Prof Bob Lambourne’s inaugural two-hour lecture as President of Wycombe Astronomical Society, was a truly tour de force performance delivered via Zoom to a well-attended audience on the subject of Black Holes. But not his perspectives, however, rather those seen through the eyes of Nobel Laureate, Prof Roger Penrose.
Members of the Penrose family have made great contributions to different fields of science – mathematics, physics, medicine – and this provided a fertile environment for Roger Penrose to grow up in. He started out as a mathematician, later turning to physics and then cosmology. His unique outlook and way of thinking was a constant struggle for him to make things understandable to others, finding great inspiration and expression from the graphic art of M C Escher. Like Escher, his ability to visualise three dimensional objects on paper that cannot physically exist in reality – the Penrose Tribar for example – gave him the ability to get his head round and explain complex concepts such as space-time, relativity and singularities.
Penrose’s work on relativity was greatly influenced and guided by Dennis Sciami and Stephen Hawking. In 1959 his visual ability to think out concepts allowed him to explain the so-called Penrose-Terrell rotation effect – the visual distortion that a passing object would appear to undergo, according to the special theory of relativity, if it were travelling at a significant fraction of the speed of light.
In 1964, Penrose applied global techniques to classical general relativity to prove the first of several singularity theories. He showed that a sufficiently massive body undergoing gravitational collapse would inevitably form a trapped surface, leading to a singularity, irrespective of the details of collapse. This work made black hole formations a robust prediction of general relativity and their existence began to gather acceptance. It was for this area of work that Penrose was awarded half of the 2020 Nobel Prize. (The other half recognised the work of Reinhard Genzel and Andrea Ghez in uncovering the supermassive black hole at the centre of our Galaxy.) Added to recent detections of gravitational waves from black hole mergers, the reality of black holes has now become inescapable (if you’ll excuse the pun!).
After a brief description of Penrose’s work on the Penrose Process (his 1969 work on the theoretical means by which energy could be extracted from a rotating black hole) Bob Lambourne concluded his talk with a description of Penrose’s work in Quantum Physics. Specifically, his Conformal Cyclic Cosmology (CCC) model which is an extension of general relativity but one that is opposed to other cosmological theories like string theory. Penrose argues that as the universe expands and cools, the average density of matter becomes less and less. Eventually this conformal universe “forgets” its size and becomes indistinguishable from the early universe. The previous aeon becomes the low-entropy Big Bang state of the next aeon cycle.
Not a lecture for the faint-hearted, this. But a reflection of the calibre of our new President and the value he will bring to Wycombe Astronomical Society.
Sandy Giles