Remarks presented by Jacques Colin, the Director of the Observatoire de la Côte d'Azur

Nice September 2, 2004

For the award of the ADION medal to P.J.E. Peebles

With general relativity and the Einstein first model of the universe, the discovery of the expansion by Hubble, and the discovery of the cosmic microwave background by Penzias and Wilson, Cosmology became a science and probably the major source of inspiration for physicists, astrophysicists and astronomers. Cosmology, that is, understanding of origin, evolution and structure of the Universe is also one of the most fundamental questions of philosophy, as the meaning of the live and the intelligence. Cosmology contains questions that each human being has in him of its origin and its environment.

For these most fundamental questions, theoreticians have proposed hypotheses, built models, opened new ways. These ideas often remained beautiful academic ideas, but sometimes observations confirmed predictions. This was the case for the expansion of the Universe predicted by the Friedman-Lemaître model. The same occurred for the Cosmic microwave background, predicted by Gamov, Peebles, Dicke and Wilkinson.

I must notice here that you, Professor Peebles, also opened new avenues in cosmology. A very important one is the paradigm of dark matter. After the discovery of the dynamically abnormal velocities of some galaxies in galactic clusters by Zwicky in 1933, you initiated, with Jeremy Ostriker, the crucial question of dark matter by showing that a large amount of dark matter must exist around spiral galaxies to explain the stability of the discs. This prediction has been largely confirmed later by the observations of the flat rotation curves and the motion of the globular clusters. This question of the dark matter, introduced by you, is now probably the most important topics and challenge for physicists.

Moreover with the recent observations of the acceleration of the expansion and the flatness of the geometry of the Universe, you introduced the new concept of dark energy or quintessence, which is a first thought on this new and extraordinary problem. Your recent papers concerning this question show the large number of different kind of energy that constitute the Universe and the interest of the cosmological constant introduced by Einstein for another aim.

I will not speak here of the method of the reconstruction of the Universe you developed in 1989. Uriel Frisch, Roya Mohayaee, Brent Tully and others work now on this method, which is partly the topics of the workshop which is held these two weeks in the Observatoire de la Côte d'Azur.

Thus, Professor Peebles, you are one of the great founders of classical and now modern cosmology. For that, all physicists, astrophysicists, astronomers, philosophers must thank you.

More humbly, on behalf of the Observatoire de la Côte d'Azur, I am very glad and particularly proud and honoured to award to you the medal of ADION for the year 2003.