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Old January 29th 07, 12:47 AM posted to sci.astro.amateur
Davoud[_1_]
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Default Looking into the past with a telescope

Davoud:
I can think of no reason why the Universe can't have a central region
in three-dimensional space if the Big Bang theory is correct.


Greg Neill:
If the BB is correct, then every place in the 3D universe was
once co-located with the center. So there is no unique place
that one can call The Center, since every place equally
fulfills the role.


David:
I have seen this argument in various guises. In /my/ /mind/ it breaks
down because of mixed verb tenses. "Every place /was/ /once/ co-located
in the center." OK, but "every place" departed the center when
space-time expanded, leaving the center behind. These "places" did not
all carry the center with them so that each one is now a center of its
own. Such a place -- a region that was denser than average due to a
quantum fluctuation and later became the core of a galaxy -- may be a
local center, but it is not the Universal center -- in /my/ /mind/ .


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.

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?

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. 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. 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.

Davoud

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