In this talk I will discuss a new method of measuring electron energies and interactions in carbon nanotubes. Carbon nanotubes are often considered leading candidates for nanoscale electronics applications. Their tiny diameters allow them to act as model one-dimensional systems, where transport is strongly affected by electron interactions. We developed techniques to perform tunneling spectroscopy on nanotubes using non-invasive superconducting probes. This allows us to measure the shape of the electron energy distribution functions, and hence energy relaxation rates, in nanotubes that have bias voltages applied between their ends. We find that at low temperatures electrons interact weakly in nanotubes of a few microns channel length, independent of end-to-end conductance values. Surprisingly, the energy relaxation rate can increase substantially when the temperature is raised to only 1.5 K. In general, tunneling spectroscopy with a superconducting probe may be a powerful new tool for characterizing electron behavior in one-dimensional systems.