Einstein created modern physics in 1905 with the invention of two revolutionary theories. His relativity theory changed the way we think about space, time, gravity and motion, while his quantum theory sparked a revolutionary new understanding of matter, atoms, and light. But as long as these remain separate domains, his revolution remains incomplete. When we seek to complete the job Einstein started we are working on the problem called quantum gravity.

Presently the field comprises older, well developed approaches as well as new ideas. At Perimeter we avoid prematurely embracing any one approach to this high risk/high payoff challenge. Instead, we have developed a unique research climate which draws inspiration from a diverse set of approaches, old and new. We especially encourage researchers to develop new ideas and attack the problem from new angles. This diverse atmosphere has made PI a leading centre for research in quantum gravity.

Several ideas currently under investigation were invented recently at PI including

**relative locality**, a novel approach to the nature of spacetime,**shape dynamics**, a reformulation of general relativity, and the**consistent boundary formulation**, which is a new approach to defining and computing quantum gravity theories. At the same time PI researchers continue to press forward with longstanding research programs in quantum gravity including loop quantum gravity, causal dynamical triangulations, causal sets, and string theory.PI researchers in quantum gravity also contribute to developments in other fields, including the foundations of quantum theory, cosmology, and quantum field theory.

## FURTHER EXPLORATION

**introductory:**

- Einstein – Relativity and Beyond – John Moffat, Lee Smolin, John Stachel, Howard Burton (moderator)
- Quantum Gravity and the Quest for Unification - Lee Smolin (basic)

**Intermediate:**

- Black Hole Wars – Leonard Susskind (intermediate)
- Einstein's Vision and the Quantum Universe – James Hartle (intermediate)

**Advanced:**