King's College London

After a review of the symmetries of supergravity theories and Kac-Moody

algebras, we explain show that M theory is likely to possess a very large

Kac-Moody symmetry of rank eleven, denoted by E_{11}. We also provide

evidence that even pure gravity and the closed bosonic string possess

analogous Kac-Moody symmetries.

Finally, we explain how the central charges of the maximal supergravity

theories arise naturally in E_{11}.