This book focuses on the gradual formation of the concept of 'light quanta' or 'photons', as they have usually been called in English since 1926. The great number of synonyms that have been used by physicists to denote this concept indicates that there are many different mental models of what 'light quanta' are: simply finite, 'quantized packages of energy' or 'bullets of light'? 'Atoms of light' or 'molecules of light'? 'Light corpuscles' or 'quantized waves'? Singularities of the field or spatially extended structures able to interfere? 'Photons' in G.N. Lewis's sense, or as defined by QED, i.e. virtual exchange particles transmitting the electromagnetic force? The term 'light quantum' made its first appearance in Albert Einstein's 1905 paper on a "heuristic point of view" to cope with the photoelectric effect and other forms of interaction of light and matter, but the mental model associated with it has a rich history both before and after 1905. Some of its semantic layers go as far back as Newton and Kepler, some are only fully expressed several decades later, while others initially increased in importance then diminished and finally vanished. In conjunction with these various terms, several mental models of light quanta were developed-six of them are explored more closely in this book. It discusses two historiographic approaches to the problem of concept formation: (a) the author's own model of conceptual development as a series of semantic accretions and (b) Mark Turner's model of 'conceptual blending'. Both of these models are shown to be useful and should be explored further. This is the first historiographically sophisticated history of the fully fledged concept and all of its twelve semantic layers. It systematically combines the history of science with the history of terms and a philosophically inspired history of ideas in conjunction with insights from cognitive science.

With contributions by leading quantum physicists, philosophers and historians, this comprehensive A-to-Z of quantum physics provides a lucid understanding of key concepts of quantum theory and experiment. It covers technical and interpretational aspects alike, and includes both traditional and new concepts, making it an indispensable resource for concise, up-to-date information about the many facets of quantum physics.

" The author] has done a great service to historians of modern physics by editing this first anthology of primary sources, excellently translated into English... The texts are well selected and range widely, from private correspondence and official memoranda to articles dealing with physics in a propagandistic or popular manner... Many of the sources are extremely interesting and appear here for the first time. Their value is further enhanced by the editor's cross-referencing and detailed notes... The book] is also a fine introduction to the entire subject. The] 101-page 'introduction' gives an admirable survey of German physics during the Nazi period as well as a thorough discussion of the historiography of the subject... The book] is of such quality and usefulness that were I to choose a single book on the history of physics in the Third Reich this might well be the one."
H. Kragh, Centaurus

With contributions by leading quantum physicists, philosophers and historians, this comprehensive A-to-Z of quantum physics provides a lucid understanding of key concepts of quantum theory and experiment. It covers technical and interpretational aspects alike, and includes both traditional and new concepts, making it an indispensable resource for concise, up-to-date information about the many facets of quantum physics.

This book focuses on the gradual formation of the concept of 'light quanta' or 'photons', as they have usually been called in English since 1926. The great number of synonyms that have been used by physicists to denote this concept indicates that there are many different mental models of what 'light quanta' are: simply finite, 'quantized packages of energy' or 'bullets of light'? 'Atoms of light' or 'molecules of light'? 'Light corpuscles' or 'quantized waves'? Singularities of the field or spatially extended structures able to interfere? 'Photons' in G.N. Lewis's sense, or as defined by QED, i.e. virtual exchange particles transmitting the electromagnetic force? The term 'light quantum' made its first appearance in Albert Einstein's 1905 paper on a "heuristic point of view" to cope with the photoelectric effect and other forms of interaction of light and matter, but the mental model associated with it has a rich history both before and after 1905. Some of its semantic layers go as far back as Newton and Kepler, some are only fully expressed several decades later, while others initially increased in importance then diminished and finally vanished. In conjunction with these various terms, several mental models of light quanta were developed-six of them are explored more closely in this book. It discusses two historiographic approaches to the problem of concept formation: (a) the author's own model of conceptual development as a series of semantic accretions and (b) Mark Turner's model of 'conceptual blending'. Both of these models are shown to be useful and should be explored further. This is the first historiographically sophisticated history of the fully fledged concept and all of its twelve semantic layers. It systematically combines the history of science with the history of terms and a philosophically inspired history of ideas in conjunction with insights from cognitive science.

1 Aim and General Description of the Anthology The purpose of this anthology is to introduce the English speaking public to the wide spectrum of texts authored predominently by physicists portraying the ac tual and perceived role of physics in the Nazi state. Up to now no broad and well balanced documentation of German physics during this time has been available in English, despite the significant role physics has played both politically (e. g. , in weaponry planning) and ideologically (e. g. , in the controversy over the value of theoretical ('Jewish') vs. experimental ('Aryan') physics), and even though prominent figures like the scientist-philosopher and emigre Albert Einstein and the controversial nuclear physicist Werner Heisenberg have become household names. This anthology will attempt to bridge this gap by presenting contempo rary documents and eye-witness accounts by the physicists themselves. Authors were chosen to represent the various political opinions and specialties within the physics community, omitting some of the more readily accessible texts by leading physicists (e. g. , Einstein, Heisenberg, Lenard) in favor of those by less well-known but nonetheless important figures (e. g. , Finkelnburg, Max Wien, Ramsauer). In this way we hope not only to circumvent the constricted 'Great Men' approach to history but also to offer a broader picture of the activities and conflicts within the field and the effects of the political forces exerted upon them.

This book focuses on the "Einstein Tower," an architecturally historic observatory built in Potsdam in 1920 to allow the German astronomer Erwin Finlay Freundlich to attempt to verify experimentally Einstein's general theory of relativity. Freundlich, who was the first German astronomer to show a genuine interest in Einstein's theory, managed to interest his architect friend Erich Mendelsohn in designing this unique building. Freundlich's researches were not a success; he came to doubt the very theory he was attempting to prove. (Adequate technology to test Einstein's theory lay many decades in the future.) By contrast, as an experiment in modernist architecture, the building led to international fame for Mendelsohn.
To develop a full historical picture of this moment in the history of science, the book interweaves several descriptive levels: the biography of Freundlich; the social context in which he interacted with teachers, co-workers, students, his patrons (including Einstein), and scientific opponents; the cognitive aspects of his attempts to verify Einstein's theory; the political milieu within the Berlin scientific research community; and a cross-national comparison of astrophysics.
Other layers of the narrative include the place of the Einstein Tower in architectural history; economics and sociopsychological components of the Tower's financing and construction; the reception of the Tower and the theory; a historical examination of the Tower's research results; and the effect on Freundlich and on the work at the Tower of the National Socialists' rise to power.

Die Relativitatstheorien (RT) Einsteins gehoren zu den meistdiskutierten Theorien der Physik des zwanzigsten Jahrhunderts. Nach der Formulie- rung der sog. 'speziellen Relativitatstheorie' (SRT) im Jahr 1905 nah- men zunachst nur einige Spezialisten von ihr Kenntnis, bis mit ungefiihr fiinf Jahren Verspatung dann auch zunehmend Nicht-Physiker sich mit ihr zu beschaftigen begannen, angeregt durch populiirwissenschaftliche, all- gemeinverstiindliche 'Einfiihrungen' von Kollegen Einsteins wie z. B. Paul Langevin in Frankreich oder Max von Laue in Deutschland. Diese Pha- senverschiebung zwischen fachwissenschaftlichem Ausbau der Theorie und offentlicher Notiznahme wiederholte sich bei Einsteins 'allgemeiner Theorie der Relativitat und Gravitation' (ART). Zwischen 1913 und 1915 in ihren wesentlichen Ziigen ausformuliert, wurde sie erst nach einer spektakuliiren experimentellen Bestatigung im Jahr 1919 einem breiterem Publikum be- kannt. In meiner Arbeit werde ich den Facettenreichtum der Ausdeutungen, die beide RT erfuhren, zunachst zu referieren und durch repriisentative Zi- tate aus der Literatur der Zeit zu belegen haben. Der Umfang dieser Arbeit geht wesentlich auf das Konto dieser ausgewahlten Belege - davon verspre- che ich mir, dafi nicht nur bislang unveroffentlichte Dokumente, sondern auch entlegene Texte hier in ihren zentralen Passagen leicht zuganglich ge- macht werden. Fernerhin werde ich aber auch zu analysieren haben, warum derartig vielfaltige, einander mitunter diametral entgegengesetzte Interpre- tationen einer wissenschaftlichen Theorie vorgelegt wurden.

Die Relativitatstheorien (RT) Einsteins gehoren zu den meistdiskutierten Theorien der Physik des zwanzigsten Jahrhunderts. Nach der Formulie- rung der sog. 'speziellen Relativitatstheorie' (SRT) im Jahr 1905 nah- men zunachst nur einige Spezialisten von ihr Kenntnis, bis mit ungefiihr fiinf Jahren Verspatung dann auch zunehmend Nicht-Physiker sich mit ihr zu beschaftigen begannen, angeregt durch populiirwissenschaftliche, all- gemeinverstiindliche 'Einfiihrungen' von Kollegen Einsteins wie z. B. Paul Langevin in Frankreich oder Max von Laue in Deutschland. Diese Pha- senverschiebung zwischen fachwissenschaftlichem Ausbau der Theorie und offentlicher Notiznahme wiederholte sich bei Einsteins 'allgemeiner Theorie der Relativitat und Gravitation' (ART). Zwischen 1913 und 1915 in ihren wesentlichen Ziigen ausformuliert, wurde sie erst nach einer spektakuliiren experimentellen Bestatigung im Jahr 1919 einem breiterem Publikum be- kannt. In meiner Arbeit werde ich den Facettenreichtum der Ausdeutungen, die beide RT erfuhren, zunachst zu referieren und durch repriisentative Zi- tate aus der Literatur der Zeit zu belegen haben. Der Umfang dieser Arbeit geht wesentlich auf das Konto dieser ausgewahlten Belege - davon verspre- che ich mir, dafi nicht nur bislang unveroffentlichte Dokumente, sondern auch entlegene Texte hier in ihren zentralen Passagen leicht zuganglich ge- macht werden. Fernerhin werde ich aber auch zu analysieren haben, warum derartig vielfaltige, einander mitunter diametral entgegengesetzte Interpre- tationen einer wissenschaftlichen Theorie vorgelegt wurden.

'Although the editors admit that they cannot present an unequivocal explanation for the strange resilience of KirchhoffaEURO (TM)s flawed theory, their book is an admirable effort to meet this challenge ... It is a concerted effort to resolve a persistent riddle in the history of physics - and an example of how expert knowledge from different specialties may be focused on a target of common interest.'ISIS JournalThe 1882 paper by the mathematical physicist Gustav Robert Kirchhoff on diffraction theory is still being discussed to this day, but has never been translated into English. This volume contains the first English translation of the Kirchhoff treatise, as well as background and commentary on it. Included are a biographical introduction to Kirchhoff's life, an analysis of the reception to Kirchhoff's paper through the ages, a discussion on why Kirchhoff's theory manages to produce accurate predictions in spite of being 'wrong', and views on the theory as well as its predecessor and subsequent developments. This anthology will make all English-speaking scientists, engineers, historians, and interested laymen aware of the great fecundity of Kirchhoff's thought and historical context.