{"id":3412,"date":"2013-11-11T17:00:54","date_gmt":"2013-11-11T05:00:54","guid":{"rendered":"https:\/\/blogs.otago.ac.nz\/emxphi\/?p=3412"},"modified":"2013-11-11T08:31:47","modified_gmt":"2013-11-10T20:31:47","slug":"observation-experiment-and-intervention-in-newtons-opticks","status":"publish","type":"post","link":"https:\/\/blogs.otago.ac.nz\/emxphi\/observation-experiment-and-intervention-in-newtons-opticks\/","title":{"rendered":"Observation, experiment and intervention in Newton\u2019s Opticks"},"content":{"rendered":"

Kirsten Walsh writes…<\/strong><\/p>\n

In my last post<\/a>, my analysis of the phenomena in Principia<\/em> revealed a continuity in Newton\u2019s methodology.\u00a0 I said:<\/p>\n

    In the Opticks, Newton isolated his explanatory targets by making observations under controlled, experimental conditions.\u00a0 In Principia, Newton isolated his explanatory targets mathematically: from astronomical data, he calculated the motions of bodies with respect to a central focus.\u00a0 Viewed in this way, Newton\u2019s phenomena and experiments are different ways of achieving the same thing: isolating explananda.<\/ol>\n

    In this post, I\u2019ll have a closer look at Newton\u2019s method of isolating explananda in the Opticks<\/em>.\u00a0 It looks like Newton made a distinction between experiment and observation: book 1, contained \u2018experiments\u2019, but books 2 and 3, contained \u2018observations\u2019.\u00a0 I\u2019ll argue that the distinction in operation here was not the standard one, which turns on level of intervention.<\/p>\n

    In current philosophy of science, the distinction between experiment and observation concerns the level of intervention involved. \u00a0In scientific investigation, intervention has two related functions: isolating a target system, and creating novel scenarios.\u00a0 On this view, experiment involves intervention on a target system, and manipulation of independent variables. \u00a0In contrast, the term \u2018observation\u2019 is usually applied to any empirical investigation that does not involve intervention or manipulation.\u00a0 This distinction is fuzzy at best: usually level of intervention is seen as a continuum, with observation nearer to one end and experiment nearer to the other.<\/p>\n

    If Newton was working with this sort of distinction, then we should find that the experiments in book 1 involve a higher level of intervention than the observations in books 2 and 3.\u00a0 That is, in contrast to the experiments in book 1, the observations should involve fewer prisms, lenses, isolated light rays, and artificially created scenarios.\u00a0 However, this is not what we find.\u00a0 Instead we find that, in<\/em> every book<\/em> of the Opticks<\/em>, Newton employed instruments to create novel scenarios that allowed him to isolate and identify certain properties of light.\u00a0 It is difficult to quantify the level of intervention involved, but it seems safe to conclude that Newton\u2019s use of the terms \u2018observation\u2019 and \u2018experiment\u2019 doesn\u2019t reflect this distinction.<\/p>\n

    To understand what kind of distinction Newton was making, we need to look at the experiments and observations more closely.\u00a0 In Opticks<\/em> book 1, Newton employed a method of \u2018proof by experiments\u2019 to support his propositions.\u00a0 Each experiment was designed to reveal a specific property of light. \u00a0Consider for example, proposition 1, part I: Lights which differ in Colour, differ also in Degrees of Refrangibility<\/em>.\u00a0 Newton provided two experiments to support this proposition.\u00a0 These experiments involved the use of prisms, lenses, candles, and red and blue coloured paper.\u00a0 From these experiments, Newton concluded that blue light refracts to a greater degree than red light, and hence that blue light is more refrangible than red light.<\/p>\n

    \"\"

    Opticks, part I, figure 12.<\/p><\/div>\n

    In the scholium that followed, Newton pointed out that the red and blue light in these experiments was not strictly homogeneous.\u00a0 Rather, both colours were, to some extent, heterogeneous mixtures of different colours.\u00a0 So it\u2019s not the case, when conducting these experiments, that all the blue light was more refrangible than all the red light. \u00a0And yet, these experiments demonstrate a general effect.\u00a0 This highlights the fact that, in book 1, Newton was describing ideal<\/em> experiments in which the target system had been perfectly isolated<\/em>.<\/p>\n

    Book 2 concerned the phenomenon now known as \u2018Newton\u2019s Rings\u2019<\/a>: the coloured rings produced by a thin film of air or water compressed between two glasses.\u00a0 It had a different structure to book 1: Newton listed twenty-four observations in part I, then compiled the results in part II, explained them in propositions in part III, and described a new set of observations in part IV.\u00a0 The observations in parts I and IV explored the phenomena of coloured rings in a sequence of increasingly sophisticated experiments.<\/p>\n

    Consider, for example, the observations in part I.\u00a0 Observation 1 was relatively simple: Newton pressed together two prisms, and noticed that, at the point where the two prisms touched, there was a transparent spot.\u00a0 The next couple of observations were variations on that first one: Newton rotated the prisms and noticed that coloured rings became visible when the incident rays hit the prisms at a particular angle.\u00a0 But Newton steadily progressed, step-by-step, from prisms to convex lenses, and then to bubbles and thin plates of glass.\u00a0 He varied the amount, colour and angle of the incident light, and the angle of observation.\u00a0 The result was a detailed, but open ended, survey of the phenomena.<\/p>\n

    I have argued that Newton\u2019s experiments and observations cannot be differentiated on the basis of intervention, but there are two other differences worth noting.\u00a0 Firstly, whereas the experiments described in book 1 were ideal experiments, involving perfectly isolated explanatory targets, the observations in books 2 and 3 were not ideal.\u00a0 Rather, through a complex sequence of observations, as the level of sophistication increased, the explanatory target was increasingly well isolated.\u00a0 When viewed in this way, the phenomena of Principia<\/em> seem to have more in common with the experiments of book 1 than the observations of books 2 and 3.<\/p>\n

    Secondly, the experiments of book 1 were employed to support particular propositions, and so, individually,<\/em> they were held to be particularly relevant and informative.\u00a0 In contrast, the observations of books 2 and 3 were only collectively<\/em> relevant and informative.\u00a0 Moreover, the sequence of observations was open ended: there were always more variations one could try.<\/p>\n

    What are we to make of these differences between observation and experiment in the Opticks<\/em>?\u00a0 I have previously argued<\/a> that, while Newton never constructed Baconian natural histories, his work contained other features of the Baconian experimental philosophy, such as experiments, queries and an anti-hypothetical stance.\u00a0 However, in viewing them as complex, open ended series\u2019 of experiments, I now suggest that the observations of books 2 and 3 look a lot like what Bacon called experientia literata<\/em>, the method by which natural histories are generated.\u00a0 I\u2019ll discuss this in my next post, but in the mean time, I\u2019d like to hear what our readers think.<\/p>\n","protected":false},"excerpt":{"rendered":"

    Kirsten Walsh writes… In my last post, my analysis of the phenomena in Principia revealed a continuity in Newton\u2019s methodology.\u00a0 I said: In the Opticks, Newton isolated his explanatory targets by making observations under controlled, experimental conditions.\u00a0 In Principia, Newton […]<\/p>\n","protected":false},"author":4582,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[113],"tags":[276,349,224,16410,348],"class_list":["post-3412","post","type-post","status-publish","format-standard","hentry","category-ideas","tag-experiment","tag-natural-history","tag-newton","tag-observation","tag-optics"],"_links":{"self":[{"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/posts\/3412","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/users\/4582"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/comments?post=3412"}],"version-history":[{"count":0,"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/posts\/3412\/revisions"}],"wp:attachment":[{"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/media?parent=3412"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/categories?post=3412"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.otago.ac.nz\/emxphi\/wp-json\/wp\/v2\/tags?post=3412"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}