Tuesday, 13th August 2024 at 18:15
Prof George Ellis

The nature of the Universe:  What we know and what we don’t know

Abstract: Our ancestors looked up at the sky and asked questions about our existence in the universe, as we do today. We now know that the universe is very old and very large, and is changing with time. It has evolved from a very small size in the distant past to its present size, with a succession of physical processes leading to structures emerging at many scales. Precise astronomical data attained by many telescopes confirms this solid understanding. But there are key issues that are not understood. What is the nature of dark matter? Of the dark energy underlying an accelerating expansion rate at recent times? What physics underlies its dynamics before the Hot Big Bang epoch? Why is there a Hubble tension? Is there an age problem?  Other issues are, Why is vacuum energy as small as it is? How did quantum fluctuations lead to classical structure? We don’t know the spatial topology of the universe, or if it is spatially infinite. Above all, we don’t know how it came into existence, nor why it allows any life at all to exist. I will claim that the future of the universe is not yet determined yet, and no, we don’t live in a simulation.

Bio: George Ellis is Professor Emeritus and Research Fellow at the University of Cape Town, South Africa. He started his research career studying General Relativity Theory and Cosmology at the Department of Applied Mathematics and Theoretical Physics, Cambridge University, where he wrote The Large Scale Structure of Spacetime with Stephen Hawking. He returned to the University of Cape Town in 1973 where he started a research group in general relativity and cosmology, but also started research in areas such as low-income housing policy, quality of life indicators, and how complexity such as the brain emerges from the underlying physics. He has been visiting professor at many universities round the world, including a period as Professor of Cosmic Physics at the International School of Advanced Studies (SISSA) in Trieste. He has written or co-authored 15 books and some hundreds of papers with over 48000 citations. He has 7 honorary degrees and was awarded the Star of South Africa medal by President Nelson Mandela. He is a Fellow of the Royal Society, London (FRS) and of the Third World Academy of Sciences (TWAS).