Hero’s Journey in Mechanics

1. Introduction

The Greco-Roman era, which extended across various parts of Europe and Egypt, had a profound influence on the development of knowledge and architectural construction. During this period, there was a notable interaction between manual labor and intellectual inquiry, culminating in the emergence of mechanics as a significant domain of human knowledge. While written texts often addressed mechanics from an abstract perspective, construction activities and the use of small machines embodied their practical applications.

Take, for example, the lever: a device with direct, practical utility in a wide range of contexts. A deeper exploration of such a device reveals foundational concepts in mechanics and mechanical engineering. This established an important two-way relationship between abstract theory and practical implementation, a mode of thinking most clearly exemplified in the works of Hero of Alexandria.

Hero’s writings were closely linked to mechanics and mechanical engineering[1], and the knowledge he produced spread across Europe and the Arabic world. He was deeply influenced by Archimedes, frequently referencing his works across multiple treatises. In doing so, Hero consolidated earlier knowledge and repurposed it for a variety of mechanical applications. He is also credited with creating what is now considered one of the earliest forms of the steam engine using a simple pneumatic device[2].

He was also indirectly influenced by Aristotelian thought; traces of Aristotle’s Mechanica can be observed in Hero’s approach and conceptual framework. A central feature of Hero’s work lies in the foundational principles through which he analyzed mechanical devices. Specifically, he focused on five fundamental mechanical elements: the wheel and axle, lever, pulley, wedge, and screw. Hero sought to relate these devices to a core geometrical principle: the circle, and further connected them to the concept of balance. This integration of geometric abstraction with practical devices was at the heart of Hero’s methodology, making him one of the earliest thinkers to approach mechanics as both a physicist and an engineer.

Another significant aspect of his work is his use of models[1], which provided new insights into the operation and design of mechanical systems. During that period, understanding how large weights could be moved using relatively small forces, such as through the use of a lever, posed a conceptual and practical challenge. Addressing this challenge led to deeper investigations into balance and the principles underlying mechanical advantage.

At the center of these intellectual developments was Hero of Alexandria. His work exemplifies the dual nature of mechanics as both an intellectual pursuit and a practical tool. Hero’s influence helped shape the treatment of mechanics as a cornerstone of ancient scientific and technological achievement. In many ways, he unified physics and technology on a single conceptual platform, offering a distinctive way of understanding natural phenomena and applying that understanding toward practical ends.

2. About Hero – Hero’s Time and Place

Let us now examine the details concerning Hero of Alexandria. As with many ancient historical figures, it is quite difficult to determine the exact dates of his life[3]. However, there is a general scholarly consensus that he lived sometime between the 1st and 2nd centuries CE in the city of Alexandria, located in present-day Egypt.

During this era, Alexandria was under the rule of Greek authorities, and the period is typically characterized by Greco-Roman influence, often referred to as the Hellenistic period. Interestingly, one of the methods by which Hero’s era has been dated involves a lunar eclipse recorded in his book Dioptra. This particular eclipse occurred on March 13, 62 CE, and scholars think[3] this observation provides a useful temporal marker for situating Hero in history.

Little is known about his personal life, aside from the fact that he lived and worked at the University of Alexandria. This conclusion is largely inferred from the numerous books he authored, which correspond closely with the scientific and technological knowledge of that time. With regard to intellectual influences, it is clear from his writings that Hero received a thorough education in Greek literature available up to that period.

In particular, his works frequently reference those of Archimedes. There is also an indirect influence of Aristotelian thought, although explicit references to Aristotle are less common than those to Archimedes. It is important to note that Archimedes’ contributions had a profound influence on scientific thought for generations, and Hero of Alexandria was no exception.

What is particularly fascinating about Hero is that he not only demonstrated a deep understanding of Archimedean work but also possessed considerable knowledge of devices and simple machines available in his time[4]. Alongside these intellectual currents, Hero was also influenced by Ctesibius of Alexandria. His writings exhibit a connection to this earlier Greek scholar, and some scholars even speculate that Hero may have been a student of Ctesibius.

It is worth noting that the transmission of influence from older scholars to later ones was largely facilitated through published works. Given that the University of Alexandria was a renowned center of learning, it is unsurprising that Hero of Alexandria was familiar with the work of many earlier scholars.

3. His Books – Hero’s Published Works

From the existing literature, Hero of Alexandria is associated with fourteen texts, of which eight are directly attributed to him, while six other works are associated with him with less certainty[1]. Among these works, his books on Pneumatica, Metrica, and Mechanics have garnered significant attention. In the context of Pneumatica, the subject pertains to the pressure of air, water, and steam, and their applications for various purposes, including entertainment.

Mechanica, of course, covers simple devices and machines, and this work is primarily preserved in the Arabic language. It is generally attributed to a few scholars from a later period. There is also an interesting piece of work titled Automata, in which automatic machines of that time are discussed in the context of mechanics and the associated engineering. It is the Metrica that is associated with the calculation of volumes of various solids and certain planes and surfaces, which has drawn considerable attention and has become a well-known source of information.

Of course, Hero also worked on war machines, and this particular work is available in Greek. The lifting of weights was a major technical challenge during that era, and Hero of Alexandria naturally approached this problem from the standpoint of mechanics. Many of his works, including Pneumatica and Mechanica, contain elaborate discussions on various forms of weights and the techniques for lifting them.

This, obviously, is associated with the engineering tasks necessary for constructing the architectural works of that period. Another interesting aspect of Hero’s work is associated with geometry, especially through the work titled Geometrica. He also investigated calculations related to three-dimensional objects, which show a close connection to measurement principles relevant not only to devices but also to surveying landscapes and measuring distances, including those associated with human constructions such as tunnels.

There are a few works associated with definitions of mathematical entities, and their attribution remains debated. Nevertheless, all this evidence indicates a prolific intellectual life of Hero of Alexandria, and many scholars attribute this productive authorship to his position as a teacher at the University of Alexandria. For example, if one examines certain works such as Pneumatica, the instructional style in such books appears to resemble manuals for students to gain an overview of devices.

Also, the discussions are not very terse, and many scholars interpret this as a recap for students who are advancing their knowledge in mechanics and related problems. It is noteworthy that the entire body of work suggests that Hero of Alexandria not only had a strong command over mechanical machines but also possessed the ability to think in abstract terms. This is evident from his writings related to mathematics.

Such a combination of application and abstraction is one of the most significant features of Hero of Alexandria.

4. Pneumatica

Now let us look at some specific works of Hero of Alexandria, beginning with Pneumatica. The word pneuma means “wind” in Greek. The adjective essentially refers to something that contains or operates using air or gas under certain pressure. In this context, Hero’s Pneumatica describes various aspects related to the utility of air and gases for mechanical motion.

The theme of this work is fascinating because it is not an abstract or purely theoretical exposition on mechanics or mechanical engineering. Rather, it is directly connected to small devices used for a variety of purposes, including entertainment. Among these are descriptions of several toys, such as birds that sing, coin-operated machines, and what is probably the first vending machine recorded in literature[2].

Among the many devices discussed, the one that has particularly captured the attention of historians of science is a device called the aeolipile[2], [5]. This is considered a prototype of the earliest steam engine. It operates using steam generated by boiling water in a kettle. The kettle is connected to a sphere with two nozzles. When the water boils, the steam enters the sphere and causes it to rotate.

The key aspect of this design is that the sphere is connected to a horizontally placed shaft. As the steam exits the nozzles, it causes the sphere to spin, thereby converting thermal energy into mechanical motion. This device has drawn the interest of many historians studying the origins of steam engines, as it represents one of the earliest known examples of thermal-to-mechanical energy conversion[2], [5].

The book itself contains fascinating descriptions of miniature devices adapted for various uses, including magic shows and theatre productions. Unlike some of Hero’s other writings, Pneumatica reads more like a manual for operating small devices, with concise and practical descriptions rather than theoretical elaboration. The quality of the diagrams in this work is particularly notable and has attracted considerable attention from historians.

One of the best-known surviving translations[6] of this work is by the Englishman Bennet Woodcroft, published in 1851 (Figure 2). This translation has become a standard reference for scholars seeking to understand the nature of Hero’s contributions. It highlights Hero’s practical orientation, which is quite distinctive among scholars of his stature.

Figure 2. An English translation of Hero’s book on Pneumatics

In comparison, the works of Archimedes and his immediate followers are generally more rigorous and focused on mathematical applications. Most of them do not discuss simple or seemingly trivial devices in the manner that Hero does in Pneumatica. Nevertheless, it is important to emphasize that Hero was deeply influenced by Archimedes. Many of the devices described in this book are based on principles associated with Archimedes and his pioneering work.

This is characteristic of Greek scholars, who regarded Archimedes as one of the earliest scientists to understand the natural world through systematic mathematics and physical models. In some of Hero’s other works, one sees this intellectual lineage in action, combining abstract analysis with practical application. This synthesis of theoretical and applied thinking positions Hero as a pioneer in engineering mechanics. Many of the devices he designed continue to be of great interest to both engineers and artists.

In this light, Pneumatica offers a compelling insight into Hero’s intellectual curiosity and his pedagogical intent, particularly in presenting devices to students through detailed and accessible instruction manuals.

5. Mechanica

Next, let us consider an overview of Hero’s book titled Mechanica. This work comprises three volumes, and the surviving text is available only in an Arabic translation. Some scholars believe that the content may have undergone certain alterations during the process of translation and transmission.

One of the earliest references to Mechanica dates to around 300 CE, made by Pappus of Alexandria, in a discussion on heavy weights and the methods used to lift them. The book is strongly grounded in principles originally proposed by Archimedes. It presents several mechanical principles with a degree of abstraction.

The concept of the balance, its theoretical foundations, and its relationship to various mechanical devices, such as pulleys, screws, and the wheel and axle, are discussed in considerable detail. A distinctive feature of this book is its treatment of the transportation of heavy objects using mechanical aids, as well as the application of the concept of the center of gravity to various solid forms and shapes.

The text includes a significant degree of abstraction and presents a theory of motion that provides insights into Hero’s understanding of mechanics and mechanical engineering. In this work, Hero refers to Archimedes as many as ten times, indicating a deep intellectual debt. Moreover, scholars have observed that Hero’s approach is indirectly influenced by Aristotelian perspectives on mechanical motion.

A notable aspect of the book is its emphasis on connecting abstract mechanical principles with practical applications. Devices such as the lever, pulley, wheel and axle, and various forms of screws are examined in depth. In this respect, Mechanica can be seen as an early treatise in engineering physics, serving as a key reference for understanding ancient mechanics and mechanical engineering.

The book’s content also reflects the context of the Hellenistic period, which was marked by elaborate construction projects. The principles and techniques discussed in Mechanica have potential relevance to these large-scale engineering efforts.

Finally, Mechanica exhibits strong intellectual continuity with Hero’s other works and shares conceptual commonalities with a few additional sources. This cohesion underscores Hero’s broader contribution to the understanding and development of mechanics in antiquity.

6. Other Works

Let us now consider a few other works of Hero of Alexandria. First among them is Metrica, a collection of three books and arguably the most well-known of his works. This text is primarily concerned with measurement and geometry and includes an elaborate discussion of what is now known as Hero’s formula—a well-known result in elementary geometry for calculating the area of a triangle given the lengths of its sides[7].

Metrica also explores the computation of square roots using iterative methods, a topic with significant applications in basic mathematics. The work focuses on the ability to perform measurements, including the calculation of volumes of solids such as Platonic solids and other fundamental geometric shapes. Ratios form another important aspect of the discussion, with solids considered in terms of divisions by arbitrary ratios, providing a geometric perspective on their structure.

The next important work is Dioptra, which deals with the measurement of length. It includes a discussion of the instrument known as the dioptra[8], which is directly related to surveying instruments that continue to be used in modified forms even today.

An interesting section of this work also discusses the odometer, a device used to measure the distance traveled by a moving object. This provides one of the earliest known references to such a device and highlights Hero’s interest in practical instrumentation.

Another fascinating work is Automata, in which Hero discusses automatic machines in great detail. This text is associated with the domains of magic, theatre, and mechanical marvels that were designed to captivate observers. There is extensive discussion on automatic doors and related architectural mechanisms, which were likely employed in temples or public spaces during Hero’s time. The work also includes ingenious systems for pouring and transporting liquids automatically, illustrating Hero’s advanced understanding of fluid mechanics and automation.

Taken together, these works reflect the rich intellectual repertoire of Hero of Alexandria. At the core of all his writings is a deep engagement with mechanics, approached both abstractly and practically. In this light, Hero’s contributions are of immense significance, offering valuable insights into the interplay between theory and application in ancient science and engineering.

7. Conclusion

Hero of Alexandria, embodied ancient human thought process that mixed physics and technology for intellectual and practical purposes. In a way, he laid the foundation to harness mechanics for practical applications and built on ideas proposed and utilised by great thinkers such as Archimedes and his followers. It is quite remarkable that a person of that era could come up with such interesting innovations for not only practical applications, but also for teaching and demonstrations for the public. Credit should also be given to the followers and students of Hero, who took his work forward and spread it across the world. Perhaps that is the best way to leave a legacy, by learning, creating and sharing knowledge.

REFERENCES:

[1] M. J. Schiefsky, “Theory and Practice in Heron’S Mechanics,” in Mechanics and Natural Philosophy Before the Scientific Revolution, W. R. Laird and S. Roux, Eds., Dordrecht: Springer Netherlands, 2008, pp. 15–49. doi: 10.1007/978-1-4020-5967-4_1.

[2] “Heron’s Aeolipile Is One of History’s Greatest Forgotten Machines,” Popular Mechanics. Accessed: Jun. 11, 2025. [Online]. Available: https://www.popularmechanics.com/science/energy/a34554479/heron-aeolipile/

[3] R. Masia, “On dating Hero of Alexandria,” Arch. Hist. Exact Sci., vol. 69, no. 3, pp. 231–255, 2015.

[4] A. G. (Aage G. Drachmann, The mechanical technology of Greek and Roman antiquity, a study of the literary sources. Copenhagen, Munksgaard; Madison, University of Wisconsin Press, 1963. Accessed: Jun. 11, 2025. [Online]. Available: http://archive.org/details/mechanicaltechno0000unse

[5] P. D. Bardis, “Hero, the Da Vinci of Alexandria: His Aeolosphaera and Other Inventions,” Sch. Sci. Math., vol. 65, no. 6, pp. 535–542, 1965, doi: 10.1111/j.1949-8594.1965.tb13497.x.

[6] H. (of Alexandria.), The Pneumatics of Hero of Alexandria: From the Original Greek. Charles Whittingham, 1851.

[7] “Heron of Alexandria | Ancient Greek Engineer & Mathematician | Britannica.” Accessed: Jun. 13, 2025. [Online]. Available: https://www.britannica.com/biography/Heron-of-Alexandria

[8] “Dioptra – Wurmpedia.” Accessed: Jun. 13, 2025. [Online]. Available: https://www.wurmpedia.com/index.php/Dioptra

Quartet of Modern World

Recently, I read an essay by James Read, a philosopher of physics at Oxford, in Aeon magazine.

The title of the essay is Why Philosophy of Physics?

It is a good read, and addresses a pertinent question of highlighting the role of philosophy of physics within the larger umbrella of physics as a discipline and human endeavor. Although the viewpoint and examples are mainly from theoretical physics, it makes a good case for the philosophy of physics.

Below are my thoughts:

I would add that both theoretical and experimental approaches to physics do raise philosophical questions that may be complementary, and in certain cases, necessary, to get a complete picture of the underlying physics.

I would go further and add that the foundations and approaches to engineering and its philosophy cannot be fully appreciated without grasping the underlying physics. This thought can be extrapolated to include mathematics, chemistry and biology too.

Engineering beautifully extracts knowledge from all the branches of science and puts them into use in the noisy world. By interacting with the external noise, it showcases the resilience and limitations of the foundational principles. Thus, it further motivates philosophical questions that will have to be addressed, going back to the first principles of science.

In that sense, science, technology, and philosophy form a trinity of ideas, each feeding the other, and sometimes creating a sum that is greater than its parts. To capture this evolution, we need the tools of history and hence a case for the history of science.

Together with history and philosophy of science, science and technology make an essential quartet. Our modern world stands on this quartet.

YouTube as an Archival Source

There are several models for using YouTube. One of them is to use it as a substitute for television and media outlets. This is where the number of views, subscriptions, and reach becomes important.

Another model is to harness YouTube as an archival source that is open to the public. This is one of the crucial elements of a platform that is easily accessible and, importantly, searchable. Such a platform becomes a repository for many informal academic discussions and interactions.

The archive model is an important category, especially if there is no need to generate revenue from the content deposited on the platform. A crucial aspect is that it can be accessed across the world and, in that sense, represents truly open-access content without paywalls, publication charges or subscriptions. Therefore, I am glad to see that many Indian academic programs, including NPTEL, ICTS, Science Activity Center/Media Center at IISER-Pune and many others are utilizing platforms such as YouTube to post their lectures and talks. Also, many individual academics in India are gradually using YouTube to discuss their work, in the context of research, teaching and entrepreneurship.

This development is slowly turning out to be an invaluable resource that can reach a large audience. Although YouTube is one of the most well-known platforms, many other platforms in the context of social media can also be tapped to spread knowledge. Given their reach and simplicity of use, both for creators and users, these tools become important in a vast country such as India.

As audio-visual public platforms join hands with artificial intelligence tools, they can positively (hopefully) affect how people, especially students, consume educational content. Going forward, I anticipate language translation through direct dubbing to be a game-changer. It could attract many new viewers who have been hesitant to watch technical content simply because it was in a foreign language. Of course, on these platforms, the noise is equally high compared to the signal, and therefore, curating good, targeted resources will be vital. Also, these platforms cannot be treated as a substitute for formal education, but as an extension or complementary source for research and education.

Interesting times ahead.

15 years at IISER Pune – Journey so far

Today, I complete 15 years as a faculty member at IISER-Pune. I have attempted to put together a list of some lessons (based on my previous writings) that I have learnt so far. A disclaimer to note is that this list is by no means a comprehensive one, but a text of self-reflection from my viewpoint on Indian academia. Of course, I write this in my personal capacity. So here it is..

People First, Infrastructure Next
As an experimental physicist, people and infrastructure in the workplace are of paramount importance. When I am forced to prioritize between them, I have chosen people over infrastructure. I am extremely fortunate to have worked with, and continue to work with, excellent students, faculty colleagues, and administrative staff members. A good workplace is mainly defined by the people who occupy it. I do not neglect the role of infrastructure in academia, especially in a country like India, but people have a greater impact on academic life.
Create Internal Standards
In academia, there will always be evaluations and judgments on research, teaching, and beyond. Every academic ecosystem has its own standards, but they are generalized and not tailored to individuals. It was important for me to define what good work meant for myself. As long as internal standards are high and consistently met, external evaluation becomes secondary. This mindset frees the mind and allows for growth, without unnecessary comparisons.
Compare with Yourself, Not Others
The biggest stress in academic life often arises from comparison with peers. I’ve found peace and motivation in comparing my past with my present. Set internal benchmarks. Be skeptical of external metrics. Strive for a positive difference over time.
Constancy and Moderation
Intellectual work thrives not on intensity alone, but on constancy. Most research outcomes evolve over months and years. Constant effort with moderation keeps motivation high and the work enjoyable. Binge-working is tempting, but rarely effective for sustained intellectual output.
Long-Term Work
We often overestimate what we can do in a day or a week, and underestimate what we can do in a year. Sustained thought and work over time can build intellectual and technical monuments. Constancy is underrated.
Self-Mentoring
Much of the academic advice available is tailored for Western systems. Some of it is transferable to Indian contexts, but much of it is not. In such situations, I find it useful to mentor myself by learning from the lives and work of people who have done extraordinary science in India. I have been deeply inspired by many people, including M. Visvesvaraya, Ashoke Sen, R. Srinivasan, and Gagandeep Kang.
Write Regularly—Writing Is Thinking
Writing is a tool to think. Not just formal academic writing, but any articulation of thought, journals, blogs, drafts, clarifies and sharpens the mind. Many of my ideas have taken shape only after I started writing about them. Writing is part of the research process, not just a means of communicating its outcomes.
Publication is an outcome, not a goal Publication is just one outcome of doing research. The act of doing the work itself is very important. It’s where the real intellectual engagement happens. Focus on the process, not just the destination.
Importance of History and Philosophy of Physics
Ever since my undergraduate days, I have been interested in the history and philosophy of science, especially physics. Although I never took a formal course, over time I have developed a deep appreciation for how historical and philosophical perspectives shape scientific understanding. They have helped me answer the fundamental question, “Why do I do what I do?” Reflecting on the evolution of ideas in physics—how they emerged, changed, and endured—has profoundly influenced both my teaching and research.
Value of Curiosity-Driven Side Projects
Some of the most fulfilling work I’ve done has emerged from side projects, not directly tied to funding deadlines or publication pressure, but driven by sheer curiosity. These projects, often small and exploratory, have helped me learn new tools, ask new questions, and sometimes even open up new directions in research. Curiosity, when protected from utilitarian pressures, can be deeply transformative.
Professor as a Post-doc
A strategy I found useful is to treat myself as a post-doc in my own lab. In India, retaining long-term post-docs is difficult. Hence, many hands-on skills and subtle knowledge are hard to transfer. During the lockdown, I was the only person in the lab for six months, doing experiments, rebuilding setups, and regaining technical depth. That experience was invaluable.
Teaching as a Social Responsibility
Scientific social responsibility is a buzzword, but for me, it finds its most meaningful expression in teaching. The impact of good teaching is often immeasurable and long-term. Watching students grow is among the most rewarding experiences in academia. Local, visible change matters.
Teaching Informally Matters
Teaching need not always be formal. Informal teaching, through conversations, mentoring, and public outreach, can be more effective and memorable. It is free of rigid expectations and evaluations. If possible, teach. And teach with joy. As Feynman showed us, it is a great way to learn.
Foster Open Criticism
In my group, anyone is free to critique my ideas, with reason. This open culture has been liberating and has helped me learn. It builds mutual respect and a more democratic intellectual space.
Share Your Knowledge
If possible, teach. Sharing knowledge is a fundamental part of academic life and enriches both the teacher and the learner. The joy of passing on what you know is priceless.
Social Media: Effective If Used Properly
Social media, if used responsibly, is a powerful tool, especially in India. It can bridge linguistic and geographical divides, connect scientists across the world, and communicate science to diverse audiences. For Indian scientists, it is a vital instrument of outreach and dialogue. My motivation to start the podcast was in this dialogue and self-reflection.
Emphasis on Mental and Physical Health
In my group, our foundational principle is clear: good health first, good work next. Mental and physical well-being are not optional; they are necessary conditions for a sustainable, meaningful academic life. There is no glory in research achieved at the cost of one’s health.
Science, Sports, and Arts: A Trinity
I enjoy outdoor sports like running, swimming, and cricket. Equally, I love music, poetry, and art from all cultures. This trinity of pursuits—science, sports, and the arts—makes us better human beings and enriches our intellectual and emotional lives. They complement and nourish each other.
Build Compassion into Science
None of this matters if the journey doesn’t make you a better human being. Be kind to students, collaborators, peers, and especially yourself. Scientific research, when done well, elevates both the individual and the collective. It has motivated me to humanize science.
Academia Can Feed the Stomach, Brain, and Heart
Academia, in its best form, can feed your stomach, brain and heart. Nurturing and enabling all three is the overarching goal of academics. And perhaps the goal of humanity.

My academic journey so far has given me plenty of reasons to love physics, India and humanity. Hopefully, it has made me a better human being.

Einstein – Science and its History & Philosophy

I have been interested in the views of Einstein related to the history and philosophy of science (HPS). The more I read about his work, the more I find that his inclination is to combine science with its historical and philosophical evolution. I am in search of his correspondence with fellow scientists and intellectuals, and have been looking at clues towards this combinational approach to science.

The above image is the title of the Physics Today article.

Recently, I came across an article in Physics Today¹ that reproduced a part of Einstein’s letter². Here it is:

I fully agree with you about the significance and educational value of methodology as well as history and philosophy of science. So many people today—and even professional scientists—seem to me like someone who has seen thousands of trees but has never seen a forest. A knowledge of the historic and philosophical background gives that kind of independence from prejudices of his generation from which most scientists are suffering. This independence created by philosophical insight is—in my opinion—the mark of distinction between a mere artisan or specialist and a real seeker after truth

It is clear that Einstein liked this combination and thought that it should be part of one’s scientific education. There is a lot more on this topic in the Physics Today article, and it is an excellent read to understand the thoughts of Einstein on this topic. More on this in a future blog…

Howard, Don A. “Albert Einstein as a Philosopher of Science.” Physics Today 58, no. 12 (December 1, 2005): 34–40. https://doi.org/10.1063/1.2169442. ↩︎
A. Einstein to R. A. Thornton, unpublished letter dated 7 December 1944
(EA 6-574), Einstein Archive, Hebrew University, Jerusalem ↩︎

Soft Matter – emergence of a physics domain

Recently, I read a nice interview with Sid Nagel, who is a pioneer in soft condensed matter physics.

Sid Nagel has given an aura to an area of physics that was not considered fashionable even as late as the 2010s. Part of his elevation is because “Soft Matter Physics” has become so vital to understand our everyday world (including biological) that it is hard to ignore it anymore. Chemical Engineers, too, have played a major role in this elevation, and the James Frank Institute at Chicago has been an epicenter for this way of thinking.

A major shift in thinking, especially among physicists, is thanks to PW Anderson. His essay – ‘More is Different” did a great service to soft matter and complex systems by highlighting the importance of emergence (side note: the word emergence does not occur in his essay, even once !) It further got a major headway with a Nobel to de Gennes. Suddenly, condensed matter physicists had something to explore beyond electrons and their density functions. The French school had a major hand in this.

For me, soft matter physics, in a way, makes physics experiments democratic. One can still dare to do some ‘breakthrough science’ in a tiny kitchen 🙂

Physics & Pratidhvani

He made physics more humane…

Today is Feynman’s birthday.

Part of my becoming a physicist is because of his books on lectures on physics.

Even today, as a professor of physics, and importantly as a student of physics, I go back to his lecture series to learn AND derive inspiration from his thinking. He made physics more humane.

Many people across the globe have fallen in love with physics because of his books and the ‘way he did physics’

Feynman was a physics genius, but he had his flaws. It is important for us to note the limitations of human beings; celebrate what is good, and be aware and critical of what is not.

There is a lesson in every human life.

It is up to us to learn from it.

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 !

Physics Portal of Aristotle

In the previous essay, we discussed engineering civilizations. Specifically, we discussed how philosophy and technology have played a critical role in the betterment of civilization. In addition, the fact that thoughts and tools have direct implications on how human beings live cannot be overstated.

Over the centuries, there have been many people who have played a critical role in advancing philosophical thoughts and engineering tools that have directly or indirectly influenced the development of physics. Before we really get into the specifics of the science of mechanics and its historical developments, we need to investigate some of the ideas that were part of the discussion in ancient civilizations. Given that mechanical tools date back to the prehistoric era, it is not surprising that human beings took an interest in understanding how the world works within their proximity.

In such a development, a human being is always curious to understand and harness nature. To do this effectively, one will have to systematically think about how nature works. According to the existing literature from a history of science viewpoint, the Greek philosophers occupy a very special position.

Part of the reason is that their thoughts were recorded in some form or another, and these thoughts date back to a period as early as 300 to 400 BCE or even before. This also coincides with the time at which writing became an important tool to propagate ideas, and therefore, one can see the emergence of historical evidence from this era. The Greek philosophers have a great reputation in Western philosophy and have influenced the development of scientific thinking for a very long period.

This does not mean that people from other civilizations did not think about tools and philosophical ideas. Just that the availability of written records, either direct or indirect, has been one of the hallmarks of Greek civilization. Thanks to the accumulation of these texts, either in the primary or in the secondary source form, it has played a critical role in identifying a specific point in Western civilization(1).

Physics, as we know it in the 21st century, has a very different avatar compared to its origin. Among the many Greek philosophers who seriously thought about natural philosophy was Aristotle(2). Aristotle has had a long legacy of being the student of some great thinkers from the Hellenistic era.

Aristotle was a student of Plato, and Plato was a student of Socrates. So, these three gentlemen have contributed to Western philosophy in such a great way that one cannot discuss anything about philosophical discourse without bringing them into the picture. The origins of physics, too, have some connection to these gentlemen, specifically to Aristotle(3), who was guided by some processes of thinking developed by Socrates and his direct guru, Plato.

The Plato school of thinking deeply influenced Aristotle, and yet he paved his own way in Western philosophy. He was also one of the first writers among these philosophers to seriously think about natural philosophy in the form and shape that resembles the current day science. His questions were related to natural phenomena, and it is by studying them that we realize Aristotle’s contribution. As I always keep saying, it is not just the answers that make great thoughts; it is also the questions that elevate the answers and make them profound. In that way, Aristotle’s questions were profound.

Therefore, I need to emphasize the quality of the questions that Aristotle asked instead of just emphasizing the answers he gave in the process of this questioning. It also indicates that current-day physics, as we now know it is not in the form Aristotle thought about, but we can see a glimpse of some interesting ideas in Aristotle, which turned out to be extremely important. It became so critical that for the next thousand years from the time of Aristotle, the Western philosophy and the science that emerged out of it kept Aristotle as an important benchmark and developed its thought either in agreement or in rejection of Aristotle’s idea.

So much so that this thinking process in reference to Aristotle’s idea not only influenced Western civilization but also had a very deep implication for Islamic civilizations. Although Aristotle’s ideas became critical in ancient Europe and the ancient Islamic world, its ideas and categorizations of knowledge found relevance across various civilizations.

So, let’s try to get a glimpse of the man himself – Aristotle. Let us look at the biographical details of this remarkable individual and learn about his work.

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The Life of Aristotle

Aristotle was born in Stagira, Macedonia, which is in the northern part of Greece, in 384 BCE. His father was a physician to one of the kings in Macedon, and Aristotle was probably influenced by his father’s way of thinking about nature and natural phenomena. Of course, this is all conjecture because nobody knows the exact nature of the interaction between Aristotle and his father. However, this reconstruction is generally accepted based on historical texts(4).

When Aristotle was around 17 years old, in 367 BCE, he was sent to Athens to join the remarkable institution known as Plato’s Academy. During that period, Plato’s Academy was one of the leading intellectual centers in Europe, playing a critical role in shaping the thinking of various philosophers, including Aristotle.

It was at this place that Aristotle honed his skills in philosophical argumentation and the observation of nature and natural phenomena. This foundation played a crucial role in shaping his later works. For approximately 20 years, Aristotle remained at Plato’s Academy.

After Plato died in 348 BCE, Aristotle moved elsewhere. Historical texts suggest two possible reasons for his departure. One possibility is that he had intellectual differences with Plato’s nephew, who took over the Academy. The second possible reason is that the political atmosphere in Athens had become increasingly hostile toward people from Macedonia. These reasons, of course, remain speculative, although they are mentioned in historical literature.

In 343 BCE, King Philip II of Macedon invited Aristotle to tutor his son, Alexander. This is the same Alexander whom history remembers as Alexander the Great, though we will refer to him simply as Alexander. Aristotle played a crucial role in educating Alexander for more than five to seven years, deeply influencing the future conqueror’s thought process.

After about seven to eight years, Aristotle returned to Athens and established the Lyceum, a school of philosophy that had a profound impact on Western thought. This school had a unique feature—philosophers often lectured while taking long walks. As a result, the school came to be known as the Peripatetic School, recognized for its tradition of philosophical discourse while on the move.

During this period, around 330 BCE, Aristotle produced some of his most significant works, particularly in the context of physics. Even before leaving Athens, he had made substantial contributions to topics related to biology. However, in this second phase of his career, his focus broadened to natural philosophy, logic, ethics, aesthetics, rhetoric, and even music. This vast intellectual repertoire is one of Aristotle’s most remarkable features(4).

Around 323 BCE, Aristotle left Athens again following the untimely death of Alexander. During that period, anti-Macedonian sentiment was widespread in Athens, which likely motivated his departure. Within a year of leaving, around 322 BCE, Aristotle passed away at the age of 62. The probable cause of his death appears to have been natural.

All this information, of course, is based on historical sources that have been passed down through the centuries(4). One should always be cautious when interpreting ancient texts, as most of these sources survive only in translation rather than their original form. There is always a possibility of inaccuracies, and one must approach these accounts with care.

Aristotle’s intellectual journey covered a vast spectrum of human inquiry, from the heavens, as in astronomy, to logic within the framework of mathematics and, of course, physics. His interests also overlapped with observational phenomena and the life around him, which is evident from the questions he explored. Among his many areas of interest, we will focus primarily on Aristotle and his contributions to physics.

Aristotle’s writings on natural philosophy cover a vast range of topics, from celestial bodies to the nature of matter and motion. His works, though sometimes speculative by modern standards, laid the foundation for centuries of philosophical and scientific thought(5). Much of what we know about Aristotle comes from the preserved writings of later scholars, as very few primary sources from Aristotle himself remain.

Before I discuss Aristotle’s book, a few words on the origin of the word Physics. The word physics is derived from a Greek word called phusikḗ, which means natural science. This word has its origin in another word, and it is called phúsis, which means nature in Greek. The modern definition of physics is essentially derived from the Latin word physikā, which essentially means the study of nature.

This word was adapted by the old French, which was further adapted by English to be transformed into the word physics, as in natural philosophy.

In the context of Aristotle, it is the Greek word phúsis, meaning nature, is central to this discussion.

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The Eight Books of Physics

Aristotle’s Physics is divided into eight books(6), each exploring different aspects of nature and motion. Specifically, he was interested in the principles and causes of change and motion of objects. Let me give you an overview of his books.

Book One introduces Aristotle’s fundamental concepts of matter and form. A key discussion in this book is the doctrine of the four causes: the material cause, which explains what something is made of; the formal cause, which defines its shape or essence; the efficient cause, which refers to the force or agent that brings about change; and the final cause, which represents the purpose or end goal of an object or process. These causes provide a framework for understanding physical interactions and transformations.

In Book Two, Aristotle argues for teleology—the idea that nature has inherent purposes. He defends the study of nature as a legitimate form of scientific inquiry and lays out a methodological foundation for observing and interpreting natural phenomena.

Book Three explores the nature of change. Aristotle distinguishes between actuality, the realized state of an object brought about by an external force, and potentiality, the inherent capability of an object to become something else. This distinction is significant in understanding motion and transformation.

In Book Four, Aristotle explores the nature of voids, rejecting the concept of a vacuum. He also presents an interesting perspective on time, defining it as a measure of change.

Book Five classifies different kinds of motion, an important step in distinguishing natural movement from forced motion.

In Book Six, Aristotle discusses the nature of continuity and the concept of infinity. He argues against the existence of actual infinity, emphasizing the finiteness of physical reality.

Book Seven introduces the concept of the Prime Mover—an external force that initiates movement. This idea becomes central to Aristotle’s broader cosmology.

Book Eight expands on the idea of the Prime Mover as the ultimate cause of cosmic motion. This notion of an external force influencing the universe had a lasting impact on Western thought, intertwining scientific and theological perspectives for centuries.

Related to these books was Aristotle’s book titled On the Heavens. In there, Aristotle discussed his celestial theories. This four-part work, On the Heavens, explores the nature of celestial bodies and their motion.

He proposes that heavenly bodies are made of ether, a perfect and unchanging substance.

Aristotle also argues that the Earth is spherical and that celestial objects move in circular orbits—a belief that persisted until Kepler’s elliptical model. He discusses why celestial objects move in circular paths, distinguishing their motion from that of objects on Earth.

Expanding on his theory of the five fundamental elements—earth, water, air, fire, and ether—Aristotle’s ideas parallel similar concepts in other ancient civilizations, such as those in India and Mesopotamia.

Aristotle also studied natural phenomena through observations, and a related 4 book series was titled Meteorology. These books addressed:

Weather phenomena (clouds, wind, rain, lightning)
Natural bodies (lakes, rivers, seas, and geological formations)
Dynamic processes such as volcanoes and the transformation of matter

Another interesting book that Aristotle wrote about was based on his views on matter. The title of the work is unconventional and reads: On Generation and Corruption. This work, consisting of two books, discusses:

The four elements and their combinations in forming matter
The processes of transformation, mixing, and decomposition of substances

One may wonder how we know so much about Aristotle, even though he lived around 350 BCE. This is one of the remarkable features of human beings. They carry forward ideas from one generation to another.

Of course, this transmission across ages may cause errors in translation, but at least we get a gist of the idea through percolation. The records that we obtain through transmission will depend on the preservation of the sources of ideas. This is where the written text becomes so important because a physical text can be preserved, transported and reproduced with relative ease compared to oral records from the past.

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Most of the information about Aristotle comes from Corpus Aristotelisium(4). This is a multinational project about preserving Aristotle’s work. Around 200 texts are associated with Aristotle, out of which 31 have survived as the ancient textual evidence. These texts are from later eras across different countries, but one can make a connection to the original source through educated guesses and cross-connections.

So, I hope you have got a glimpse of and range of topics Aristotle was interested in from a physics viewpoint. Aristotle’s broad approach to physics covered motion, change, matter, and the cosmos. While many of his explanations were later refuted, his method of questioning and systematic exploration laid the groundwork for future scientific inquiry(5). His emphasis on philosophical reasoning remains an essential part of the intellectual history of physics.

In this essay, we discussed the origins of physics from Aristotle’s philosophical viewpoint. We learnt about his life and remarkable scholarly output. Going forward, we will explore other ideas and thinkers from the ancient age whose work you will generally find in physics textbooks. Can you guess what ideas they are and whom I am referring to? Think about it for a while…

References:

1. Adamson P. Classical Philosophy: A history of philosophy without any gaps, Volume 1. Oxford, New York: Oxford University Press; 2014. 368 p. (A History of Philosophy).

2. Shields C. Aristotle. In: Zalta EN, Nodelman U, editors. The Stanford Encyclopedia of Philosophy [Internet]. Winter 2023. Metaphysics Research Lab, Stanford University; 2023 [cited 2025 Mar 27]. Available from: https://plato.stanford.edu/archives/win2023/entries/aristotle/

3. Bodnar I. Aristotle’s Natural Philosophy. In: Zalta EN, Nodelman U, editors. The Stanford Encyclopedia of Philosophy [Internet]. Spring 2025. Metaphysics Research Lab, Stanford University; 2025 [cited 2025 Mar 27]. Available from: https://plato.stanford.edu/archives/spr2025/entries/aristotle-natphil/

4. Winzenrieth J. The Textual Transmission of the Aristotelian Corpus. In: Zalta EN, Nodelman U, editors. The Stanford Encyclopedia of Philosophy [Internet]. Spring 2025. Metaphysics Research Lab, Stanford University; 2025 [cited 2025 Apr 2]. Available from: https://plato.stanford.edu/archives/spr2025/entries/aristotle-text/

5. Rovelli C. Aristotle’s Physics: A Physicist’s Look. J Am Philos Assoc [Internet]. 2015 Apr [cited 2025 Mar 31];1(1):23–40. Available from: https://www.cambridge.org/core/journals/journal-of-the-american-philosophical-association/article/aristotles-physics-a-physicists-look/60964532EE56BA65655971A314FD9717

6. Aristotle. Physics (around 350 BCE) [Internet]. [cited 2025 Apr 2]. Available from: https://classics.mit.edu/Aristotle/physics.html