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Ever since the emergence of the scientific approach to describing Nature, there has been a tension between, on one side, the physical approach to understanding Nature, and, on the other side, the philosophical/theological approach. What is their relation? Where is the boundary between what can be described using the methods of the physical sciences, and what lies - even in principle - beyond it?
The quest of the physical sciences has been to explain the observed features of Nature by means of fundamental laws based on mathematical logic. The presence of human beings on Earth is, however, a key aspect of the observed world. Human experiences, emotions and intellectual creativity are beyond the realm of what can be described in terms of the scientific approach to understanding Nature. Where does the boundary lie between the realm of the physical sciences and what will lie forever beyond? This is one of the central questions surrounding the issue of the role of humanity in Nature.
Recently, the attention of scientists working at the forefront of fundamental physics and astronomy has been drawn to another issue: All physical laws contain parameters which are measured in experiment, such as the values of the masses of elementary particles. Why do these constants take on the values they do? In many cases, these fundamental constants appear to have precisely the values which make it possible for Life to exist. Does this mean that the existence of Humanity is manifested in the based laws of physics? In other words, are the physical laws the way they are in order to allow for human beings? This view - called the “anthropic view” is at odds with the long-standing goal of most physical scientists to find an explanation for all aspects of physical reality based on purely mathematical logic and our knowledge of the basic forces of Nature.
For a long time, most physicists refused to think about anthropic ideas. Indulging in speculations about the possible anthropic explanation for some of the basic constants of nature was considered to be against the spirit of the physical sciences. However, both as a consequence of recent discoveries in observational cosmology and of developments in superstring theory, the theory believed by many to yield a unified quantum theory of all four forces of nature, over the past few years many physicists have turned to anthropic reasoning in their theoretical arguments. On the observational side, the most notable change in our view of cosmology is the discovery that more than 70% of the energy in the universe consists of some unknown entity named “dark energy”, and that dark energy is becoming dominant for the evolution of space-time at precisely the present time. What explains this coincidence? Do we need to invoke anthropic arguments?
Coming from purely theoretical considerations, superstring theory appears to contain an unfathomably large number of possible states the universe could take on, almost all of them having no resemblance to the one we live in. What is responsible for selecting the state we live in? Once again, do we need to invoke anthropic reasoning?
In this, the second Lorne Trottier Public Science Symposium we are bringing together four leading scientist to debate the question of the role of human existence in the reality of the physical world.
The panelists will be Professor Paul Davies from Arizona State University, Professor Leonard Susskind from Stanford University, Professor David Gross from the Kavli Institute for Theoretical Physics in Santa Barbara, and Professor George Efstathiou from Cambridge University.
Professor P. C. W. Davies is a physicist and philosopher who has been thinking and writing about issues related to the role of humanity in the physical world for many years. Professor Davies has made fundamental contributions to the development of Einstein's Theory of General Relativity. In parallel, he is one of the most accomplished popular science writers, having written close to twenty five books with titles such as God and the New Physics, Space and Time in the Modern Universe and The Goldilocks Enigma: Why is the universe just right for life? his latest book which was just released in the UK in October 2006. He was awarded the prestigious Templeton Prize in 1995 for his work on the deeper significance of science.
Professor L. Susskind holds the Felix Bloch Chair of Physics at Stanford University. He is one of the fathers of superstring theory and has made many other fundamental contributions to theoretical physics. In recent years, his research has been focused on understanding black hole physics. He has become one of the most outspoken proponents of the need to use anthropic arguments to explain the World as we observe it.
Professor D. Gross, Director of the Kavli Institute for Theoretical Physics at the University of California in Santa Barbara, was awarded the Nobel Prize in Physics in 2004 for the discovery of “asymptotic freedom”, a property of the strong nuclear force which revolutionized physicists' understanding of physics on sub-atomic scales. Professor Gross has also made key contributions in many other areas of theoretical physics, most notably to the development of superstring theory. Professor Gross will be defending a point of view opposite to that maintained by Professor Susskind, namely that appealing to the anthropic principle is giving up on the basic goal of fundamental physics. The goal of fundamental physics must always be to been to find more basic theories which are able to explain the mysteries of our current theories which appear to call out for an anthropic explanation.
Professor George Efstathiou, our fourth panelist is Professor at the Institute of Astronomy of Cambridge University. He is one of the internationally most distinguished astronomers, having played a leading role in large-scale projects to map out the distribution of galaxies to ever increasing depths, and in projects to perform precision measurements of the small ripples in the cosmic microwave background, ripples which tell us a lot about the early history of the universe (incidentally, this year's Nobel Prize in Physics was awarded for the first detailed measurements of the cosmic microwave background anisotropies which were made by the COBE satellite team in 1992). Professor Efstathiou has played a leading role in developing the theory of microwave anisotropies. More than fifteen years before their observational confirmation, he performed the key calculations of the cosmic microwave anisotropies predicted in the inflationary universe scenario, and the observational confirmation has transformed the inflationary scenario into our current paradigm for the evolution of the early universe.
One of the most puzzling results to emerge from recent astronomical observations (many of which Professor Efstathiou was involved in) is that more than 70% of the energy in the universe is contained in some mysterious component called “dark energy”. Dark energy appears to be important for the universe to be as old as it is, and for us to exist. Why is the amount of dark energy just right for life? This question has forced physicists and astronomers to confront the questions “Why is the universe just right for life?” with a new urgency.
Physicists have over the past decades not made much progress towards achieving the goal of finding the ultimate explanation for all of the parameters which current theories make use of. Thirty years ago they managed to combine three of the observed forces of nature into a unified framework, the so-called grand-unified theories. However, the number of constants in the dynamical equations did not decrease. In fact it increased. In recent years, superstring theory is providing the hope to unify all four forces of nature into a unified quantum theory. The underlying theory lives in ten or eleven space-time dimensions, and the reduction to four space-time dimensions appears to introduce even more arbitrariness into the emergent picture of the world at low energies.
Thus, it has become imperative to ask the question whether the quest for a unified theory which explains all constants of nature is still viable, or whether it is simply misguided. Do we, instead, need to adopt the anthropic view, namely the view that the constants of nature must have the values which allow life to develop within it at some stage in its history? In 1973, theoretical physicist Brandon Carter (Observatoire de Paris, Meudon) coined the term “Anthropic Principle” for this view. Theoretical physicists John Barrow (Cambridge Univ.) and Frank Tipler later on formulated various versions of the anthropic principle. Nobel laureate Steven Weinberg (Univ. of Texas) has for a number of years advocated the anthropic principle as the only way to understand the small value of the cosmological constant, the constant term which enters Einstein's equations for space-time, and whose value is predicted by our current quantum theories of matter, to be many orders of magnitude larger than what observations indicate, With the recent realization that string theory may have a large ”landscape” of ground states, many high energy physicists and string theorists such as Professor Susskind have embraced this point of view. Other physicists such as Professor Gross vehemently object and state that adopting the anthropic principle is admitting defeat of the scientific principle and will stifle future research.
The anthropic principle is currently widely debated in physics and astronomy, but it has been a central point in theology and philosophy for many centuries. Are we are the present time entering a new phase of dialog between physicists, theologians and philosophers? Symptomatic for the increasing interactions between physicists and astronomers on one side, and theologians and philosophers on the other has been the award of the prestigious Templeton Prize in theology to three theoretical physicists who have grappled with issues surrounding the anthropic principle, namely Paul Davies (Australia), George Ellis (Capetown) and most recently John Barrow. Paul Davies will present the historical and philosophical perspective at this forum. Professor Efstathiou will introduce the audience to the urgency by which recent observations force physicists and astronomers to tackle the question why the universe appears to be just right for life precisely at this time in the evolution of the universe, an evolution which has lasted billions of years.
Professor Robert Brandenberger
Canada Research Chair
Department of Physics
McGill University
Faculty of Science - Symposium Office
Dawson Hall, Room 409
853 Sherbrooke Street West, Montreal, QC H3A 2T6 Canada
Telephone: 514-398-2852
email:
[email protected]
Series website: http://www.mcgill.ca/science/trottier-symposium/