> John Clark <firstname.lastname@example.org> wrote:
> The evidence is starting to look pretty good that the neutrino
> does have a rest mass although a very tiny one, it's by far
> the lightest known particle with mass,
My reading of the literature, science magazines & web information agrees with this.
> however there are so
> many neutrinos they could make up the bulk of the universe.
This, I would question. In my surveys of the dark matter literature, I've read several discussions that indicate that even with neutrinos with mass at the high end of the proposed ranges, there would not be enough of them to account for the dark matter (which according to some (most?) arguments are 80-90% of the universe).
I would cite, that Alcock (the dean of Gravitational Microlensing observations) attributes black holes as the possible source for his observations & missing mass. In my discussions with other astronomers, they cite interstellar/intergalactic hydrogen as an explanation for the missing mass. Some astronomers argue brown dwarfs or combinations of brown dwarfs and gas clouds. Neutrinos are *very* far down on the list of "the bulk of the universe" for everyone except perhaps those scientists running the experiments looking for neutrino mass.