Title: When classical algebra meets modern geometry

Abstract: Modern algebraic geometry is usually understood as a mechanism linking commutative algebra to geometry. I will discuss how elementary non-commutative algebra fits into the picture, with a focus on the modern geometry hidden in the most classical of algebraic objects: Hamilton's quaternions and their generalizations. The discovery of this hidden geometry has allowed dramatic progress in our understanding of the fine structural properties of these algebras, further strengthening and deepening the link between algebra, number theory, and geometry. I'll begin at the beginning - with Hamilton in 1843 - and end with a description of the limits of our knowledge in 2011. In spite of our new powerful tools, the distance between 1843 and 2011 is remarkably small.