Neutrinos have mass, which becomes measurable at late times through its influence on the growth of structure.

(a) Explain how the expansion of the universe is changed if there is a single dominant neutrino species of mass 100 meV.

(b) Modify the equations for neutrino phase-space trajectories described in the preceding problem to allow for neutrino rest mass, and outline how this will affect the growth of perturbations.

(c) Describe how you could, in principle, measure the individual neutrino masses using cosmological observations.