The Dark Side of the Universe

The dark side of the Universe 1 June 1998 The Dark Side of the Universe Outposts and perspectives of astrophysics and contemporary cosmology by Jean-Pierre Petit Astrophysicist Director of Research Centre Nationale de Recherche Scientifique Marseille Observatory, France. Translated by Sydney Keith and John Murphy. The dark side of the Universe 2 Prologue Our understanding of the universe is changing. New observation techniques have become operational and the Hubble space telescope, finally cured of its bad eyesight, has revealed unsuspected things. In immense molecular clouds we have discovered star nurseries whose children still attached to their uterus by "umbilical cords". Infra-red telescopes are showing us the universe from an unprecedented angle. We will be able to see things as a whole. We are sailing towards a new world. Our conception of the cosmos depends on observations. Without them, we would turn in sterile circles playing with equations. Observation bought about the cosmological revolution at the beginning of this century and will provoke the revolution of the now so close twenty-first century. To account for these new observations, we must improve, and perhaps profoundly modify, our conception of the universe. We have always considered the universe to be made of clumps, hierarchically arranged. Galaxies are clumps of stars, and clusters of galaxies form clumps too.