In the past fifteen years, dozens of tidal streams of stars pulled from dwarf galaxies and globular clusters have been discovered in the Milky Way’s stellar halo. Recently, it has been discovered that as the dwarf galaxies fall into our galaxy they perturb the stars in the disk, causing wavelike disturbances that are seen in the densities and velocities of disk stars. These disturbances could be driving force behind spiral structure in galaxies. MilkyWay@home is a petaFLOPS scale volunteer computing platform that is mapping the densities of stars in the larger tidal streams in the stellar halo and using that information to measure the mass and density profile of both the stars and the dark matter in the progenitor dwarf galaxies, using only information from the stars in the tidal streams. Eventually, MilkyWay@home will fit the shape of the Galactic potential using tidal streams.