The talk will cover two topics. One will be about constraints from the CMB and LSS on the number of neutrinos and their interactions. I will show what can be done with the present data and argue that a significant improvement will be possible with the Planck satellite.
The second topic will deal with neutrinos from a galactic supernova.
I will show that the neutrino signal from a future supernova may carry an imprint of turbulence operating behind the shock front. An observation of this effect would allow us to test the current paradigm of the explosion mechanism and also to gain information about the neutrino spectrum (the sign of the mass hierarchy and a lower bound on theta_13).