us a terrific amount of diverse information.”

The photon is one of the elementary particles* in Professor Murayama’s specialized field and the real identity of light that is all around us. The electron is also one of the elementary particles. We humans live a “miraculous” existence, born on a planet called Earth in a solar system in a corner of the galaxy within a vast universe. Making use of light and electrons that miraculously reach our planet from somewhere in the same universe, we’re stuck to Earth’s surface and lead our lives as individuals carving out a 4.8 billion-year history along with diverse kinds of other living creatures. However, all of that is only a tiny fragment of the truth behind the universe. We still do not fully understand photons, other elementary particles, and dark matter and dark energy. Even the mind contains secrets of how it was born and how it works so wonderfully.

The famous words “The universe is written in the language of mathematics,” by Galileo Galilei, are inscribed on a pillar (obelisk) in Piazza Fujiwara at Kavli IPMU. Reading it seems to naturally make us think, “I want to know more about the world!” This is the inspiration we get from the life of Professor Murayama and the mission of Kavli IPMU.

* The following 17 types of elementary particles have been discovered or predicted by the Standard Model of particle physics

I want you to know that there is a world we don’t know about

Professor Murayama
Professor Murayama

Professor Murayama, his eyes lighting up with excitement after talking about science and the universe, also introduced a book he would like young people of the next generation to read: “The Adventures of Mr. Tompkins,” by George Gamow. The book conveys the world of quantum mechanics by way of easy-to-understand adventure stories.

“I think it’s good to know that there is a world that we don’t really know about. Our real world is a surprising place that doesn’t need science fiction to make it interesting.”

The GPS (global positioning system) we take for granted in our lives would not function at all if we did not apply the theory of relativity. I think as adults, we must take responsibility for helping our children focus on science, a subject that also happens to make our lives more convenient. If children ask us “Why?” we should be patient and answer their questions as best we can without acting as if giving them an answer is an annoying chore.

Professor Murayama often tells students at UC Berkeley, “Once you find and understand the problem, it’s already half-solved.” He also advises, “Don’t just vaguely say, ‘I don’t understand.’  Instead say, ‘Here is what puzzles me,’ and if you can do that, then you will start seeing what you now have to do.” This is a basic problem-solving principle that works for both adults and children.

Professor Murayama felt the expansiveness and diversity of the world while still in the early stage of his life, and chose a path and environment that developed his own talents. By focusing on what he tells us, we can get a wide-ranging hint about fostering the young people who will sustain the growth of science in Japan—and our future.