After returning home in 1924, he was appointed as "Rasbihari Ghosh Professor" in the newly formed Department of Applied Mathematics of Calcutta University. With Sen conducting and supervising research in areas related to the theory of relativity, he was considered the founder of the Calcutta School of Relativity in the 1930s. The Calcutta school investigated the effect of mass, density, radius, temperature and pressure in the stellar bodies. Sen refined models of the universe based on the General Theory of Relativity yet he was critical of Eddington and Milne's models.