K. S. Krishnan

Anyone asking who was K. S. Krishnan must begin in Watrap, a small town in the Tamil-speaking south of British India, where Kariamanikkam Srinivasa Krishnan was born on December 4, 1898 ^[1]. His family belonged to a rural landholding community, and he grew up steeped in Tamil literature and classical learning, an attachment he kept for the rest of his life. Friends and colleagues later remarked on his ability to quote Tamil poetry from memory in the middle of scientific conversation ^[2].

Krishnan received his early schooling locally before moving on to the American College in Madurai and then to Madras Christian College, one of the leading institutions of higher education in the Madras Presidency. He took his degree in physics there and stayed on for a period as a demonstrator in chemistry, gaining laboratory experience that would serve him well ^[1]. The teaching post also gave him a modest income at a time when research careers for Indians were scarce and poorly funded.

The decisive turn came in 1920, when he traveled north to Calcutta to join the Indian Association for the Cultivation of Science (IACS), the private research institution where C. V. Raman held court in the evenings and on weekends while employed by day in the finance department of the colonial government ^[2]. Calcutta was then the liveliest center of physical research in India, and Krishnan entered it as a research student with little more than a good degree and a capacity for sustained, precise experiment.

At the IACS, Krishnan became one of Raman's closest collaborators in the study of the scattering of light by liquids and gases. Through 1927 and early 1928 the two men, together with other students in the laboratory, pursued a faint secondary radiation that appeared when sunlight passed through purified liquids. In February 1928 the work culminated in the observation of a new kind of scattered light whose wavelength differed from that of the incident beam, an inelastic scattering process now known as the Raman effect ^[3].

Krishnan's laboratory notebooks from that period record the day-by-day progress of the experiments, and he was co-author with Raman of the key 1928 paper in Nature announcing the discovery ^[3]. When the Nobel Prize in Physics went to Raman alone in 1930, some historians of science later argued that Krishnan's contribution had been substantial enough to merit a share, a question that has been examined at length in biographical studies of both men ^[2]. Krishnan himself never pressed any public claim and remained on respectful terms with his former chief.

Even before the famous discovery, Krishnan had begun independent theoretical work on light scattering, including a 1925 study of scattering in liquids that anticipated aspects of the later experiments ^[4]. In 1928 he left Calcutta for the University of Dacca in eastern Bengal, where he served as a reader in physics. There he opened the second great line of his research, the magnetic behavior of crystals, working with students including Santilal Banerjee on the magnetic anisotropy of crystalline substances ^[1].

Any fair list of K. S. Krishnan achievements has to give first place to his magnetism research. Returning to Calcutta in 1933 as the Mahendralal Sircar Research Professor at the IACS, he developed elegant experimental methods for measuring how the magnetic susceptibility of a crystal varies with direction. His technique of suspending a small crystal from a fine fiber and observing its oscillations in a magnetic field allowed anisotropies to be measured with unusual accuracy, and his measurements on aromatic organic crystals helped connect diamagnetism to the mobile electrons of the benzene ring ^[4].

His studies of graphite were especially influential. With colleagues he showed that graphite exhibits an enormous diamagnetic susceptibility perpendicular to its layer planes, a result that fed directly into the emerging electronic theory of layered solids ^[4]. This body of work on crystal magnetism, published through the 1930s in the Proceedings of the Royal Society and other journals, earned him election as a Fellow of the Royal Society in 1940, one of only a handful of Indian scientists then so honored ^[1].

In 1942 Krishnan accepted the chair of physics at the University of Allahabad, where he shifted his attention to the thermal and electrical properties of metals, including careful experiments on thermionic emission from metal filaments ^[5]. Recognition accumulated: he was knighted in the 1946 New Year Honours, one of the last Indian scientists to receive a British knighthood before independence, and in 1954 the Government of India awarded him the Padma Bhushan in the first year that honor was conferred ^[1]. He delivered lectures abroad, represented India at international scientific gatherings, and was widely regarded as one of the two or three most accomplished experimental physicists the country had produced ^[2].

Independence in 1947 transformed Krishnan from a professor into an institution builder. Jawaharlal Nehru's government chose him as the first director of the National Physical Laboratory of India (NPL) in New Delhi, one of the chain of national laboratories established under the Council of Scientific and Industrial Research ^[5]. Krishnan planned its divisions, recruited its early staff, and shaped it as the custodian of physical standards and measurement for the new republic. He held the directorship from 1947 until his death ^[5].

His influence reached well beyond one laboratory. Krishnan served as a member of the Atomic Energy Commission of India from its creation in 1948, sitting alongside Homi Bhabha and S. S. Bhatnagar in the small group that set the direction of India's nuclear program ^[6]. He was a delegate to international conferences on the peaceful uses of atomic energy in Geneva in the 1950s and advised the government on scientific manpower and policy ^[6].

Even amid heavy administration he kept a hand in research. At the NPL he returned to problems of thermionics and the emission of electrons from hot metals, publishing a series of papers with collaborators during the 1950s ^[5]. Colleagues recalled that he read widely across physics until the end and remained a demanding but generous critic of experimental work ^[2].

Krishnan married Rajam Krishnan, and the couple raised a large family; several accounts of his life describe a household that blended traditional South Indian observance with the itinerant demands of a scientific career that moved from Madras to Calcutta, Dacca, Allahabad, and Delhi ^[2]. He was known personally for simplicity of habit, a fondness for long walks, and conversation that ranged from spectroscopy to Sanskrit and Tamil classics.

Among K. S. Krishnan facts often repeated by those who knew him is his reputation as a captivating lecturer and raconteur. He carried his learning lightly, and his public talks on science in India drew audiences well beyond the physics community ^[2]. Contemporaries including Kathleen Lonsdale, who wrote his Royal Society memoir, emphasized the breadth of his culture as much as the precision of his experiments ^[1].

Through the late 1950s Krishnan remained at the center of Indian science administration while his health gradually declined. He continued to direct the NPL, to serve on national committees, and to represent India abroad, including participation in United Nations and UNESCO scientific bodies ^[6]. In 1961 the Government of India was reported to be considering him for still higher honors when his life was cut short.

Krishnan died of a heart attack in New Delhi on June 14, 1961, at the age of 62, while still in office as director of the National Physical Laboratory ^[1]. Obituaries in Indian and international journals mourned the loss of a scientist who had bridged the heroic era of Raman's Calcutta laboratory and the state-sponsored science of independent India ^[1]. His death, four years after that of his patron Bhatnagar and five years before Bhabha's, thinned the first generation of India's scientific statesmen.

Any K. S. Krishnan biography ultimately turns on two legacies, one scientific and one institutional. In science, his name is permanently attached to the 1928 discovery of the Raman effect, and his magnetism work remains cited in the study of diamagnetic anisotropy and the electronic structure of graphite, a subject that gained new life with the rise of graphene research decades later ^[4]. Historians of science, most fully D. C. V. Mallik and Sabyasachi Chatterjee in their 2012 study of his life and work, have restored detail to his role in the Calcutta experiments through his own notebooks and letters ^[2].

Institutionally, the National Physical Laboratory he built continues as India's national measurement institute, and the structures of the Atomic Energy Commission he helped guide grew into the country's nuclear establishment ^[5]. Memorial lectures and fellowships bear his name, including honors administered by Indian scientific academies of which he had been a fellow and officer ^[6].

Krishnan's career is often cited as an example of what Indian experimental physics accomplished with slender resources in the colonial period, and of how that generation converted personal distinction into durable public institutions after 1947. Six decades after his death, students of the Raman effect and of Indian science policy alike still encounter his signature at the founding moments of both ^[2].