This book is dedicated to significant contributions made to physics by Poincaré
and Einstein 100 years ago [1,2] (see also [3]). As we celebrate the International
Year of Physics, we might ask: Is Physics in good health? Everyone has
his own answer to this simple question. Consequently, we decided to publish
this book under the intriguing title “Einstein and Poincaré: the physical vacuum.”
The reader may be puzzled by the choice of theme, which would seem
to have been fully studied years ago. We fully sympathize with him: it was and
is indeed astonishing for us that after more than 100 years of research the topic
is still full of surprises. In a way, it has a life of its own. The highly respected
authors of this volume appear to have agreed with us in presenting their
thoughtful pieces of research. These are Profs. Vigier, Duffy, Selleri, Kholmetskii,
Barbosa, Sidharth, Munera, Onoochin and Weber, Pierseaux, Cahill,
Krasnoholovets, Martin and Roscoe. Special thanks to them all! While their
papers speak for themselves, I feel compelled to say few words for myself.