In der vorliegenden Arbeit wird über die verschiedenen Aspekte der sogenannten FitzGerald-Lorentz-Kontraktion berichtet. Nach einem kurzen Abriß der Entwicklung der Ätherkonzeption wird eine Beschreibung des Michelson-Morley Versuchs gegeben und seine Rolle in der Entstehungsgeschichte der speziellen Relativitätstheorie diskutiert. Anschließend wird die Kontraktionshypothese vorgestellt und die Frage erörtert, ob die Kontraktion „wirklich“ oder nur „scheinbar“ ist. Einige Gedankenexperimente werden vorgestellt, die zeigen, daß die Kontraktion bewegter Körper kein bloßer Schein ist. Ferner wird die noch bei Einstein unklare Beantwortung nach der Frage (...) der Sichtbarkeit der Längenkontraktion durch die Analyse der Begriffe „Beobachten“ und „Sehen“ aufgehellt. Abschließend wird auf die Frage nach der Falsifizierbarkeit der Kontraktionshypothese eingegangen, die von Popper aufgeworfen wurde. (shrink)

The FitzGerald–Lorentz contraction hypothesis has become well known in connection with Einstein's theory of relativity, and its role in the origin of that theory has been the subject of considerable study. But the origins of the contraction idea itself, and particularly of G. F. FitzGerald's first statement of it in 1889, have attracted much less attention and are surrounded by several misconceptions. The hypothesis has usually been depicted as a rather wild idea put forward without any real theoretical justification simply (...) to explain away the troublesome null result of Michelson and Morley's 1887 ether drift experiment. In the words of Gerald Holton, ‘it has traditionally been called the very paradigm of anad hochypothesis’. H. A. Lorentz, who hit upon the contraction idea independently in 1892, has been credited with giving it some justification in terms of his electron theory, but little or none of this credit has been extended to FitzGerald. His statement of the contraction hypothesis has usually been viewed, in the words of his friend R. T. Glazebrook, as nothing more than ‘the brilliant baseless guess of an Irish genius’. (shrink)

Many condensed matter systems are such that their collective excitations at low energies can be described by fields satisfying equations of motion formally indistinguishable from those of relativistic field theory. The finite speed of propagation of the disturbances in the effective fields (in the simplest models, the speed of sound) plays here the role of the speed of light in fundamental physics. However, these apparently relativistic fields are immersed in an external Newtonian world (the condensed matter system itself and the (...) laboratory can be considered Newtonian, since all the velocities involved are much smaller than the velocity of light) which provides a privileged coordinate system and therefore seems to destroy the possibility of having a perfectly defined relativistic emergent world. In this essay we ask ourselves the following question: In a homogeneous condensed matter medium, is there a way for internal observers, dealing exclusively with the low-energy collective phenomena, to detect their state of uniform motion with respect to the medium? By proposing a thought experiment based on the construction of a Michelson-Morley interferometer made of quasi-particles, we show that a real Lorentz-FitzGerald contraction takes place, so that internal observers are unable to find out anything about their ‘absolute’ state of motion. Therefore, we also show that an effective but perfectly defined relativistic world can emerge in a fishbowl world situated inside a Newtonian (laboratory) system. This leads us to reflect on the various levels of description in physics, in particular regarding the quest towards a theory of quantum gravity. (shrink)

Astronomical observations of redshifts and the cosmic background radiation show that there is a local frame of reference relative to which the solar system has a well-defined velocity. Also, in cosmology the cosmological principle implies the existence of cosmic time and unique local reference frames at all spacetime points. On the other hand, in a fundamental postulate, the theory of special relativity excludes the possibility of the velocity of the Earth from entering into theories of local physics.The theory put forward (...) in this paper resolves this conflict between local physics and cosmology. The theory retains the essential ingredient of the mathematical structure of special relativity, namely covariance under the Lorentz symmetry group, but changes radically the interpretation of the physical significance of the Lorentz transformation. The theory is based on the postulate that in free space the fundamental interactions in physics are propagated with constant velocity with respect to the local rest frame. In Minkowski spacetime the local rest frame of reference defines a unique time axis and consequently a unique three-dimensional spatial hyperplane. One particularly important result of this is that the theory includes the classical notion of simultaneity. From the fundamental postulate it follows that the equations of local physics, when expressed in terms of the rest frame coordinate system, must be covariant under the Lorentz symmetry group. By the identification of the local rest frame with the (unique) cosmological local reference frame the two theories become mutually consistent.The effects of the motion of the Earth on laboratory experiments are discussed. It is pointed out that existing experimental data do not discriminate between the present theory and that of special relativity: a proposal for an experimental test is made. (shrink)

It is argued that an unheralded moment marking the beginnings of relativity theory occurred in 1889, when G. F. FitzGerald, no doubt with the puzzling 1887 Michelson-Morley experiment fresh in mind, wrote to Heaviside about the possible effects of motion on inter-molecular forces in bodies. Emphasis is placed on the difference between FitzGerald's and Lorentz's independent justifications of the shape distortion effect involved. Finally, the importance of the their `constructive' approach to kinematics---stripped of any commitment to the physicality of the (...) ether--- will be defended, in the spirit of Pauli, Swann and Bell. (shrink)