On 28 May 2009, at a closed meeting in Brussels, ministers and state secretaries of education and science from several EU countries decided to build the European Spallation Source (ESS) in Lund, Sweden. Or did they? It is common for big European science projects to be surrounded by secrecy and political deceit, but the ESS is extraordinary in its elusiveness. There is a remarkable lack of concrete economic, political, technical and scientific underpinnings to the project but a boasting certainty in the promises of future paybacks. The ESS is an accelerator-based neutron spallation facility that will cost billions of Euros to build and run. It is expected to bring new knowledge in several fields including materials science, energy research, and the life sciences. But its financing is not yet certain, and future returns hard to predict. How then could the decision to build ESS occur? Why was there so little organized resistance? This book places the ESS project in its political and scientific context. It links the decisions taken to the history of Big Science in Europe and in Sweden. It looks at the dynamic political processes of establishing this megaproject in a small town in the south of Sweden. The eight chapters start from a paradoxical state of affairs: The ESS is not funded, and not formally decided in any binding agreements yet it is treated as a future reality, locally and nationally, loaded with promises of scientific, economic and social returns. The book makes a much-needed first contribution to the analysis of the ESS project and its political, environmental, and social ramifications. It should be read by scholars of science and technology studies, politicians and the interested general public. Contents: Introduction. In pursuit of a promise Olof Hallonsten 1. Timeline of major events Karl-Fredrik Berggren & Olof Hallonsten 2. Science at the ESS: a brief outline Karl-Fredrik Berggren & Aleksandar Matic 3. Tensions and change in the framing of science policy: the value of academic values in an era of globalization Aant Elzinga 4. Contextualizing the European Spallation Source: what we can learn from the history, politics, and sociology of Big Science Olof Hallonsten 5. The ESS project as a generator of conflict and collaboration: an assessment of the official picture of costs and benefits and the research-community response Anders Granberg 6. Big Science in a small country: constraints and possibilities of research policy Mats Benner 7. Organized local resistance: investigating a local environmental movements activities against the ESS Emelie Stenborg & Mikael Klintman 8. Selling Big Science: perceptions of prospects and risk in the public case for the ESS in Lund Wilhelm Agrell Afterword. Clues to the continuing story of an open-ended case Thomas Kaiserfeld