Current Science

Naresh Dadhich ¹

Affiliations
1 Centre for Theoretical Physics, Jamia Millia Islamia, New Delhi, 110 025, IN

Abstract

The most outstanding contribution to general relativity in this era came in 1953 (published in 1955 (ref. 1)) in the form of the Raychaudhuri equation. It is in 1960s that the observations began to confront the eupherial theory and thus began exploration of GR as a legitimate physical theory in right earnest. The remarkable discoveries of cosmic microwave background radiation, quasars, rotating (Kerr) black hole and the powerful singularity theorems heralded a new canvas of relativistic astrophysics and cosmology. I would attempt to give a brief account of Indian participation in these exciting times.

Keywords

General Relativity, Gravitational Collapse, Gravitation Waves, Penrose Process.

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Naresh Dadhich ¹

Affiliations
1 Centre for Theoretical Physics, Jamia Millia Islamia, New Delhi 110 025, IN

Abstract

No Abstract.

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Naresh Dadhich ¹

Affiliations
1 Centre for Theoretical Physics, Jamia Millia Islamia, New Delhi 110 025, IN

Abstract

The two defining features of the Einsteinian gravity are that it is self-interactive and it links universally to all particles, including zero-mass particles. In the process of obtaining the Schwarzschild solution for gravitational field of a mass point, we demonstrate how these features are incorporated? We also show, unlike the Newtonian gravity, why gravitational potential in the Schwarzschild solution can have its zero only at infinity and nowhere else, i.e. it is determined absolutely. Further we consider particle orbits to expose certain insightful and subtle points of concept and principle.

Keywords

Gravitational Field, Mass Point, Particle Orbits, Sefl-Interaction.

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Naresh Dadhich ¹, Bala Iyer ²

Affiliations
1 Inter-University Center for Astronomy and Astrophysics, Pune 411 007, IN
2 International Centre for Theoretical Sciences – TIFR, Bengaluru 560 089, IN

Abstract

C. V. Vishveshwara (Vishu) is associated to most of us with quasi-normal modes or the ringdown of a black hole. The prediction that his simple calculations made was dramatically verified after 46 years with the discovery of gravitational waves by LIGO, which was almost a year before he breathed his last on 16 January 2017 in Bengaluru. It was, therefore, most fortuitous that he could experience the exhilaration and satisfaction of his contribution when the whole world was cheering and applauding. Vishu will be remembered for a long time not only for his seminal contributions to understanding black holes, but also fondly for the word pictures and the Sydney Harris-like cartoons he created to share with his professional colleagues and the lay public the esoteric consequences of Einstein's general theory of relativity. His talks inspired generations of students to a career in science, and through the activities at the Jawaharlal Nehru Planetarium, Bengaluru and the Bangalore Association for Science Education (BASE) the inspiration lives on.

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Naresh Dadhich ¹

Affiliations
1 The Inter-University Centre for Astronomy and Astrophysics (IUCAA), Post Bag 4, Ganeshkhind, Pune 411 007, IN

Abstract

No Abstract.

Keywords

No Keywords.

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Naresh Dadhich ¹

Affiliations
1 Inter University Centre for Astronomy and Astrophysics, Post Bag 4, Pune 411 007, IN

Abstract

Scientific discoveries are not made in vacuum; they all have a background (or shoulders of Giants to stand on in Newton’s pronouncement) to anchor and build on. The famous and powerful singularity theorems of Hawking and Penrose of mid-1960s were strongly anchored on the remarkable Raychaudhri equation discovered in 1953. The most remarkable and profound prediction that followed from the equation was that gravitational collapse would inevitably lead to singularity in Einstein’s theory of gravitation – general relativity. Hawking and Penrose generalized and located this result to a more general setting that Einstein’s equation under very general conditions cannot admit a solution that has no singularity. They proved powerful rigorous mathematical theorems employing the techniques of global analysis that gravitational collapse would not only end up in singularity but before that a black hole would be formed. It is this robust prediction that has won Roger Penrose the 2020 Nobel Prize in Physics. In this note, I will recount the Indian contributions that have gone into making the background.

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