Michel Janssen

Editor, Einstein Papers Project, Boston (1995–2000); assistant professor, philosophy, Boston University (1997–2000); assistant professor (2000–2005), associate professor (2005– ), history of science, University of Minnesota.

Co-director of History and Foundations of Quantum Physics project; Member of organizing committee for History of Quantum Physics (HQ) conferences: Berlin, 2006 (HQ0), Berlin, 2007 (HQ1), Utrecht, 2008 (HQ2); Member of organizing committee for History of General Relativity (HGR) conferences: Johnstown, 1991 (HGR3), Berlin, 1995 (HGR4), Notre Dame, 1999 (HGR5), Amsterdam, 2002 (HGR6), and Tenerife, 2005 (HGR7); Member of the advisory board for The Seven Pines Symposium on the foundations of physics (Chair since Summer 2007; Vice-chair since 2005); Co-editor (with Christoph Lehner) of The Cambridge Companion to Einstein (in preparation).

In his miraculous year 1905, Albert Einstein, technical expert third class at the Swiss Patent Office in Bern, laid the foundations for a revolution in physics that would unfold in the following decades and affect a host of fundamental physical concepts such as space and time, energy and momentum, particles and fields. This revolution has fascinated me since I first learned about it as an undergraduate in philosophy. To understand it, I switched from philosophy to physics and then to history of science. My research has focused on the origins and ramifications of one half of this revolution, relativity theory, both the special theory of 1905 and the general theory of 1915. Over the years I have deepened my understanding of the other half of the revolution, the development of quantum mechanics, especially since I started teaching a graduate course in history of modern physics after coming to Minnesota in the fall of 2000.

In the history of general relativity, I am currently working on a paper that tells the fascinating tale of Einstein's heroic but ultimately unsuccessful struggle to find a true theory of relativity. My work for the Einstein Papers Project editing all material on general relativity in Vols. 7 and 8 of Einstein's Collected Papers has put me in an ideal position to tell this tale. The moral of my story is that Einstein's struggle was not in vain. Along the way, he achieved important results that are still with us today: a new theory of gravity improving greatly on Newton’s and opening up entirely new fields such as gravitational waves, gravitational lensing, and the analysis of singularities. It also led him to introduce the cosmological constant which is making a spectacular comeback these days. One of my students suggested the perfect title for my paper, capturing both the success and the failure of Einstein’s efforts: "A journey more important than its destination: Einstein’s quest for general relativity, 1907–1920." This story will also be the subject of my contribution to the Cambridge Companion to Einstein of which I am one of the two editors.

In the history of special relativity, I am currently working on a paper called "The transition from Newtonian particle mechanics to relativistic continuum mechanics, 1895–1911." This paper will discuss the broader ramifications of several episodes I have analyzed separately before. I want to draw attention to a hitherto neglected aspect of the history of special relativity. Historical scholarship typically focuses on the transformations of our concepts of space and time, treating such well-known phenomena as the slowing-down of moving clocks and the universal contraction of moving objects. The profound implications of special relativity for mechanics usually go unaddressed, even though the theory’s most famous formula, E = mc2, is part of relativistic mechanics. Classical mechanics lacked the resources to deal with systems involving the interaction of matter and electromagnetic fields, an area of particular interest in the early 1900s. Classical theory led to such baffling and counter-intuitive predictions that electric forces would move a charged body into a position in which its energy is at a maximum rather than at a minimum; or that charged bodies carry momentum that is at right angles with their direction of motion. Many of these puzzles arose from the experiments by Trouton and Noble, analyzed in my dissertation. They are easily solved once classical mechanics is replaced by relativistic mechanics. Even though Einstein identified this transition in 1912 as the watershed advance in relativity theory, it has never been systematically discussed in the extensive literature on the history of special relativity.