travel – VISMAYA – History & Philosophy of Science

Frankfurt in 5 hours…

On my way back to India from Leipzig, I spent an evening in Frankfurt (19th Sept 2025). I arrived on an intercity train from Leipzig to Frankfurt in the late afternoon and had about 22 hours for my flight. I quickly checked into the hotel, did a bit of research online and picked a few places to visit in the evening. As suggested, I took a 1-day train ticket and went to Frankfurt Hauptwache, and visited the following places on foot: Museum of Modern Electronic Music, city center walkway, Iron Bridge, love locks on the bridge, walkway around the bridge, including a beautiful view of the sunset and cruise ship, the historical Römerberg that has statues of Minerva and the goddess of justice.

It was a long walk on a bright evening, and what a few hours of historical learning…pictures below.

Bach @ Leipzig

The musician Johann Sebastian Bach (1685 – 1750) has a major presence in Leipzig, Germany. As one walks across the streets of Leipzig, one will find Bach’s presence in the form of symbols and statues. His presence is felt both in the lavish churches and in the open markets, which indicates his influence in the period. A museum adjoining St. Thomas’ church has many musical instruments and notes that belonged to Bach. When I visited this place, the organ was being played, and the quality of the acoustics was excellent. Below are a few snapshots from the visit (15th Sept 2025).

Leipzig – where Heisenberg worked…

From 16th to 18th Sept, 2025, I attended and gave a talk at Optofluidix 2025, thanks to the invitation of Prof. Frank Cichos and his team, Department of Physics, University of Leipzig.

This department is steeped in history, and this post is to give you a pictorial glimpse of some people who worked there.

Werner Heisenberg, aged 25, became a Professor at the University of Leipzig, Germany. It was an illustrious department then, had professors such as Peter Debye, Gustav Hertz (of the Franck-Hertz experiment fame), Friedrich Hund and many others. Felix Bloch was a student of Heisenberg in Leipzig.

As the AIP archives describe, “Only 25 years old in October 1927, Heisenberg accepted appointment as professor of theoretical physics at the University of Leipzig, Germany. Friedrich Hund soon joined his former Göttingen colleague as Leipzig’s second professor of theoretical physics. Heisenberg headed the Institute for Theoretical Physics, which was a sub-section of the university’s Physics Institute, headed until 1936 by the experimentalist Peter Debye. Each of the three professors had his own students, assistants, postdocs, and laboratory technicians.”

Below are a few snapshots that I took while visiting the department. Special thanks to Diptabrata Paul (my former PhD student and currently a post-doc in Cichos’ group) for showing me around the department.

Sir MV on Education

In India, “National Engineers’ Day is celebrated every year on September 15 to honor the birth anniversary of Sir Mokshagundam Visvesvaraya, one of India’s greatest engineers”. Sir MV, as he was known, is one of the 20th-century Indians I admire. He was a forward-looking statesman who contributed immensely to building India (literally and figuratively). MV was a well-read and well-travelled person for his era, and wrote a few books and memos that are still pertinent to the current developments in India and the world.

Reconstructing India (1920)

One of his books, Reconstructing India (1920), reveals his thoughts on how and why India needs to reconstruct itself based on knowledge in science, technology and humanities. The title page is shown below, and the book is free to read online, thanks to the Internet Archive.

The book, as mentioned by MV in the preface, was written just after the First World War, and contemplates problems faced by India in light of geopolitical developments. In the 17 chapters of the book, divided into 4 parts, MV discusses specific issues faced by India, and proposes that political and administrative reforms can help India become a progressive society.

The largest part of the book is on economic reconstruction, in which he proposes contemporary methods (for the 1920s) to improve various sectors of manufacturing, including agricultural technology and communication media.

The third part of the book is on social reforms, and in there, he has a dedicated chapter on Education, which caught my attention, and I found it relevant even for today’s India.

Education, Humanities, and STEM

It is important that students of science and technology have a good exposure to some aspects of the humanities, including economics, history and philosophy. The pursuit and ability to choose good problems in science and technology critically depend on the social and economic structure in which they are practiced in universities and research institutions. MV anticipated this and highlights it as:

“Secondary and university education, though producing many able recruits for subordinate positions in the Civil Service, does not provide the men needed to carry on the work of agriculture, engineering, commerce and technology. The provision for training in economics and history is inadequate, and the study of those subjects is even discouraged. An attempt is actually made to teach economics in such a way as to render India’s emergence from a state of dependency difficult.”

Even in 2025, I would suggest that STEM students pay attention to economics, as it anchors them to understand the need and functions of a society, and therefore, their work can be calibrated accordingly. This is not to discourage open-ended research, but to understand how natural sciences are connected to the societal thoughts and needs. It gives us a broader understanding of the context, which is so important while understanding the evolution of ideas.

Comparative Education Systems

There is always a lot to learn from various societies and cultures. In order to do so, one needs comparative analysis. This helps one to choose some good elements from a society that can be emulated elsewhere. MV compares and comments on the 1900s British educational system in contrast to the German and Japanese counterparts. Note that India in the 1920s was still a British colony, and in a way, MV is critical of the system in which he himself was educated and trained. As he notes:

“Britain herself has had to pay a heavy price for her hand-to-mouth policy in regard to education. The educational chaos still existing there compares unfavourably with the great yet orderly progress made by Germany and Japan, both of which countries, after weighing and testing the educational systems of the world, absorbed the best of all.”

These were words written long before the Second World War, and give us a glimpse of how German and Japanese systems were functioning in the 1920s and had a lot to offer to the world. Of course, history took its own path, and German and Japanese society had other ideas.

Incidentally, I am writing this piece sitting in Leipzig (eastern Germany), and I am amazed by its architectural marvels that date back centuries. Indeed, German society had (and has) a lot to offer to the world. As MV indicates above, we need to absorb the best that is on offer. In doing so, we also need to reject that which is not good for any society.

Liberal Education and Financial Support

He further adds how liberal education adds value to a society, and calls not only the government but also the people to recognize the importance of financial support for education.

“Both the Government and the people must recognize that only by pursuing a liberal educational policy, and making generous financial provision for schools and colleges can they lift India out of her present low condition and ensure rapid progress.”

These words still hold good, and as a society, India has to re-emphasize modern education that helps us become not only better doctors and engineers, but also better human characters that can add value to the “modern” world.

Call to Action

In the final part of the book, MV makes a passionate appeal to the people of India, calling them to take action and move towards becoming a progressive nation:

“Do the people of India propose to profit by the lessons which world experience has to teach them, or will they be content to allow matters to drift and themselves grow weaker and poorer year by year?
This is the problem of the hour. They have to choose whether they will be educated or remain ignorant; whether they will come into closer touch with the outer world and become responsive to its influences, or remain secluded and indifferent; whether they will be organized or disunited, bold or timid, enterprising or passive ; an industrial or an agricultural nation ; rich or poor ; strong and respected, or weak and dominated by forward nations. The future is in their own hands.”

Indeed, the future is in our hands, and these words written more than 100 years ago still resonate loudly. We need more engineers like Sir MV. The reason he was so effective was that he combined thinking and doing. Importantly, the lesson we can learn from MV’s life and by reading this book, is that an open mind can grasp good ideas at any time and anywhere. Implementing those ideas is an equally important challenge, and MV was up to this in his own way. Are we, as Indians, open to this prospect and engineer our future?

ConForce 25 – highlights

From 15th to 18th June 2025, I attended a focused meeting called ConForce.

The location was at an interesting place: Casuarina Resort Park- Kurunji, which is about 70 km from Pune. It was a scenic and raw place, with an amazing landscape. The resort facilities were ok with limited facilities, but the landscape was just breathtaking. It rained almost all the time, but it created a wonderful visual across the horizon with lush green patches of mountains and grey clouds (see image).

The main theme of the meeting was related to force spectroscopy, with a greater tilt towards biophysical applications. I spoke in the optical tweezers section and enjoyed the discussion with various participants and speakers. Specifically, I presented some of our recent, unpublished work on optical binding and its optical perturbation.

From Yukawa Archives: a draft, a letter & a rejection

I have been amazed to explore the archives on Hideki Yukawa, which have been systematically categorized and meticulously maintained by Osaka University in Japan. My sincere thanks and acknowledgment to the Yukawa Memorial.

Below are a few gems from their public archives :

Draft of the paper written in 1934 – The making of the groundbreaking paper of Yukawa, which eventually led to his Nobel Prize in 1949.

The archive draft is accompanied by a note which reads:

Yukawa had not published any paper before then. In 1933, Yukawa began working at Osaka Imperial University and tackled the challenge of elucidating the mystery of nuclear forces while Seishi Kikuchi and other prominent researchers were producing achievements in nuclear physics and quantum physics. The idea of γ’ (gamma prime) that Yukawa came up with in early October led to the discovery of a new particle (meson) that mediates nuclear forces. The idea of introducing a new particle for the purpose of explaining the forces that act between particles was revolutionary at that time. Yukawa estimated the mass of the new particle and the degree of its force. No other physicists in the world had thought of this idea before.

2. Letters between Tomonaga and Yukawa

Sin-Itiro Tomonaga was a legendary theoretical physicist from Japan, who independently formulated the theory of quantum electrodynamics (apart from Feynman and Schwinger) and went on to win the Nobel Prize in physics in 1965.

Tomonaga was a friend and classmate of Yukawa, and they inspired each other’s work. Below is a snapshot of the letter from 1933 written in Japanese.

Both these theoreticians were intensely working on interrelated problems and constantly exchanged ideas. The archival note related to the letter has to say the following:

During this period, Yukawa and Tomonaga concentrated on elucidating nuclear forces day in and day out, and communicated their thoughts to each other. In this letter, before starting the explanation, Tomonaga wrote “I am presently working on calculations and I believe that the ongoing process is not very interesting, so I omit details.” While analyzing the Heisenberg theory of interactions between neutrons and protons, Tomonaga attempted to explain the mass defects of deuterium by using the hypothesis that is now known as Yukawa potential. The determination of potential was arbitrary and the latest Pegrum’s experiment at that time was taken into consideration. Tomonaga also compared his results with Wigner’s theorem and Majorana’s theory.

3. Rejection letter from Physical Review

Which physicist can escape a rejection from the journal Physical Review?

Even Yukawa was not spared :-) Below is a snapshot of a rejection letter from 1936, and John Tate does the honours.

The influence of Yukawa and Tomonaga can be seen and felt at many of the physics departments across Japan. Specifically, their influence on nuclear and particle physics is deep and wide, and has inspired many in Japan to do physics. As the archive note says:

Yukawa and Tomonaga fostered the theory of elementary particles in Japan from each other’s standpoint. Younger researchers who were brought up by them, so to speak, must not forget that the establishment of Japan’s rich foundation for the research of the theory of elementary particles owes largely to Yukawa and Tomonaga.

4. Lastly, below is a picture of the legends from the archive: Enrico Fermi, Emilio Segrè, Hideki Yukawa, and James Chadwick.

From the archive note on the picture from September 1948:

Yukawa met Prof. Fermi and other physicists of the University of Chicago who were staying in Berkeley for the summer lectures. From the left: Enrico Fermi, Emilio Segrè, Hideki Yukawa, and James Chadwick.

Tomorrow, I will conclude my third trip to Japan. I always take a lot of inspiration from this wonderful country. As usual, I have not only met and learnt a lot from contemporary Japanese researchers, but also have metaphorically visited the past masters who continue to inspire physicists like me across the world.

For this, I have to say: Dōmo arigatōgozaimasu !

Where Ideas Merge: A Visit to the Institute of Science Tokyo

New ideas are often created by the merging of two old ideas. How often is this true, and how often do we tend to forget this?

Today I visited the Institute of Science Tokyo, formerly known as Tokyo Tech. This is a new avatar of a very interesting institution funded by the government of Japan. By merging the Tokyo Institute of Technology with the Tokyo Medical and Dental University, a very interesting concept has emerged: the Institute of Science Tokyo. These two institutions have been important pillars of the research and educational landscape of Tokyo, and I had the privilege of visiting this new place, which is a result of a new merger.

Thanks to the invitation and fantastic hospitality of Prof. Daiki Nishiguchi, a faculty member in the Physics Department of the Institute of Science Tokyo, I had a memorable experience. I met Daiki a couple of years ago at the University of Tokyo, where he previously held a faculty position. Recently, he has moved to the Institute of Science Tokyo to establish his independent research group as an Associate Professor.

Daiki has done amazing work on topological soft matter, and his recent results include remarkable observations related to turbulence and vorticity in suspensions of bacteria under spatial confinement. He has also been setting up interesting experiments involving Janus particles, and I got a nice overview of his work. Thanks to him and his research group, I got a flavor of the research being carried out in their lab, and I was also treated to a wonderful lunch by Daiki.

I gave a physics seminar on some of our work on structured light and confinement of soft matter, especially thermally active colloidal matter in optothermal potentials. Since Daiki and his group (see image below) have expertise in topological soft matter, my seminar emphasized structured topological beams, including ring optical beams and optical vortices. I gave an overview of our experimental results and highlighted the prospect of utilizing the topology of light to interact with topological soft matter.

There is much to explore at this interface, and again, it brings me back to the point that new ideas often emerge from the merging of evolving old ideas, such as topological light and topological soft matter.

This is my third visit to Japan, and I always find their calm, focused, and deeply committed research environment inspiring. There is much to learn from their approach to science and technology, and my visit to the Institute of Science Tokyo reinforced this thought.

I thank Daiki and his research group for the wonderful time I had at their laboratory and offer my best wishes to him in his new explorations.

Talk at Kyoto University

Whereas Sunday was bright, sunny, and clear for outdoor activities, Monday started cloudy with a forecast of rain. I started from my living place to Kyoto University around 10 in the morning. I took the city bus, which shuttles people from the city centre to the university. Within half an hour, I was in a serene, green, and beautiful campus, typical of a Japanese university. Kyoto University has a rich blend of modern and ancient architecture, and I was not surprised to see a large maroon-coloured ark at the entrance of the university.

With Prof. Tetsuro, who hosted me at the Graduate School of Informatics at Kyoto University.

I met Tesuji Tetsuro upon arrival (our previous in-person meeting was in the 2023 Optics & Photonics Congress on optical manipulation at Yokohama). He had just arrived from his run (he is a regular marathon runner), and we had a brief chat. He had arranged an office for me to occupy for the day. We had a short discussion and thereafter went for lunch. Prof. Kazuo Aoki (Tetsuro’s erstwhile advisor at Kyoto University) accompanied us, and I was delighted to meet him. We had a delicious lunch at a small Italian restaurant.

Around 3 pm, we met at the seminar hall where I gave my talk titled Hot Brownian Dynamics Driven by Structured Light. One of the key points I emphasized in my talk was the relevance of structured light in driving Brownian dynamics of colloids. I spoke about various parts of the stochastic differential equation (see equation 1 below) that represent the dynamics of a colloidal system interacting with an external force.

A key element of my discussion was the generalized driving force on the right-hand side of the equation, where the conventional restoring force in an optical trap can be generalized to an external driving force due to structured light. This versatile force is a result of a large set of linear and angular momentum states of structured light. These states can drive soft matter, further resulting in unconventional assembly and dynamics. Furthermore, the generalized driving force can include not only the optical force but also the thermal and hydrodynamic effects initiated by optical illumination. The combination of these forces culminates in a resultant force, offering an unconventional driving mechanism to drive the structure, assembly, and dynamics of colloids and other kinds of soft matter systems, including droplets and fluids. I showed some of our experimental results related to the above-mentioned concepts with emphasis on rotational and orbital degrees of freedom. I also presented our recent results on synchronization in an optothermal trap.

We had a long discussion on how to measure fluid dynamic properties around such colloids, especially when there is an external perturbation force, such as a laser beam, which can itself influence the colloidal dynamics. Tetsuro also mentioned his protocols and certain simulation strategies utilized to study thermo-osmotic flows in such situations. I learned about interesting methods they have been developing to numerically simulate the interactions using differential temperatures. The strategy is interesting and deserves further attention by the community. He also showed his experimental setup and gave a tour of his laboratory facilities.

Overall, it was a long, thoughtful day with wonderful discussions on topics of common scientific interest. We ended with a delicious dinner at a Japanese izakaya, and I thank Tetsuro for his invitation and hospitality. Kyoto University has a wonderful atmosphere for research, and I hope to visit again.

Kyoto digital archives 02 – Japan’s physics Who’s Who…

Continuing on archival research on physics @ Kyoto, I found a remarkable photo.

The who’s who of Japan’s theoretical physics (and future Nobels) in 1951. They were meeting at Kyoto to establish an inter-university research institute.

This photo was further reproduced at :

Takaiwa, Yoshinobu, Masako Bando, Haruyoshi Gotoh, Hisao Hayakawa, Kohji Hirata, Kazuyuki Ito, Kenji Ito, et al. 2014. “Memorial Archival Libraries of Yukawa, Tomonaga, and Sakata.” In Proceedings of the 12th Asia Pacific Physics Conference (APPC12). Vol. 1. JPS Conference Proceedings 1. Journal of the Physical Society of Japan. https://doi.org/10.7566/JPSCP.1.019005.

Kyoto digital archives 01 – Yukawa’s book

Duff’s famous physics textbook from 1900 (5th edition) owned by Yukawa

Yukawa’s name on the book

Hideki Yukawa’s picture on the Nobel website

Apart from sipping the wonderful Japanese coffee and exploring the streets of Kyoto on foot, I have been looking into the archives of Kyoto University. I am mainly searching for records and books related to their physics department, and obviously, one of the names that pops out very often is Hideki Yukawa.

Yukawa was one of the Nobel laureates from this university. He obtained his Nobel Prize in Physics in 1949 for his prediction of the existence of mesons on the basis of theoretical work on nuclear forces. He is a big name in physics, and there is a physical potential named after him, which means one can understand the intellectual heft he carries as a physicist. Yukawa spent most of his scientific career at Kyoto, specifically at the Kyoto Imperial University (now, no more imperial :-) ), and is regarded as one of the inspirations for a battery of many excellent theoretical physicists to have emerged out of not only Kyoto but also Japan, and perhaps many parts of the world.
While looking through the archival records, I came across one of the textbooks owned by Yukawa, which has his signature on it. It made my day !

The textbook titled “A Text-Book of Physics,” edited by A. Wilmer Duff, is a classic. Yukawa had the 5th edition (1921), and this book went on to have 3 more editions. I hope to write more about this particular textbook because the author, Wilmer Duff, had a connection to Madras University (as a Professor) in India and was also on the faculty of my post-doc alma mater – Purdue University !

The scientific world is a small place with unanticipated, wonderful connections :-)