Recently one of the tightest limits was placed on the sum of the neutrino
masses. This was an upper bound of 0.28 eV at the 95% confidence level.
However, this result was not the consequence of a new particle physics
experiment. Instead it was derived from observations of galaxies over the
largest reaches of the observable Universe. I will describe what goes into
such a project with an overview of the cosmological model and the
significant physical effects that these elusive neutrinos alter. In
addition, I will highlight the uncertainties and caveats of such an
ambitious attempt to measure the neutrino mass. Finally, I will describe
plans for the future and the importance of this interplay between particle
physics and cosmology.