Hong Joo Ryoo '24 on the Intersection of Philosophy and Physics

June 27, 2025

Hong Joo Ryoo is a UC Berkeley alum, having completed a quadruple major in Math, Physics, Philosophy and Cognitive Science in 3.5 years. He is currently pursuing a dual graduate degree at Johns Hopkins University, working toward a PhD in Physics and a Masters in Philosophy as a National Science Foundation (NSF) Graduate Research Fellow. At Berkeley, he was a recipient of the SURF and Rose Hills Fellowships, and was also a member of the Arts & Humanities Dean's Leadership Team. His work centers an interdisciplinary approach, situated at an intersection between physical and philosophical inquiry. 


I would love to hear you introduce yourself! What are some of your main interests, and what did you study while at Berkeley?

I’m Hong Joo. I’m involved in both physics and philosophy, and I’m generally drawn to the deepest questions about reality and truth.* I know that’s super broad, but as always, assume there’s an invisible footnote behind every sentence. When you’re speaking with philosophers, you need to be super precise, and it’s the same with physicists. 

To explore these questions more fully, I work at the intersection of the two fields, seeing how they mesh and drawing out their differences to get a fuller picture of what’s going on. Have you heard this quote?

To develop a complete mind: Study the science of art; Study the art of science. Learn how to see. Realize that everything connects to everything else.

It’s by Leonardo DaVinci. That line has stayed with me because it perfectly captures the interdisciplinary spirit that drives my work.

My curiosity took shape at Berkeley, where I completed an interdisciplinary undergraduate path and wrote an Honors Thesis in Physics during my senior year. Now, I’m pursuing graduate studies in both disciplines at Johns Hopkins, and I am continuing to explore how these fields intersect.

*These questions include: What is the fundamental ontology of the universe? What is everything made out of? Can we have a theory that explains every phenomenon? How are we to best understand the world around us? What is the relationship between our perception and logic? What are the preconditions for these questions to even make sense?

Can you describe some of your recent research projects, in both physics and philosophy?

Of course. A good starting point will be my honors thesis, with Professor Yasunori Nomura. I explored the paradoxes that arise when quantum mechanics meets black hole physics. These paradoxes are called the “information paradox” and “firewall paradox”. The problem here was that there are different effective formulations for how the black hole’s quantum state should be, so I examined how those formulations come together with proposed solutions for those paradoxes. This is physical and philosophical. A lot of these solutions invoke the idea of complementarity. It’s essentially the notion that certain physical features may manifest differently depending on the observer’s position, motion, or access to information. Famous examples include the wave-particle duality, black hole complementarity, and the Unruh effect. That was my physics project during my second year. 

Building on this, I noticed that many philosophical accounts of explanation try to generate a sense of understanding through structured relationships between propositions. Traditional models often overlook how outcomes can vary depending on the observer’s perspective or reference frame—this, again, is the idea of complementarity. In a recent paper, I developed a mapping structure within the philosophy of explanation that incorporates these context-sensitive features by grounding explanations in specific observational inputs. If I’m outside of a black hole, these solutions tend to play out one way, but if I’m falling into a black hole, it works differently. The mapping incorporates features like this one by grounding explanations in a specific observational context. This approach lets philosophers draw on a deeper layer of physics, particularly the kinds of simultaneity and relationality seen in quantum mechanics. It’s useful in the philosophy of explanation, because it captures how context is relevant to an explanation; where you are or and how much you accelerate makes a difference to the outcome of the phenomena. 

Right now, I’m working on two fronts in philosophy: (1) situating this mapping within the broader landscape of the philosophy of explanation, and (2) developing physics-informed arguments for what constitutes a context in such frameworks. My upcoming work at Johns Hopkins will examine how different contexts of this mapping, and potentially some metaphysical commitments, may emerge from various foundational frameworks in physics. For those who are curious, these include abstract mathematics like C*-algebras, non-Markovian dynamics, Hilbert spaces, and the numerous interpretations thereof. Meanwhile, we’re seeing rapid progress in technology, from quantum computing to artificial intelligence and advanced photon detectors. In a recent project in theoretical nuclear and particle physics with Professor Raúl Briceño, I showed support for a method that uses mathematical functions (correlators) accessed from quantum computers. These are then used to calculate scattering observables, which are key to predicting how particles interact. This method helps overcome difficult problems in low-energy regimes and provides more robust theoretical inputs for large-scale experiments. 

Speaking of experiments, I also worked on the Eos particle detector, with Professor Gabriel Orebi Gann, from its earliest stages to full construction. At the Lawrence Berkeley National Laboratory (LBNL) and in the former nuclear reactor basement of Etcheverry Hall, I carried out calibration studies to characterize novel photon detectors that go within the detector. Eos is a first-of-its-kind, large-scale hybrid detector that distinguishes between different kinds of light (Cherenkov and scintillation) produced during particle interactions. This dual-light capability enables both directional and energy reconstruction within a single device. It offers an exciting example of interdisciplinary research and has various societal motivations including fundamental physics, engineering R&D, and nuclear nonproliferation. 

As technology advances, it transforms both what we can observe and how we come to understand and explain it. Scientists, philosophers, and society alike may find that as our tools evolve, so do our ways of making sense of the world.

How have you found your research in STEM to differ from your work in philosophy, and where are points of intersection between the two? 

My experiences in both disciplines grapple with the foundations of our universe, truth and knowledge. It’s clear that the similarity is that they both ask ambitious fundamental questions, at least in the realms that I operate in. 

The difference between these two lies in who I’ve asked my questions to. For physics, I’ve asked the world directly. I have asked the particles within quantum computers about how other particles behave. I asked the photon detectors about how many experimental events there were in the last 60 nanoseconds. I’ve asked the world for their observables and their data sets. In philosophy, I’ve had to ask humans these questions. In philosophy of explanation — who am I explaining to? We ask ourselves, we ask our collaborators, what other people value in an explanation, and what counts as a ‘correct’ explanation to us. It all depends on who we’re asking. What makes a good explanation? Do we have contradictions? Are we OK with contradictions insofar as we get the results we want and we’re satisfied with how those do not affect our conclusions?

I know that an interdisciplinary approach can be intimidating to undergraduate students, who may not feel as comfortable working in multiple fields. Do you have advice for students who are interested in an interdisciplinary approach, but nervous to try it? 

I wish I had more guidance in this myself, as a student navigating this right now. One thing I’ve learned from an interdisciplinary path is that academia doesn’t have to mean choosing one lens through which you get to see the world. Instead, it’s about how learning different ways of thinking sharpen and challenge each other. Remember that knowledge isn’t neatly divided, and is often really messy, sometimes connected, and ultimately human. 

For students who are interested in these multiple disciplines, I would say to lean into that curiosity. Don’t wait for permission to cross boundaries, since a lot of these exciting ideas happen at the edges anyway. UC Berkeley is a wonderful place to pursue your interests. Let your questions guide you, even if they don’t fit neatly into one department’s expectations. Often, the structure of academia follows those who lead with curiosity. 

Do you have advice for undergraduates who are interested in pursuing graduate studies? 

When applying for PhD programs, prioritize universities that will best accommodate your ambitions. Will this environment let you grow in the ways that you care most about? Will you be surrounded by people who challenge and inspire you? The right program is one where your questions are taken seriously, and your goals are met with genuine mentorship. For me, this was Hopkins by a mile. 

Refine what drives you. Graduate school isn’t necessarily about being good at something. It’s more about caring enough to stay with the hard problems for a long time. Typically, graduate programs are very long, so your motivations should be clear to yourself and in the application materials. Don’t be afraid to reach out to faculty beforehand; fantastic programs are looking for people who are beyond their resumes.

Funding opportunities like the NSF GRFP can also give you more flexibility in choosing programs based on fit rather than just financial considerations.

What are some of the undergraduate opportunities you pursued that you would recommend other undergraduate students to look into?

In physics, there are tons of funding opportunities, like SURF, Rose Hills Research Scholarships, department funding like BPURS, or organization funding like N3AS and LBNL. There are a ton of mentorship programs as well, like ULabs, MPS. Professor Raúl Briceño hosts Python4Physics and REYES which also do wonderful mentorship programs. 

In philosophy, I would recommend taking seminars. You get exposure first-hand to an environment where you discuss modern literature and, depending on the class, it’s often very intensive which allows you to train your philosophical thinking on the spot. For example, my graduate seminar, with Professor Ezra Rubenstein, was a launch-pad for philosophy research to test ideas and to receive valuable feedback.

Always apply to funding opportunities as well, and don’t doubt yourself. You get feedback from all of these anyways, so even if you don’t get it, don’t let it take away from your motivation. It’s not just about whether you're a fit for the program; it’s also whether the program is a fit for you. Keep it clear to yourself and, again, refine what drives you.

What book would you recommend to everyone reading this interview?

I took French for my R1B class, and the book that stands out both from my undergrad is a book from that class. It’s a book called The Stranger by Albert Camus. It’s a must-read for people who are interested in philosophy and literature. It taught me the importance of recognizing that, absurdly enough, the world does not owe us an explanation, as much as we’d like it to. It’s more important to ask our questions critically and then to reflect on our endeavors with an open-mind.