>1) Why do some galaxies collide if everything is supposed to be >expanding?
> I assume that the reason is some post BB phenomenon, but >have no idea
>what that might be.
Arguments for this have already been given. You can also think of a crowd
dispersing from a concert. The density of people keeps going down, and the
odds of bumping into someone else goes down, but people still bump into one
another.
>
>2) I'm not a proponent of the steady state theory, so please don't
> >interpret this question as such, I just want to juxtapose stuff that
> >I've read. One of the arguments against the steady state idea is >the
>problem of entropy, but doesn't the BB violate conservation of >matter?
Conservation of mass? Yes it does, but that's a bit more complicated than
one expects. The way mass is conventionally defined now: as rest mass, mass
is not conserved. For example, gammas have zero rest mass, and when a pi-0
goes to gamma-gamma, mass is not conserved. This is a bit tricky, because
the system still has the same mass as before, but the individual photons do
not. In this exact sense, mass is not conserved in the big bang.
The explanation I have is fairly old, from my grad. school days, so it
probably has been updated a bit. It is that the big bang came from a
freezing of the vacuum in the Higgs field: spontaneous symmetry breaking.
The latent heat of fusion from this freezing provided all of the energy
needed for the big bang.
Dan'm Traeki Ring of Crystallized Knowledge.
Known for calculating, but not known for shutting up
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