VISMAYA: History & Philosophy of Physics

Tag: physics

  • My Response to Kaplan

    Recently, anthropic co-founder Jared Kaplan, who has a background in physics, made the following comment, which was circulated on X. Below is the excerpt:

    Below is my response:

    A Remarkable Human Being = Remarkable Attribute(s) + Human Being

    The first term in the RHS can be replaced by AI, but not the second term, for the following reasons.

    1. Machines, including AI, can surely change the way humans think, work and live, but it will be difficult to match human connection. A machine can enhance human life, but can it inspire a human life?
    2. People inspire people. Ask a child or any adult who inspires them. It will generally be a fellow human being. Machines add value, but human beings represent a valuable life. We utilize the former, and get inspired by the latter. It is this inspiration that propels people forward to do things that may further turn out to be remarkable. This contribution is not easily quantified, but it is hard to gauge a human life without inspiration.
    3. People like Ed Witten, Ashoke Sen and Terry Tao add value to humanity not only through their work and ideas, but their lives show that human beings can think and do something remarkable. It assures human beings that, individually, our species can do something good.
      Human beings derive meaning by interacting with fellow human beings and are inspired by the interaction. They also get inspired and draw meaning by studying people from the past. A human’s search for meaning and purpose is always in the background of other human beings. We are 8 billion plus, and it is hard to ignore each other.

    It will be very unusual to find a serious student of theoretical physics who says I am inspired to live by ‘ChatGPT’.

    Probably a young Kaplan, too, was inspired by a fellow human being! So, my question to Mr. Kaplan.
    Who inspired you to do physics?

  • Raman Effect – The paper that announced it…

    Here I discuss the paper that announced the Raman effect to the world…

  • 26 Jan – Indian Republic Day…and a few more

    Happy Republic Day to all my fellow Indians !

    26th Jan is also an important day in the history of physics/engineering –

     Oliver Hutchinson — subject of the earliest photograph of a television image, early 1926. National Media Museum (for image on right). Image from: The International Journal for the History of Engineering & Technology 84 (2): 227–47.

    26th Jan 1926 – J.L. Baird “demonstrated television at his premises in Frith Street, London, to about forty people including members of the Royal Institution…..The Times was the only newspaper invited, and its reporter published the story on 28 January”. This exactly a 100 years today !

    26th Jan 1939 – Niels Bohr publicly announced nuclear fission, specifically the splitting of the uranium atom.

    26th Jan 1954 – Morris Tanenbaum et al. at Bell Laboratories showed a working silicon transistor.

    References for further reading:

    McLean, Donald F. 2014. “The Achievement of Television: The Quality and Features of John Logie Baird’s System in 1926.” The International Journal for the History of Engineering & Technology 84 (2): 227–47. https://doi.org/10.1179/1758120614Z.00000000048.

    “Niels Bohr Announces the Discovery of Fission – Nuclear Museum.” n.d. Https://Ahf.Nuclearmuseum.Org/. Accessed January 26, 2026. https://ahf.nuclearmuseum.org/niels-bohr-announces-discovery-fission/.

    “The Lost History of the Transistor.” 2004. IEEE Spectrum 41 (5): 44–49. https://doi.org/10.1109/MSPEC.2004.1296014.

    Wikipedia. 2025. “History of the transistor.” December 22. https://en.wikipedia.org/w/index.php?title=History_of_the_transistor&oldid=1328866801.

  • C V Raman and long term thinking

    A small sampling of Raman’s publication. These papers are related to light scattering and form the foundation on which he made his famous discovery. Raman wrote more than 400 research papers in his lifetime (apart from monographs, lectures and public talks). Writing such a series of papers on a particular topic can be observed throughout his career.

    A note to young scholars: intellectual monuments are built this way: thought after thought, day after day, paper after paper. Never underestimate what can be achieved with consistent, honest effort.

  • Brillouin on Sommerfeld

    “Everybody wondered (and still wonders) why the Stockholm committee systematically ignored Sommerfeld’s pioneer work in modern physics. Such an omission is actually impossible to understand.”

    Leon Brillouin, in the foreword of his book WAVE PROPAGATION AND GROUP VELOCITY (1959)

    Brillouin further mentions the teachers who taught him, and rates Sommerfeld among the best:

    “I had the great privilege of attending, as a student, lectures given by some prominent physicists, such as H. A. Lorentz, H. Poincaré, and P. Langevin. But I was especially impressed by Sommerfeld’s mastery as a teacher.“

  • Conversation with Srubabati Goswami

    Srubabati Goswami is a pioneering Indian physicist specializing in high-energy physics, particularly neutrino physics. She is probably the first Indian woman to earn a PhD in neutrino oscillations from the University of Calcutta. She advanced research at Physical Research Laboratory, Ahmedabad (PRL), Saha Institute of Nuclear Physics, and Harish-Chandra Research Institute before becoming Senior Professor at PRL. A fellow of India’s three science academies, she unravels neutrino mysteries and champions women in science.

    In this episode, we explored her intellectual history and her remarkable journey as a physicist.

    References:

    1. Srubabati Goswami | LinkedIn’. Accessed 16 January 2026. https://www.linkedin.com/in/srubabati-goswami-9b5ab520/?originalSubdomain=in.
    2. Dogra, Aashima. A Trailblazer Looks for the Keys to the Next Generation of Physics Research – The Wire Science. 7 September 2017. https://science.thewire.in/science/srubabati-goswami-neutrino-ino-dino-kamiokande-prl/.
    3. Godbole, Edited Rohini, and Ram Ramaswamy. LILAVATI’S DAUGHTERS. n.d.
    4. ‘Indian Academy of Sciences’. Accessed 16 January 2026. https://fellows.ias.ac.in/profile/v/FL2017008.
    5. Sciences (TWAS), The World Academy of. ‘Goswami, Srubabati | TWAS’. Accessed 16 January 2026. https://twas.org/directory/goswami-srubabati.
    6. ‘Srubabati Detangles Weird Phenomena’. The Life of Science, 6 September 2017. https://thelifeofscience.com/2017/09/06/srubabati-detangles-weird-phenomena/.
    7. ‘‪Srubabati Goswami – ‪Google Scholar’. Accessed 16 January 2026. https://scholar.google.co.in/citations?user=YbhShAcAAAAJ&hl=en.
    8. ‘The Neutrino Story: From Impossible Dreams to Unreachable Stars (ONLINE) by Srubabati Goswami – YouTube’. Accessed 16 January 2026. https://www.youtube.com/watch?v=XZKadiBqhrA.
    9. ‘Women Shaping Scientific Frontiers: From Lab Coats to Leadership (27 Stories of Women Leaders in Physics and Engineering) | Exotic India Art’. Accessed 16 January 2026. https://www.exoticindiaart.com/book/details/women-shaping-scientific-frontiers-from-lab-coats-to-leadership-27-stories-of-women-leaders-in-physics-and-engineering-hba517/.
    10. X (Formerly Twitter). ‘(1) Srubabati Goswami (@srubabati) / X’. 29 December 2025. https://x.com/srubabati.

  • Raman-Chandra Letters

    ref: https://www.jstor.org/stable/24097489?seq=3

  • Saha and Bose translate Einstein

    In physics, the general theory of relativity is one of the most remarkable achievements. It has turned out to be one of the most profound theories in the history of physics. In 1916, Albert Einstein proposed this theory, and it was confirmed in 1919.

    Right after this confirmation, around 1920, two Indian gentlemen named Satyendranath Bose and Meghnad Saha translated Einstein’s German work into English. What you are seeing as an image is the remarkable book Principles of Relativity, containing the original papers by Einstein and Minkowski. This translation was done by M.N. Saha and S. N. Bose, who were then at the University College of Science, Calcutta University. It was published in 1920 by the University of Calcutta.

    The book also contains a historical introduction by Mahalanobis, the celebrated statistician, although he was originally trained as a physicist himself. This historical introduction is itself quite remarkable.

    If you look at the table of contents of this book, you will find the following:

    1. A historical introduction.
    2. The Electrodynamics of Moving Bodies, which is an important paper and is necessary for understanding what follows.
    3. A short biographical note on Albert Einstein was written by Saha.
    4. The Principle of Relativity, mainly the Minkowski papers, translated by Saha, along with an appendix.
    5. The General Principles of Relativity, Einstein’s epoch-making 1916 paper, translated by S. N. Bose, followed by notes by these gentlemen.

    The historical introduction discusses the evolution of ideas that led to the fruition of the general theory of relativity. This turned out to be one of the most important expositions of the general theory of relativity, soon after the emergence of the theory and its subsequent confirmation by Eddington through his famous solar eclipse expedition. This is a remarkable document, and it is available on the Internet Archive.

  • Quantum Optics course – thoughts and notes

    Jan 2026 – Apr 2026 – I am teaching a course on Quantum Optics. Below you will find some random thoughts and notes related to my reading. I will be updating the list as I go along the semester. You can add your comments below.

    Lectures:

    Pavan’s lectures on Quantum Optics (not the whole course)

    Some timelines for reference:

    Interactive timeline – includes pre-quantum optics

    1. Anyone interested in physics should know a bit about renormalized QED and the efforts that went behind it… It still remains a benchmark of how experiments and theory work in elevating each other…
      • Hari Dass (erstwhile, IMSc) on FB made an interesting observation:it’s unfortunate that after all those and subsequent developments, a mystery is being built out of renormalisation..it was the price to pay for assuming, without any justification, that the microscopic description held to arbitrarily small distances..wilson,schwinger and even feynman have clarified that the right way to do physics is to start with an effective description with a cutoff, which can be fully quantum in nature, and keep extending it to higher and higher scales with the help of further data, as well as with better theoretical understanding..
    2. “The photon is the only particle that was known as a field before it was detected as a particle.” 
      • This is how Weinberg introduces the birth of quantum field theory. He further adds:  “Thus it is natural that the formalism of quantum field theory should have been developed in the first instance in connection with radiation and only later applied to other particles and fields.”Ref: S. Weinberg (in Quantum Theory of Fields, p.15,  1995)
        • Sudipta Sarkar (IIT G) made an interesting observation in facebook:
          • “In some sense, it did right! Dirac started QFT with the effort to quantise radiation! But formally, it is not easy to write down the quantum version of electrodynamics owing to gauge symmetry. It took quite a bit of time to understand how to manage a quantum theory with massless states!“
          • My reply: “indeed..the reconciliation of symmetry was a bottleneck. I am also amazed by the progress of thought, especially by Dirac, who took the harmonic oscillator problem and treated it the way he did. Historically, the question of quantization of particles was already an established programme, but to quantize the field was indeed a major challenge, and hence ‘second quantization’.“
          • The concept of creation and annihilation operators is an intriguing one because it brings in the thoughts from the commutation relationship that existed in classical physics and transfers that into quantum mechanics. This intellectual connection is mainly attributed to Dirac, and historically, this has been one of the most important connections to be made. The question of field quantization already existed in 1920s, but it is thanks to Dirac who really made this connection in a systematic and mathematically consistent way.
    3. In the context of the quantum harmonic oscillator model of electromagnetic radiation, the shift from canonical variables such as position and momentum to creation and annihilation operators is a fascinating one. Interestingly, this progression further leads to the so-called number operator. It is also a progression from Hermitian to non-Hermitian and again back to a Hermitian operator. In the process of understanding the number operators, one realizes that the ground-state results in the so-called zero-point energy. Taken further, the commutation of the number operator with the electric field of the electromagnetic radiation results in the number-amplitude uncertainty. This further gives an insight into why the field amplitude has a non-zero spread, even for the n = 0 state, and therefore results in the so-called vacuum fluctuations.
      • It can’t get more quantum than this…
    4. An essay on Quantum States in Argand Diagrams: https://historyofscience.in/2026/02/03/quantum-states-in-argand-diagrams-vacuum-coherent-and-squeezed/
    5. The word photon has an interesting and surprising origin – see this paper.
    6. Born & Wolf to Mandel & Wolf – a blog on a famous book and on the connection between radio astronomy and quantum optics.
    7. Intensity Interferometer – connection to coherence
    8. References related to Hong-Ou-Mandel experiments:
      • Original paper
        • Hong, C. K., Z. Y. Ou, and L. Mandel. ‘Measurement of Subpicosecond Time Intervals between Two Photons by Interference’. Physical Review Letters 59, no. 18 (1987): 2044–46. https://doi.org/10.1103/PhysRevLett.59.2044.
      • The references below discuss a few contemporary yet simple approaches toward the HOM experiment. 
        • DiBrita, Nicholas S., and Enrique J. Galvez. ‘An Easier-to-Align Hong–Ou–Mandel Interference Demonstration’. American Journal of Physics 91, no. 4 (2023): 307–15. https://doi.org/10.1119/5.0119906.
        • Bjurlin, Cyrus, and Theresa Chmiel. ‘A Versatile Hong–Ou–Mandel Interference Experiment in Optical Fiber for the Undergraduate Laboratory’. American Journal of Physics 93, no. 2 (2025): 180–86. https://doi.org/10.1119/5.0210869.

    Prof. Supradeepa from IISc made an important observation related to the non-Poissonian distribution and anti-bunching as follows: When I taught quantum optics earlier this semester, there was an interesting discussion with students which I had not had given thought previously. I have seen the terms anti-bunching and g2(0) < 1 sometimes interchanged. But the idea is that g2(0) < 1 is only non-poissonian while, the stronger condition that g2(0) < g2(\tau) is also needed to have anti-bunching. An easy to calculate example was fock states with |n> for n > 1. g2(tau) = 1-1/n, so these states are non-poissonian because g2(0)<1, but not anti-bunched.

    My reply: This is an important point, and Fox’s book has a small discussion related to this non-equivalence: sub-Poisson distribution and anti-bunching can overlap, but need not be the same. As you mentioned, g2(0) < 1 and g2(0) < g2(\tau) have to be satisfied. The criteria for a single-photon source are much stricter than those for a sub-Poisson light source. In my lecture, I do mention this as seen in the picture…

  • Raman in a marriage reception

    C.V. Raman was obsessed with science, and he was actively thinking about research problems even on odd occasions when he was supposed to be socializing. Nagendra Nath, in 1971, recounts1:

    In November 1969, he and Lady Lokasundari Raman were graciously pleased to attend the marriage reception of my daughter. Professor drew me aside outside the reception hall and told me for nearly half-an-hour that his latest problem was to give a proper theory of earthquakes. The present theories were based on models which were highly deficient as they did not properly take into account the shape of the earth and the wave nature of the disturbance.

    Nearly half an hour !!
    Imagine the condition of Nagendra Nath :-)

    1. Nath, N. S. Nagendra. ‘My Professor’. Current Science 40, no. 9 (1971): 234–35. https://www.jstor.org/stable/24074207.
      ↩︎