The proceedings of the 1998 Spanish relativity meeting in honour of Lluís Bel contain several topics which Bel and his collaborators have worked on, namely the superenergy tensor and frames of reference. There are also many communications on cosmology, mathematical relativity and gravitational collapse.

The proceedings of the 1998 Spanish relativity meeting in honour of Lluis Bel contain several topics which Bel and his collaborators have worked on, namely the superenergy tensor and frames of reference. There are also many communications on cosmology, mathematical relativity and gravitational collapse.

From the infinitesimal scale of particle physics to the cosmic scale of the universe, research is concerned with the nature of mass. While there have been spectacular advances in physics during the past century, mass still remains a mysterious entity at the forefront of current research. Our current perspective on gravitation has arisen over millennia, through the contemplation of falling apples, lift thought experiments and notions of stars spiraling into black holes. In this volume, the world’s leading scientists offer a multifaceted approach to mass by giving a concise and introductory presentation based on insights from their respective fields of research on gravity. The main theme is mass and its motion within general relativity and other theories of gravity, particularly for compact bodies. Within this framework, all articles are tied together coherently, covering post-Newtonian and related methods as well as the self-force approach to the analysis of motion in curved space-time, closing with an overview of the historical development and a snapshot on the actual state of the art. All contributions reflect the fundamental role of mass in physics, from issues related to Newton’s laws, to the effect of self-force and radiation reaction within theories of gravitation, to the role of the Higgs boson in modern physics. High-precision measurements are described in detail, modified theories of gravity reproducing experimental data are investigated as alternatives to dark matter, and the fundamental problem of reconciling any theory of gravity with the physics of quantum fields is addressed. Auxiliary chapters set the framework for theoretical contributions within the broader context of experimental physics. The book is based upon the lectures of the CNRS School on Mass held in Orléans, France, in June 2008. All contributions have been anonymously refereed and, with the cooperation of the authors, revised by the editors to ensure overall consistency.

From the late fifteenth to the nineteenth centuries, the Hispanic Monarchy was one of the largest and most diverse political communities known in history. At its apogee, it stretched from the Castilian plateau to the high peaks of the Andes; from the cosmopolitan cities of Seville, Naples, or Mexico City to Santa Fe and San Francisco; from Brussels to Buenos Aires and from Milan to Manila. During those centuries, Spain left its imprint across vast continents and distant oceans contributing in no minor way to the emergence of our globalised era. This was true not only in an economic sense-the Hispano-American silver peso transported across the Atlantic and the Pacific by the Spanish fleets was arguably the first global currency, thus facilitating the creation of a world economic system-but intellectually and artistically as well. The most extraordinary cultural exchanges took place in practically every corner of the Hispanic world, no matter how distant from the metropolis. At various times a descendant of the Aztec nobility was translating a Baroque play into Nahuatl to the delight of an Amerindian and mixed audience in the market of Tlatelolco; an Andalusian Dominican priest was writing the first Western grammar of the Chinese language in Fuzhou, a Chinese city that enjoyed a trade monopoly with the Spanish Philippines; a Franciscan friar was composing a piece of polyphonic music with lyrics in Quechua to be played in a church decorated with Moorish-style ceilings in a Peruvian valley; or a multi-ethnic team of Amerindian and Spanish naturalists was describing in Latin, Spanish and local vernacular languages thousands of medicinal plants, animals and minerals previously unknown to the West. And, most probably, at the same time that one of those exchanges were happening, the members of the School of Salamanca were laying the foundations of modern international law or formulating some of the first modern theories of price, value and money, Cervantes was writing Don Quixote, Velázquez was painting Las Meninas, or Goya was exposing both the dark and bright sides of the European Enlightenment. Actually, whenever we contemplate the galleries devoted to Velázquez, El Greco, Zurbarán, Murillo or Goya in the Prado Museum in Madrid; when we visit the National Palace in Mexico City, a mission in California, a Jesuit church in Rome or the Intramuros quarter in Manila; or when we hear Spanish being spoken in a myriad of accents in the streets of San Francisco, New Orleans or Manhattan we are experiencing some of the past and present fruits of an always vibrant and still expanding cultural community. As the reader can infer by now, this book is about how Spain and the larger Hispanic world have contributed to world history and in particular to the history of civilisation, not only at the zenith of the Hispanic Monarchy but throughout a much longer span of time.