Physical Reality – Construction or Discovery?: An Introduction to the Methodology and Aims of Physics PDF
Preview Physical Reality – Construction or Discovery?: An Introduction to the Methodology and Aims of Physics
Michael Grodzicki Physical Reality – Construction or Discovery? An Introduction to the Methodology and Aims of Physics – Physical Reality Construction or Discovery? Michael Grodzicki – Physical Reality Construction or Discovery? An Introduction to the Methodology and Aims of Physics 123 Michael Grodzicki Department ofChemistry andPhysics of Materials SalzburgUniversity Salzburg, Austria ISBN978-3-030-74578-3 ISBN978-3-030-74579-0 (eBook) https://doi.org/10.1007/978-3-030-74579-0 Translation from the German language edition: Physikalische Wirklichkeit – Konstruktion oder Entdeckung?,©LivingEdition/STARNA2015.AllRightsReserved. ©TheEditor(s)(ifapplicable)andTheAuthor(s),underexclusivelicensetoSpringerNature SwitzerlandAG2021 Thisworkissubjecttocopyright.AllrightsaresolelyandexclusivelylicensedbythePublisher,whether thewholeorpartofthematerialisconcerned,specificallytherightsofreprinting,reuseofillustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission orinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodologynowknownorhereafterdeveloped. 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ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSwitzerlandAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland Preface Physics owes its numerous practical successes largely to the fact that it seg- regated from its philosophical roots during the seventeenth century and sub- sequently developed a self-contained, generally accepted methodology. The preoccupation with questions about this methodology and the legitimacy of its foundations (“meta”-physics), as well as considerations about the struc- ture of physical knowledge, are not a prerequisite for gaining and producing physicalknowledge,andareconsideredasunnecessaryballastbymanywork- ing physicists. However, for anybody who has to teach physics (whether at school, university, or any other educational establishment), these issues can- not be ignored if an appropriate view of physics and its methodology is to be imparted which represents a more current understanding. This concerns primarily the following issues: • Factualknowledge:whatisaphysicallaw(constitutiveproperties,method- ological function) and what is a physical theory (structure, function)? • Procedural knowledge: what are the characteristic features of physical methodology, in particular, whose methods can be used to obtain struc- tured, secured, and reality-relevant knowledge? • How can the relations between theory and experience be described in an appropriate fashion? • What are the aims of physics? Thereisnogeneralagreementamongphysicistsconcerningtheseissues,most likely because these problems are rarely discussed in physics. Rather the competence to study and to answer these questions is generally claimed by philosophers of science. Nevertheless, they have not yet succeeded in devel- oping an authoritative conception of theory which provides an appropriate description of the structure of physical theories, and nor have they provided an adequate representation of the relationships between theory and experi- ence. It is precisely for this reason that this book has come about. In the early 1980s, I started to hold seminars on the methodology of physics that supple- v vi Preface mented my courses on theoretical physics, primarily for future high-school teachers. A search of the available literature about the structure of phys- ical theories and the relationships between theory and experience did not yield material relevant to physics, so I was forced to develop my own ideas abouttheoreticalconceptformation,thestructureofphysicalknowledge,and the objectives of physics. Initially planned merely as material for the semi- nar talks with the students, it eventually became a detailed treatise on the methodological issues of physics. Due to this historical origin, the book is a combination of textbook and original contributions. The third and fourth chapters in particular contain material that cannot be found in the available literaturetothebestofmyknowledge.Thesechaptersarebasedalmostexclu- sively on concrete examples from physics taken directly from my lectures on theoretical,molecular,andsolidstatephysics.Theseexampleseitherprovide the starting point for the derivation and discussion of more abstract issues, or elucidate the general conclusions. Moreover, this extensive use of concrete examplesfromphysicsshowsthatathoroughunderstandingofphysicallaws and theories and of the relationships between theory and experience cannot be acquired via formal considerations, as is usually attempted in philosophy of science. Although there are several connections with philosophical considerations, this book is definitely about the issues of physics itself. It is the translation of the German edition (Physikalische Wirklichkeit – Konstruktion oder En- teckung?), which was edited in 2015 by the publishing house Living Edition, Starna GmbH. Note that translations of quotes from other sources are also my own. Duetothepositiveresonanceamongstudentsandcolleagues,Iwasencour- aged to prepare an English translation in order to make the text available to abroaderaudience.Inthiscontext,myspecialthanksgotomyeditorAngela Lahee at Springer and also to Stephen Lyle for his assistance in improving the style and occasionally clarifying ambiguous formulations. University of Salzburg, Michael Grodzicki February 2021 Contents 1 The World View of Physics I: Presuppositions ............ 1 1.1 Introduction ........................................... 1 1.2 Constructive Realism ................................... 6 1.3 Factual Knowledge: The Structure of Bohr’s Theory ........ 15 1.4 Procedural Knowledge: The Method of Consistent Adjustment 23 1.5 The Evolution of Thought Patterns....................... 27 1.6 Tacit Assumptions...................................... 31 References ................................................. 40 2 Methodology of Physics .................................. 43 2.1 Scientific Methodology .................................. 43 2.2 Empirical Basis ........................................ 54 2.3 Experimental Methodology .............................. 65 2.4 Empirical-Inductive Methodology......................... 75 2.5 Theoretical Concept Formation........................... 87 2.6 Theoretical Orders...................................... 98 2.7 Modeling .............................................. 109 References ................................................. 119 3 The Structure of Physical Theories ....................... 121 3.1 Descriptive Theories .................................... 121 3.2 Formation of Hypotheses ................................ 135 3.3 Explanatory Theories ................................... 149 3.4 Axiomatization......................................... 169 3.5 Unification ............................................ 184 References ................................................. 201 4 Theory and Experience ................................... 203 4.1 The Structure of Physical Knowledge ..................... 203 4.2 Physical Laws.......................................... 212 4.3 Theory–Experiment Comparisons......................... 223 vii viii Contents 4.4 The Duhemian Theses .................................. 234 4.5 Consistent Adjustment: Examples ........................ 245 4.6 Consistent Adjustment: Methods ......................... 253 References ................................................. 265 5 The World View of Physics II: Implications............... 269 5.1 Aims of Physics ........................................ 269 5.2 The Problem of Causality ............................... 281 5.3 Explanation and Prediction.............................. 291 5.4 The Problem of Truth................................... 301 5.5 Physical Reality........................................ 315 References ................................................. 332 Chapter 1 The World View of Physics I: Presuppositions Thebasicrequirementsforanappropriaterepresentationofthepropertiesof physicalmethodsandknowledgearebrieflydescribed,andshowntobeindis- tinctcontrasttoempiricistviews.Acomprehensiveunderstandingofphysics requires one to include metaphysical and sociological elements in addition to factual and procedural knowledge. The philosophical basis of physics is de- fined as a “constructive realism” that is subsequently specified and extended by a number of implicit or “tacit” assumptions. A preliminary explication of the conception of a theory is exemplified by Bohr’s theory. The method of consistent adjustment, which is of crucial importance to understanding the relations between theory and experience, is elucidated using a simple mathematical example. 1.1 Introduction Since the foundations of physics as a mathematical natural science were laid in the seventeenth century, the achievements of science have exerted an ever increasing influence on our view of the world. In establishing the scientific world view, physics has played the leading role, and it still does, irrespective of the developments in other branches of science. Firstly, the most striking indications are the directly perceptible technical advances based on physical knowledge.Secondly,physicsprovidesthebasisformostoftheothernatural sciences and influences them accordingly. Finally, the methods of working and reasoning in physics are regarded as paradigmatic for the scientific at- titude and rationality. As a result, these methods do not just establish the standard view of scientific methodology, but also constitute the basic pat- tern for numerous modes of thinking and working in extra-scientific areas. Consequently,thesemethodsareappliedtoissuesforwhichtheywerenotde- velopedandarenotwellsuited.Thishasattractedcriticismwhichisjustified, at least partially, because such applications are frequently based on concep- The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 1 M. Grodzicki, Physical Reality – Construction or Discovery?, https://doi.org/10.1007/978-3-030-74579-0_1 2 1 TheWorld ViewofPhysics I:Presuppositions tions of physical methodology dating back to the seventeenth and eighteenth centuries and do not even properly accord with the methodology of classi- cal physics. Certainly, the most widespread prejudice is that (experimental) experience in relation to theory has the distinct priority in the process of gaining and corroborating physical knowledge, as shown by representative textbook citations: Observingnatureonesoonarrivesattheinsightthatitisgovernedbystrictly valid laws. [...] In physics one attempts to read out of experiences relations ofasgeneralaspossibleimportance,andthensinglelawsbeingvalidwithina subareatoassembletoawholesystemwithoutleavingagaporcontradiction. [...]Theexperimentallyobtainedfactsareuntouchableforthephysicistasfar astheappliedobservationalprocedurewithstandsallcriticism.Atheorymust bechangedassoonasasinglesecuredexperimentisincontradictionwiththis theory. [...] Fundamental physical laws can be extracted from nature only by observation(Fleischmann1980). [Physicalaxioms]areempiricalfundamentallawswhosecorrectness[...]emerges solelyfromimmediately givenfacts(Stroppe1981). Newton’s equations [...] were initially empirical formulations of immediately observablequantities(Dransfeldetal.1974). [Physical axioms] emerge as generalization of a finite number of observations. [...]Anaturallawonceestablishedcanberefuted(falsified)byasingleobser- vationorasingle experiment(Fließbach1996). Experimentisthe solejudgeofscientifictruth(Feynman etal.1964). Physics is an experimental science. Everything we know about the physical world and about the principles that govern its behaviour has been learned throughexperiment,thatis,throughobservationsofthephenomenaofnature. The ultimate test of any physical theory is its agreement with experimental observations(Searsetal. 1987). Theviewofphysicsemergingfromthesequotationsisasfollows.Physicsisan empiricalsciencebecauseobservationsandexperimentsarethesole,trustwor- thy source of knowledge and the sole criterion for corroborating theoretical results. Nature is governed by strictly valid laws (“natural laws”) discovered throughcarefulobservationofnatureorbygeneralizationofdirectlyaccessi- ble facts. The physicist “asks” nature and obtains unequivocal answers that may, in principle, be scrutinized by any other person. As the aggregation of these laws, physical theories are void of speculative and subjective elements, so that physical knowledge is objective and value-free. Neither the histori- calprocessofacquiringknowledgenorindividual,social,oreconomicfactors play any role. Amodernphilosophicalcounterpartofthisconceptionisneopositivismor logical empiricism (Haller 1993), developed during the 1920s. Understanding itself as an empiricism supplemented with the results of modern logic, it is characterized by the following assumptions:
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