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).
Bell explains that most physicists provided “this wrong answer” (136) because their training was rooted in Einstein’s perspective, which views length contraction as observer-dependent and, therefore, only apparent. In contrast, those versed in the Larmor-Lorentz-Poincaré approach “have stronger and sounder instincts” (Bell, 1976, 136), seeing the contraction as physically real—a modification of the molecular forces maintaining the rod’s equilibrium. From this standpoint, it seems more natural to expect the thread to break (Bell, 1976, 136).
In this paper, I argue that the debate that erupted at the tables of the CERN canteen in the 1970s bears a remarkable structural similarity to an earlier dispute in the 1910s on pages of the Physikalische Zeitschrift.