Dear gregory.lee.bartholomew:

wrote in message
ups.com...
On Aug 9, 7:56 pm, "N:dlzc D:aol T:com \(dlzc\)"
wrote:
wrote in message
Stretching space sounds like grounds for and
aether to me though.

I liken expansion of space to the purchasing
power of a unit of money. Spacetime is just a
relationship between bits of matter and energy.
It is no sort of "stuff".

But whatever lubricates your gears is what you
should use. Just remember that our models are
also our limitations, so choose wisely, and
release as needed.

I understand that space-time is not "stuff" in the
[sense] of having a material existence but if it
has properties (even as trivial of a property as
relative sizes of units of dimension) which can
be changed then it must be viewed as a thing
(non-material and non-energy) rather than the
total absence of anything.

I don't propose the total absence of anything. I propose that
spacetime is as meaningful as the energy of a specific photon.
Nothing unchanging, nothing that is identical for every
observer.

This also seems, in my simple mind, to violate
the whole "no absolute frame of reference"
concept of GR to me. It may even restrict
space-time to a Euclidean coordinate system.

So why invoke it?

Maybe I'm just to simple minded, but the
changing of something that doesn't exist just
sounds like magical nonsense to me.

Also, earlier, someone said that we are close
to "zero" time dilation:

That was me. The changing of "something that doesn't exist"
isn't really what we are talking about. We are talking about
the
changes between a distant, younger galaxy (or star), and a
similar one that is close to us. We really are not talking
about
the "space in between" so much as we are talking about the
endpoints. The endpoints we can see and measure.

Another thought, what about the rate of travel of light
in all that interstellar space between the galaxies?
Wouldn't light be able to get from there to here very
quickly from our perspective (being in a zone where
time moves much slower)?

No. We are pretty close to "zero" time dilation now.
GPS satellites have a really tiny gravitaional correction,
and they are very far from any strong gravitational wells.

I'm having a hard time with this, as well, as I am
viewing our relative time dilation using the (I know,
"horrible") rubber sheet diagram. On this diagram, the
"gradient" of space-time at our location (Earth) is
extremely steep with respect to the very flatspace-time
between the galaxies. The steep gradient is holding our
very massive and fast moving planet in orbit about Sol.

You have no idea how much you are straining at gnats here. The
fact that it takes huge gobs of fossil fuels (we get hydrogen
for
our rockets by harvesting it from fossil fuels) to get a
spacecraft into orbit, does not make our gradient "huge".

Now consider that even if it were huge, we are *comparing*:
1) wavelengths detected on Earth of a fairly local specimen, and
2) wavelengths detected on Earth of a distant similar specimen.
Note that contributions of where our instruments are *cancels
out*, as they are in the same gradient for both sets of
observations. Only the "two" sources matter.

Does that help?

David A. Smith