Three colour (BVI) image of a distant overdense region of
galaxies taken by the Hubble Space Telescope. The image is
focused on a spiral galaxy similar to the Milky Way but located
at z = 1, i.e. 8 billion years ago. Twice the mass of the Milky
Way, it has a star formation rate thirty times higher due to the
surrounding galaxy overdensity. Observational Cosmology has
reached an important turning point. After years of seeking the
parameters that govern the evolution of the Universe, there
seems to be increasing consensus in acknowledging the dominant
influence of dark matter on baryons and that of dark energy on
dark matter. Paradoxically, the behaviour of the two “dark”
components that make up 95% of the energy content of the
Universe is easy to model (dark matter is nondissipative and
subject only to gravity, while dark energy acts as an anti-
gravitational factor), even though our knowledge of their nature
remains highly speculative. This has led to the scientific
community’s leaning increasingly toward what