We all are pretty familiar with the Friedmann models of the expanding universe, but at present I would like to concentrate on the model where the universe goes on expanding with the lapse of time. We know that if we mark spots on a balloon and inflate it, distance between these spots increases gradually(with time, of course). We may draw an analogy that these spots represent the galaxies. Now imagine a space within one of these spots, whose dimensions is indeed less than that of the spot concerned. With time, the dimensions of this space goes on increasing with time. If we compare this space to the interstellar(as well as interplanetary) space, and by the process stated above, go on imagining spaces within the one imagined before, we arrive at a limit where the rate of dimension variation of the space with time becomes very small in magnitude. Here I ask my question: could it happen so that objects in the universe(even solids) are expanding at a rate so very feeble(much much smaller than even the rate at which the universe expands), because all objects, be they solid or any other physical form, constitute some space within this universe, on account of its existence, and can be designated as a space within the spot considered in our balloon model. It is indeed a mere whim of mine to compare a universe model with that of a balloon-spot model! Nonetheless, please remove my doubts upon this trifling matter, that has perplexed me a good deal.
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1possible duplicate of Why does space expansion not expand matter? – John Rennie Apr 30 '14 at 17:45
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See the duplicate I've suggested. In interacting systems, like galaxies or the atoms in our bodies, the interaction strength is far greater than the forces produced by the expansion of spacetime so the systems don't expand. See however the Big Rip. – John Rennie Apr 30 '14 at 17:47