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Photo of William G. Unruh

William G. Unruh Theoretical physicist

William Unruh is renowned for pivotal contributions to the understanding of a range of subtle problems arising at the crossroads of quantum physics, gravitational theory and cosmology. He has developed concepts and tools that now bear his name, including the Unruh particle detector, Unruh vacuum, and Unruh temperature. His 1976 discovery that what is defined as the vacuum by inertial observers is perceived by an accelerated observer as a thermal bath at a characteristic temperature proportional to his acceleration, was instrumental (along with Hawking’s parallel discovery of black hole evaporation) in opening new vistas in fundamental physics. His research is concerned with understanding the key physical principles which are important in explaining the very earliest stages in the formation of the universe. In particular, the way in which gravity and quantum mechanics interact in those extreme early stages. He is also interested in the gravitational structures of cosmic strings. Though big questions, these concepts have impact on our understanding of the world around us. Cosmic strings, for example, have close theoretical ties with the magnetic flux tubes found in many types of superconductors. Understanding the role of time in quantum gravity means we must understand ordinary quantum theory much better than we do at present.


Founding Director of CIFAR program in Cosmology & Gravity, 1985-1996.

Steacie Prize, National Research Council, 1984.

Herzberg Medal, Canadian Association of Physicists, 1983.

Rutherford Medal, Royal Society of Canada, 1982.

Fellow, Royal Societies of Canada and London

Relevant Publications

W. G. Unruh and R. M. Wald, "Time and the interpretation of canonical quantum gravity," Phys. Rev. D, vol. 40, pp. 2598, Oct. 1989.



Associate Fellow Gravity & the Extreme Universe


University of British ColumbiaDepartment of Physics and Astronomy


PhD (Physics) Princeton University

MSc Princeton University



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