A carbon nanotube is a one-dimensional system in which confinement of charge carriers and an unusual band structure lead to a variety of interesting effects. Many electronic and optical properties of a nanotube depend strongly on its geometry — the way in which a two-dimensional lattice of carbon atoms is rolled up to form the nanotube. In contrast, recent Rayleigh scattering measurements by the Park group at Cornell reveal that the peak optical conductivity is approximately equal for all single-walled carbon nanotubes, independent of their geometric structure. In this talk, I will describe our efforts to understand the origin of this uniform peak conductivity. I will review the electronic and optical properties of carbon nanotubes, show how the relativistic band structure and strong Coulomb interaction in a carbon nanotube can lead to a uniform peak conductivity, and describe a simple exciton model that reproduces many properties of the experimental data. Our analysis suggests that the uniform peak conductivity will persist over a wide range of experimental conditions, and it illustrates the importance of accurately modeling relaxation processes in numerical simulations of carbon nanotubes.