Oxford Physics Public Lectures

Particle 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.

Particle 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.

Professor Heino Falcke of Radboud University, Nijmegen delivers the 19th Hintze Lecture - reviewing the latest results of the Event Horizon Telescope, its scientific implications and future expansions of the array One of the most bizarre, but perhaps also most fundamental predictions of Einstein's theory of general relativity are black holes. They are extreme concentrations of matter with a gravitational attraction so strong, that not even light can escape. The inside of black holes is shielded from observations by an event horizon, a virtual one-way membrane through which matter, light and information can enter but never leave. This loss of information, however, contradicts some basic tenets of quantum physics. Does such an event horizon really exist? What are its effects on the ambient light and surrounding matter? How does a black hole really look? Can one see it? Indeed, recently we have made the first image of a black hole and detected its dark shadow in the radio galaxy M87 with the global Event Horizon Telescope experiment. Detailed supercomputer simulations faithfully reproduce these observations. Simulations and observations together provide strong support for the notion that we are literally looking into the abyss of the event horizon of a supermassive black hole. The talk will review the latest results of the Event Horizon Telescope, its scientific implications and future expansions of the array.

Professor Heino Falcke of Radboud University, Nijmegen delivers the 19th Hintze Lecture - reviewing the latest results of the Event Horizon Telescope, its scientific implications and future expansions of the array One of the most bizarre, but perhaps also most fundamental predictions of Einstein's theory of general relativity are black holes. They are extreme concentrations of matter with a gravitational attraction so strong, that not even light can escape. The inside of black holes is shielded from observations by an event horizon, a virtual one-way membrane through which matter, light and information can enter but never leave. This loss of information, however, contradicts some basic tenets of quantum physics. Does such an event horizon really exist? What are its effects on the ambient light and surrounding matter? How does a black hole really look? Can one see it? Indeed, recently we have made the first image of a black hole and detected its dark shadow in the radio galaxy M87 with the global Event Horizon Telescope experiment. Detailed supercomputer simulations faithfully reproduce these observations. Simulations and observations together provide strong support for the notion that we are literally looking into the abyss of the event horizon of a supermassive black hole. The talk will review the latest results of the Event Horizon Telescope, its scientific implications and future expansions of the array.

Professor Stephen Blundell explores the many universes of quantum materials for the 2019 Quantum Materials Public Lecture. Physicists try to find the laws that govern the Universe, discover new particles and explain phenomena. But what if the rules that govern the Universe were different? What would happen then? This question is not just an academic one. Every new material discovered is behaves like a new Universe, with different laws and sometimes new particles. This talk explains how this idea works in practice and how the different universes discovered in so-called quantum materials are changing the way we think about the physical world.

Professor Stephen Blundell explores the many universes of quantum materials for the 2019 Quantum Materials Public Lecture. Physicists try to find the laws that govern the Universe, discover new particles and explain phenomena. But what if the rules that govern the Universe were different? What would happen then? This question is not just an academic one. Every new material discovered is behaves like a new Universe, with different laws and sometimes new particles. This talk explains how this idea works in practice and how the different universes discovered in so-called quantum materials are changing the way we think about the physical world.

Professor Barry C Barish gives a talk on the quest for the detection of gravitational waves. The quest for gravitational waves, following their prediction by Einstein in 1916 to their detection 100 years later will be traced. The subsequent opening of exciting new science, from rigorous tests of general relativity to using gravitational waves to explore the universe will be discussed. Prof Barish is a Ronald and Maxine Linde Professor of Physics, Emeritus at CalTech University in the USA, and has received a Nobel Prize in Physics 2017 “for decisive contributions to the LIGO detector and the observation of gravitational waves”.

Professor Barry C Barish gives a talk on the quest for the detection of gravitational waves. The quest for gravitational waves, following their prediction by Einstein in 1916 to their detection 100 years later will be traced. The subsequent opening of exciting new science, from rigorous tests of general relativity to using gravitational waves to explore the universe will be discussed. Prof Barish is a Ronald and Maxine Linde Professor of Physics, Emeritus at CalTech University in the USA, and has received a Nobel Prize in Physics 2017 “for decisive contributions to the LIGO detector and the observation of gravitational waves”.

Bill Diamond, President & CEO The SETI Institute gives an an update on the search for life in the Universe. Hosted by Ian Shipsey, Head of Physics.

Bill Diamond, President & CEO The SETI Institute gives an an update on the search for life in the Universe. Hosted by Ian Shipsey, Head of Physics.

What is the Dark Matter which makes 85% of the matter in the Universe? We have been asking this question for many decades and used a variety of experimental approaches to address it, with detectors on Earth and in space. Yet, the nature of Dark Matter remains a mystery. An answer to this fundamental question will likely come from ongoing and future searches with accelerators, indirect and direct detection. Detection of a Dark Matter signal in an ultra-low background terrestrial detector will provide the most direct evidence of its existence and will represent a ground-breaking discovery in physics and cosmology. Among the variety of dark matter detectors, liquid xenon time projection chambers have shown to be the most sensitive, thanks to a combination of very large target mass, ultra-low background and excellent signal-to-noise discrimination. Experiments based on this technology have led the field for the past decade. I will focus on the XENON project and its prospects to continue to be at the forefront of dark matter direct detection in the coming decade. Professor Elena Aprile is Professor of Physics at Columbia University in New York City. After obtaining her undergraduate degree in Physics in Naples, Italy, she earned her PhD at the University of Geneva, Switzerland. She started her research on noble liquid imaging detectors under the mentorship of Professor Carlo Rubbia, first as a student at CERN and later as postdoc at Harvard University. At Columbia, she pioneered the development of a Compton telescope for gamma-ray astrophysics based on a liquid xenon time projection chamber. She later turned her attention to the dark matter question proposing the XENON project for its direct detection using liquid xenon as target and detector medium. She founded the XENON Dark Matter Collaboration in 2002 and has served as its scientific spokesperson ever since; her international team includes more than 170 scientists and students representing 24 nationalities and 22 institutions. Aprile has been principal investigator on more than 20 research grants worth nearly $30 million over the last three decades and holds a patent for a vacuum ultraviolet light source. She has served on numerous panels and committees, for NASA, NSF, DOE, Fermilab, CNRS, ERC, etc. She is a Fellow of the American Physical Society since 2000. In 2017, she received an honorary degree from the University of Stockholm. She is the recipient of the 2019 AAS Lancelot Berkeley Prize.

What is the Dark Matter which makes 85% of the matter in the Universe? We have been asking this question for many decades and used a variety of experimental approaches to address it, with detectors on Earth and in space. Yet, the nature of Dark Matter remains a mystery. An answer to this fundamental question will likely come from ongoing and future searches with accelerators, indirect and direct detection. Detection of a Dark Matter signal in an ultra-low background terrestrial detector will provide the most direct evidence of its existence and will represent a ground-breaking discovery in physics and cosmology. Among the variety of dark matter detectors, liquid xenon time projection chambers have shown to be the most sensitive, thanks to a combination of very large target mass, ultra-low background and excellent signal-to-noise discrimination. Experiments based on this technology have led the field for the past decade. I will focus on the XENON project and its prospects to continue to be at the forefront of dark matter direct detection in the coming decade. Professor Elena Aprile is Professor of Physics at Columbia University in New York City. After obtaining her undergraduate degree in Physics in Naples, Italy, she earned her PhD at the University of Geneva, Switzerland. She started her research on noble liquid imaging detectors under the mentorship of Professor Carlo Rubbia, first as a student at CERN and later as postdoc at Harvard University. At Columbia, she pioneered the development of a Compton telescope for gamma-ray astrophysics based on a liquid xenon time projection chamber. She later turned her attention to the dark matter question proposing the XENON project for its direct detection using liquid xenon as target and detector medium. She founded the XENON Dark Matter Collaboration in 2002 and has served as its scientific spokesperson ever since; her international team includes more than 170 scientists and students representing 24 nationalities and 22 institutions. Aprile has been principal investigator on more than 20 research grants worth nearly $30 million over the last three decades and holds a patent for a vacuum ultraviolet light source. She has served on numerous panels and committees, for NASA, NSF, DOE, Fermilab, CNRS, ERC, etc. She is a Fellow of the American Physical Society since 2000. In 2017, she received an honorary degree from the University of Stockholm. She is the recipient of the 2019 AAS Lancelot Berkeley Prize.

The 2019 Halley lecture n February 2016, the Laser Interferometer Gravitational Wave Observatory (LIGO) announced the discovery of the merger of two black holes, each of which weighed around 30 times the mass of the Sun. Shortly thereafter, it was speculated that these black holes might make up the dark matter that has long been known to exist in galaxies (like our own Milky Way). I will review this possibility and explain why the hypothesis may or may not work.

The 2019 Halley lecture n February 2016, the Laser Interferometer Gravitational Wave Observatory (LIGO) announced the discovery of the merger of two black holes, each of which weighed around 30 times the mass of the Sun. Shortly thereafter, it was speculated that these black holes might make up the dark matter that has long been known to exist in galaxies (like our own Milky Way). I will review this possibility and explain why the hypothesis may or may not work.

Professor Jacqueline van Gorkom delivers the 18th Hintze Lecture. How do galaxies get their gas and how do they lose it? Theories of galaxy formation predict that the growth of galaxies is regulated by the infall of hydrogen gas. This gas is the fuel for star formation. When galaxies run out of gas star formation stops. Interestingly, observationally we know much more about the stars in galaxies and how the star formation rate has evolved over time than we know about the gas. The gas is hard to observe. Currently a renaissance is taking place in observational radio astronomy, new telescopes have been developed, which can image this gas, and even better ones are being constructed. I will show what we already have learned, discuss remaining puzzles and outline what the future might bring.

Professor Jacqueline van Gorkom delivers the 18th Hintze Lecture. How do galaxies get their gas and how do they lose it? Theories of galaxy formation predict that the growth of galaxies is regulated by the infall of hydrogen gas. This gas is the fuel for star formation. When galaxies run out of gas star formation stops. Interestingly, observationally we know much more about the stars in galaxies and how the star formation rate has evolved over time than we know about the gas. The gas is hard to observe. Currently a renaissance is taking place in observational radio astronomy, new telescopes have been developed, which can image this gas, and even better ones are being constructed. I will show what we already have learned, discuss remaining puzzles and outline what the future might bring.

Professor Mark Newton describes some of the key events in the discovery and development of Electron Paramagnetic Resonance (EPR). Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy as it is also known is a method for studying systems with unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but it is electron spins that are excited instead of the spins of atomic nuclei. EPR was first observed in Kazan State University by Soviet physicist Yevgeny Zavoisky in 1944 and was developed independently at the same time by Brebis Bleaney at the University of Oxford. In the 75 years that have followed EPR has found many applications in physics, chemistry, biology, medicine, geology and archaeology. In this talk I will endeavour to describe some of the key events in the discovery and development EPR but spend most of the time focusing on applications of the technique and its many derivatives. EPR is very much an evolving technique, with detection of single electron spins now routine in some systems, such that we can optimistically look for applications ranging from studies of single molecules, to enhanced sensitivity and spatial resolution in magnetic resonance imaging. This annual lecture commemorating Professor Brebis Bleaney (1915-2006) was endowed by Bleaney's pupil Professor Michael Baker (1930-2017).

Professor Mark Newton describes some of the key events in the discovery and development of Electron Paramagnetic Resonance (EPR). Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy as it is also known is a method for studying systems with unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but it is electron spins that are excited instead of the spins of atomic nuclei. EPR was first observed in Kazan State University by Soviet physicist Yevgeny Zavoisky in 1944 and was developed independently at the same time by Brebis Bleaney at the University of Oxford. In the 75 years that have followed EPR has found many applications in physics, chemistry, biology, medicine, geology and archaeology. In this talk I will endeavour to describe some of the key events in the discovery and development EPR but spend most of the time focusing on applications of the technique and its many derivatives. EPR is very much an evolving technique, with detection of single electron spins now routine in some systems, such that we can optimistically look for applications ranging from studies of single molecules, to enhanced sensitivity and spatial resolution in magnetic resonance imaging. This annual lecture commemorating Professor Brebis Bleaney (1915-2006) was endowed by Bleaney's pupil Professor Michael Baker (1930-2017).

The 17th Hintze Lecture, given by Professor Rocky Kolb, Arthur Holly Compton Distinguished Service Professor of Astronomy and Astrophysics, The University of Chicago. In daily life we do not experience the quantum nature of the world on the scale of elementary particles, nor do we sense the expansion and evolution of the universe on cosmic scales. Humans, midway in size between quantum and cosmic scales, evolved to perceive nature not as it actually is, but merely as required to survive in our environment. How remarkable that we have developed an understanding of the quantum realm and the cosmic realm, and realized that the inner space of the quantum and the outer space of the cosmos are intimately connected. In this lecture I will highlight some of the remarkable connections between the quantum and the cosmos.

Dr James Green, current Chief Scientist of NASA gives a talk on the how life may be distributed on Earth and in the Solar System with consideration of the age of our sun. This talk was a joint lecture held by the The Department of Physics and the Worshipful Company of Scientific Instrument Makers. NASA's Gravity Assist podcast, hosted by Dr. James Green: https://www.nasa.gov/mediacast/gravity-assist-explorer-1-jim-green-s-gravity-assist

The 3rd Wetton lecture, 19th June 2018 delivered by Professor David W. Hogg, Center for Cosmology and Particle Physics, New York University In the last 20 years, the astronomical community has found thousands of planets around other stars, and we now know that many or even most stars in our Galaxy host planets. These planets have been found by making exceedingly precise measurements of stars. Some of the planets we find are extremely strange; most known planetary systems are very different from our own Solar System. Here we will look at how these measurements are made, and how planets are found in the data. The data analysis - the search for the planets in the mountains of data - involves cutting-edge ideas from data science and machine learning. These technologies are transforming our capabilities in astronomy.

The 16th Hintze lecture, 25th April 2018 delivered by Professor René Doyon, Director, Mont-Mégantic Observatory & Institute for Research on Exoplanets, University of Montreal, Canada It is now well established that planetary systems are very common in the Solar neighbourhood, in particular small rocky planets, similar to Earth, around low-mass stars. Thanks to new ground-and spaced-based infrared facilities soon to be deployed, it will be possible not only to find the closest habitable worlds but also to detect their atmosphere and obtain constraints on their composition. This will be a major stepping stone towards the detection of life outside the Solar system. This lecture will highlight recent exoplanet discoveries and present an overview of ongoing and future projects aiming for the detection and characterisation of nearby habitable worlds. The detection of a biosignature, the evidence for biological activity beyond the Solar System, may be just a few decades away.

The 2018 Astor Visiting Lecture 14th March 2018 delivered by Professor Adam Leroy, Ohio State University. The Atacama Large Millimeter/sub-millimeter Array (ALMA) is the largest, most complex ground-based telescope ever built. From its perch high in the Chilean Andes, ALMA is now unveiling the birth of planets, stars, and galaxies. I will give a taste of the revolution ushered in by ALMA. This includes resolving the disks that form new Solar systems, finding the seeds of gaseous giant planets, weighing – and maybe even directly imaging – black holes, and watching galaxies form at the edge of the universe. Then, I will show how my colleagues and I are using ALMA to understand the origins of stars in galaxies. As part of ALMA's largest project to date, we are studying all of the stellar nurseries across the nearby universe. We see that the cold clouds of gas and dust that form stars appear to be shaped by violent, dynamic processes that vary from galaxy to galaxy. We also see that the birth of stars from these clouds is both inefficient and terribly destructive.

Our Universe was created in 'The Big Bang' and has been expanding ever since. Professor Schmidt describes the vital statistics of the Universe, and tries to make sense of the Universe's past, present, and future.

An introduction to the fascinating world of superconductors and the many surprising phenomena they exhibit, from zero resistance to quantum levitation. Superconductors are metals with remarkable and unexpected properties at low temperatures which defied explanation for many decades. In this talk, illustrated with practical demonstrations, Professor Andrew Boothroyd recounts the long history of superconductivity and gives simple explanations for how superconductors work and what they are useful for.

How can we test a quantum computer? An exploration of some of the theoretical puzzles of this field and how we can investigate them with experimental physics. What is the relationship between quantum physics, computer science and complexity theory? In this talk, Dr Jelmer Renema will introduce a conceptual problem that sits at the intersection between these fields, namely: how can we show that a quantum computer can outperform an ordinary computer?

A family-friendly demonstration of superconductors in action. Fran explores the low temperatures we need to make them work, and how we can use superconductors for levitating trains. When something superconducts, it behaves as a magnetic mirror, so will be repelled from magnetic fields. We can use this property to float a superconductor above a bed of magnets. However, for this to work, the superconductor has to be very cold. Graduate student Fran Kirschner uses liquid nitrogen to cool some superconductors (among other things) and show what they can do. Along the way, she explains some of the history and uses of these amazing materials.

Public Lecture organised by the Aeronautical Society of Oxford in conjunction with the Department of Physics.

The 2017 Halley Lecture 7th June 2017 delivered by Professor Rainer Weiss, MIT on behalf of the LIGO Scientific Collaboration The recent observations of gravitational waves from the merger of binary black holes open a new way to learn about the universe as well as to test General Relativity in the limit of strong gravitational interactions – the dynamics of massive bodies traveling at relativistic speeds in a highly curved space-time. The lecture will describe some of the difficult history of gravitational waves proposed 100 years ago. The concepts used in the instruments and the methods for data analysis that enable the measurement of gravitational wave strains of 10-21 and smaller will be presented. The results derived from the measured waveforms, their relation to the Einstein field equations and the astrophysical implications are discussed. The talk will end with our vision for the future of gravitational wave astronomy.

Physics Colloquium 26th May 2017 delivered by Professor Miles Padgett, University of Glasgow Ghost imaging and ghost diffraction were first demonstrated by Shih and co-workers using photon pairs created by parametric down-conversion. They were able to obtain an image or a diffraction pattern using photons that had never interacted with the object, relying instead on the correlations with photons that have. In a typical ghost-imaging configuration, the down-converted photons are directed into two separate optical arms. The object is placed in one arm and a single-pixel “heralding” detector detects the photons transmitted through this object. The signal from this detector triggers a camera positioned in the other arm, which then detects the spatial position of the correlated photon. The image is recovered from the coincidence detection of the two photons. But what sets the resolution of the resulting images? The resolution of the heralding arm, the resolution of the camera optics, or something else? This talk will present an examination of the resolution limits of the ghost imaging and ghost diffraction. Beyond consideration of these limits, our ghost diffraction is an implementation of Popper's thought experiment, and while our results agree with his experimental predictions, we show how these results do not contradict the Copenhagen Interpretation.

Physics Colloquium 5th May 2017 delivered by Dame Professor Jocelyn Bell Burnell Pulsars, or pulsating radio stars, were discovered accidentally 50 years ago. Dame Professor Bell Burnell will give a brief account of the equipment used and the discovery. We now understand pulsars to be rapidly rotating neutron stars (1ms < P 10s, R ≈ 10km, surface speed 10%c) which manifest extreme physics in several dimensions (average density = nuclear, surface B up to 1011T). Dame Professor Bell Burnell will describe the main features of pulsars and indicate how they are impacting our understanding of physics today.

The 14th Hintze Biannual Lecture 4th May 2017 delivered by Professor Conny Aerts - Director, Institute of Astronomy KU Leuven Thanks to the recent space missions CoRoT and Kepler, a new era of stellar physics has dawned. Asteroseismology, the observation and interpretation of starquakes, has produced a number of surprises about the deep interiors of stars. These results have altered our view of the lifecycle of stars including the generations of stars that preceded the Sun. Starquakes allow us to estimate the distances and ages of stars with unprecedented precision. Asteroseismology from space has revealed radically different physics in the heart of massive stars compared to the Sun. These massive stars are the chemical factories of the Universe, forcing us to rethink the output from the manufacturing sector of our Galaxy. Furthermore asteroseismology has paved the way for archaeological studies of our own Milky Way. After reviewing these developments I will look to the future projects that can address the new open questions posed by starquakes.

4th Annual Lobanov-Rostovsky Lecture in Planetary Geology delivered by Professor John Grotzinger, Caltech, USA The Mars Science Laboratory rover, Curiosity, touched down on the surface of Mars on August 5, 2012. Curiosity was built to search and explore for habitable environments and has a lifetime of at least one Mars year (~23 months), and drive capability of at least 20 km. The MSL science payload can assess ancient habitability which requires the detection of former water, as well as a source of energy to fuel microbial metabolism, and key elements such carbon, sulfur, nitrogen, and phosphorous. The search for complex organic molecules is an additional goal and our general approach applies some of the practices that have functioned well in exploration for hydrocarbons on Earth. The selection of the Gale Crater exploration region was based on the recognition that it contained multiple and diverse objectives, ranked with different priorities, and thus increasing the chances of success that one of these might provide the correct combination of environmental factors to define a potentially habitable paleoenvironment. Another important factor in exploration risk reduction included mapping the landing ellipse ahead of landing so that no matter where the rover touched down, our first drive would take us in the direction of a science target deemed to have the greatest value as weighed against longer term objectives, and the risk of mobility failure. Within 8 months of landing we were able to confirm full mission success. This was based on the discovery of fine-grained sedimentary rocks, inferred to represent an ancient lake. These Fe-Mg-rich smectitic mudstones preserve evidence of an aqueous paleoenvironment that would have been suited to support a Martian biosphere founded on chemolithoautotrophy and characterized by neutral pH, low salinity, and variable redox states of both iron and sulfur species. The environment likely had a minimum duration of hundreds to tens of thousands of years. In the past year simple chlorobenzene and chloroalkane molecules were confirmed to exist within the mudstone. These results highlight the biological viability of fluvial-lacustrine environments in the ancient history of Mars and the value of robots in geologic exploration.

Physics Colloquium 10th March 2017 delivered by Professor Howard Milchberg, University of Maryland, USA When an optical pulse propagating through a nonlinear medium exceeds a certain threshold power, it can focus itself and collapse, in theory, to a singularity. In practice, several physical mechanisms mitigate or arrest the catastrophic collapse and the pulse continues propagation as a filamentary structure. This scenario has played out in many nonlinear optics systems over decades: among them are air filamentation, relativistic self-focusing in plasmas, laser-material processing, and nonlinear generation of broadband light. Recently, we showed that self-focusing collapse and collapse arrest is universally accompanied by the generation of robust topological structures: spatio-temporal optical vortices (STOVs). I'll describe our experiments and simulations leading to this result.

Physics Colloquium 24 February 2017 delivered by Professor Tom McLeish FRS, Department of Physics and Institute for Medieval and Renaissance Studies, Durham University, UK For the English polymath, Robert Grosseteste, light was the fundamental first form that gave dimensionality and stability to the material world. In a dozen scientific treatises written in the early 13th Century, he postulated a physics of light, colour and the rainbow. In his De luce (on light) he extends it to the origin of the Universe in what has been referred to as the ‘Medieval Big Bang'. His arguments are so taut that they can be translated into mathematics - our resulting numerical simulations show that Grosseteste's model does actually work. He also described the method for developing a universal principle from repeated observations under controlled conditions and argued that the explanation needing fewer suppositions and premises was the best. In his theory of colour, we have found through close examination of the manuscript evidence for his De colore (on colour) and his De iride (on the rainbow) and a mathematical analysis of their content, that he presents the first three-dimensional theory of perceptual colour space. In this talk, I introduce Robert Grossteste (ca 1170 -1253), the scientist, teacher, theologian and bishop and describe how a unique collaborative research approach has revealed new insights into his thought, particularly on light. An interdisciplinary team of historians, scientists, linguists and philosophers has developed techniques of joint reading of the medieval texts that have shown them to be logically consistent and founded on mathematically based models. We reflect on how a study of this extraordinary medieval science can help throw fresh light on the history of scientific thought, and bridge the current perception gap between the study of science and humanities.

Physics Colloquium 17 February 2016 delivered by Professor Valerio Scarani Since its formulation in 1964, Bell's theorem has been classified under "foundations of physics". Ekert's 1991 attempt to relate it to an applied task, quantum cryptography, was quenched by an approach that relied on a different basis and was allegedly equivalent. Ekert's intuition was finally vindicated with the discovery of "device-independent certification" of quantum devices. In this colloquium, I shall revisit the tortuous history of that discovery and mention some of the subsequent results.

Physics Colloquium 3 February 2017 delivered by Professor Val Gibson, Cambridge The Large Hadron Collider (LHC) has just completed another very successful year of data-taking, exceeding many of its design parameters, and collecting a huge amount of data. The LHCb experiment at the LHC is designed to search for new phenomena in heavy quark (beauty and charm) systems, which could ultimately explain why we live in a universe made of matter and not antimatter, as well as giving insight into the origin of dark matter in the Universe. This colloquium will focus on the latest results from the LHCb experiment: the precision measurements that benchmark the Standard Model; the results that tantalisingly deviate from the Standard Model; and the discovery of many new particles, including pentaquarks.

Physics Colloquium 27 January 2017 delivered by Professor Nicola Spaldin, ETH Zurich The behaviour of the early universe just after the Big Bang is one of the most intriguing basic questions in all of science, and is extraordinarily difficult to answer because of insurmountable issues associated with replaying the Big Bang in the laboratory. One route towards the answer -- which lies at the intersection between cosmology and materials physics -- is to use laboratory materials to test the so-called "Kibble-Zurek" scaling laws proposed for the formation of defects such as cosmic strings in the early universe. Here Professor Spaldin will show that a popular multiferroic material -- with its coexisting magnetic, ferroelectric and structural phase transitions -- generates the crystallographic equivalent of cosmic strings. Professor Spaldin will describe how straightforward solution of the Schroedinger equation for the material allows the important features of its behaviour to be identified and quantified, and present experimental results of what seem to be the first unambiguous demonstration of Kibble-Zurek scaling in real materials. Professor Spaldin will end with some very recent data showing that things might be less unambiguous than they seem.

Panel discussion with Prof John Womersley (STFC), Prof John Wheater (Department of Physics), Prof Ian Shipsey (Particle Physics), Prof Dave Wark (Particle Physics), Prof Daniella Bortoletto (Physics) and Prof Subir Sarkar (Particle Theory Group)

Professor John Womersley (STFC) gives the Particle Physics Christmas Lecture. In the past five years particle physicists have made major advances in understanding the nature of our universe – discovering the Higgs boson, and more recently detecting gravitational waves from a distant galaxy. Paradoxically we have also learned a lot more about what we don't know: that the particles and forces we understand in ever greater detail make up only a small fraction of what's in the cosmos, and that our theoretical prejudices about what remains to be discovered may have been very wrong. A new generation of ambitious experiments at accelerator laboratories, underground, and studying at the large scale structure of the universe will answer these questions – and surely open up others. I will also outline why it is essential that the country remains at the forefront of frontier research of this kind and how it contributes more broadly to society.

Physics Colloquium 25 November 2016 delivered by Dr Jamie Holder The gamma-ray band of the electromagnetic spectrum probes some of the most extreme environments in the Universe. Photons of these very-high energies can only be produced by the interactions of subatomic particles that have been accelerated to almost the speed of light. This acceleration occurs in a surprisingly wide variety of astrophysical sources: close to black holes and neutron stars, in the blast waves of supernova explosions, and in the relativistic jets of active galaxies. Gamma-ray emission might also result from the interactions of dark matter particles, and so provide a non-gravitational method to detect dark matter in the Universe and to determine its nature. Dr Holder will describe the detection methods for gamma-ray astronomy and highlight some of the most exciting results from the VERITAS observatory, which has been studying astrophysical sources from a mountain in Arizona since 2007. He will also describe the status and prospects for the Cherenkov Telescope Array, a next-generation gamma-ray observatory on a much larger scale.

Physics Colloquium 11 November 2016 delivered by Professor Jon Rosner The early 1960s witnessed a wealth of elementary particles described in terms of simple combinations of a few more elementary units, dubbed quarks. The known mesons and baryons could all be described as states of quark-antiquark or three quarks. However, it was not understood why certain more elaborate combinations, such as (two quarks + two antiquarks) or (four quarks + one antiquark) had not been observed. It has taken nearly half a century, but these “exotic” particles are now beginning to be seen and understood. This colloquium will trace their discovery and interpretation, with an eye to their future study.

The 13th Hintze Biannual Lecture delivered by Professor David Spergel Observations of the microwave background, the left-over heat from the big bang, the large-scale distribution of galaxies and the properties of distant supernova have led to a remarkable simple model for our universe. With only five parameters (the density of atoms, the density of matter, the age of the universe, the amplitude of fluctuations in the early universe and their scale dependance), this model can fit a host of astronomical observations. We have now determined these basic parameters at the few percent level or better. While simple, our universe is very strange. Atoms make up only 5% of the universe, most of the universe is made of mysterious dark matter and dark energy. We do not understand how the universe began or why there is more matter than anti-matter. I will review our current understanding and look forward to future measurements that can address these big open questions.

Physics Colloquium 27th October 2016 delivered by Professor Gabriela Gonzalez On September 14 2015, the two LIGO gravitational wave detectors in Hanford, Washington and Livingston, Louisiana registered a nearly simultaneous signal with time-frequency properties consistent with gravitational-wave emission by the merger of two massive compact objects. Further analysis of the signals by the LIGO Scientific Collaboration and the Virgo Collaboration revealed that the gravitational waves detected by LIGO came from the merger of a binary black hole system. This observation, followed by another one in December 2015, marked the beginning of gravitational wave astronomy. I will describe some details of the observation, the status of LIGO and Virgo ground-based interferometric detectors, and prospects for future observations.

Physics Colloquium 28 October 2016 delivered by Professor Séamus Davis Everything around us, everything each of us has ever experienced, and virtually everything underpinning our technological society and economy is governed by quantum mechanics. Yet this most fundamental physical theory of nature often feels as if it is a set of somewhat eerie and counterintuitive ideas of no direct relevance to our lives. Why is this? One reason is that we cannot perceive the strangeness (and astonishing beauty) of the quantum mechanical phenomena all around us by using our own senses. I will describe the recent development of techniques that allow us to image electronic quantum phenomena directly at the atomic scale. As examples, we will visually explore the previously unseen and very beautiful forms of quantum matter making up electronic liquid crystals and high temperature superconductors and find that they are closely related. I will discuss the implications for fundamental physics research and also for advanced materials and new technologies, arising from quantum matter visualization.

Physics Colloquium 21st October 2016 delivered by Professor Theodore (Ted) Shepherd Pretty much all that is known with any confidence about climate change concerns its energetic and thermodynamic aspects. Atmospheric circulation, which also involves consideration of dynamics, is much more uncertain yet plays a critical role in climate change at the regional scale. How to approach this issue represents a major scientific challenge. In this talk Prof Shepherd will explain the nature of the problem and discuss some of the potential ways forward.

Physics Colloquium 14th October 2016 delivered by Professor Thierry Foglizzo The supernova explosion of massive stars is primarily powered by the gravitational contraction of their core into a neutron star, before the formation of a black hole. Despite numerous observations of supernovae in distant galaxies, the underlying mechanism is still a major challenge to theorists. Prof Foglizzo will review the state of the art, with an emphasis on the multidimensional effects of hydro and MHD instabilities. Non axisymmetric one-armed instabilities known as the Standing Accretion Shock Instability and the corotation instability are able to redistribute angular momentum radially even for moderate rotation rates. Numerical simulations of simplified models are used to evaluate their effect on the explosion and the pulsar spin. Surprisingly, both instabilities can be illustrated with a simple hydraulic experiment based on a shallow water analogy. Results are analyzed in view of the constraints on the angular momentum budget set by stellar evolution on the one hand and by the spin properties of pulsars on the other hand.

Physics Colloquium 10th June 2016 delivered by Professor Swapan Chattopadhyay Tremendous advances have been made in the last two decades in precision ‘Quantum' technologies and techniques in multiple disciplines e.g. cavity electrodynamics, atomic beam interferometry, SQUIDS, quantum optical “squeezed state” techniques for noise-free single photon detection, qubit-based quantum entanglement techniques, high-Q superconducting cavities, precision NMR detection via designer materials, etc. These advances promise to enable transformational research using ultra-sensitive probes to explore very “weak effects” on a laboratory scale. These weak effects are manifest everywhere in nature in material and living systems from the laboratory to outer space. Potential “mezzo-scale” experiments and facilities can be envisaged using “quantum sensors” to search for ultra-weak physical, chemical or biological signals of fundamental significance to the material and living world around us as well as explore the “inner” and “outer” dimension of “vacuum” believed to be manifest in the so-called “dark” universe. This talk will illustrate this potential via a few exciting examples discussed at the recent US DOE Round Table on Quantum Sensors in February 2016.

3rd Annual Lobanov-Rostovsky Lecture in Planetary Geology delivered by Professor Raymond T Pierrehumbert. Atmospheres are dynamic entities, formed from the volatile substances that accrete when a planet is formed and later in its history, cooked out in the hot-high pressure interior of the planet, and exchanging with the interior through crustal processes (for planets which have a solid surface) or mixing into the deep interior (for fluid planets). Loss of atmosphere to space is also a major mechanism whereby the chemical composition of entire planets evolve. There is thus no distinct boundary between the disciplines of planetary geology and planetary atmospheres, and the dawning age of exoplanet discovery has made it even more essential to think across the boundaries of the two disciplines. The likely characteristics of known exoplanets greatly expand the range of substances that have to be thought of as atmospheric components, with many things thought of as “rocks and minerals” on Earth being atmospheric or cloud forming substances. There are planets hot enough to have permanent magma oceans which may give rise to rock vapor atmospheres, and others where clouds may be formed of enstatite or even sapphire (or more prosaically, corundum). Some of these atmospheres are supersonic and local; others may be global and subsonic. There is also a host of new problems to be thought about in connection with “gas midgets,” which are mostly fluid but small enough that they need not have a hydrogen dominated composition. In this lecture, I will provide a survey of the emerging field of integrated planetary science, and conclude with some thoughts on how to train the next generation of planetary scientists to deal with the leading-edge problems of the future.

Physics Colloquium 20th May 2016 delivered by Ian Shipsey Cochlear implants are the first device to successfully restore neural function. They have instigated a popular but controversial revolution in the treatment of deafness, and they serve as a model for research in neuroscience and biomedical engineering. After a visual tour of the physiology of natural hearing the function of cochlear implants will be described in the context of electrical engineering, psychophysics, clinical evaluation, and my own personal experience. About the speaker: Ian Shipsey is a particle physicist, and a Professor of Physics at Oxford University. He has been profoundly deaf since 1989. In 2002 he heard the voice of his daughter for the first time, and his wife's voice for the first time in thirteen years thanks to a cochlear implant.

The 2016 Hintze Biannual Lecture delivered by Professor Robert Kennicutt Understanding the birth of stars is one of grand challenges of 21st century astrophysics, with impacts extending from the formation of planets to the birth and shaping of galaxies themselves. The challenge has been all the more difficult because the most active birth sites are largely hidden in visible light. Thanks to a new generation of infrared and submillimetre space telescopes this veil has been lifted, and a complete picture of starbirth in the Universe is emerging. They reveal an extraordinary diversity of activities in galaxies, and an emerging history of star formation cosmic time, extending back to some of the first stars and seeds of galaxies. This talk will summarise what we have learnt about starbirth on cosmic scales, and highlight the challenges and opportunities which lie ahead.