Popper and Dingle on special relativity and the issue of symmetry

Karl Popper and Herbert Dingle engaged in a fascinating debate concerning the kind of theory the special theory of relativity is. One of the issues was whether applications of the theory could be made consistent with the principle of relativity, a cornerstone of the theory itself. The principle of relativity seems to imply some sort of symmetry in results obtained for similar experiments as observed in two different inertial reference frames. Peter Hayes has recently dealt with the Dingle–Popper debate on this matter, as well as other issues. The present paper seeks to clarify what kind of symmetry is appropriate in a situation discussed by Popper, Dingle, and Hayes.     

Popper’s response to Dingle on special relativity and the problem of the observer

Dingle contended that Einstein’s special theory of relativity was physically impossible for the simple reason that it required clocks to be simultaneously faster and slower than each other. McCrea refuted Dingle using an operationalist argument. An operational response did not satisfy Popper, who wrote an unpublished essay to counter Dingle’s claim. Popper developed an analysis that avoided operationalism by using a system of coinciding clocks, contending that this system showed that special relativity withstood Dingle’s criticism that it was not a symmetrical and consistent physical theory. However, Popper mistakenly included an asymmetric calculation in his analysis. Once this is corrected, the amended result supports Dingle’s position. Popper went on to argue that to avoid determinism, special relativity had to be reconciled with absolute time; this too supports Dingle. Popper’s failure to refute Dingle calls into question his claim that ‘the observer’ is superfluous to special relativity.     

Can we trust Einstein’s accounts of the genesis of special relativity?

There are three kinds of sources available to reconstruct the reflections that led Einstein to special relativity: a few contemporary letters and documents, his impersonal accounts of the genesis of this theory, and recollections of his own path. At first glance, contradictions within and between these sources hamper the reliability of Einstein’s accounts. Yet, a closer analysis reveals much more consistency than foreseen and helps eliminate the dubious, contradictory elements. It then becomes possible to combine the three kinds of sources to produce a minimally speculative and yet fairly coherent account of the genesis of special relativity.     

Einstein's reinterpretation of the Fizeau experiment: How it turned out to be crucial for special relativity

In this article, we aim at clarifying the role played by Fizeau’s 1851 experiment, both in the context of discovery and in the context of justification of the special theory of relativity. In 1907 Laue proved that Fresnel's formula was a consequence of the relativistic composition of velocities; since then, Einstein regarded Fizeau's experiment as confirmatory evidence for his theory, and even as a crucial experiment in favor of the relativistic addition of velocities. On the other hand, in the 1920's Einstein stated that this experiment was decisive in the path that led him to the discovery of his theory before 1905, but he did not explain why. We survey all the available evidence on this subject and conclude that the original ether-drag experiment was reinterpreted within a new conceptual framework in which the meaning of the very concept of velocity undergoes a radical change.     

Mesh and measure in early general relativity

In the early days of general relativity, several of Einstein׳s readers misunderstood the role of coordinates or “mesh-system” in ways that threatened the basic predictions of the theory. This confusion largely derived from intrinsic defects of Einstein׳s first systematic exposition of his theory. A few of Einstein׳s followers, including Arthur Eddington, Hermann Weyl, and Max von Laue, identified the interpretive difficulties and solved them by combining a deeply geometrical understanding of the theory with detailed attention to the concrete conditions of measurement.     

Regulation of mitochondrial dynamics: convergences and divergences between yeast and vertebrates

In eukaryotic cells, the shape of mitochondria can be tuned to various physiological conditions by a balance of fusion and fission processes termed mitochondrial dynamics. Mitochondrial dynamics controls not only the morphology but also the function of mitochondria, and therefore is crucial in many aspects of a cell’s life. Consequently, dysfunction of mitochondrial dynamics has been implicated in a variety of human diseases including cancer. Several proteins important for mitochondrial fusion and fission have been discovered over the past decade. However, there is emerging evidence that there are as yet unidentified proteins important for these processes and that the fusion/fission machinery is not completely conserved between yeast and vertebrates. The recent characterization of several mammalian proteins important for the process that were not conserved in yeast, may indicate that the molecular mechanisms regulating and controlling the morphology and function of mitochondria are more elaborate and complex in vertebrates. This difference could possibly be a consequence of different needs in the different cell types of multicellular organisms. Here, we review recent advances in the field of mitochondrial dynamics. We highlight and discuss the mechanisms regulating recruitment of cytosolic Drp1 to the mitochondrial outer membrane by Fis1, Mff, and MIEF1 in mammals and the divergences in regulation of mitochondrial dynamics between yeast and vertebrates.     

Trust in expert testimony: Eddington's 1919 eclipse expedition and the British response to general relativity

The 1919 British astronomical expedition led by Arthur Stanley Eddington to observe the deflection of starlight by the sun, as predicted by Einstein's relativistic theory of gravitation, is a fascinating example of the importance of expert testimony in the social transmission of scientific knowledge. While Popper lauded the expedition as science at its best, accounts by Earman and Glymour, Collins and Pinch, and Waller are more critical of Eddington's work. Here I revisit the eclipse expedition to dispute the characterization of the British response to general relativity as the blind acceptance of a partisan's pro-relativity claims by colleagues incapable of criticism. Many factors served to make Eddington the trusted British expert on relativity in 1919, and his experimental results rested on debatable choices of data analysis, choices criticized widely since but apparently not widely by his British contemporaries. By attending to how and to whom Eddington presented his testimony and how and by whom this testimony was received, I suggest, we may recognize as evidentially significant corroborating testimony from those who were expert not in relativity but in observational astronomy. We are reminded that even extraordinary expert testimony is neither offered nor accepted entirely in an epistemic vacuum.     

板材液压拉深试验装置开发

开发了一种用于板材液压拉深成形性能研究的试验装置,包括拉深模具及液压控制系统。该装置不需要复杂的外部供液系统、压边系统及凸模导向系统,在普通的单动压力机上就能实现对不同材料及尺寸板材的普通拉深和液压拉深试验。初步的试验表明,该装置结构简单、操作方便、工作可靠,满足板材液压拉深试验要求,能够有效的改善板材的成形性能。     

Evidence of direct nervous connections between the neuromasts of the lateral line system of fishes

Zusammenfassung Auf histochemischer Basis wird anTilapia (Cichlidae, Teleostei) die bereits 1880 vonSolger geäusserte und später in Vergessenheit geratene Auffassung bestätigt, dass die Verbindungsstränge zwischen den Neuromasten in den Seitenkanälen bei Knochenfischen marklose Nervenfasern, ähnlich jenen des vegetativen Nervensystems, sind.

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Acknowledgments: I am most grateful to Dr.K. Reutter (Anatomisches Institut der Universität Tübingen) who undertook the histochemical investigations for this account. This work was supported by the Deutsche Forschungsgemeinschaft.