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Postscript-The Hammer and the Pendulum

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Postscript-The Hammer and The Pendulum To my mind there appears to be no necessary theoretical antagonism between Catastrophism and Uniformitarianism. On the contrary, it is very conceivable that catastrophes may be parr and parcel of uniformity. Let me illustrate my case by analogy. The working of a clock is a model of uniform aCtion; good time-keeping means uniformity of aCtion. But the striking of the clock is essentially a catastro­ phe; the hammer might be made ro blow up a barrel ofgunpowder, or turn on a deluge of water; and, by proper arrangement, the clock, instead of marking the hours, mighr strike ar all sorrs of irregular intervals, never twice alike in the intervals, force, or number of its blows. Nevertheless, all rhese irregular and apparenrly lawless carastrophes would be rhe resulr of an absolurely uniformi­ tarian action action; and we mighr have twO schools of clock-rheorisrs, one studying the hammer and rhe other the pendulum. Srill less is rhere any necessary antagonism berween eirher of rhese doctrines and rhar of Evolurion, which embraces all rhar is sound in borh Carastrophism and Uniformirarianism, while ir rejeCts rhe arbirrary assumprions of rhe one and rhe, as arbitrary, limirarions of rhe orher. Nor is rhe value of rhe doCtrine of Evolurion to the philosophic rhinker diminished by rhe faCt rhar ir applies rhe same merhod ro rhe living and rhe nor-living world, and embraces in one stupendous analogy rhe growrh of a solar sysrem from molecular chaos, rhe shaping of rhe earth from rhe nebulous cubhood of irs yourh, rhrough innumerable changes and immeas­ urable ages, to irs present form, and rhe development of a living being from rhe shapeless mass of proroplasm we rerm a germ. T.H.Huxley, Anniversary Address of the President, Quarterly journal ofthe Geological Society ofLondon 25, xlvi-xlvii (1869) A shorr extract from Thomas Huxley's address to the Geological Society 10 1869, just ten years after the publication of Charles Darwin's On the Origin ofSpecies, 345 346 Postscript-The Hammer and the Pendulum was quoted in Section 2.8. The rather longer quorarion from rhe same section given above enables us to see JUSt how perceptive Darwin's "bulldog" was, in recognizing thar the course of evolution must have involved catastrophic events as well as gradualist processes, all operating within the framework of natural laws. However, his wise words were ignored for well over a century, during which time it was thought that the only mechanisms worthy of consideration were rhose consistent with gradualism. Only now, at long last, is it becoming possible I(lr debates about the contribution of catastrophism to evolutionary ptocesses to take place in a proper, open-minded, fashion. That is not to say that they are always conducted in an atmosphere of sweet reasonableness for, as with any academic discussion where there is more than one school of thought and particularly where, as here, fundamentally different worldviews are involved, passions continue to be aroused and prejudices displayed. Nevertheless, they are happening, and that in itself is a step forward. No one can now suggest, and retain any credibility, that carastrophist mecha­ nisms should, as a matter ofprinciple, be excluded from consideration. All arguments, whether catastrophist or gradualist, have to be judged on equal terms, by testing them against the evidence. That is as it should be. Without any question, debates over the past 15 years about the possible influence ofcatastrophism on evolution have proved consistently lively and increasingly productive. Let us hope the same is true ofthe next 15 years. Despite the recent advances, there are still an enormous number of questions that need to be answered. References Chapter 1 1. H. Couper and N. HenbesL The Planets, Pan Books. London (1985). 2. P Moore, New Gllide to the Planets. Sidgwick and Jackson. London (1993); P Moore, Stan and PICllleIJ, Chancellor Press, London (1992). 3. c.]. Allegre and S. H. Schneider, The evolution of the Earth, Sci. Alii. 271(4),44-5 I. ([994); S. R. Taylor, Solar Systelll E"ollilioll, Cambridge University Press (1992); S. Bowler. Formarion ofrhe Earth. Neu'Scientist 14 December 1996, IltSitie Srimce supplement number 96, pp. 1-4; N. Murray, B. Hansen, M. Holman, and S. Tremaine, Migraring planets, Science (Wash .. DC) 279. 69-72 (1998); I. icolson, D. A. Rorhery, and F. Taylor. 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  • A Tomography Approach to Investigate Impactite Structure

    A Tomography Approach to Investigate Impactite Structure

    3rd International Conference on Tomography of Materials and Structures Lund, Sweden, 26-30 June 2017, ICTMS2017-110 A TOMOGRAPHY APPROACH TO INVESTIGATE IMPACTITE STRUCTURE A. Fedrigo*1,2, K. Marstal1,3, A. Bjorholm Dahl1, M. Lyksborg1, C. Gundlach1, M. Strobl2 & C. Bender Koch4 1Danish Technical University, Denmark 2European Spallation Source ESS ERIC, Sweden 3ERASMUS MC, Netherland 4Copenhagen University, Denmark Keywords: Neutron imaging, image registration, bimodal imaging, computed tomography. Summary: We investigate the structure of impactites from the Wabar iron meteorite impact site in Saudi Arabia. In order to understand the physical and chemical processes involved in the formation of the impactite, we applied a non-destructive investigation approach, which combines X-ray and neutron tomography. This bi-modal imaging method allowed for a better understanding of the impactite’s chemical composition. 1. INTRODUCTION Meteorite impacts have recently been recognised among the most important processes able to modify planetary surfaces. It also happens to be one of the least understood in details. In particular it is a challenge to understand both the extent of impacts and the physical and chemical changes that occur during and following the impact, where materials (e.g., rocks, sand, meteorite fragments, etc.) are subjected to temperatures of several thousands degrees and pressures of several GPa. In addition, most accessible Earth impact areas are highly affected by weathering, which causes extensive secondary chemical alterations. Iron meteorites impact on planetary surfaces cause shock-induced rock deformations that happens both at macroscopic and at microscopic level, e.g. shatter cones (macroscopic) and planar deformation features in quartz (microscopic). Another indicator often correlated to meteoritic impacts is the presence of iridium concentration anomalies [1, 2].