by Gurbir Singh
Figure 4‑5 Raman in Europe. Credit IISc Archives
However, during the period of World War II, two individuals came under Raman’s influence who had a very direct impact on India’s space programme, Vikram Sarabhai, who completed most of his PhD at the IISc, and Homi Bhabha, who taught at the institute, first as a reader and then as a professor. Perhaps, inspired by Raman, both went on to dedicate their professional lives to scientific development in India. Had Raman managed to attract scientists and theoreticians from Europe, the tradition of high-class research in India today would probably have been established sooner. With deeper roots in science, perhaps the technological progress that India is making today could have been made a decade or two earlier.
Satyendra Nath Bose
Science has provided answers to some fundamental questions, such as how old the universe is, how big it is and what it is made from. Physicists classify everything that exists in the universe either as fermions or bosons. Fermions make up all the matter in the universe. Four bosons mediate the four known forces, gravity, strong nuclear force, weak nuclear force and electromagnetic force, between them.[232] The term ‘boson’ was coined by Paul Dirac (1902–1984), a British theoretical physicist, acknowledging the work of Bengali mathematician and physicist Satyendra Nath Bose (1894–1974).[233]
Bose was born and educated in Calcutta (now Kolkata), the epicentre of the scientific renaissance in India during the early 20th century. He was a polyglot, who was comfortable communicating in French, German, Italian, Sanskrit, Bengali, English and Hindi. He developed an interest in experimental physics, the subject in vogue at the time. Optics, spectroscopy and wireless technologies were emerging just as his formal education was coming to an end. During his career, Bose designed and built equipment for X-ray (crystallography, diffraction and spectroscopy), optical spectroscopy and wireless technology,[234] but his unique theoretical work in mathematics and quantum physics remains his greatest contribution.
The regular supply of fresh scientific literature coming into India dried up in 1915 as World War I engulfed Europe. This turned out to be a blessing in disguise for Bose. A chance contact with an Austrian instructor P.J. Brühl, working at the Bengal Engineering College, got Bose reading books on mathematics, magnetism and physics in German. He borrowed from Brühl’s personal collection several books, including Max Planck's (1858–1947) Theories der Wärmestrahlung (Theory of Heat Radiation) and Max von Laue’s (1879–1960) Das Relativitätsprinzip (Principles of Relativity). This chance encounter with the German language and the leading-edge work in physics and mathematics being done in Germany eventually put Bose in touch with Albert Einstein that would eventually elevate Bose to international recognition.
In 1918, Bose, jointly with Meghnad Saha, wrote his first research paper titled ‘The influence of the finite volume of molecules on the equation of state’. The paper dealt with the properties and behaviour of actual (but complex) gases instead of idealised (but simple) gases. It was published in the Philosophical Magazine in London, the same publication where C.V. Raman had published his first scientific paper a decade earlier. In late 1923, Bose submitted another paper to the Philosophical Magazine, but it was rejected by the referees.[235] In the rejected paper, Bose was covering new ground in quantum theory, which itself was so new and revolutionary that not many people, probably including the referees, understood its underlying concepts.
In 1900, Max Planck had introduced the concept of quanta where the energy of electromagnetic radiation existed only in predefined fixed quantities (quanta) rather than any value from within a continuum. His work introduced a new fundamental constant, Planck’s constant, and ushered in the quantum theory (also known as quantum mechanics) to explain the phenomena at the subatomic level that classical physics could not. During the early 20th century, physicists had still not resolved the bigger question of what light was made of, waves or particles. In the paper that was rejected by the Philosophical Magazine, Bose had developed Planck’s work using a new form of statistics, in which he introduced properties of waves, as well as quanta, to establish a quantum theory of ‘ideal’ gases.
Figure 4‑6 Transcript of S.N. Bose’s 1924 Letter to Albert Einstein. Credit S.N. Bose
Confident of the quality of his work, Bose wanted his rejected paper published in a highly respected German publication, Zeitschrift für Physik. Although he had a good understanding of the German language, Bose was not sufficiently competent to write a full scientific paper in German. In 1924, Bose wrote to Einstein, by then a Nobel laureate, asking him to forward Bose’s paper for publication to Zeitschrift für Physik if he considered it worthy, a remarkably audacious act for a young unknown researcher in a corner of the British Empire[236] This was not the first interaction Bose had had with Einstein. In 1918, Bose had contacted Einstein requesting consent to translate from German to English Einstein’s jointly authored book The Principle of Relativity, a collection of writings, including Einstein’s seminal paper, ‘The General Theory of Relativity’, first published in 1915. Einstein had agreed, and the first English translation of Einstein’s ‘General Theory of Relativity’ was published in India by the University of Calcutta in 1920.[237] In 1924, four years after completing the translation of Einstein’s work from German to English, Bose wrote to Einstein asking him to return the favour.
Einstein was impressed with Bose’s paper ‘Planck’s Law and Light Quantum Hypothesis’. He translated it into German and submitted it for publication, adding “In my opinion, Bose’s derivation of the Planck formula signifies an important advance.” He informed Bose with a postcard dated 2 July that he had submitted it for publication. This one postcard helped Bose secure a two-year research trip to Europe with a generous “stipend, a separation allowance for the family, with sumptuous travel allowance with round-trip fare”, and ultimately crystallised his place in the history of science.[238] Bose departed from Bombay in September and arrived in Paris on 18 October 1924. He had never travelled out of India before. During the following two years in France and Germany, Bose worked and made personal contact with leading figures in science, many of whom would achieve the ultimate recognition as Nobel laureates. In France, he had the opportunity to communicate in French and get hands-on experience of X-ray spectroscopy at the laboratory of Maurice de Broglie (1875–1960) and of radioactivity with Madame Curie (1867–1934) at her Radium Institute in Paris.
Einstein extended Bose’ original paper and they jointly predicted a new state of matter that when cooled to almost absolute zero (-273K) produce this new state of matter called Bose-Einstein Condensate (BEC). BEC exhibits two unique properties, superfluidity, where the flow is devoid of friction, and superconductivity, where there is no electrical resistance. BEC was a product of the statistics that Bose had introduced, but the technology to create it did not exist in his time. While predicted in 1924–25, it was created for the first time in 1995 by scientists in the US. Today, BEC is used to help understand dark matter, one of the key topics that preoccupy present-day cosmologists.[239]
In October 1925, Bose arrived in Berlin, where he gave and attended lectures, meetings and seminars. Bose held seminars in German on low-temperature statistics, which concluded with detailed and lengthy question and answer sessions. During his time in Berlin, Bose conducted experiments on the refracting index of X-rays at the Kaiser Wilhelm Institute. In his letter dated 9 May 1926, Herman Mark (1895–1992) states “his most valuable quality which makes him of inestimable value to a collaborator is his deep and clear insight into the fundamentals of science.”[240]
He also met several luminaries from Germany and beyond, including Max Born, Theodore von Kármán (1881–1963), Max Planck, Leo Szilard (1898–1964), Fritz Haber (1868–1934), Werner Heisenberg (1901–1976), Hans Geiger (1882–1945), Wolfgang Pauli (1900–1958), Herman Mark, Lise Meitner (1878–1968) and Albert Einstein. In an interview recorded in 1974, Herman Mark recalled a jovial and friendly Bose.[241] During the many social gatherings, Bose even
sang in German. Herman also recalled the time Bose and Einstein spent together walking in the grounds of the Institute in Dahlem. Although they spent much time together, they did not undertake any further joint work, and nothing was formally published as a result. As Bose’s time in Europe was coming to an end, Herman Mark took Bose to Vienna for a few days, where he was invited to give a seminar, and he made personal contact with Erwin Schrödinger (1887–1961), Hans Thirring (1888–1976) and Ludwig Flamm (1885–1964).[242]
On his return to India in 1926, Bose accepted the role of the professor of physics at Dacca University (now University of Dhaka). Over the next two decades, starting from scratch, he developed laboratories and libraries and nurtured a tradition of experimental research. He did not limit the activities of his department to areas of his personal interest. He encouraged disparate specialisms, which eventually included spectroscopy, magnetic properties of matter, wireless and crystallography. Laboratory equipment (including a demountable X-ray unit, differential thermal analyser and fully automatic scanning spectrophotometers for thermoluminescence studies) was not imported from Europe but made in-house using local material by students under Bose’s guidance.
During his lifetime, Bose published 24 papers. Following his return from Europe in 1926, he devoted most of his time to building his department and published only 17 papers. When Madame Jacqueline Eisenmann (1904–1998), a scientist Bose met during his first visit to Paris in 1924 and again in 1951, asked Bose why he had not published more, he said “he had spent a great deal of time in preparing experimental research work for his pupils in Dacca”.[243] Bose was dedicated to his students. Madame Eisenmann recalled in an interview in July 1973 that Bose “had no ambition for himself, … a very modest man who had an extraordinary heart.”[244]
For a man with a tranquil temperament, Bose harboured strong anti-colonial tendencies. He had experienced tumultuous events in Bengal throughout his life. In 1905, while he was still in school, Bengal was partitioned. Later in 1943, Bengal suffered a severe famine with a loss of life on a catastrophic scale. After India gained independence from the Britain in 1947, Bengal experienced extreme violence during partition into West Bengal and East Pakistan, and this was followed by the Bangladesh Liberation War in 1971. During his student days, he was a member of several secret societies and attended meetings in the pursuit of Indian independence. His visit to Europe was not just motivated by his science but his politics, too.[245] Some accounts claim that Bose out of pride chose not to visit the Britain prior to India’s achieving its independence. Bose, however, had written to Ernest Rutherford and William Bragg during his 1924 trip to Europe but neither could host him at that time.[246]
Figure 4‑7 Bose-Einstein Condensate. Credit Massachusetts Institute of Technology
Bose’s work was recognised, somewhat belatedly, when he was elected as a Fellow of the Royal Society in 1958. Subrahmanyan Chandrasekhar, the Indian astrophysicist (later an American national), who personally knew many of the key Indian scientists, including Homi Bhabha, Meghnad Saha, C.V. Raman and J.C. Bose, said “from human point of view, [S.N. Bose] was the best of them all. He was very generous, gentle, easy-going and not particularly caring about the glamorous aspects of science.” Rabindranath Tagore, perhaps the first intellectual from India to receive widespread recognition in the West, published a collection of essays on science, Visva Parichay—An Introduction to the Universe, and dedicated it to Bose.
Homi Jehangir Bhabha
Homi Bhabha lived through perhaps one of the most intensive periods of fundamental discovery that physics has ever seen. Many of the heavyweights in physics, Albert Einstein, Patrick Blackett, C.V. Raman, Niels Bohr, Wolfgang Pauli, Enrico Fermi, Werner Heisenberg, Paul Dirac, Erwin Schrödinger and John Cockcroft (1897–1967) were his contemporaries, teachers or colleagues and a few his friends. Bhabha came from a successful family of industrialists synonymous with India. Dorabji Tata was his uncle, a name that continues to be associated with Indian commerce and industry in the 21st century. His father had envisaged that Bhabha would study engineering and join the extended family firm Tata Steel as a metallurgist, but that is not how things turned out. He excelled in his education, contributed unique research and developed a reputation as a high-calibre scientist in a premier European scientific institution. In the two decades that followed India’s independence, Bhabha was instrumental in establishing India’s first pure research institute, civil nuclear energy programme, nuclear weapons programme and space programme.
In 1924, at the age of 15, Bhabha passed the Cambridge entrance exam in India with distinction. Since the minimum age for Cambridge was 18, he spent the next three years studying Art and Science before arriving at Gonville and Caius College, Cambridge, in 1927, to study mechanical engineering.[247] Europe at this time was a hothouse for scientific discoveries in physics. By chance, much of it was happening at the Cavendish Laboratory in Cambridge, exactly where Bhabha was studying. Intelligent, ambitious and inquisitive, it was almost inevitable that he would be hooked by physics. In 1928, he wrote to his father expressing his interest in physics saying “I seriously say to you that business or a job as an engineer is not the thing for me. It is totally foreign to my nature and radically opposed to my temperament and opinions. Physics is my line ... I am burning with a desire to do physics”. His father relented but insisted that he complete his engineering degree first before moving to physics. He earned a degree in mechanical engineering, and in 1932, another in mathematics. Both first class.
In the next three years, he completed his PhD, won additional scholarships and split his time between writing and publishing scientific papers and working with noted physicists in Europe and the US. The year 1932 was a particularly productive one for Cambridge, and Bhabha was there to experience it first-hand. In February 1932, James Chadwick (1891–1974) discovered the neutron (one of the two elementary particles inside the nucleus of the atom), and in April, John Cockcroft and Ernest Walton (1903–1995) demonstrated the idea of transmutation, changing one element into another. They changed large lithium atoms into smaller helium atoms by firing high-speed protons at a sample of lithium. While in Europe, Bhabha travelled to meet Enrico Fermi in Rome, Niels Bohr in Copenhagen and Wolfgang Pauli in Zurich. While in Zurich in 1933, with assistance from Pauli, Bhabha published his first paper in German 'Zur Absorption der Höhenstrahlung' in Zeitschrift für Physik on the absorption of cosmic rays.[248] Cosmic rays are a mixture of high-speed particles (mostly protons) and high-energy radiation (X-rays and gamma-rays) from outside the solar system. After travelling for potentially billions of years through the vacuum of space to Earth, cosmic rays interact with the molecules in the Earth’s upper atmosphere. Bhabha investigated these interactions for his PhD in nuclear physics, which he completed in 1935.
Figure 4‑8 Homi Bhabha (second from the left) in Cambridge. Credit. Tata Institute of Fundamental Research
In 1897, physicist J.J. Thomson (1856–1940) discovered the first subatomic particle, the electron. An indivisible bit of matter had been contemplated since the beginning of human civilisation. A new category of particles called antiparticles was discovered in 1932 by Carl Anderson (1905–1991).[249] Anderson’s discovery of a particle identical to the electron but with a positive charge ushered in the era of antimatter. Nuclear physicists had to invent new terms and mechanisms to understand and calculate interactions associated with antiparticles.
The positron had been predicted in 1933 that “the positron appeared as one of a pair of positive and negative electrons produced when a gamma-ray was converted into matter.”[250] This idea that energy can be transformed into matter was established by Einstein’s famous equation E=mc2. If matter can be turned into energy, then energy, too, can be turned into matter. This is what nuclear scientists were seeing in the interactions between nuclear particles. Three years after antimatter was discovered, Bhabha published a paper describing what happens when matter and antimatter particles meet. He described mathematicall
y the interaction between an electron and a positron moving at very high speeds. When they meet, they mutually destroy each other (annihilate) producing a gamma-ray (mass changed to energy). Bhabha went on to describe the scenario in reverse. When high energy particles collide, the interaction produces gamma-rays. Gamma-rays decay producing an electron and positron pairs spontaneously (energy changed to mass). This is Bhabha Scattering, and his work is used in modern particle accelerators to calibrate positron beams.[251] Before the age of 30, Bhabha had established his name in the field of cosmic rays and within the community of physicists responsible for the fundamental discoveries made during what turned out to be the golden age of physics.
In 1937, Bhabha attended a weekend conference in Manchester, the UK, where Werner Heisenberg and Patrick Blackett were also in attendance. Heisenberg had already been awarded a Nobel Prize, and Blackett was still a decade away from his. Despite Blackett's senior position, the 28-year-old Bhabha confidently argued his assertion that only a new unknown particle, heavier than an electron, can explain the penetrating attributes of cosmic rays observed in experiments. Blackett insisted that quantum theory would fail at higher energies associated with heavier particles. Subsequently, Bhabha was proved right. Bhabha was confident, bright and self-assured. Although neither of them knew it then, Bhabha would engage Blackett to help him embed science in rebuilding independent India. Heisenberg and Bhabha would have cooperated further, but the tumult of the impending war changed the destinies of nations, as well as individuals.