Meghnad Saha

Meghnad Saha মেঘনাদ সাহা
Meghnad Saha
Born	(1893-10-06)6 October 1893 Shaoratoli, Dhaka, British India (present Bangladesh)
Died	Delhi, India
Residence	India
Nationality	Indian
Fields	Physics and Maths
Institutions	Allahabad University University of Calcutta Imperial College London Indian Association for the Cultivation of Science
Alma mater	Dhaka College University of Calcutta
Known for	Thermal ionisation Saha ionization equation

Meghnad Saha FRS (6 October 1893 – 16 February 1956) was an Indian astrophysicist best known for his development of the Saha equation, used to describe chemical and physical conditions in stars.

Biography

Meghnad Saha was born in Shaoratoli village near Dhaka, British India (present Bangladesh). Son of Jagannath Saha, Meghnad Saha belonged to a poor family and struggled to rise in life. He had his initial schooling at Dhaka Collegiate School, and later moved to Dhaka College. He was also a student at the Presidency College, Kolkata; a professor at Allahabad University from 1923 to 1938, and thereafter a professor and Dean of the Faculty of Science at the University of Calcutta until his death in 1956. He became Fellow of the Royal Society in 1927. He was president of the 21st session of the Indian Science Congress in 1934.

Saha was fortunate to have brilliant teachers and class fellows. In his student days, Jagadish Chandra Bose, Sarada Prasanna Das and Prafulla Chandra Ray were at the pinnacle of their fame. Amongst his class fellows were Satyendra Nath Bose, Jnan Ghosh and J. N. Mukherjee. In later life he was close to Amiya Charan Banerjee, a renowned mathematician at Allahabad University.

On his religious views, Saha was an atheist.

Saha died on 16 February 1956.

Career

Meghnad Saha in Berlin, 1921

Meghnad Saha with other scientists at Calcutta University

Meghnad Saha's best-known work concerned the thermal ionisation of elements, and it led him to formulate what is known as the Saha equation. This equation is one of the basic tools for interpretation of the spectra of stars in astrophysics. By studying the spectra of various stars, one can find their temperature and from that, using Saha's equation, determine the ionisation state of the various elements making up the star. This work was soon extended by Ralph H. Fowler and Edward Arthur Milne. Saha had previously reached the following conclusion on the subject.

"It will be admitted from what has gone before that the temperature plays the leading role in determining the nature of the stellar spectrum. Too much importance must not be attached to the figures given, for the theory is only a first attempt for quantitatively estimating the physical processes taking place at high temperature. We have practically no laboratory data to guide us, but the stellar spectra may be regarded as unfolding to us, in an unbroken sequence, the physical processes succeeding each other as the temperature is continually varied from 3000° K to 40,000° K."

Saha also invented an instrument to measure the weight and pressure of solar rays and helped to build several scientific institutions, such as the Physics Department in Allahabad University and the Institute of Nuclear Physics in Calcutta. He founded the journal Science and Culture and was the editor until his death. He was the leading spirit in organizing several scientific societies, such as the National Academy of Science (1930), the Indian Physical Society (1934), Indian Institute of Science (1935) and the Indian Association for the Cultivation of Science (1944). A lasting memorial to him is the Saha Institute of Nuclear Physics, founded in 1943 in Kolkata

Saha was also one of the prominient among the works on halley's comet.

Saha was the chief architect of river planning in India and prepared the original plan for the Damodar Valley Project. His own observation with respect to his transition into government projects and political affairs is as follows:

"Scientists are often accused of living in the "Ivory Tower" and not troubling their mind with realities and apart from my association with political movements in my juvenile years, I had lived in ivory tower up to 1930. But science and technology are as important for administration now-a-days as law and order. I have gradually glided into politics because I wanted to be of some use to the country in my own humble way."

Tributes to Saha

Bust of Meghnad Saha in the garden of Birla Industrial & Technological Museum.

• "Meghnad Saha’s ionization equation (c. 1920), which opened the door to stellar astrophysics” was one of the top ten achievements of 20th century Indian science [and] could be considered in the Nobel Prize class." - Jayant Narlikar
• "The impetus given to astrophysics by Saha’s work can scarcely be overestimated, as nearly all later progress in this field has been influenced by it and much of the subsequent work has the character of refinements of Saha’s ideas." - S. Rosseland
• "He (Saha) was extremely simple, almost austere, in his habits and personal needs. Outwardly, he sometimes gave an impression of being remote, matter of fact, and even harsh, but once the outer shell was broken, one invariably found in him a person of extreme warmth, deep humanity, sympathy and understanding; and though almost altogether unmindful of his own personal comforts, he was extremely solicitous in the case of others. It was not in his nature to placate others. He was a man of undaunted spirit, resolute determination, untiring energy and dedication." - D. S. Kothari

Further reading

• Obituary - The Observatory 76 (1956) 40
• Obituary - Proceedings of the Astronomical Society of the Pacific 68 (1956) 282
• Saha and His formula - G Venkataraman

External links

• Biography
• Chitra Roy on her father
• Biography
• ScienceWorld: Saha Equation
• List of M. N. Saha's papers
• The Quantum Indians: film on Meghnad Saha, Bose and Raman on YouTube by Raja Choudhury and produced by PSBT and Indian Public Diplomacy.