Not even the Perimeter Institute for Theoretical Physics in Waterloo, Ont., is immune to the rhythms of the seasons. Summer there this year was quiet and casual, with several regular faces away on vacation. And yet there were plenty of signs that the little think tank is heading into an ambitious new era.

Stephen Hawking was on a six-week working visit from Cambridge, England. Every day you could see a caregiver pushing his wheelchair along the footpaths outside the building at surprising speed. The most famous scientist in the world does not like to dawdle. Amyotrophic lateral sclerosis has left him no control over most of his body. Twitching a cheek muscle to compose even a short sentence with his speech synthesizer can take 20 minutes. So he is keenly aware of wasted time. “I encouraged lots of people to go and talk to him,” Neil Turok, Perimeter’s South African director and a Hawking friend and colleague of long standing, told me.

“A lot of people did. Several of them came away saying, ‘I went and explained to him what I’m doing—and he didn’t seem very interested!’ I entirely sympathize with him. He has very high standards and if you start telling him something that doesn’t sound plausible he’ll very quickly tell you, ‘I’ve had enough.’ ”

Leonard Susskind, a white-bearded and soft-spoken Stanford University prof, was on a similar extended visit. Susskind has no human story of physical courage to match Hawking’s, but to physicists he is in Hawking’s intellectual class. He is a pioneer in the surreal but influential field of string theory, which describes a universe made of tiny vibrating strings curled up across many more dimensions than the three we know. Hawking and Susskind are two of Perimeter’s 20 Distinguished Research Chairs, eminent international theorists who visit Waterloo occasionally to work without the distractions of home.

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