In a brief, accessible article, John Stewart Bell (1976) describes presenting a thought experiment to his colleagues, which attracted considerable attention at the time. The scenario involved two spaceships, initially at rest and connected by a fragile thread, that begin to accelerate simultaneously and identically as measured in an inertial frame. Although their separation remains constant in that frame, relativistic effects imply that the thread undergoes increasing tension due to length contraction not being experienced by the thread itself. Eventually, confidence led to its breaking. “Is it really so?” Bell asked his colleagues. According to Bell’s account, “a clear consensus emerged that the thread would not break!” (Bell, 1976, 136).
Continue readingEinstein’s Relativity/Thermodynamics Analogy. Some Evidence from His Later Years
In a 1919 article for the Times of London, Einstein declared the relativity to be a ‘principle theory’, like thermodynamics, rather than a “constructive theory”, like the kinetic theory of gases.
Continue readingLettres épistémologiques
Don Howard and Sebastián Murgueitio Ramírez have just put online the complete issues of Lettres épistémologiques, a small journal dedicated to the foundations of physics published from 1973 to 1984 by the Institut de la Méthode in Bienne, Switzerland.
The Untranslated Appendix to Reichenbach’s ‘The Philosophy of Space and Time’
In 1958 Hans Reichenbach’s second wife Maria Reichenbach and John Freund edited an English translation of the Philosophie der Raum-Zeit-Lehre . The Philosophy of space and time turned out to be one of the most influential books in the history of philosophy of physics. For those who never read the German original, it might come as a surprise that the English version is missing the translation of an Appendix entitled ‘Weyl’s Extension of Riemann’s Concept of Space and the Geometrical Interpretation of Electromagnetism.’ The Appendix covers around 50 pages of the German original, the Philosophie der Raum-Zeit-Lehre—not few considering that Reichenbach dedicated roughly 60 pages of the book to general relativity.
Adding Comments to Equations
I was searching for quite a long time for a simple way of inserting short comments into latex equations. Recently I stumbled upon this solution by Steven B. Segletes that serves my needs. I have slightly modified the code to introduce arrows with both orientations and positioned above and under the equation.