Professor Shih-I Pai (1913-1996)
The Shih-I Pai Lecture Series honors the memory, accomplishments and many contributions of Professor Shih-I Pai (1913-1996), who served on the faculty at the University of Maryland at College Park from 1949 until his retirement with Emeritus status in 1983. Professor Pai was a pioneer in the field of aerodynamics, helping to advance that field from its infancy to its current level of sophistication. His breakthrough discoveries about the effects of structure on turbulent flow laid the foundations for him and fellow engineers to move from low-speed aerodynamics through high subsonic and on to supersonic and hypersonic speeds. He was the recipient of a Centennial Medal from the A. James Clark School of Engineering and a founding member of the Institute for Fluid Dynamics and Applied Mathematics, now the Institute for Physical Science and Technology.
Shih-I Pai was born in Anhui Province in China. After graduating from the National Central University in Nanjing, he moved to the United States where he received a master's degree from MIT and then a doctorate in aeronautics and applied mathematics from Caltech. Over his career he authored 14 books and 130 articles on aerodynamics, fluid dynamics and viscous flow, and garnered international recognition for his research.
The Twenty-Fourth Shih-I Pai Lecture was held on October 9, 2018, and was dedicated to the memory of Alice Wang Pai, the late wife of Shih-I Pai, who passed away in 2018.
Shih-I Pai Lecturers
Fung is recognized international for his pioneer studies on the mechanics of living tissues and organs. His work was the first to use the principles of mechanical fluid dynamics to study living tissues and organs and has studied circulation, blood vessels, blood cells, the heart, the lung, the relationship between growth and physical stress, and tissue engineering. Author of several books and hundreds of articles, Dr. Fung is a member of the U.S. Academy of Sciences, the U.S. National Academy of Engineering, and the U.S. Institute of Medicine.
Gems at the Border of Physical and Biological Sciences
A mu is an area about 1/6 of an acre. Chu Hsi said that the source of living water lies outside one's own field. I agree, and can testify to it with my own experience. My field is mechanics. In 1957 I was in Gottingen, Germany on a sabbatical leave from Caltech. My mother was in China suffering from glaucoma. I read up on the disease in the library of the Institute of Physiology in Gottingen. Gradually, I became aware that none of the books in the Gottingen physiology library contained the word "mechanics". Yet I saw force and motion in every biological problem. Down the road, in the library of the Aerodynamics Institute, none of [the] books contained the word "biology". Yet every[one] was searching for nonlinear problems to work on. Thus arose the idea: why not combine the two? I will share with you my experience in this adventure. The gems I picked up are mainly concerned with the cardio-vascular system, related to the flow of blood, water, and gas in our bodies, to hypertension, and atherogenesis. Recently, my colleague and I began concentrating on tissue remodeling and tissue engineering. I hope that some new findings will be of interest to you.
Zierep is a professor emeritus at the University of Karlsruhe, Germany. He is internationally recognized for his foundational studies of gas dynamics, transonic and hypersonic flows, and the shape and structures of shock waves.
Dr. Zierep received a doctorate of engineering from the Technical University in Berlin. He has published 157 scientific papers, including fix textbooks, and has supervised 40 doctoral students. Dr. Zierep co-founded the periodical journal Acta Mechanica and has been co-editor since 1965.
He has been president of the Society for Applied Mathematics and Mechanics (GAMM), 1983-1986; Honorary Professor at Beijing University, 1988; promoted Dr.techn.E.h. by the Technical University of Vienna, 1989 and received the Cross of the Order of Merit of the Federal Republic of Germany, 1995.
Condensation in Transonic Flow
Transonic flow in Laval nozzles, around profiles and in cascades with phase changes combined with energy addition are of fundamental importance and of great technical interest. Well known examples are flows in steam turbines, in cryogenic channels (N2 condensation) and the flow around an airplane in humid air. Nowadays flows with more general phase changes like Organic Rankine Processes and those in retrograde (dense) media are of increasing importance. We discuss condensation in flows by means of different geometries. After a historical glance back we sketch the very actual situation of calculation of these flow fields and the validation of those methods by experiments.
Our numerical method (finite volume) solves the unsteady 2D-Euler equations. The iteration is finished when the stationary solution is reached. All equations are used in conservation form and the condensation is simulated by two successive processes. For homogeneous condensation we start with the nucleation theory by Vomer and continue downstream with the droplet growth model by Hertz and Knudsen. Depending on the stagnation humidity we arrive at different structures of condensation in the supersonic part of a Laval nozzle (subcritical heat addition with X-shock, supercritical heat addition with normal shock). The agreement between calculation and experiment is convincing. Concerning profile flow we get a strong dependence of drag and lift due to condensation. The details depend on the one hand whether we have equilibrium or nonequilibrium condensation and on the other hand which profile geometry we use.
The numerical results for condensing flow over NACA-0012 and a circular arc profile (10% thickness) are completely different. The pressure drag increases in the first case up to 60% and decreases in the second case down to 40% in comparison with the adiabatic case. Interesting is the existence of a double shock configuration completely confirmed by experiments.
Li was chairman and founder of Y.T. Li Engineering, Inc.; honorary chairman, treasurer and co-founder of Setra Systems, Zinc. (1965- ), and president and co-founder of Dynisco Inc. (1952-1960). He was professor emeritus of MIT (1947-1979), member of the U.S. National Academy of Engineering, and second president of the National Association of Chinese Americans (1980-1984).
Dr. Li received his B.S. from National Beijing University of Technology (1934), M.S. degrees from National Central University in Nanking (1936) and MIT (1938), and his Sc.D. from MIT in 1939.
He was internationally known for his innovative engineering work and leadership. Dr. Li’s work “Technological Innovation in Education and Industry” (Van Nostrand, 1980) has had significant impact on both engineering practice and national policy. Deceased, 1914-2011.
Developing Orbital Rod Evaporator as a Model of Developing Technology-Intensive Industry in China
Using orbital evaporation to improve the performance of seawater desalination was initially used as an academic exercise in the early Eighties to illustrate the process of innovation and as an example for developing a technology intensive industry in China.
A DOE grant in 1982 was followed by the support of several US companies for biotech applications and the collaboration of the government agencies in mainland China and Taiwan for desalination applications. This effort allowed the author to identify several interesting issues along the path of new product development, but without tangible commercial success.
A breakthrough occurred when the orbital technology was licensed to Paul Mueller Company for thermal energy storage application-making ice at night to be used in the daytime for air-conditioning. That company now enjoys risk sales of their new ORE products in US, Japan and South Korea. Another major US firm, Aqua-Chem, is now developing ORE under license for seawater desalination and waste treatment.
In the meantime, China has identified a great need for social-economic infrastructure type of industries in the wake of rapid economic growth of labor intensive industries. Consequently, environmental protection and water treatment technology receive high priority in China's 9th Five-Year plan. Collaboration with Y.T. Li Engineering, Inc. to develop ORE technology in China has therefore been initiated with several Chinese organizations, with the satisfying implication that the original goal of the author is finally coming to fruition.
Kadanoff was the John D. and Catherine T. MacArthur Distinguished Service Professor in Physics and Mathematics at the James Franck Institute, University of Chicago.
He was a member of the National Academy of Sciences, member of the American Philosophical Society, Fellow of the American Physical Society, Fellow of the American Academy of Arts and Sciences, Fellow of the American Association for the Advancement of Science, recipient of the Boltzman Medal of the International Union of Pure and Applied Physics (1990), The Elliot Cresson Medal of the Franklin Institute(1986), Wolf Foundation Prize in Physics (1980), the Buckley Prize of the American Physical Society (1977), and the Onsager Prize of the American Physical Society (1998).
He received A.B., M.A. and Ph.D. degrees from Harvard University in 1957, 1958, and 1960; was National Science Foundation Fellow in 1957-61 and Sloan Foundation Fellow in 1963-67. He was a faculty member of the University of Illinois, Urbana and Brown University before joining the University of Chicago in 1978.
Dr. Kadanoff authored the book “Electricity Magnetism and Heat” and co-authored “Quantum Statistical Mechanics”.
His research interests included dynamics in granular materials; development of singularities in fluid flow; turbulence and applications of dynamical systems theory. Deceased, 1937-2015.
Drips and Jets: Singularities, Topology Changes, and Scaling
We investigate the behavior of the interface between two fluids. We are interested in the singularities which develop when a mass of fluid breaks into two. Then there is a bridge connecting two pieces of fluid which goes to zero thickness. Experiments, computer simulations, and theory are used to analyze several different physical situations: a dripping faucet, the pinch-off of a jet flow, two fluids being sucked up by a straw, and a liquid which comes to a sharp point.
Swinney is the Sid Richardson Foundation Regents Professor in Physics at the University of Texas at Austin and Director of the Center for Nonlinear Dynamics also at the University of Austin. He is a member of the National Academy of Sciences, Fellow of the American Academy of Arts and Sciences, Fellow of the American Association for the Advancement of Science, Fellow of the American Physical Society, and member of the Johns Hopkins Society of Scholars.
Other honors include:
- American Physical Society Fluid Dynamics Prize (1995)
- John Simon Guggenheim Foundation Fellowship (1983-84)
- Morris Loeb Lecturer, Harvard University (1982)
He received his B.S. degree with Honors from Rhodes College in 1961 and his Ph.D. from Johns Hopkins University in 1968. He was a faculty member of Johns Hopkins University, New York University, and City College of CUNY before joining the University of Texas at Austin in 1978.
His current research interests include bifurcations and the formation of spatial and temporal patterns in fluid, chemicals and granular systems; dynamics of oceanic and atmospheric type flows and interfacial phenomena.
Emergence of Patterns in Nonequilibrium Systems
We consider macroscopic systems driven away from thermodynamic equilibrium by an imposed gradient in temperature, velocity or concentration. For a sufficiently small imposed gradient, the system will exist in a base state, which has the symmetry of the boundary conditions. However, when the imposed gradient is increased, a critical value is reached at which the base state becomes unstable-the system spontaneously breaks the symmetry of the boundary conditions and forms a spatial pattern, which in two dimensions could be an array of squares, stripes, hexagons, or traveling waves (e.g., a rotating spiral). With larger imposed gradients, the patterns can become disordered in both space and time. The general principles of pattern formation in systems driven away from equilibrium will be discussed and illustrated with examples from physics, chemistry, and biology.
Ahlers is Professor of Physics at the University of California at Santa Barbara. He is a Member of the National Academy of Sciences, Fellow of the American Association for the Advancement of Science, and Fellow of the American Physical Society.
Other honors include:
- Tenth Fritz London Memorial Award in Low Temperature Physics (1978)
- Morris Loeb Lecturer, Harvard University (1979)
- Alexander von Humboldt Senior U.S. Scientist Award (1989-90)
- Guggenheim Fellowship (1997-98)
He received his B.A. degree in Chemistry from the University of California at Riverside in 1959 and his Ph.D. in Physical Chemistry from the University of California at Berkeley in 1963. He was a member of the Technical Staff at Bell Laboratories from 1963 until he joined the University of California at Santa Barbara in 1979.
His current research interests include: critical phenomena near the superfluid transition of 4He; nonequilibrium phenomena with an emphasis on the problem of pattern formation; spatio-temporal chaos; formation of localized structures or pulses.
Fluctuations Near Bifurcations in Systems Far from Equilibrium
In spatially‑extended nonlinear dissipative systems far from equilibrium, bifurcations are usually discussed in terms of deterministic equations for the macroscopic variables which neglect the microscopic degrees of freedom. An example is the use of the Navier‑Stokes equation for Rayleigh‑Bénard convection (RBC). There is then a sharp bifurcation point R = Rc at which an exchange of stability occurs between the spatially‑uniform state and the state with spatial variation.
If the system is subjected to external noise, then even below the bifurcation there are fluctuations of the macroscopic variables away from the uniform state. The relevant fields then each have zero mean but a positive (albeit small) mean square. This talk will review the experimental measurements of the properties of these fluctuations. In the case of RBC, the exponents of the power laws which describe these properties have their classical (mean‑field) exponents. However, for electroconvection in a nematic liquid crystal (which is more susceptible to noise) there are deviations from the classical behavior when the system comes within a few percent of the bifurcation point. As near equilibrium critical points, the exponent values then differ from the classical ones.
Sreenivasan is the Harold W. Cheel Professor of Mechanical Engineering, Physics and Applied Physics at the Mason Laboratory, Yale University. He is a Member of the National Academy of Engineering, Fellow of the American Association for the Advancement of Science, Foreign Fellow of the Third World Academy of Sciences, Fellow of the American Academy of Arts and Science, Fellow of the American Physical Society, and Fellow of the American Society of Mechanical Engineers.
Other honors include:
- Humboldt Fellow (1983
- Guggenheim Fellow (1989)
- Otto Laporte Award of the American Physical Society (1995)
- Distinguished Scholar Award, American Chapter of the Indian Physics Association (1996)
He received his B.E. degree in Mechanical Engineering from Bangalore University in 1968, his M.E. and Ph.D. degrees in Aeronautical Engineering from the Indian Institute of Science in 1970 and 1975, and an M.A. (Privatim) degree from Yale University in 1985.
His current research interests include fluid turbulence, complex fluids, combustion, cryogenic helium and nonlinear dynamics.
In stars as in earth’s atmosphere, and in a variety of engineering applications, a dominant mode of fluid motion is convection. This is the motion that occurs when a fluid is heated against gravity. It is usually turbulent. We discuss our understanding of turbulent convection by exploring existing theories as well as experiments in the laboratory and the atmosphere. Very little prior knowledge will be assumed.
Barenglatt is Professor in Residence in the Department of Mathematics at the University of California at Berkeley, and Mathematician, Lawrence Berkeley National Laboratory. He is a Foreign Associate of the National Academy of Sciences, Foreign Honorary Member of the American Academy of Arts and Sciences, Foreign Associate of the National Academy of Engineering, and Foreign Member of the Royal Society of London.
Other honors include:
- G.I. Taylor Medal of the Society of Engineering Science
- Modesto Panetti Prize and Medal
- J.C. Maxwell Medal and Prize from the International Congress for Industrial and Applied Mathematics
He received his D.Sc. and Ph.D. degrees from Moscow University, and M.A. degree from Cambridge University. His current research interest include self-similarities, nonlinear waves and intermediate asymptotics, fracture, turbulence, and theory of fluid and gas flows in porous media.
Turbulence: The Last Problem of Classical Physics, new approach and perspectives
Turbulence is a state of vortex fluid motion where the velocity, pressure, and other properties of the flow field vary in time and space randomly. Despite the long-standing interest in the subject and the vast advances made, turbulence remains the greatest challenge of applied mathematics as well as classical physics. There exists however a class of developed (high Reynolds number) turbulent flows where the flow yield can be considered to be local. These are the wall-bounded flows. In the last decade our group (Professor A. J. Chorin, Professor V. M. Prostokishin, and the present author) has developed a different approach from the classical approach of Th. von Kármán, L. Prandtl and their followers. The results obtained suggest new possibilities for further studies of a wide class of fundamentally and practically interesting flows such as turbulent jets, mixing layers, etc. The new approach also reveals certain general properties of developed turbulent flows.
Ruelle is Professor Emeritus at Institut des Hautes Études Scientifiques, Bures-sur-Yvette, France. He is a Foreign Associate of the National Academy of Sciences, Foreign Honorary Member of the American Academy of Arts and Sciences, Member of the Academie des Sciences de Paris, and Member of the Academia Europaea.
Other academic honors include:
- Boris Pregel Award for Research in Chemical Physics, New York Academy of Sciences (1974)
- Prix Albert Ier de Monaco, Academie des Sciences de Paris (1979)
- Dannie Heineman Prize for Mathematical Physics, American Physical Society and American Institute of Physics (1985)
- Boltzmann Medal, IUPAP (1986)
- Holweck Medal, Societe Francaise de Physique and Institute of Physics (1993)
- Ludwig Boltzmann-Forschungspreis, Lane Steiermark and Universitat Graz (1995)
He obtained his undergraduate degree and a Ph.D. in Physics at the Free University of Brussels in 1957 and 1959 and was a Member of the Institute of Advanced Study in Princeton in 1962-64 and 1970-71.
His long term scientific interest are on the borderline between physics and mathematics: particularly dynamical systems on the mathematical side, and statistical mechanics on the physical SIDE. Currently he works on the ergodic theory of hyperbolic differentiable dynamical systems and nonequilibrium (classical) statistical mechanics.
Statistical Mechanics far from Equilibrium: Towards a General Theory
There is currently a strong revival of interest in nonequilibrium statistical mechanics. Diverse approaches are taken, but there is a common willingness to face technically difficult problems, and not to try to avoid there by mere definitions. In this lecture we shall outline an approach to nonequilibrium based on the Hoover-Evans isokinetic thermostat and the Gallavotti-Cohen chaotic hypothesis. We shall show how the ergodic theory of differentiable dynamical systems provides us with a linear response formula far from equilibrium. Using this formula we shall see how an entropy can be associated with nonequilibrium steady states. Finally, we shall discuss the need to extend our mathematical understanding beyond the isokinetic thermostat and the (uniformly hyperbolic) chaotic hypothesis.
Libchaber is the Detlev W. Bronk Professor at the Center for Studies in Physics and Biology, Rockefeller University, New York. He is a Corresponding Member of the French Academy of Sciences, Member of the American Academy of Arts and Sciences, and Member of the New York Academy of Sciences. He served as Directeur de Recherche de Recherche Scientifique, France.
Other academic honors include:
- Grad de Physique, SFP (1980)
- Wolf Prize in Physics (1986)
- MacArthur Foundation Fellowship (1991)
He obtained his undergraduate degree in Mathematics from the University of Paris, and his Ph.D. in physics from the Ecole Normale Superieure, Paris, where he continued research until joining the faculty of the University of Chicago (1983). Subsequent appointments were at Princeton University (1991) and Rockefeller University (1994).
His current research interests include: self-assembly of the protein RecA on single-stranded DNA; “artificial cells” using wheat germ cell extracts and gene constructs in a micron-scale volume fed by micro-fluidic channels; molecular evolution focusing on the evolution of the transcription machinery of the phase T7; thermophoresis and its effect on DNA in Solution.
Techniques from Physics, Problems from Biology
This lecture has the following three themes:
- Optical resonances as ideal detectors in biology
- Thermal convection for a hypothesis on the origin of life
- Quantum dots for developmental biology
Kieffer is Walgreen Chair and Professor of Geology and Physics at the University of Illinois, Urbana, Illinois. She is a Member of the National Academy of Sciences, and Fellow of the American Academy of Arts and Sciences.
Other academic honors include:
- Alfred P. Sloan Foundation Fellowship (1977-1979)
- Mineralogical Society of America Award (1980)
- W.H. Mendenhall Lecturer of the U.S. Geological Survey (1980)
- Spendiarov Award of the USSR Academy of Sciences (1989)
- Day Medal of the Geological Society of America (1992)
She obtained her undergraduate degree in Physics and Mathematics from Allegheny College, Pennsylvania (1964), followed by an M.S. in Geological Sciences (1967) and a Ph.D. in Planetary Sciences (1971), both awarded by the California Institute of Technology, Pasadena, California.
Her previous appointments were: Assistant Professor of Geology, University of California, Los Angeles (1973-1979), Geologist, U.S. Geological Survey, Flagstaff, Arizona (1979-1990), Professor and Regents’ Professor of Geology, Arizona State University (1990-1993), Professor and Head of Geological Sciences, University of British Columbia (1993-1995), and Mac Arthur Fellow (1995-2000).
Her current main research interests are: planetary sciences, geological fluid dynamics including geothermal, epithermal, and volcanic environments; solid-state geophysics and mineral thermodynamics.
Geysers and Volcanoes: Supersonic Challenges in Geology
It has been little recognized in the earth sciences that concepts from supersonic flow are relevant to some important processes. These situations arise because some geological fluids can have very low sound speeds. For example, boiling water can have sound speeds as low as 1 m/s because it has the density of the liquid, but the compressibility of steam. Thus, in a geothermal well discharge or geyser eruption, if the fluids are flowing faster than this, they are internally supersonic, and shock and rarefaction waves can occur. For another example, particulate flows of gas and solids, such as from an erupting volcano, also can have very low sound speeds (they can be thought of as very heavy molecular weight gases). The lateral blast at Mount St. Helens had a large supersonic core. New supercomputer simulations will be presented of the lateral blast dynamics.
Kopell is William Goodwin Aurelio Professor of Mathematics and Science and Co-Director of the Center for BioDynamics at Boston University, Boston, Massachusetts. She is a Member of the National Academy of Sciences and Fellow of the American Academy of Arts and Sciences.
Other academic honors include:
- Honorary Woodrow Wilson Fellowship (1963-1964)
- N.S.F. Graduate Fellowship (1963-1967)
- Alfred P. Sloan Fellowship (1975-1977)
- J.S. Guggenheim Fellowship (1984-1985)
- John D. and Catherine T. MacArthur Fellowship (1990-1995)
- Honorary Doctorate, New Jersey Institute of Technology (2006)
She obtained her undergraduate degree in Mathematics from Cornell University, New York (1963), followed by an M.A. (1965) and a Ph.D. (1967) in Dynamical Systems, both awarded by the University of California at Berkeley, California.
Her previous appointments were: C.L.E. Moore Instructor of Mathematics, Massachusetts Institute of Technology (1967-1969); Assistant Professor of Mathematics, Associate Professor of Mathematics, and Professor of Mathematics, Northeastern University (1969-1986).
Her current research interests are: Biophysical bases of electrical activity of the nervous system; dynamics of networks of neurons; brain rhythms in olfaction, audition, attention, learning and recall; pathologies of normal brain rhythms in Parkinson’s Disease and Schizophrenia; mechanistic bases of anesthesia; dynamics of sleep rhythms and of dopaminergic neurons associated with reward signals; reduction of dimensions in neural systems, geometric singular perturbation theory.
Rhythms of the Nervous System: From Biophysics to Cognition
The nervous system produces electrical activity in both waking and sleep. The spectral content of this activity depends on tasks being performed, and on cognitive states such as attention. A major open question is how the brain makes use of this activity for a cognitive function. This talk discuses some of the work that has been done on this issue, starting from the biophysics that gives rise to different frequency bands in the electrical activity. It then suggests, by means of case studies, how the biophysics gives clues to the uses of rhythms in cognition.
Rubin was a Staff Member, Astronomy, at the Department of Terrestrial Magnetism at the Carnegie Institution of Washington since 1965, and became a Senior Fellow in 2001. She was a Member of the National Academy of Sciences and the Pontifical Academy of Sciences, and a Fellow of the American Academy of Arts and Sciences.
Other academic honors include:
- U.S. National Medal of Science (1993)
- Gold Medal of the Royal Astronomical Society, London (1996)
- James Craig Watson Medal of the National Academy of Sciences (2004)
- Honorary Doctor of Science degrees from Creighton University (1978), Harvard University (1988), Yale University (1990), Williams College (1993), University of Michigan (1996), Ohio State University (1998), Smith College (2001), Grinnell College (2002), Ohio Wesleyan University (2003)
- Honorary Doctor of Humane Letters from Georgetown University (1997)
She obtained her undergraduate degree in Astronomy from Vassar College (1948), an M.A. in Astronomy from Cornell University (1951), and a Ph.D. in Astronomy from Georgetown University (1954).
Her research interests included masses of galaxies, but mostly very small, very low surface brightness galaxies. These galaxies are totally dark matter dominated, so may offer some insights missing from the study of large spirals. They are also important in considerations of modifying Newton’s laws, rather than postulating the existence of dark matter. Deceased, 1928-2016.
The Universe of Galaxies
Every civilization, from the time of the earliest humans to the present day, tells stories about the universe. What we know about the universe is dictated in large measure by the available technology. In the last century, we learned that we live in a galaxy of 200 billion stars, that the universe is populated by billions of galaxies, and that galaxies are moving away from each other. Equally important, we now understand that everything evolves: stars are born, evolve, and die; galaxies grow at the expense of smaller galaxies and gas clouds in their neighborhood.
Evidence will be discussed that leads to the conclusion that the stars, galaxies and clusters of galaxies that populate the universe make up less than 5% of its matter. The remaining matter is dark, and is only detected by its gravitational effect on the bright matter we can study. Also mysterious is the force that is causing the expansion of the universe to accelerate. While virtually everything we know about the universe we have learned in the 20th century, much still remains unknown.
Kalnay is a Distinguished University Professor in the Department of Atmospheric Oceanic Science (formerly the Department of Meteorology) and the Institute for Physical Science & Technology, University of Maryland, College Park, Maryland; she is also the Eugenia Brin Professor in Data Assimilation at the University. She is a Member of the National Academy of Engineering, Fellow of the American Academy of Arts and Sciences, Fellow of the American Geophysical Union and the American Meteorological Society, Foreign Member of the Academia Europaea, and Member of the Argentine Academy of Exact and Natural Sciences.
Other academic honors include:
- Kirwan Faculty Research and Scholarship Prize, University of Maryland (2006)
- U.S. Department of Commerce Gold Medals (1997, 1993)
- U.S. Senior Executive Service Presidential Rank Award (1996)
- American Meteorological Society Jule G. Charney Award (1995)
- U.S. National Aeronautics and Space Administration Gold Medal (1981)
She obtained her undergraduate degree in Meteorology from the University of Buenos Aires (1965) and a Ph.D. in Meteorology from the Massachusetts Institute of Technology (1971).
Her previous appointments include Director of Environmental Modeling Center of the National Centers for Environmental Prediction, U.S. National Weather Service (1987-1997), and Senior Research Meteorologist and Head, Simulation Branch, Goddard Laboratory for Atmospheres, U.S. National Aeronautics and Space Administration (1979-1986).
Her current research interests are: data assimilation and predictability, ensemble Kalman Filtering, coupled ocean-atmosphere modeling, and climate change.
Amidst the Chaos, Good Predictions: How Meteorology Beats the Odds
We will review ideas of weather predictability, with the Lorenz (1963) discovery of chaos (a name coined by Jim Yorke in 1975). Lorenz concluded that even if we had perfect models of the atmosphere and perfect knowledge of the initial conditions (“except for a butterfly”), we could not predict the weather beyond two weeks. At that time, weather forecasts were useless beyond a day, so this limit on predictability was only of academic interest.
A widely-used example of a chaotic system is the Lorenz (1963) 3-variable model with a solution that switches chaotically between two regimes. Four undergraduate women interns were able to use a simple method known as “breeding” fast-growing perturbations to develop accurate rules forecasting when the current regime would end and how long the next regime would last. These same ideas, showing that even in complex systems, chaos has simple structures, are applied to models used for weather forecasting. Chaos is attacked using ensemble forecasts, extending the skill of weather forecasts to 10 days, and approaching the theoretical limit of predictability. The El Niño phenomenon, being due to instabilities in coupled ocean-atmosphere, makes possible predictions of mean weather conditions several months in advance.
Levin is George M. Moffett professor of Biology in the Department of Ecology and Evolutionary Biology and Director of the Center for Bio-Complexity at Princeton University. He is also Adjunct Professor in Ecology and Evolutionary Biology in the Center for Applied Mathematics at Cornell University, and Visiting Distinguished Professor at the University of California, Irvine. He is a Member of the National Academy of Sciences, Member of the American Philosophical Society, Fellow of the American Academy of Arts and Sciences, Fellow of the American Association for the Advancement of Science, and Fellow of the Society for Industrial and Applied Mathematics.
Other academic honors include:
- Foreign Member, Istituto Veneto de Scienze, Lettere ed Arti, Venice, Italy (2008)
- Beijer Fellow, Beijer Institute of Ecological Economics, Stockholm Sweden (2007)
- American Institute of Biological Sciences Distinguished Scientist Award (2007)
- SIAM I.E. Block Community Lecture Award (2006)
- Kyoto Prize in Basic Sciences, Inamori Foundation, Japan (2005)
- Clay Mathematics Senior Scholar-in-Residence (2005)
- A.H. Heineken Prize for Environmental Sciences, Royal Netherlands Academy of Arts and Sciences (2004)
- Medallion of the Universite de Montpellier (2004)
- Honorary Doctor of Humane Letters Honoris Causa, Whittier College (2004)
He earned his undergraduate degree in Mathematics from Johns Hopkins University (1961), and Ph.D. in Mathematics from the University of Maryland (1964).
His current research interests include: modeling of ecological systems; dynamics of populations and communities; spatial heterogeneity and problem of scale; evolutionary, mathematical and theoretical ecology and evolution of cooperation maintenance of social norms.
The Challenge of Sustainability: Lessons from an Evolutionary Perspective
The continual increase in the human population, magnified by increasing per capita demands on Earth’s limited resources, raise the urgent man-date of understanding the degree to which these patterns are sustainable. The scientific challenges posed by this simply stated goal are enormous, and cross disciplines. What measures of human welfare should be at the core of definitions of sustainability, and how do we discount the future and deal with problems of intra-generational and inter-generational equality? How do environmental and socioeconomic systems become organized as complex adaptive systems, and what are the implications for dealing with public goods at scales from the local to the global? How does the increasing inter-connectedness of coupled natural and human systems affect the robustness of aspects of importance to us, and what are the implications for management, what is the role of social norms, and how do we achieve cooperation at the global level? All these issues have parallels in evolutionary biology, and this lecture will explore what lessons can be learned from ecology and evolutionary theory for addressing the problems posed by achieving a sustainable future.
Yorke is Distinguished University Professor of the Departments of Mathematics and Physics and the Institute for Physical Science and Technology at the University of Maryland in College Park, Maryland. Since 2007 he has been Chair of the Mathematics Department, and in 1988-2001 he was Director of the Institute for Physical Science and Technology. He won the Japan Prize in Science and Technology in 2003. He is a Guggenheim Fellow (1980), A Fellow of the American Academy of Arts and Sciences (1998), and a Fellow of the American Physical Society (2003).
Other academic honors include:
- Annual Chaim Weizmann Memorial Lecture at the Weizmann Institute in Rehovot, Israel (1997)
- Centennial Speaker for the American Physical Society (1998-1999)
- Norbert Wiener Lecturer at Tufts University (2006)
- Marker Lecturer in Mathematics at Pennsylvania State University (2006)
He is the coauthor of three books on chaos and two books on dynamics. He attained his undergraduate degree with major in Mathematics from Columbia University (1963), and Ph.D. in Mathematics from the University of Maryland (1966).
His current research interests include: period-doubling cascades galore; better methods for determining the genetic sequence of large genomes; modeling the population dynamics of HIV; chaos and weather prediction; a mathematical theory of observation; topological horseshoes and other topological phenomena; explosions of chaotic sets as a parameter is varied; tools for the numerical exploration of nonlinear dynamical systems and a physical realization of the Plykin attractor.
Everyone knows our lives are all chaotic and unpredictable in the long run, and the most successful people are those who are good at plan B. Scientists were probably the last people to find out about chaos. Chaos is an area of science and mathematics that describes situations in which small changes can cascade into larger and larger long-term effects. Chaos is a battle between stability and instability. I will describe phenomena that arise in this battle.
Acrivos is Professor Emeritus of Chemical Engineering at Stanford University. He is also the Albert Einstein Professor Emeritus of Science and Engineering, and former Director of the Levich Institute in the City College of the City University of New York. He is a member of the U.S. National Academy of Sciences and of the U.S. National Academy of Engineering, and is a Fellow of the American Academy of Arts and Sciences. He received the 2001 National Medal of Science from the President of the United States, George W. Bush, at the White House in 2002.
Other academic honors include:
- Colburn, Professional Progress and Lewis Awards from the American Institute of Chemical Engineers
- Fluid Dynamics Prize from the American Physical Society
- G.I. Taylor Medal from the Society of Engineering Science
- Bingham Medal from the Society of Rheology
He obtained his B.S. degree from Syracuse University in 1950, his M.S. degree from the University of Minnesota in 1951, and his Ph.D. degree from the University of Minnesota in 1954, all in Chemical Engineering.
Although formally retired since 2000, Professor Acrivos remains active professionally and, via the internet, cooperates informally with a number of fluid dynamicists the world over.
The Rheology of Concentrated Suspensions of Non-Brownian Particles: A Historical Survey of Some Recent Variations on a Theme by Albert Einstein
In one of his landmark 1905 papers, Albert Einstein published his famous expression for the effective viscosity of a dilute suspension of small, non-Brownian, spheres in viscous Newtonian fluids subject only to hydrodynamic forces, which, over the next half a century, was extended to higher particle concentrations by numerous investigators. Underlying all these studies, however, has been the assumption (taken on faith) that, even at particle concentrations φ beyond the dilute regime, such two-phase materials flow exactly like a Newtonian (isotropic) fluid with its viscosity, relative to that of the suspending liquid, being a unique function of φ.
Beginning in the mid-60’s, however, it was found experimentally that non-dilute suspensions flowed in a manner which, at times, was strikingly different from that of a corresponding Newtonian fluid due, as was eventually realized, to the fact that the chaotic motions of the hydrodynamically interacting particles create both a structure within such suspensions, which renders them anisotropic, as well as a shear-induced non-uniform particle concentration profile that greatly affects their rheology. Several examples of such flows will be presented and discussed which illustrate these effects.
Berry is Melville Wills Professor of Physics at the University of Bristol. In 1962 he obtained a Bachelor’s degree in Physics with honors from Exeter University. In 1965 he was awarded a Ph.D. in theoretical physics by St. Andrews University. Subsequently, he was awarded a Doctor of Science Degree from Exeter University, an Honorary Professorship at Wuhan University, and Honorary Doctorates at ten other universities. In 1967 Professor Berry joined Bristol University and in succession he has been Lecturer in Physics, Reader in Physics, Professor of Physics, Royal Society Research Professor, and Melville Wills Professor of Physics.
He has been elected Fellow, Member or Foreign Member of: Royal Society of London, Royal Society of Arts, Royal Institution, Royal Society of Sciences in Uppsala, European Academy, Indian Academy of Sciences, National Academy of Science of the USA, London Mathematical Society, The Weizmann Institute, Institute of Physics, Royal Netherlands Academy of Arts and Sciences, Royal Society of Edinburgh, and the Mexican Mathematical Society.
His prizes include:
- Maxwell Model and Prize (Institute of Physics)
- Julius Edgar Lilienfeld Prize (American Physical Society)
- Paul Dirac Medal and Prize (Institute of Physics)
- Naylor Prize (London Mathematical Society)
- Louis-Vuitton Moet-Hennessey Science for Art Prize (Paris)
- Hewlett-Packard Europhysics Prize
- Dirac Medal and Prize (Intl. Centre for Theoretical Physics, Trieste)
- Knight Bachelor Queen’s Birthday Honours (London)
- Kapitsa Medal (Russian Academy of Sciences), Wolf Prize (Physics)
- IgNobel Prize (Physics), Onsager Medal (Norwegian Technical Univ.)
- 2002 Novartis/Daily Telegraph Visions of Science Competition, Polya Prize (London Mathematical Society)
- Chancellor’s Medal (University of Bristol)
Hamilton’s diabolical singularity
Hamilton’s first application of the concept of phase-space – later so fruitful in the transition to quantum physics – was a prediction in optics: conical refraction in biaxial crystals. This created a sensation at the time (1831), probably because it was one of the first successful uses of mathematics to predict a qualitatively new phenomenon. At the heart of conical refraction is a singularity, anticipating the simplest geometric phase and the conical intersections extensively studied in quantum chemistry and now resurrected in graphene. The light emerging from the crystal contains many subtle diffraction details, whose definitive understanding and observation have been achieved only recently. Generalizations of the phenomenon involve radically different mathematical structures, reflecting the different physics of real symmetric, complex hermitian, and nonhermitian two by two matrices that are still being explored theoretically and experimentally.
Williams joined BP as Chief Scientist in January, 2010. She is responsible for supporting the basic science that underpins the company’s technology programs, assessment and research in strategic technology issues and engagement with BP’s university research programs around the world. Some of her technical priorities are the use of modelling and computation to speed discovery and development, use of sensors systems and data analytics to improve operations, and assessments of risks and opportunities related to natural resource constraints, climate variability and emerging technologies.
Prior to joining BP, Ellen worked for over thirty years in academia, obtaining her Ph.D. at Caltech in 1981, and then moving to the University of Maryland, where she rose to become a Distinguished University Professor in the Institute for Physical Science and Technology and the Department of Physics.
She founded the University of Maryland Materials Research Science and Engineering Center and served as its director for 15 years. In parallel, Ellen has worked extensively in providing technical advice to the U.S. government, primarily through the Departments of Energy and Defense.
Energy and our other Natural Resources: Minerals, Land, Water and the Atmosphere
Energy is essential to human civilization, and the production of energy and electrical power intersects other natural resources, specifically minerals, water, land and earth’s atmosphere. Of these resources, the strongest energy linkage is with the atmosphere. However, the growing quality of life for more and more of the world’s population places additional stresses on minerals, land and water, as well as increasing the demand for energy.
In this talk, we will address the question of whether the growing demand for energy can be sustained in the face of competing pressures on our other natural resources. The trends in GHG emissions, and the technical drivers for resource use, especially water, in energy production will be reviewed. We will show how technical choices available now could prevent some energy-resource collisions, and discuss areas of continuing concern.
Overall, there are potential good news stories about resource use for energy, but these will depend on human decisions and priorities to become a worldwide reality.
Levelt Sengers was born and raised in the Netherlands. She completed her undergraduate and graduate studies at the University of Amsterdam, Netherlands, obtaining her doctorate in Physics in 1958. In 1963, she and her husband, Jan Sengers, immigrated to the United States. She joined the U.S. National Bureau of Standards, later renamed National Institute of Standards and Technology (NIST). She was a Group Leader from 1979 through 1987, became a NIST Fellow in 1984, and is presently a scientist emeritus at NIST. As a research physicist, Dr. Levelt Sengers worked with collaborators on critical phenomena in fluids and fluid mixtures, from theory to experiment, and developed databases for practical applications. She has held leadership positions and is an Honorary Fellow of the International Association for the Properties of Water and Steam, which serves the electric power industry. She has published extensively in the archival literature, and contributed 14 book chapters.
Dr. Levelt Sengers’ honors include:
- Member of the U.S. National Academy of Sciences and U.S. National Academy of Engineering
- Correspondent of the Royal Netherlands Academy of Sciences
- Honorary doctorate from the Technical University Delft, Netherlands
She is a Fellow of the American Physical Society, the American Society of Mechanical Engineers, and the American Association for the Advancement of Science. She was elected the L’Oréal-UNESCO “For Women in Science” 2003 Laureate for North America. In 2004/05, she co-chaired the Advisory Panel “Women for Science” of the InterAcademy Council. In 2010, the Inter-American Network of Academies of Sciences (IANAS) appointed her chair of its new Women-for-Science Working Group, and in 2013 the group published a collection of inspiring stories in their book “Women Scientists in the Americas”.
Pride and Prejudice in Science and Engineering
During my career I have worked with scientists, engineers, and postdoctoral collaborators, both men and women, from the US and from many foreign countries. In the past ten years, within the context of the Network of the Academies of Sciences (www.iap.org), I have chaired first a global, then a Western Hemisphere initiative (www.ianas.org) addressing the low representation of women in science and technology. Sociologists have produced solid evidence of gender prejudice even within the physical sciences that take pride in their objectivity. The IANAS book, “Women Scientists in the Americas; their Inspiring Stories,” strikingly illustrates culture-dependent gender prejudice that keeps the physical sciences and engineering preponderantly male occupations in countries such as the US, UK, and Germany. The near-absence of women from engineering, as well as ignorance about local culture and gender roles adversely affect development work by foreign engineers serving the poor in the third world. Indeed, both women engineers and social scientists have unique roles to play in overcoming cultural prejudices which waste women’s talents and hamper development work.
Yang is a Distinguished Professor and the John L. Colaizzi Endowed Chair in the Department of Chemical Biology at the Ernest Mario School of Pharmacy of Rutgers University. Dr. Yang received his B.S. degree from National Taiwan University and his Ph.D. degree in biochemistry and molecular biology from Cornell University. After postdoctoral training at Scripps Institute and Yale University, he began his teaching/research career at New Jersey Medical School in 1971. He moved to Rutgers University in 1988 as a Distinguished Professor and served as Chair of the Department of Chemical Biology from 2002 to 2010.
Dr. Yang's major research interests are in the prevention of cancer and other diseases by tea, tocopherols (vitamin E) and other agents. In the 1980s, he co-initiated the large scale US-China Collaborative Nutritional Prevention Studies for esophageal cancer prevention in Linxian, China. He then characterized the molecular alterations of human esophageal cancer and created animal models for esophageal, colon and prostate cancers. Recently, he has extended his tea studies to the prevention of metabolic syndrome and related chronic diseases. He is also interacting with many scientists in China, including mentoring young scientists.
Dr. Yang has been actively serving on journal editorial boards and grant review committees. He has more than 500 publications and trained over 100 graduate students, postdoctoral fellows and research associates. In 2010 he was elected Fellow of the American Association of the Advancement of Science.
U.S. Training of Chinese Scientists and Its Impact
In the 19th century, the agrarian Chinese society and the Manchu government could not defend China against the invasion of the industrialized Western powers. After a series of humiliating defeats, the Chinese leaders realized the need to learn Western industry and military technology. The government thereafter selected top students for training abroad. Many of the scholars, such as Hu Shi and Zhu Kenzhen who came to the U.S. in 1910, made a major impact in China, not only in science and education but also in cultural movement and societal change.
This lecture will highlight the stories of Professor Shih-I Pai and his contemporaries, who came from China to the U.S. to study in the 1930s and 1940s, and their contributions to both China and the U.S.. This group of scientists included the gifted inventor Yao-Tzu Li, the famous rocket scientist Qian Hsusen and the Nobel laureates Chen-Ning Yang and Tsung-Dao Lee. After the normalization of diplomatic relationships between the U.S. and China in the mid-1970s, there has been tremendous scientific interactions, and many U.S.-trained Chinese scientists have actively contributed to the advancement of science and technology. I will highlight some activities in the biomedical field that I witnessed.
In conclusion, U.S-trained Chinese scientists contributed greatly to the scientific development in both the U.S. and China and to societal change in China. They continue to benefit not only the U.S. and China, but the entire world.
Bustamante is Professor of Molecular and Cell Biology, Physics, and Chemistry at the University of California, Berkeley and a Howard Hughes Medical Institute Investigator.
Dr. Bustamante received his B.S. degree in biology from the Universidad Peruana Cayetano Heredia; his M.S. degree in biochemistry from the Universidad Nacional Mayor de San Marcos and his Ph.D. in biophysics from the University of California, Berkeley. Dr. Bustamante’s laboratory develops and applies single-molecule manipulation and detection methods, such as optical tweezers, magnetic tweezers, and single molecule fluorescence microscopy to characterize the dynamics and the mechanochemical properties of various molecular motors that interact with DNA, RNA, or proteins.
His lab also uses and develops novel methods for superresolution microscopy to study the organization and function of protein complexes in cells.
Dr. Bustamante is a Fellow of the American Physical Society, an elected member of the National Academy of Sciences and the Chilean Academy of Science and a member of the Board of Directors of the American Association for the Advancement of Science. He is the recipient of the 2012 Raymond and Beverly Sackler International Prize in Biophysics for his seminal contributions to single molecule biophysics.
The Folding Cooperativity of a Protein is Controlled by the Topology of its Polypeptide Chain
Proteins are complex functional molecules that tend to segregate into structural regions. Throughout evolution, biology has harnessed this modularity to carry out specialized roles and regulate higher-order functions such as allostery. Cooperative communication between such protein regions is important for catalysis, regulation, and efficient folding; indeed, lack of domain coupling has been implicated in the formation of fibrils and other misfolding pathologies. How domains communicate and contribute to a protein’s energetics and folding, however, is still poorly understood. Bulk methods rely on a simultaneous and global perturbation of the system (temperature or chemical denaturants) and can miss potential intermediates, thereby overestimating protein cooperativity and domain coupling. I will show that by using optical tweezers it is possible to mechanically induce the selective unfolding of particular regions of single T4 lysozyme molecules and establish the response of regions not directly affected by the force. In particular, I will discuss how the coupling between distinct domains in the protein depends on the topological organization of the polypeptide chain. To reveal the status of protein regions not directly subjected to force, we determined the free energy changes during mechanical unfolding using Crooks’ Fluctuation Theorem. We evaluate the cooperativity between domains by determining the unfolding energy of topological variants pulled along different directions. We show that topology of the polypeptide chain critically determines the folding cooperativity between domains and, thus, what parts of the folding/unfolding landscape are explored. We speculate that proteins may have evolved to select certain topologies that increase coupling between regions to avoid areas of the landscape that lead to kinetic trapping and misfolding.
Bassett is Associate Professor and Eduardo D. Glandt Faculty Fellow in the Bioengineering Department at the University of Pennsylvania. Dr. Bassett received her B.S. (04) in physics from Pennsylvania State University and her Ph.D. (09) in physics from the University of Cambridge.
Dr. Bassett’s research group studies biological, physical, and social systems by using and developing tools from network science and complex systems theory. They are developing analytic tools to probe the hard-wired pathways and transient communication patterns inside the brain in an effort to identify organizational principles, to develop novel diagnostics of disease, and to design personalized therapeutics for rehabilitation and treatment of brain injury, neurological disease, and psychiatric disorders.
Dr. Bassett was a postdoctoral associate (09–2011) and a Sage Junior Research Fellow (11–2013) at the University of California, Santa Barbara, before joining the faculty of the University of Pennsylvania. Her scientific papers have appeared in journals such as the Proceedings of the National Academy of Sciences (PNAS), Neuron, Nature Neuroscience, Physical Review E, Journal of Complex Networks, Journal of Computational Neuroscience and Chaos, among others. In 2014 she became the youngest recipient of the prestigious MacArthur Fellowship.
Perturbation and Control of Human Brain Network Dynamics
The human brain is a complex organ characterized by heterogeneous patterns of interconnections. New non-invasive imaging techniques now allow for these patterns to be carefully and comprehensively mapped in individual humans, paving the way for a better understanding of how wiring supports our thought processes. While a large body of work now focuses on descriptive statistics to characterize these wiring patterns, a critical open question lies in how the organization of these networks constrains the potential repertoire of brain dynamics.
In this talk, I will describe an approach for understanding how perturbations to brain dynamics propagate through complex wiring patterns, driving the brain into new states of activity. Drawing on a range of disciplinary tools – from graph theory to network control theory and optimization – I will identify control points in brain networks, characterize trajectories of brain activity states following perturbation to those points, and propose a mechanism for how network control evolves in our brains as we grow from children into adults.
Finally, I will describe how these computational tools and approaches can be used to better understand how the brain controls its own dynamics (and we in turn control our own behavior), but also how we can inform stimulation devices to control abnormal brain dynamics, for example in patients with severe epilepsy.
Bennett, an IBM Fellow at the IBM Thomas J. Watson Research Center, received his B.S. in chemistry from Brandeis University in 1964 and his Ph.D. in the study of molecular dynamics (computer simulations of molecular movements) from Harvard University in 1971.
He joined IBM's research labs in 1972 where he performed pioneering research in the physics of information processing, and in fundamental quantum mechanics. Building on the work of IBM’s Rolf Landauer, he showed that general-purpose computation can be performed by a logically and thermodynamically reversible apparatus. In collaboration with Gilles Brassard, Université de Montréal, he developed a system of quantum cryptography, known as BB84, which allows secure communication between parties who share no secret information initially, based on the uncertainty principle.
Bennett and Brassard, with collaborators, discovered “quantum teleportation,” an effect in which the complete information in an unknown quantum state is decomposed into purely classical information and purely non-classical Einstein-Podolsky-Rosen (EPR) correlations, sent through two separate channels, and later reassembled in a new location to produce an exact replica of the original quantum state that was destroyed in the sending process.
Bennett and colleagues. helped found the quantitative theory of entanglement and introduced several techniques for faithful transmission of classical and quantum information through noisy channels, part of the larger and recently very active field of quantum information and computation theory.
Bennett is the recipient of the Rank Award for Optoelectronics; Harvey Prize; Okawa Prize; Dirac Medal and the Wolf Prize in Physics. He is a member of the National Academy of Sciences and Fellow of the American Physical Society.
Occam's Razor, Boltzmann's Brain, and Wigner's Friend
Modern cosmology has revived interest in some early 20th century puzzles that had seemed to be more in the realm of unanswerable philosophy than science: the Boltzmann’s brain problem of whether we might be merely a rare statistical fluctuation in an old dead universe, rather than inhabitants of a thriving young one, and the Wigner’s friend problem, of what it feels like to be inside an unobserved quantum superposition.
Ismael, Professor of Philosophy at Columbia University, received her Ph.D. from Princeton University, was a Mellon Fellow at Stanford, and taught at the University of Arizona before joining Columbia University in 2018.
Ismael's research focuses on the philosophy of physics and metaphysics, especially areas involving the structure of space and time, quantum mechanics, and the foundations of physical laws. She has published on such issues as the conflict between lived experience and physics, the implications of physics on issues of freedom, death, the nature of the self, and the problem of free will.
Ismael has held a number of prestigious fellowships, including an NEH fellowship at the National Humanities Center, a Queen Elizabeth II Research Fellowship from the Australian Research Council, and fellowships from the Templeton Foundation and CASBS (Center for Advanced Studies in Behavioral Science at Stanford). She is a member of the Foundational Questions Institute.
Information, Time, and Life
The differences between past and future frame every aspect of our experience of the world. It is a remarkable fact that research that began in the mid-nineteenth century and was originally focused on trying to derive the phenomenological asymmetries embodied in the second law of thermodynamics from the time-symmetric laws of classical mechanics turned into a very general account of the sources of temporal asymmetry in our world. So a conversation that started by being about why (for example) gas will disperse to fill an open container, turned into a conversation about why we remember the past but not the future, why time seems to flow from past to future, and why we can affect the future but not the past.
There is much that remains to be understood, but we can assemble the pieces that we have into a picture that has intelligible contours and gives us deep insight not only into the nature of time, but the asymmetries that structure living processes, and our own place in the universe. I’ll sketch the elements of this picture in broad strokes, highlighting the role of information.