The Department of Physics public lecture series. An exciting series of lectures about the research at Oxford Physics take place throughout the academic year. Looking at topics diverse as the creation of the universe to the science of climate change. Features episodes previously published as: (1) 'Oxford Physics Alumni': "Informal interviews with physics alumni at events, lectures and other alumni related activities." (2) 'Physics and Philosophy: Arguments, Experiments and a Few Things in Between': "A series which explores some of the links between physics and philosophy, two of the most fundamental ways with which we try to answer our questions about the world around us. A number of the most pertinent topics which bridge the disciplines are discussed - the nature of space and time, the unpredictable results of quantum mechanics and their surprising consequences and perhaps most fundamentally, the nature of the mind and how far science can go towards explaining and understanding it. Featuring interviews with Dr. Christopher Palmer, Prof. Frank Arntzenius, Prof. Vlatko Vedral, Dr. David Wallace and Prof. Roger Penrose."
IceCube: Opening a New Window on the Universe from the South Pole
1:24:59Particle Physics Christmas Lecture, hosted by Prof. Daniela Bortoletto, Head of Particle Physics and senior members of the department with guest speaker, Professor Francis Halzen. Professor Francis Halzen is Wisconsin IceCube Particle Astrophysics Center and Department of Physics, University of Wisconsin - Madison. Prof Halzen is a theoretician studying problems at the interface of particle physics, astrophysics and cosmology. In 1987 he began working on the AMANDA experiment, a prototype neutrino telescope buried under the South Pole. It provided a proof-of-concept for IceCube, a kilometer-scale detector completed in 2010 which in 2013 discovered an extraterrestrial flux of high energy neutrinos. More recently in 2018 the first cosmic source of such neutrinos was tentatively identified. IceCube has also made precision measurements of neutrino oscillations, searched for dark matter and even contributed to our understanding of glaciology. Prof Halzen will discuss these achievements as well as plans for a much bigger detector that will firmly establish neutrino astronomy as a new window on the universe. The IceCube project has transformed a cubic kilometre of natural Antarctic ice into a neutrino detector. The instrument detects more than 100,000 neutrinos per year in the GeV to 10,000 TeV energy range. Among those, we have isolated a flux of high-energy neutrinos of cosmic origin. We will explore the use of IceCube data for neutrino physics and astrophysics emphasizing the significance of the discovery of cosmic neutrinos. We identified their first source: alerted by IceCube on September 22, 2017, several astronomical telescopes pinpointed a flaring galaxy powered by an active supermassive black hole, as the source of a cosmic neutrino with an energy of 310 TeV. Most importantly, the large cosmic neutrino flux observed implies that the Universe’s energy density in high-energy neutrinos is close to that in gamma rays, suggesting that the sources are connected and that a multitude of astronomical objects await discovery.
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The Einstein Lens and a Tale of Two Eclipses
51:50Physics Colloquium 20th November 2015 delivered by Professor Tom Ray This year marks the centenary of Einstein’s General Theory of Relativity. As is well known, physicists became convinced that Einstein was right after Eddington’s and Dyson’s famous expedition to measure the gravitational deflection of starlight. Recently the speaker has found the equipment that proved critical in testing Einstein’s theory after it being lost for almost 70 years. Remarkably its discovery has led to the finding that earlier eclipse data may have been conveniently ignored. The finger of suspicion points at Sir Frank Dyson, the Astronomer Royal, who was trying to protect Eddington from being conscripted into the British Army during World War I.
Turning in the Widening Gyre: Accretion Processes in the Universe
56:37Inaugural Lecture by Professor Steven Balbus looking at the history of the universe A one sentence summary of much of the history of our Universe might be that it is the formation of ever more complex and compact structure from a diffuse background. The build-up of a compact core of material from more tenuous surroundings is known as accretion, and it is a process common to much of astrophysics, from the early creation of giant clusters of galaxies to current star, planet, and black hole formation. In this Lecture, I will give a general and personal overview of accretion physics. I will discuss some of the theoretical successes the community has enjoyed in its struggle to understand accretion, together with ongoing challenges. Above all, I will try to convey a sense of the richness of accretion as a physical process, and the role it has played in enhancing a deeper understanding of many astrophysical phenomena.
Lorenz Gödel and Penrose: new perspectives on determinism and unpredictability, from fundamental physics to the science of climate change
1:06:28The 9th Dennis Sciama Memorial Lecture, looking at chaos theory and climate change Lorenz is one of the pioneers of chaos theory. However, over 50 years before Lorenz, Poincaré discovered the sensitive dependence on initial conditions that characterises chaos. So what makes Lorenz’s contribution so important? I argue it is the discovery of the fractal invariant set in state space: the Lorenz attractor. Quite amazingly, properties of the Lorenz attractor can be shown to link the calculus of dynamical systems theory to deep and diverse areas of mathematics such as Wiles’ proof of Fermat’s Last Theorem and Gödel’s incompleteness theorem. But more than this, I argue that the fractal invariant set has implications for physics – not only for practical problems such as climate prediction, but also for the deepest problems of fundamental physics. In particular, I will put some meat on the bones of Penrose’s suggestion that “the correct theory of quantum gravity might be a deterministic but non-computable theory” by treating the universe as a dynamical system with fractal invariant set. The result is a novel perspective, not only on the quantum gravity programme, but also on quantum physics in general.
Building stars, planets and the ingredients for life between the stars
56:42Halley Lecture 2013 by Professor Dr Ewine van Dishoeck on new developments in astronomy One of the most exciting developments in astronomy is the discovery of planets around stars other than our Sun. Nearly 1000 exo-planets have now been detected. But how do these planets form, and why are they so different from our own solar system? Which ingredients are available to build them? How are their parent stars formed? Thanks to powerful new telescopes, astronomers are starting to address these age-old questions scientifically. In this talk, an overview will be given of how stars and planets are born in the extremely cold and tenuous clouds between the stars in the Milky Way. These clouds also contain water and a surprisingly rich variety of organic material. How and where was the water formed that is now in our oceans on Earth? Can these organic molecules end up on new planets and form the basis for pre-biotic material and eventually life? The Atacama Large Millimeter/submillimeter Array (ALMA), under construction in Chile and planned to be fully operational by late 2013, will be able to zoom into the planet-forming zones of disks around young stars and revolutionize this field in the near future. First exciting and surprising ALMA results will be presented.