Prof. Rajaram Nityananda (Centre Director, National Centre for Radio Astrophysics, Pune)

Gravity and Light - Prof. Rajaram Nityananda Colloquium

ATNF Marsfield Lecture Theatre

Abstract

The effect of a gravitational field on light was the subject of
speculation by Newton and Laplace, and a crucial experiment, both gedanken
and real, in the development of Einstein's general theory of relativity.
Theoretical work started early, on possible mass determination
of
astronomical objects. But actual observations came only sixty years
later. The observed phenomena can be characterised as microlensing, strong
lensing, and weak lensing, and each of these throws light on (largely
dark) mass on different scales in the universe. The recent
exciting results on high redshift supernovae and the CMBR assume, as an
input, the effect of the mass-energy content of the universe on the
propagation of a light beam, and thus also come under this general theme.

The effect of gravity on light has thus travelled all the way from wild
dream to standard tool. Our system of training astronomers and physicists
should reflect this in future!