🚀 go-pugleaf

Chris Muffett 
>     There is a cosmological theory that suggests that neutrinos do have
> a very small mass, and because there are so many of them in the
> Universe, this could account for the discrepancy in the mass of the
> Universe. This discrepancy is known as "hidden mass" or "dark matter"
> and is responsible for about 90% of the Universe's mass.
> 
>     The difference between "rest mass" and "real" (inertial or
> gravitational) mass becomes important when considering particles that
> travel at relativistic speeds (speeds approaching 1.0c). For example,
> the rest mass of a photon is zero, but actual mass of a moving photon
> will not be zero. Gravitational effects must always consider the real
> mass, not the rest mass. Rest mass is simply a theoretical value used by
> particle physicists.
> 
>     I'd like to know whether this has cleared up any of the questions
> you have.

Clarafied but even more confused. If a neutrino has 400 keV, after
climbing out of the emitting gravity well, how can it mater for purposes
of calculating gravitational force, whether it has any or all of that
energy in rest mass? And as an interesting aside, just exactly where is
the energy, (for purposes of finding the mass and the gravitational
force), that is lost by the objects emitted from deep gravity wells? I
think that you said that the photon inertial mass is simple
gravitational mass, at least under certain conditions. Is there
something special about having a little rest mass that I am missing?