Achievements by Indian Physical Scientists

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Achievements by Indian Physical Scientists

Overview

In 1871 the Indian Association for the Cultivation of Science, the first of two centers for modern science in India, was founded to give young Indians the opportunity, discouraged by the colonial British government, to conduct laboratory research. The second center was a college of science established at the University of Calcutta by an amateur mathematician whose fundraising was so effective that he was able to endow two professorial chairs, in physics and chemistry, for qualified Indian scientists. In 1930 the first occupant of the chair in physics became the first Indian as well as the first Asian to win the Nobel Prize.

Background

Chandrasekhara Venkata Raman (1888-1970) received a master's degree in science and joined the Indian Finance Department in 1907. He took up a post in Calcutta and, discovering a local scientific association, began to conduct research outside of his working hours at the finance department. By the time he was granted a university position in physics ten years later, he had already published 25 papers in journals such as Nature and Physical Review.

As a boy, Raman had acquired a love of music, and his early research concentrated on vibrations and sound and the theory of musical instruments. But in the early 1920s, in an effort to find out why the sea is blue, Raman showed that its color is caused by molecular scattering of light by water molecules. He then embarked on a serious study of how light is scattered by liquids, solids, and gases.

Raman's best-known contribution to science was his discovery of what is now known as the "Raman effect." When a beam of light passes through a transparent material, a portion of the light emerges at right angles to the original direction. Some of this scattered light shows changes in wavelength. The reason, Raman explained, is that sometimes energy is exchanged between the light and the material it is traversing. Because "Raman scattering" provides information about the energy states of scattering material, it is used as a standard laboratory tool for investigating the chemical composition of substances. Raman's work on the scattering of light won him the Nobel Prize in physics in 1930.

Satyendra Nath Bose (1894-1974) began a mathematics career in Calcutta. In 1921 Bose left Calcutta to take up a position at the University of Dacca. Three years later, he sent a brief manuscript entitled "Planck's Law and the Hypothesis of Light Quanta" to Albert Einstein (1879-1955) for comment. The paper proposed a solution to a problem having to do with German physicist Max Planck's (1858-1947) theory of how energy is emitted by a hot object, the socalled "blackbody radiation." In 1900 Planck had proposed that energy exists in the form of little lumps, or "quanta," rather than in the form of a wave. Five years later, Einstein applied Planck's theory to the study of light. At the time, Europeans were slow to accept either idea, but Indian physicists took to them quickly. In a paper published in 1919 in an astrophysical journal, Bose's colleague Meghnad Saha (see below) used the light quantum to describe radiation pressure. That same year, Bose and Saha translated Einstein's papers on the general theory of relativity, in which Einstein questioned some of Planck's assumptions. Starting from the notion that particles of light obey statistical laws different from those that describe the everyday world, Bose was able to show that Einstein's model and Planck's law were consistent, in the bargain putting Planck's law on firm mathematical footing.

Einstein himself translated Bose's manuscript for publication in the Zeitschrift für Physik. Louis de Broglie (1892-1987), a French physicist, used Bose's new statistics—now known as "Bose-Einstein statistics"—to show that, just as light could behave as particles, particles (molecules) sometimes behaved as waves. The Austrian physicist Erwin Schrödinger (1887-1961) based his description of the quantum world on Bose's statistics.

Einstein's support for his work made it possible for Bose to obtain a two-year fellowship to Europe, where he studied radioactivity under Paul Langevin (1872-1946) in France. On his return to India, he turned to a variety of studies, for example, x-ray crystallography (a technique for determining molecular structure) and thermoluminescence, which refers to the light emitted when stored radiation energy is heated. But his major contribution to physics would remain his work on quantum statistics.

Meghnad Saha (1893-1956) was a classmate of Bose in Calcutta. An astrophysicist, he began his research in electromagnetic theory and the theory of stellar spectra. In 1919 Saha was awarded a two-year fellowship that took him first to the Royal College of Science in London and then to Berlin. He returned to India in 1921, where he assumed a succession of university positions.

The work for which Saha is best known is his thermal ionization equation. Stars emit a range of colors (spectra) that depend on the chemical composition of the light source. By linking information about a star's spectrum with the temperature of the light source, Saha's equation could be used to determine the temperature of the star and its chemical makeup. For example, cool stars typically show the presence of familiar metals such as iron and magnesium. The spectra of hotter stars, on the other hand, are consistent with elements that require more energy to produce, such as oxygen and carbon. Saha's theory has been called the starting point of modern astrophysics.

Subrahmanyan Chandrasekhar (1911-1995) was the nephew of Chandrasekhara Venkata Raman. Chandrasekhar left India at 19 to study astronomy and physics at Cambridge University. On the boat taking him to Europe, it occurred to him that the immense pressures on ordinary matter at the core of dying stars called white dwarfs would cause the stars to collapse in on themselves. At the time, it was believed that, after exhausting their fuel, these stars contracted under the influence of gravity to dense but stable remnants about the size of Earth. Chandrasekhar published his idea about collapsing stars in an astrophysical journal and in 1930 developed it more fully, using Einstein's special theory of relativity and the principles of quantum physics. He defined a certain maximum mass possible (1.44 times the mass of the Sun) for a stable white dwarf that became known as the "Chandrasekhar limit." Stars with a mass above this limit continue to collapse into enormously dense objects now known as neutron stars and black holes.

Chandrasekhar presented his results at a meeting of the Royal Astronomical Society in January 1935, but his announcement was greeted with great skepticism by his English colleagues. In 1936 a disappointed Chandrasekhar left England for the United States, where he accepted a position at the University of Chicago. Today, the structures implied by his early work are a central part of the field of astrophysics. Chandrasekhar began his career working on the structure and evolution of stars. But his investigations ranged from the transfer of energy by radiation in stellar atmospheres to the mathematical theory of black holes to ruminations on truth and beauty in science. For his discovery of the Chandrasekhar limit, he was awarded a Nobel Prize in 1983.

Impact

Indian physical scientists in the first half of the twentieth century did more than make important new discoveries in science. They challenged an entire climate of opinion. Beginning in the eighteenth century and until its independence in 1947, India was a colony of Great Britain. One of the more unfortunate legacies of colonialism was the establishment of a social order under which colonials were treated as superior and native Indians inferior. Applied to education, this hierarchy meant that the intent of the colonial government in building schools, colleges, and universities was not to provide Indians a liberal education but to train them for subordinate civil-service positions. Occasionally, however, an exceptional student opted to pursue a scientific career. Raman, Bose, Saha, and Chandrasekhar were all products of India's determination to develop world-class scientists. The magnitude of the contributions of these scientific leaders upended colonial assumptions about Indians' capabilities and helped India move toward self-reliance.

In addition to carrying out pioneering studies, these four scientists helped establish the infrastructure for conducting basic scientific research in India. Saha created an institute of nuclear physics at the University of Calcutta. Raman, whose influence on the growth of science in India was so profound that he became a political and cultural hero, founded the Indian Academy of Science. All were ardent teachers. Late in his life, Raman stated that the principal function of older scientists was to recognize and encourage talent and genius in younger ones. One year, Chandrasekhar drove over a hundred miles each week to teach just two students, both of whom later won the Nobel Prize. Raman's simple light-scattering technique became a routine laboratory tool, Bose laid the foundation for quantum statistics, Saha's theory of ionization became integral to work on stellar atmospheres, and Chandrasekhar's theory on the evolution of stars furthered our understanding of the cosmos. By their achievements, these researchers both advanced international science and made a place for India in it.

GISELLE WEISS