Stability of expanding homographic configurations formed by an even number of bodies of equal mass and placed at the vertices of regular polygons and polyhedrons is studied. It is shown that for every configuration considered, there is always an unstable perturbation that divides the system into pairs of bodies.

The KLUN (Kinematics of the Local UNiverse) sample of 6600 spiral galaxies is used in studying dark matter on different scales:

1. • The Morphological Type dependence of the zero-point of the Tully-Fisher relation indicates mass to light ratio M/L ≈ 9 − 16 on galactic scales.

2. • Preliminary results from a study of selection effects influencing double galaxies give a larger value M/L ≈ 30 − 50.

3. • Study of the Perseus-Pisces supercluster, using Malmquist bias corrected TF distances and Tolman-Bondi solutions indicates M/L ≈ 200 − 600 for large clusters. Similar results were obtained in our previous work on Virgo galaxies.

4. • Application of a modified version of Sandage-Tammann-Hardy test of the linearity of Hubble law inside the observed hierarchical (fractal) galaxy distribution up to 200 Mpc suggests that either Ω0 is very small (0.01) or the major part of the matter is uniformly distributed dark matter.