A corner of the WMAP scan of the cosmological microwave background.
But is what we see typical of the universe as a whole?
(Photograph courtesy of Max Tegmark, MIT.)
The initiative, funded by the John Templeton Foundation, is of three years in duration and will culminate in a major international conference. The enduring impact of the project will be to isolate and clarify the outstanding conceptual problems in the foundations of cosmology, to seed and stimulate future research in the subject, and to define philosophy of cosmology as a new field in its own right, with its own distinctive problems and motivations.
Chief among them, according to Simon Saunders of Oxford University, ‘is the problem of how to compensate for selection effects – of making sense of the so-called ‘anthropic principle’. Even if we knew the structure of the universe, the whole story from beginning to end, what should we expect to see from our particular corner of it? What are the probabilities? And of course that’s what’s relevant to experiments.’ The problem isn’t restricted to the distribution of stars or galaxies; it could extend to the values of supposedly fundamental constants, such as the cosmological constant --- or dark energy, as it is known.
"Explaining the value of the cosmological constant is one of the most critical problems in theoretical physics" says John Barrow, whose book The Anthropic Cosmological Principle, co-written with Frank Tipler, set the agenda for anthropic reasoning in cosmology the last two decades. “This problem goes deeper than merely describing the accelerated expansion of the universe: it requires an understanding of the vacuum, how the quantum nature of reality impacts on the universe as a whole, and what probability means when used to evaluate observed properties of the universe.”
The initiative is being made now in part because cosmology has in recent years turned into a spectacularly successful empirical discipline. But there is another reason too. “One of the key obstacles to progress in understanding the universe as a whole – particularly the early universe -- is the lack of a realist understanding of quantum theory”, says Saunders. “There are different aspects to the realism problem. One of them is about the nature of reality at the microscopic level; another is about how to apply quantum theory to systems ‘from the inside’ – to so-called closed systems. The latter is called the measurement problem. The universe as a whole is closed in this sense.” How then is it possible to apply quantum theory to cosmology – to obtain a genuinely quantum cosmology? “There has been real progress on that front in the last twenty years” Saunders continues. “That’s where our group and the East Coast group has an edge. We are interested in exploring these questions in quantum theories that are free of the measurement problem. Physicists try to be neutral on these questions, but it’s hard to do that and make sense of quantum cosmology”.
A major component of the Oxford-Cambridge project, like that of the US cluster led by Barry Loewer at Rutgers University, is to establish a community of scholars able to engage with such foundational questions in cosmology. To that end Joe Silk at Oxford, and John Barrow at Cambridge, will host a series of lecture courses, to be given by eminent figures in cosmology. These will be filmed and archived on a website dedicated to providing research materials and teaching resources in cosmology. Another component is related to the ‘PLUS’ e-magazine, associated with the Millennium Mathematics Project at Cambridge University, which will house a series of interviews with leaders in cosmology on key questions in foundations. The three-year project will culminate in a major international conference, and the publication of a volume of papers devoted to the philosophy of cosmology.
The US cluster includes Columbia University, Yale University, New York University, and the University of California at Santa Cruz. It encompasses nine scholars: Barry Loewer, Dean Zimmerman, Sheldon Goldstein and Roderich Tumulka of Rutgers; Albert and Brian Greene of Columbia, Tim Maudlin of New York University, Priya Natarajan of Yale, and Joel Primack of the University of California, Santa Cruz. Loewer, Zimmerman, Albert and Maudlin are philosophers; Goldstein and Tumulka, mathematicians; Greene, Natarajan, and Primack, physicists. The US cluster, like the Oxford-Cambridge partnership, is funded by a $960,000 grant from the John Templeton Foundation.
Source: www.philosophy.ox.ac.uk
