In 1905, Einstein "abolished" the ether from physics. Yet the idea of a physical plenum has persisted in modern theoretical models. The essays in this volume seek to answer the question: What is the current status of the "physical vacuum"?

Valeri V. Dvoeglazov is a professor in the Faculty of Physics at University of Zacatecas, Mexico. He holds a degree in physics and education from the Saratov University and a Ph.D. from the Joint Institute of Nuclear Research at Dubna, both in Russia. A present and past member of several professional associations, he is currently an honorary professor at Albert Schweizer International University and Institute for Basic Research. He serves as an editor with a number of technical journals, including Hadronic Journal, Annales de la Fondation Louis de Broglie, Apeiron, Electromagnetic Phenomena, and the "Contemporary Fundamental Physics" and "Relativity, Gravitation, and Cosmology" series published by Nova Science.