  In two recent papers, Abramowicz et al. claim that the expansion of the
Universe can be interpreted only as the expansion of space. In fact, what they
really prove is that the cosmological expansion cannot be described in terms of
real motions in Minkowski spacetime. However, there is no controversy about
this issue. Abramowicz et al. show that in general, the cosmological redshift
is not a Doppler shift and they consider this fact as a proof that space
expands. Again, nobody believes (perhaps except Milne) that for non-empty
universes the origin of the redshift is purely Dopplerian. From the Principle
of Equivalence it follows that there must be also a gravitational shift in
presence of matter. Indeed, it is well known in cosmology that for small
redshifts, the cosmological redshift can be decomposed into a Doppler component
and a gravitational component. In a forthcoming paper, we shall perform such a
decomposition for arbitrarily large values of the redshift.
