Meghnad Saha  (6 October 1893 – 16 February 1956) was an Indian astrophysicist who helped devise the theory of thermal ionisation. His ionisation equation allowed astronomers to accurately relate the spectral classes of stars to their actual temperatures. He was elected to the Parliament of India in 1952.

Biography

Meghnad Saha was born in 1893 into a poor Bengali family in Shaoratoli village, Dhaka, Bengal Presidency of British India (present-day Gazipur District, Bangladesh). He was the son of grocer Jagannath Saha and Smt. Bhubneshwari Devi.

During his youth, he was forced to leave Dhaka Collegiate School because he participated in the Swadeshi movement. He earned his Indian School Certificate from Dhaka College. He was also a student at the Presidency College, Kolkata and Rajabazar Science College CU. Saha faced discrimination from other students due to his caste  When he was at the Eden Hindu Hostel, upper-caste students objected to him eating in the same dining hall as them. 

He was 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 a Fellow of the Royal Society in 1927. He was president of the 21st session of the Indian Science Congress in 1934.

Amongst Saha's classmates were Satyendra Nath Bose, Jnan Ghosh and Jnanendra Nath Mukherjee. In his later life, he was close to Amiya Charan Banerjee. Saha was an atheist.

Career
Saha's study of the thermal ionisation of elements led him to formulate what is known as the Saha ionisation equation. This equation is one of the basic tools for interpreting the spectra of stars. By studying the spectra of stars, one can find their temperature and using Saha's equation determine the ionisation state of the elements making up the star. This was extended by Ralph H. Fowler and Edward Arthur Milne. Saha had previously reached the following conclusion on the subject:

Saha also invented an instrument to measure the weight and pressure of solar rays and helped establish several scientific institutions, including the Physics Department at Allahabad University and the Institute of Nuclear Physics in Kolkata. He founded the journal Science and Culture and was the editor until his death. He was the leading figure in organising several scientific societies, such as the National Academy of Science (1930), the Indian Physical Society (1934), and the Indian Institute of Science (1935). He was the director at Indian Association for the Cultivation of Science from 1953 to 1956. The Saha Institute of Nuclear Physics, founded in 1943 in Kolkata, is named after him.

Saha stood as a candidate for North-West Calcutta in the 1951 Loksabha election. He ran as a member of the Union of Socialists and Progressives, but maintained his independence from the party. His goal was to improve the planning of education, industrialisation, healthcare, and river valley development. He was up against Prabhu Dayal Himatsingka. Due to low funding for his campaign, Saha wrote to the publisher of his textbook Treatise on Heat to ask for an advance of ₹5000. He was elected by a margin of 16%.

Saha participated in the areas of education, refugees, rehabilitation, atomic energy, multipurpose river projects, flood control, and long term planning. In the book Meghnad Saha in Parliament, Saha is described as:"Never unduly critical... forthright, so incisive, so thorough in pointing out lapses that the treasury bench was constantly on the defensive. This is brought out by the way he was accused of leaving his laboratory and straying into a territory not his own. But the reason why he was slowly drifting towards this public role (he was never a politician in the correct sense of the term) was the gradually widening gulf between his dream and the reality—between his vision of an industrialised India and the Government implementation of the plan."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 was:

Death
Saha died on the way to the hospital on 16 February 1956 after getting cardiac arrest. He was going to the office of the Planning Commission in the Rashtrapati Bhavan. It was reported he had been dealing with hypertension for ten months prior to his death. His remains were cremated at the Keoratola crematorium,  Kolkata the following day.

Tributes

 "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." — Svein 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." — Daulat Singh Kothari

References

Further reading
 
 Obituary - The Observatory 76 (1956) 40
 Obituary – Proceedings of the Astronomical Society of the Pacific 68 (1956) 282
 
 Jibamitra Ganguly: Meghnad Saha : his science and persona through letters and writings. Indian National Science Academy, New Delhi 2019.
 Collected works of Meghnad Saha. ed. by Santimay Chatterjee. Calcutta [u.a.]: Institute of Nuclear Physics [u.a.], 1982.

External links

  
 Meghnad N. Saha at the Encyclopædia Britannica
 
 
 
 
  by Raja Choudhury and produced by PSBT and Indian Public Diplomacy.

1893 births
1956 deaths
India MPs 1952–1957
20th-century Indian physicists
Bengali astronomers
Bengali physicists
Dhaka College alumni
Indian Hindus
Fellows of the Indian National Science Academy
Fellows of the Royal Society
Hare School alumni
Indian astrophysicists
Lok Sabha members from West Bengal
People from Dhaka
Plasma physicists
Politicians from Kolkata
Presidency University, Kolkata alumni
Presidents of The Asiatic Society
Academic staff of the University of Allahabad
University of Calcutta alumni
Academic staff of the University of Calcutta
Bengali scientists
Dhaka Collegiate School alumni
Dalit