Where have all the neutrinos gone? I’m no cosmologist, and my understanding of nuclear physics is pretty primitive. I haven’t yet found answers to some simple questions: Where have all the neutrinos created so prolifically by stars over the last 13,8 billion years gone? Are they still pervading the universe as a faint background flux of rarely-interacting almost imperceptible entities? Has the status of neutrinos as ‘hot’ dark matter or energy been quite ruled out? Does their proliferation in any way assist or drive the expansion of the Universe, possibly as mandated by the virial theorem?