Black holes: where physics reaches its limit

Black holes: where physics reaches its limit

Date:  Saturday, September 20, 2014 - 10:30

Venue:  Theoretical Physics, 1 Keble Road, Oxford OX1 3NP

The fifth Saturday Morning of Theoretical Physics saw three talks discussing ideas from theoretical physics are currently being applied to Black Holes.

In 1916 within a year of Einstein publishing his relativistic theory of gravity, Karl Schwarzschild had discovered the solution of these equations that describes a spherical black hole. 47 years later Roy Kerr found a solution for a spinning black hole. But black holes were dismissed as mathematical artefacts by many until Penrose and Hawking proved that starting from realistic circumstances, a solution to Einstein's equations would inevitably form a black hole. When the X-ray sky was first explored in the late 1960s, objects were found that had to contain black holes with masses ~10 Msun. About the same time quasars were discovered, and it was argued that they must be powered by accretion onto black holes with masses in excess of a million Msun. In the 1990s it was established that at the centre of every substantial galaxy there sits a black hole with a mass that ranges from ~ 10^6 to 10^10 Msun.




Dr Andrei Starinets

Black holes in Einstein’s gravity and beyond

Video podcast Presentation (PDF)

In this lecture, we discuss the basic ingredients of Einstein's General Theory of Relativity and the Riemannian geometry: the metric, the curvature and the relation between the geometry of space-time and matter-energy. Black holes emerge as theoretical solutions of Einstein's equations of motion. Their properties including the existence of an event horizon and a singularity are described in some detail before introducing more advanced topics such as Hawking radiation, black hole thermodynamics and holography.


Dr John Magorrian

Black holes in the nearby Universe

Video Podcast Presentation (PDF)

The evidence that black holes exist is overwhelming, but indirect: there are not (yet) any "smoking-gun" observations that can be unambigiously attributed to general-relativistic effects around a black hole. We describe the astrophysical evidence for the existence of black holes in the nearby universe. Nature has found at least two distinct ways of constructing these objects: (i) stellar-mass black holes form from the collapse of very massive stars when their source of fuel is exhausted; (ii) "supermassive" black holes are produced in the process of galaxy formation, although exactly how is not yet well understood.


Prof James Binney FRS

The impact of black holes on the Universe

Video podcast Presentation (PDF)

Accretion onto black holes powers quasars. By summing radiation from quasars it was deduced that galaxies like ours must host black holes with masses > 10 million Msun. Gas falling into a black swirls around it as an accretion disc. We examine energy and angular-momentum balance in a disc, first in the absence of a jet, and then when a jet is driven perpendicular to the disc. Magnetism is responsible for heating the disc and for driving the jet. Jets prevent gas cooling near the centres of dark halos and in this way terminate star formation and galaxy growth.