jjw wrote:
"Can you envision space expanding by some means wherein a vacuum is enlarged and is made to envelope a larger voluum while the vacuum betwen particles remains the same?"

I too find the explanation somewhat weak but it is the current state of physics.

However to answer your question I am going to do a bit of an intentional waffle by suggesting that the answer may well lie in something else for which our explanations are less than adequate: dark energy and dark matter.

It seems very likely that the distribution of dark matter corresponds to that of "normal" matter and that dark matter does not exist in the inter-galactic expanses. Perhaps the answer lies there.

Also keep in mind that we are not talking about space but rather space-time. Perhaps time is warped in ways we don't fully understand. And then, of course, there is the fact that if I alter the speed of light I can simulate any degree of expansion I wish. And the force of gravity, perhaps, can remain constant.

DA Morgan