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.

On the other hand, I don't know that anyone is really quite sure wtf is 
going on out there. :-)

>   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.

It's like saying a car on a treadmill can outrun the backwards drift of the 
treadmill, so the treadmill isn't actually moving.

> 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.

>   It also seems to be some kind of common misconception that the expansion
> of the Universe would somehow change units of measurements accordingly.
> Why would it? It simply means that distances between galaxies is growing.

Well there's two ways to expand space. One is to add more space, the other 
is to make each bit of space bigger. We wouldn't necessarily know about the 
latter one.

> 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? 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?

> 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).

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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