>>11
Your matter ball (or let's say, matter/energy ball) would remain constant in mass/energy if the prohibition against creating/destroying energy is adhered to. Relative size is another matter. The expansion of the space ball could be measured relative to the matter/energy ball, but what if instead the matter/energy ball was measured relative to the space ball? In that case, the space ball is constant while the matter/energy ball is, while constant relative to itself, is shrinking relative to the space ball that surrounds it.
>>12
relative to what? The only reference for the universe as a whole is itself.