Modern physics is split in two. To explain the large-scale Universe, we talk of the curved and expanding spacetime of Einstein’s General Theory of Relativity. For the small-scale, we talk about probabilities and uncertainties and the language of quantum mechanics. Whilst these two pillars of physics are both supremely accurate and immensely powerful theories, they are, at heart, incompatible. But to understand the past, present and future history of the universe, we must get these two theories to play nicely together.

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This lecture was recorded at the Royal Institution on 2 December 2021.

0:00 Introduction
2:04 Historical guide to understanding the Universe
8:12 The difference between relativity and quantum mechanics
13:04 Uniting the two theories
16:39 Categorising research areas using the two theories
20:25 Understanding the Universe
27:58 Big bang nuclear synthesis
33:27 How do we understand what comes out of the big bang?
37:01 The balancing act of stars
39:35 What's happening in the heart of the Sun?
45:08 Getting elements out of stars and into the Universe
52:34 The future of the universe
55:13 Why don't dead stars collapse?
1:01:46 The struggle in describing Hawking radiation
1:04:28 Closing the chasm of ignorance

Thumbnail image credit: Illustris Collaboration | https://www.illustris-project.org/media/

Geraint Lewis was born in South Wales and is a Professor of Astrophysics at the Sydney Institute for Astronomy, part of the University of Sydney's School of Physics. His research focuses on the 'dark side of the universe', the matter and energy that shapes our cosmos. Geraint is also a teacher, an author, and science communicator.​

As well as two books on cosmology, Geraint has published more than 400 hundred papers in international refereed journals.

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