Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> >   As far as I have understood, explanation #1 is a misconception. Distances
> > between subatomic particles is not growing because the forces keeping atoms
> > and molecules together is way stronger than any minuscule drift that the
> > expansion of the universe might cause.

> It doesn't make sense that new space would only appear outside the galaxies. 
> The fact that things are falling back together again faster than new space 
> is appearing doesn't mean new space isn't appearing.

  I don't know if "new space" is appearing everywhere at the same rate or
at a faster rate far away from gravity wells (I'm in no way a physicist),
but as far as I can understand, forces like atomic bonds and gravity keep
masses and entire galaxies from expanding for the simple reason that they
are stronger than the (probably extremely minuscule) drift caused by the
universe expanding.

  Think about two small spheres connected by a wire on the surface of a
balloon: Even if you inflate the balloon, the wire will keep the spheres
at the same distance from each other, against the separating force caused
by the inflation of the balloon.

  If I have understood correctly, only galaxies are far enough from each
other to be drifted by the expansion of the universe. The gravity pull
between galaxies is not strong enough to stop them from recessing.

> >   The same is true at macroscopic levels: The Earth is not expanding because
> > atomic bonds and gravity are strong enough to stop any expansive drift from
> > happening. 

> It doesn't stop the drift. It compensates for the drift.

  Terminology.

> > The Sun's gravity is strong enough to stop planets from drifting
> > away due to the expansion of the Universe. All the way up to galactic sizes:
> > The gravity of a galaxy is strong enough to stop stars from drifting away
> > due to the expansion of the Universe.

> Sure. That doesn't mean space isn't expanding.

  But even though new space is forming all the time, that doesn't necessarily
change units of measurement. The only thing which is changing is the overall
size of the universe (and given that, as far as we know, the amount of mass
and energy is constant in the universe, the overall density of mass/energy
in the universe is correspondingly decreasing).

> > It doesn't mean that units of distance are changing too. The diameter of
> > a proton will still be the same in 1 billion years than it is now. 

> How do you know?

  Is there any plausible theory, backed up by measurements, that would say
otherwise? Is there any scientifical reason to think otherwise?

> How would you determine if everything in the entire 
> universe suddenly got twice as big?  How would you know, for that matter, if 
> everything in the universe suddenly started going at half speed?

  By measuring redshift? The speed of light doesn't change, and is
completely independent on the speed of the observer, as far as we know.
Redshift is thus a reliable measurement of speed changes between objects.

> > expansion of the universe only makes the universe bigger, it doesn't make
> > *everything* bigger, down to subatomic particles. It doesn't even make
> > galaxies bigger (AFAIK).

> True, but there may be more than one way in which space is expanding. You 
> can get more space (which is what seems to be happening between galaxies) or 
> you can get space that's twice as big (by some absolute measurement we have 
> no access to).

  But if you propose that everything is getting bigger in an absolute scale,
that would mean that also c is getting larger at the same rate (so that we
are unable to measure everything getting bigger). Is there any reason to
believe so?

-- 
                                                          - Warp

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