**Perimeter Associate Faculty member Sung-Sik Lee is a condensed matter physicist -- but he has his eye on quantum gravity.**

**Lee lays out the problem: "Physics has one theory to describe how planets orbit the sun and another to describe how electrons 'orbit' an atomic nucleus. Both theories -- gravity as described by Einstein's general relativity and quantum field theory -- are great triumphs. Both are well-tested and powerful. The trouble is, we can't use both at once."**

**Relativity says that spacetime is smooth, and only big things can warp it, in ways that are exactly known. Quantum theory says that the smallest parts of the universe are constantly fluctuating and dramatically uncertain. How can something be both smooth and fluctuating, both exact and uncertain? How, in other words, can we make a quantum theory of gravity?**

**Physicists simply don't know. Researchers in both string theory and loop quantum gravity have made progress, but a fully functional unified theory has remained out of reach for more than 80 years.**

**Enter -- of all things -- condensed matter physics.**

**click here.**