A translator for the universe

Hitoshi Murayama is a physicist who thinks big. Really big.

“This is a redshift cosmic microwave background radiation picture of the Big Bang 13.8 billion years ago, or 380,000 years after the birth of our universe,” Murayama tells an audience at the Council for the Advancement of Science Writing’s New Horizons in Science briefings at the ScienceWriters2024 conference in Raleigh, N.C, Nov. 10.  On the screen is a projected image of the cosmic microwave background (CMB), made from data collected by telescopes outfitted with mirrors large enough to detect waves of light as faint as a 100-watt light bulb on the moon’s surface. “Remember that,” Murayama says. “It will be useful in a minute.”

In the next slide, Murayama extracts the red and blue pieces from the CMB map and converts them into three-dimensional bins that are 8 billion light-years in width, 1 billion light-years in height, and a significantly shallower 250 million light-years in depth. Murayama explains that the colors represent differences in temperature density, with blue signifying colder regions and red for hotter and denser regions. Physicists use these measurements to understand fundamental questions about the universe, which Murayama pursues in his work: How did the universe begin, why do we exist within it, and even—dare we ask—how will the universe end?

Murayama began his quest to answer these questions as a student at the University of Tokyo, where he earned his doctorate in particle physics in 1991. That same year, construction began on both the Subaru telescope on Mauna Kea, Hilo, Hawaii and the Super-Kamiokande observatory, a neutrino observatory in Japan. 

After his talk, I spoke with Murayama about why he got into science, how he came to chair the Particle Physics Project Prioritization Panel (P5), and what the future of physics looks like in a warming world. Our conversation has been edited for length and clarity.

CN: Could you tell me about how you first got into science? I read that your childhood asthma played a role.

HM: Yeah, my asthma was really bad. I was getting an IV a couple of times a month, and because I was so sick, I had to find something to do at home. I had to figure out what I would be interested in. And watching some of the educational programs was great in those days.

One of the shows I watched was about the smell of Japanese eel. I love eating eels. And the show was exploring, What about smells is so interesting? There was one stand where the cook was grilling eels and a strange guy appeared. And this guy keeps smelling the aroma and goes back, never buys it. And in the end, this cook got mad at him, and he gave him an invoice for smelling the eel.

To figure out if he has to pay for it, they start to put a glass shield between them, and then there’s no smell. Something is floating through the air from the grill to his nose. And so that kind of story really got my attention—the fact that you can smell something is based on some principles. These are the kinds of things that attracted me to understand things more and more at the more basic levels. And math was one of them.

CN: How did you go on to study math and physics?

HM: One thing I learned over the years is that mathematics is a language, and you have to use that language because the human language wasn’t developed in a way of describing things we don’t experience in daily life. Like in quantum mechanics, the particle is a wave, and the wave is a particle. A single particle can pass through many paths at the same time. You never know which path the particle took. These concepts are very difficult to understand using plain English. You have to rely on mathematics to do that. So once you actually get this idea that you have to rely on math to describe physics, then in some sense, you’re forced to learn about it.

Physics was attractive because it’s so simple and you can really break down things to some basic levels and build up from it. That’s the joy of actually doing physics. I understand why the sky is blue, why the sun is red, why things look the way they do, why we can do wi-fi through the walls. And these things can be really explained from the basic principles.

CN: How did you come to chair the P5?

HM: I was nominated. First, there was the community consisting of thousands of physicists who run a series of workshops called the Snowmass process, because we initially met in Snowmass, Colorado. The purpose of Snowmass is to provide a bottom-up process, and everybody joins in and argues what they like to do. Then the P5 process was started by the funding agencies. After a consultation between Snowmass and P5, the decision was made that somebody should run the process, and for some reason, they chose me.

When I met with agency folks after they decided to pick me, I wanted to back out. I told them I was scared to death to do this, and they said, “That’s why you’re qualified.”

CN: What did they mean?

HM:  Well, apparently, they had been contacted by many people, especially senior people in the community, that said, “I know the answer. I know what to do. It’s easy. Let me run it.” Meanwhile I was turning it down, and that’s when they knew I was the right person for the job.

When you have a panel of physicists talking to each other, and we have to come up with major decisions, and they all feel very strongly about what they do, it can be challenging at times.

But when I appointed them to serve on the panel, I told them at the beginning that this is not about promoting a particular field of yours. You are great scientists. You have to think broadly about what is the best for the community, not to you. And they took that work very seriously.

CN: Can we investigate theoretical questions about the physical universe if we cannot do the math like you can?

HM:  I think so, because math, as I said, is a language that is meant to describe physics in a very robust, rigorous, precise way. But you can have a more casual conversation. If you’re talking about music, then the talented musicians can really analyze how the piece is structured. What themes are there? What kind of special attention was paid to instrumentation? But you can also have a much more casual conversation. “Oh, that was great. It made me weep. That made me laugh.”

At that level, everyone can talk about music. There are different levels of conversation you can have. And all levels of conversation, I believe, are meaningful.

CN: As we are approaching COP29, do you see climate change having an impact on your research in the coming decades?

HM:  Oh yeah, we do. It seems to be accelerating. That’s what we feel now instead of just talking or a piece of paper. So it’s getting more and more serious, it seems to me, and it definitely affects how we conduct research. Some of these machines, particle accelerators, can consume a lot of power, and we must think about that. Additionally, if you build a big accelerator, you must dig an underground tunnel. Concrete is one of our modern society’s most significant carbon dioxide sources. And we don’t have a good alternative to concrete at this moment. So we pay attention to these things.