Tag: physics

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

Herschel, IR radiation and the 3 steps of science

I came across a nice article on the discovery of Infra-red (IR) radiation by William Herschel. It has some information on how he detected the IR part of the electromagnetic spectrum.

It was interesting to note that Herschel’s viewpoint after writing a few papers on this topic was to conclude with uncertainty on the interpretation of his own result.

One may argue that he was not confident in his work, but to truly discover something new, one will have to be at the boundary of the unknown. At such an inflection point, uncertainty and self-criticism are so important, and I don’t blame Herschel for being circumspect.

Nevertheless, his work received attention in spite of his doubts and motivated other researchers, such as Ritter and Röntgen, to explore the extended spectrum of electromagnetic radiation.

Scientific progress is two steps forward and one step backward. The backward step (as in questioning new findings, verification, clarification and debate) is one of the hallmarks of scientific thinking, without which we may take many forward steps, albeit in a totally wrong direction.

A Global History of Physics

Welcome to essays in A Global History of Physics, where I discuss people, ideas, philosophy and technology involved in the development of physics across the world

  1. Engineering Civilizations
  2. Physics Portal of Aristotle
  3. Maths, Mechanics & Eureka
  4. Hero’s Journey in Mechanics
  5. Eunice Newton Foote: Activist, Climate Scientist & Inventor
  6. C. V. Raman as a Science Communicator: A Historical Perspective
  7. Gerhard Herzberg (1904–1999): A Pioneer in Molecular Spectroscopy

Some aspects of the essays are written as part of my podcast, and some are published as essays in journals and magazines. The intention is to eventually collate them into book(s). You are free to use it for educational and non-commercial purposes with attribution.

Engineering Civilizations

1.    Introduction:

Welcome to essays in the global history of physics, where we discuss people, ideas and technology connected to physics in the historical context. Let me explain why the global history of physics is important. Physics, as you know, is one of the central disciplines of natural sciences from which various branches of science and technology have emanated.

Understanding the evolution of such an important output of human thought is imperative. It not only gives us a glimpse of how people over the ages have thought about ideas but also reveals how those ideas are connected to philosophical and technological questions that were of interest to people in the past. In fact, it is that dual connection of physics to philosophy and technology that makes it interesting, important and intellectually rich.

This series of essays aims to capture the historical evolution of physics by paying attention to the global evolution of the subject. In doing so, we will visit the people from the past and learn about their ideas and technologies that eventually led to the topics within physics. 

Here, I need to emphasize the global aspect of history. Conventionally, the history of science as a discipline has been criticized for being Eurocentric in nature. In recent years, as highlighted by James Poskett’s excellent book Horizons (1), there has been an emerging scholarship in the history of science to reveal a decentralized evolution of science and that includes some developments in physics itself. In these essays, I will give credit to people, ideas and technology irrespective of their origin and emphasize curiosity as a basic human instinct prevalent across space and time.

This thought reinforces science, specifically physics, as a global intellectual pursuit over many ages and times. The way I will do this is to take on a particular branch of physics and discuss its evolution in chronological order. Of course, my aim is not to cover everything that is known but to highlight some interesting developments in that field with attention to some interesting people, ideas, tools and technologies at the relevant place and time.

Such an exercise cannot be done in one single essay. So, I intend to cover the chronological evolution with a series of essays spanning all the branches of physics. Yes, it will be a long journey, and I hope you will accompany me in this one endeavor.

2.    How a physical phenomenon is explained.

 One starts with a concrete situation of a particular problem. Associated with this situation is a general law. One applies the general law to the situation in a logical manner and utilizes mathematical descriptions where precision is needed. This logical and mathematical description leads to an explanation witha concrete prediction. Observations must test this prediction. The ability to predict a future observation is one of the remarkable traits of science in general and physics in particular (2). It is through this ability to predict that one can envisage the utility of a physical concept. That utility forms the seed of development towards technology.

As you may observe, there is a nice connection between scientific inquiry and the eventual realization of technology. This connection is what makes science and technology go hand in hand. Importantly, this is one of the outstanding features of physics and historical explanation, as we intend to do in these essays, which will justify the claim.

This connection between science and technology is not a one-way coupling. In fact, many interesting questions in physics have emerged out of technological development across various eras of human history. This recognition of jugalbandhi between science and technology is at the heart of the essay series.

Physics has played a critical role in engineering civilization over the centuries. This role has been explicit in recent times, say around the last 300 years or so. But what is interesting is that inquiries in physical sciences have implicitly influenced the growth of a civilization.

This growth is not only materialistic but also intellectual in nature. Therefore, understanding the evolution of physics gives us a glimpse of the evolution of humankind. Of course, it may not be the complete picture, but at least we learn about people, ideas and technology that gave rise to the world that we identify as a physical, real entity.

3.    Engineering Civilizations

Let us start with some ancient civilizations. The oldest tools used by humans were stones. In fact, the ‘Stone Age’ gets its name from this. According to archeological explorations, the earliest stone tools found in Lomekwi, Kenya, date back to 3.3 million years ago (3). This is the Paleolithic age, in which hunting and gathering were the main occupations of human beings. The stone tools found within India at Attirampakkam, a village close to Chennai in Tamil Nadu, date back to around 300 thousand years ago (4). From such archeological evidence, humans were acquainted with toolmaking long ago. Towards the Neolithic age, we also have evidence of pottery in civilizations, indicating a gradual change to farming and agricultural occupations that were assisted by toolmaking based on clay and fire.  I need to emphasize that knowledge of these tools was handed over from one generation to another without a formal writing process. The oldest written record dates to around 3500 BCE in the form of a cuneiform script from Mesopotamian civilization, which is somewhere around present-day Iraq (2). Such writing itself needs small tools, such as a stylus and a platform, such as clay, to imprint the written text. Well before any form of writing became part of any civilization, tools and structures had to be invented.

An interesting element of the Indus Valley Civilization was that they used measurement scales (5). In the Harappan museum, one can find a linear scale made of a shell that has nine divisions with a small circle engraved on it. A periodically divided scale indicates a quantitative measure of length and indicates the sophistication of thought, both from device and utility viewpoints.

A remarkable aspect of this scale is the utility of the shell as the material. Given that shells are robust and can sustain large temperature fluctuations, they make for an excellent choice as a material for scale. One must really marvel at how humans came to the point where such a design was implemented without modern tools, scientific knowledge or a written script.

To emphasize this fact, one of the earliest texts from the Indus Valley civilization dates to around 3000 BCE. Of course, in this case, the script is yet to be deciphered completely. What is interesting is that ancient civilizations achieved remarkable engineering feats even before any formalization of scientific disciplines, including physics, came into the picture.

This is because for civilization to survive, grow and sustain, they had to manage their natural resources and construct structures. These tasks would not have been feasible without an intricate understanding of how things work and how they can be used to construct physical structures. This can be achieved only through certain tools and techniques.

The civilizations would not have evolved without this engineering and, therefore, deserve credit as a human achievement. These tools and techniques have implicit physics in them. Of course, there was no formal discipline called physics until around 300 BCE, but the empirical knowledge about tools and techniques for construction was already present long before physics became a formal discipline of science.

4.   The role of philosophy

As human beings cultivated crops, their mobility was confined to a smaller region compared to the hunter-gatherer era. This settlement at a place gave humans leisure to think and wonder about nature. As a consequence of this thinking, philosophical thoughts emerged (6).

Questions pertaining to philosophy, such as what life is and how humans live and interact with nature, occupied human minds. This exploratory era also gave rise to the need to understand the world, explore nature and harness it. Inquiries pertaining to the motion of celestial objects and that of common living and non-living things captured the attention.

To understand the intellectual foundations of physics, one needs to understand its connection to philosophy in general and philosophy of science in particular. The connection between reality and physical law is through an abstract formulation (2). Reality has its own complications, and a physical law retains only a small set of the complications that are evident in reality.

Although this connection between reality and a physical law looks to be straightforward, historically, there has been a large intellectual struggle to come to this point. It has not been an obvious task to connect reality to physical laws. And by studying the history of physics, it is evident that the route has been anything but smooth.

Another important aspect I need to emphasize is how reality becomes a raw material for scientific investigation. In essence, reality provides a kind of formless raw material on which physical laws can be formulated. These physical laws are drawn from a simplified structure of reality, and there is a process of encoding reality in a language that is amenable to scientific investigation.

This process of going from a multi-faceted reality to a slightly more precise physical law is done through assumptions, and these assumptions play a critical role. The pathway from reality to general laws has been through inductive methods, at least in the historical context. In the inductive method, there is an extrapolation from the finite to the general principles.

Based on certain observations in a concrete situation, one derives a general law. Now, the question is, how does one derive such a general law? This generalization is based on a logical process, and one of the best tools to implement logical analysis is mathematics. This is where the role of mathematics becomes so important in physics. If one needs to go from a concrete, realistic situation to an abstract principle, one will have to utilize mathematical tools such as geometry to convert the reality into an abstract formulation. An important aspect of physics and science, in general, is that once this abstract formulation has been postulated, the physical law can be tested going forward. The results can be checked by performing observations, and these observations can confirm or reject the induced hypothesis.

When it comes to the observation, there are two elements. The first is the observed object, and the second is the observer themselves. The demarcation between the observer and the observed object seems trivial; historically, it has not been the case. Because the observed object can interact with the observer, the physical laws that are derived from such observations must ensure that the observers themselves are not perturbing the physical reality. 

Also, the judgment of objectivity itself is a complex process because the criteria of truth have a social connection. This means what we call a factor of truth is closely connected to the social realities in which the observation is performed. This social connection brings in another layer of complication, and one must understand the philosophy behind these processes. 

As you can see, formulating science and, in our case, physics has not been a trivial task, given that these philosophical questions must be addressed to get a satisfactory answer. Understanding and discriminating science from other forms of human activity has not been a trivial exercise either, but it is with the help of philosophy that progress has been made.

This also highlights the intricate connection between philosophy, physics, experimental observation and technological developments as a network of events that interact with each other. Each part of this network plays a critical role and, many times, feeds back important information in the process. Therefore, to understand physics, we need to not only appreciate the philosophical questions but also be aware of technological developments.

Because many of the developments in the realm of scientific philosophy were motivated by technology and vice versa, this is also the reason why the history of physics is so interesting. It brings together all these epistemological components into one single platform and creates an intellectual magic that has played a critical role in understanding nature and the universe, that which can be observed and, in some cases, that which cannot be observed.

So, how did ancient people think about a subject called physics? What were the initiating thoughts of philosophers that led to physics? If we want to address these questions, we need to pay attention to some of the philosophers who thought and wrote about science. Among them, one of the earliest to do so was Aristotle. In the next essay, we will discuss his physics. 

References:

[1]       J. Poskett, Horizons: A Global History of Science. Penguin UK, 2022.

[2]       K. Simonyi, A Cultural History of Physics, 1st edition. Boca Raton, Fla: A K Peters/CRC Press, 2012.

[3]       “Lomekwi Stone Tools: the oldest artifact in the world.” Accessed: Mar. 24, 2025. [Online]. Available: https://www.thearchaeologist.org/blog/lomekwi-stone-tools-the-oldest-artifact-in-the-world

[4]       S. Pappu, Y. Gunnell, M. Taieb, J. Brugal, and Y. Touchard, “Excavations at the Palaeolithic Site of Attirampakkam, South India: Preliminary Findings,” Curr. Anthropol., vol. 44, no. 4, pp. 591–598, 2003, doi: 10.1086/377652.

[5]       S. Guha, A History of India through 75 Objects. Hachette UK, 2022.

[6]       P. Adamson, Classical Philosophy: A history of philosophy without any gaps, Volume 1. in A History of Philosophy. Oxford, New York: Oxford University Press, 2014.

not sufficiently “crazy”

Weinberg at 1977 APS meeting.

Writing in 1976, Weinberg made an interesting observation [1]:

A number of years ago, when I was an in-
structor at Columbia University, I heard a
rumor that Werner Heisenberg and Wolfgang
Pauli, two of the great figures in physics in this
century, had developed a new theory which
would unify the physics of elementary particles.
Thus, you can imagine my excitement when I
received an invitation to attend what was de-
scribed as a secret seminar to be conducted by
Heisenberg and Pauli. On the appointed day, I
was somewhat disconcerted to find some 500
distinguished theoretical physicists attempting to
crowd into the room; however, my enthusiasm
returned when I saw Niels Bohr seated in the
front row. (I had been a graduate student at
Copenhagen and had learned to look on Bohr
as an oracle.) After Heisenberg and Pauli dis-
cussed their theory, Bohr commented on it, con-
cluding that he doubted the theory would be
the great new revolution in physics because it
was not sufficiently “crazy.”

He further adds :

This remark reflects an opinion, very common among
physicists for the past forty years, that the next
significant advance in theoretical physics would
appear as another revolution – a break with the
concepts of the past as radical as the great revo-
lutions of the first third of the twentieth century:
the theory of relativity and the development of
quantum mechanics. That opinion may yet be
proved true, but what has been developing in
the last few years is, in fact, a different sort of
synthesis. There is now a feeling that the pieces
of physics are falling into place, not because of
any single revolutionary idea or because of the
efforts of any one physicist, but because of a
flowering of many seeds of theory, most of them
planted long ago

I like this way of thinking in terms of synthesis. It is closer to how science is done today than giving all the credit to an individual. Weinberg was a fine thinker who deeply thought about physics and its history. This is evident in his writing and talks.

Reference:

[1] S. Weinberg, “The Forces of Nature,” Bulletin of the American Academy of Arts and Sciences, vol. 29, no. 4, pp. 13–29, 1976, doi: 10.2307/3823787.

Stern-Gerlach experiment – the first picture

The above picture is from Friedrich, Bretislav, and Dudley Herschbach. “Stern and Gerlach: How a Bad Cigar Helped Reorient Atomic Physics.” Physics Today 56, no. 12 (December 1, 2003): 53–59. https://doi.org/10.1063/1.1650229.

During the formative years of quantum mechanics (early 1900s), the spin and orbital angular momentum of atoms were found to be quantized by theoretical arguments. Experimental proof was lacking.

Stern-Gerlach experiment provided the first experimental proof in 1922. They took a beam of neutral silver atoms and deflected them through an inhomogeneous magnetic field.

Silver atoms have an unpaired electron in their outermost orbit. If they were to obey quantum mechanics, they should exhibit a spin of +1/2 or -1/2. When subjected to an external magnetic field, the electrons with +1/2 or -1/2 should spatially split into two. That is exactly what Stern and Gerlach observed, and below is the first picture of the same.

To quote the authors:

Gerlach’s postcard, dated 8 February 1922, to Niels Bohr. It shows a photograph of the beam splitting, with the message, in translation: “Attached [is] the experimental proof of directional quantization. We congratulate [you] on the confirmation of your theory.” (Courtesy AIP Emilio Segrè Visual Archives.)

This experiment was one of the most important observations in quantum mechanics and further confirmed the quantization of spins, which is now common knowledge in physics.

Willow in comparison – Google quantum chip

In scientific research, comparative analysis is an excellent way to objectively quantify two measurable entities. The recent Google quantum chip (named Willow) does that efficiently as it compares its capability with today’s fastest supercomputers. The comparison note on Google’s blog is worth reading.

In scientific analysis, such comparison teaches us three things:

a) how a scientific boundary is claimed to be pushed?

b) how a benchmark problem is used to achieve comparison?

c) what is the current state-of-the-art in that research area?

Some further observations on the work:

  • The theme of the Nature paper reporting this breakthrough is mainly on error correction. Technically, it shows how error tolerance is measured for a quantum device. This device is based on superconducting circuits, which were tested first on a 72-qubit processor and then on a 105-qubit processor.
  • Interestingly, as the authors mention in the paper, the origins of the errors are not understood well.
  • The paper is quite technical to read, and, to my limited understanding as an outsider, it makes a good case for the claim. The introduction and the outlook of the paper are written well, and give more technical information that can be appreciated by a general scientific audience.
  • There is more to come ! It looks like Google has further plans to expand on this work, and it will be interesting to see in which direction they will take the capability. The Google blog shows a roadmap and mentions their ambition as follows: “The next challenge for the field is to demonstrate a first “useful, beyond-classical” computation on today’s quantum chips that is relevant to a real-world application. We’re optimistic that the Willow generation of chips can help us achieve this goal.”
  • In the past 12 months or so, there has been a lot of buzz related to AI tools (thanks to GPTs, Nobels and perplexities :-), which are mainly in the realm of software theoretical development. This breakthrough in the realm of ‘hardware’ tells us how the physical world is still important!

More to learn and explore…interesting times ahead..

Conversation with Ayan Banerjee

Ayan is an experimental optical physicist and a Professor at IISER Kolkata: https://www.iiserkol.ac.in/~ayan/group_leader.html.

He is also a playwriter, theatre actor and a mentor to many science and arts enthusiasts.

What drives him to do all these things? We discuss this and many other things in this episode.

References:

  1. “Group Leader | Light-Matter Lab.” Accessed December 2, 2024. https://www.iiserkol.ac.in/~ayan/group_leader.html.
  2. “IISER Kolkata – Ayan.” Accessed December 2, 2024. https://www.iiserkol.ac.in/web/en/people/faculty/dps/ayan/.
  3. “Ayan Banerjee – Professor – Indian Institute of Science Education & Research (IISER), Kolkata | LinkedIn.” Accessed December 2, 2024. https://in.linkedin.com/in/ayan-banerjee-3034208.
  4. Department of Physical Sciences (DPS), IISER Kolkata, 2022. https://www.youtube.com/watch?v=vgv7iODxYTY.
  5. “Department of Physical Sciences : Home.” Accessed December 2, 2024. https://physics.iiserkol.ac.in/.
  6. Ayan Banerjee. Accessed December 2, 2024. https://www.facebook.com/ayan.banerjee.5895.
  7. “‪Ayan Banerjee – ‪Google Scholar.” Accessed December 2, 2024. https://scholar.google.co.in/citations?user=GQo7yG4AAAAJ&hl=en.
  8. Gupta, Subhasish Dutta, Nirmalya Ghosh, and Ayan Banerjee. Wave Optics: Basic Concepts and Contemporary Trends. CRC Press, 2015.
  9. Haldar, Arijit, Sambit Bikas Pal, Basudev Roy, S. Dutta Gupta, and Ayan Banerjee. “Self-Assembly of Microparticles in Stable Ring Structures in an Optical Trap.” Physical Review A 85, no. 3 (March 27, 2012): 033832. https://doi.org/10.1103/PhysRevA.85.033832.
  10. “Indian Institute of Science.” Accessed December 2, 2024. https://iisc.ac.in/events/remembering-prof-vasant-natarajan-1965-2021/.
  11. “LML.” Accessed December 2, 2024. https://sites.google.com/iiserkol.ac.in/light-matter-lab-iiserk/.
  12. “LML – Physics of Micro-Bubbles.” Accessed December 2, 2024. https://sites.google.com/iiserkol.ac.in/light-matter-lab-iiserk/research/physics-of-micro-bubbles.
  13. Network, N. F. N. “Theatre At IISER-K Against Misinterpretation of Science And Superstition,” January 17, 2019. https://newsfromnadia.in/theatre-at-iiser-k-against-misinterpretation-of-science-and-superstition/.
  14. “Self-Assembly of Mesoscopic Materials To Form Controlled and Continuous Patterns by Thermo-Optically Manipulated Laser Induced Microbubbles | Langmuir.” Accessed December 2, 2024. https://pubs.acs.org/doi/full/10.1021/la402777e.
  15. X (formerly Twitter). “Ayan Banerjee (@ayanban7) / X,” November 26, 2024. https://x.com/ayanban7.