Thanu Padmanabhan (10 March 1957 – 17 September 2021) was an Indian theoretical physicist and cosmologist whose research spanned a wide variety of topics in gravitation, structure formation in the universe and quantum gravity.

He made several contributions related to the analysis and modelling of dark energy in the universe and the interpretation of gravity as an emergent phenomenon.

He moved to Pune to work at the Inter-University Centre for Astronomy and Astrophysics in 1992 and served as its Dean, Core Academic Programmes, for 18 years (1997–2015).

In addition to advising the Government on policy issues, this also required him to coordinate the International Year of Astronomy 2009 activities in the country.

[29][30] Padmanabhan's research was on the fields of gravitation and cosmology which includes quantum gravity and nature of dark energy.

[31][32] During 2002–2015, he provided a clear interpretation of gravity as an emergent phenomenon (like elasticity or fluid dynamics) and showed that this paradigm extends to a wide class of theories of gravitation including, but not limited to, general relativity.

[33][34] Padmanabhan could show that several peculiar aspects of classical gravitational theories find natural interpretations in this approach.

In the earlier part of Padmanabhan's career (1980–2001), he made important contributions to quantum cosmology, structure formation in the universe and statistical mechanics of gravitating systems.

Quantum gravitational considerations advocate an astonishingly simple value for CosmIn: 4π, the number of information 'bits' on the surface of a sphere of unit radius.

Using these considerations, CosmIn was able to relate the numerical value of the cosmological constant – possibly the deepest unsolved problem in theoretical physics today – to the energy scale at which the universe made the quantum-to-classical transition.

[47] This is the first time that a model with no adjustable parameters is able to provide a holistic explanation for both these observations, which has far-reaching implications for the quantum structure of spacetime.