"Davoud" wrote in message ...


Greg Neill:
Your difficulty with this seems to stem from your adhering to
a model where things exploded out from a center into a
pre-existing space or void. This is not the case in the BB
model where space itself expanded. There was nothing at
all (not even space) "outside".

Ah, well, you didn't read my post in its entirety. I adhere to no such
model. I conceded that the standard model is difficult for me to grasp,
as I wrote "But I can't get my mind around an immaterial edge
beyond which is nothing whatsoever, not even empty space. One
cosmologist, half joking, said 'It could be a brick wall, for all we
know.' " The latter statement eases my frustration a bit; I've heard
plenty of learned scientists say that they can't make sense out of it,
either.

No, I read your post. It still appears to me that your model includes
some outside that we can point to. The BB model does not have
any edge or boundary that is reachable from within our universe
by travelling in any direction in space.


Simple common sense says that the two-dimensional surface of a sphere
has no center -- I figured that out for myself while playing with a
solid-color, featureless rubber ball as a child -- but if you look
beyond the surface, inside the sphere, you will find a center.

That's fine if you have the ability to look beyond the surface.
If you can't, then you're confined to looking on the surface.
The same thing holds for us, who can only point to things inside
the universe. There is no direction in all of space that we can
point to that is in the direction of a unique center in 3D space,
yet every direction points to the Big Bang (since we look back
in time as we look further out).

Perhaps we have not yet seen far enough?

The BB model says that there is no "far enough", as there
is no boundary in 3D space.


I understand that what you raise is a possibility, even if it flies in
the face of reason. Reason says that, unless the Universe is infinite
in time and extent it has a center.

There is no center just as there is no center on the surface of
a balloon. The center of expansion of a balloon lies outside
of the surface, and is not accessible in any way to a 2D
being living on it -- he couldn't even point to it.

Among other possibilities are that
the expanding Universe left in place a point from which that expansion
began, and that the Universe (also) has a center of mass.

For the balloon analogy, that center would lie outside of space and
time. There would be no place on the surface of the balloon that
would correspond to a center of mass.

In addition
to the balloon analogy, I envision the similar raisin bread analogy;
the raisin bread begins as a ball of dough unaffected by any outside
influence (because there is no outside.) As it expands due to internal
forces (because there is no outside) it remains a ball, and what was
the center remains the center as every single place in the bread down
to the smallest possible place (is that called the Planck distance?)
moves away from the center.

The raisin bread analogy fails to capture the essence of the BB
geometry precisely because of the fact that it presupposes that the
bread is expanding into an existing 3D space. The balloon analogy
(although itslef rather limited) does a slightly better job here, although
it requires one to extrapolate the situation from 2D to 3D.