  In this paper we investigate how well Planck and Lyman-Alpha forest data will
be able to constrain the sum of the neutrino masses, and thus, in conjunction
with flavour oscillation experiments, be able to determine the absolute masses
of the neutrinos. It seems possible that Planck, together with a Lyman-Alpha
survey, will be able to put pressure on an inverted hierarchial model for the
neutrino masses. However, even for optimistic assumptions of the precision of
future Lyman-Alpha datasets, it will not be possible to confirm a minimal-mass
normal hierarchy.
