This lecture provides us with Newtonian approaches for the interpretation of
two puzzling cosmological observations that are still discussed subject : a
bulk flow and a foam like structure in the distribution of galaxies. For the
first one, we model the motions describing all planar distortions from Hubble
flow, in addition of two classes of planar-axial distortions with or without
rotation, when spatial distribution of gravitational sources is homogenous.
This provides us with an alternative to models which assume the presence of
gravitational structures similar to Great Attractor as origin of a bulk flow.
For the second one, the model accounts for an isotropic universe constituted by
a spherical void surrounded by a uniform distribution of dust. It does not
correspond to the usual embedding of a void solution into a cosmological
background solution, but to a global solution of fluid mechanics. The general
behavior of the void expansion shows a huge initial burst, which freezes
asymptotically up to match Hubble expansion. While the corrective factor to
Hubble law on the shell depends weakly on cosmological constant at early
stages, it enables us to disentangle significantly cosmological models around
redshift z ~ 1.7. The magnification of spherical voids increases with the
density parameter and with the cosmological constant. An interesting feature is
that for spatially closed Friedmann models, the empty regions are swept out,
what provides us with a stability criterion.Comment: 15 pages, 1 figur