The Hebrew University of Jerusalem
Abstract. Using the history and philosophy of science (HPS) in science teaching can be framed within the paradigm of discipline-culture, which structures fundamental science discipline in three areas – nucleus (the central principles), body of knowledge (applications of the nucleus) and periphery (knowledge elements contradicting to the nucleus). All three types of knowledge elements create in the learner the cultural knowledge of the discipline and may cause its meaningful learning by (a) cognitive resonance in students serving as a remedial tool for misconceptions, and (b) creating the space of learning in which the "correct" knowledge emerges from a discourse between alternatives. Developing teaching modules within European project HIPST we found two possible types of scientific knowledge: those which represent the "correct" knowledge (Type I) and those reviving the views alternative to the commonly adopted in science today (Type II). We argue for the essential importance of the second type for the meaningful learning of the contemporary taught knowledge in physics classes. By shedding light on the scientific concepts and their operational definition, understanding the meaning of theories, laws, principles, models, experiments the units should lead to epistemological maturity of the learners, and benefits to their views on the nature of scientific knowledge. Revealing conceptual dialogue between the alternative ideas in science not only impedes misconceptions, but performs enculturation of students into modern science.
Using the history and philosophy of science (HPS) in science teaching has a long history and many researchers argued for its benefits to students and teachers (e.g., Matthews, 1994). Importantly, the argumentation for using the HPS did not remain as it was but develop with time reflecting cultural evolution taking place (Galili, 2008). However, even after intensive support for using the HPS in science teaching and articulation of its advantages in a list of benefits caused by such using (e.g., ibid, p. 38), the issue continues to be controversial, as it emerges from research reports (e.g. Galili & Hazan, 2001a). Physics teachers and physics researchers who lecture physics often refuse to significantly include the HPS materials beyond cultural references and anecdotes that may remove the tension of formal instruction, but not essentially used in the instruction. Furthermore, there is a widespread myth among science teachers that science teaching can be neutral, in the sense being free of any philosophy (Tseitlin & Galili, 2006).
Historians often criticize the historical materials for teaching and learning produced by educators, accusing them in presenting "bad history" (selective and “Whiggish”). The philosophers of science, in their turn, cannot conceal their dissatisfaction with the philosophically superficial – and sometimes simply wrong – ideas on the nature of science, suspecting educators in incompetence in the philosophy of science (Matthews, 2009). However, even after all such critique, often substantial and serious indeed, there remain researchers in science education discourse, who continue advocate for the enormous potential of the HPS for science education, although they are aware about numerous difficulties of actual application of such materials in class instruction (Gauld, 1991; Galili, 2008, Höttecke 2009). They claim that the current cumbersome situation with the use of the HPS in education has been created due to the complexity of the subject which should be investigated and clarified.
The situation apparently requires the investment of intensive research effort of both theoretical and empirical nature. Only complementary efforts of both kinds might provide a solid basis and determine the form for the effective use of the HPS in science education. This study belongs to such trend in science education research. It suggests the framework of the disciplinary knowledge structure in physics, discipline-culture, that not only legitimizes the use of the HPS based materials in physics education, but also argues for its possible essential contribution to the meaningful learning of science through addressing the essential features of scientific theories – "critical details" (Viennot, 2004). Moreover, we found important to distinguish between two types of historical materials, those addressing correct and incorrect scientific knowledge (in view of the modern science), and speculate regarding their relative importance for science curriculum. Finally, the presented ideas were illustrated by describing some features of the historical units – excurses – that we have recently produced within the international European project for using the History and Philosophy of Science in Teaching (HIPST, 2008).
Among the reasons for rejection historical materials by school teachers and university lecturers they mention that such materials are often obsolete and simply incorrect, in light of the present knowledge. Their contents may include conceptions, views, values, terminology that are foreign to the modern learner. Indeed, in education, we do not use the original treatises from the past, but modern textbooks. Thus, even for teaching and learning the fundamental laws of motion in Newtonian mechanics, which are obligatory in modern school, we never use Newtonian Principia (1687/1999), but the modern presentation of this theory in a regular textbook which is very different in form from the original (e.g., Halliday & Resnick, 1988; Reif, 1995). Moreover, even when we decide to go and read the original treatise, we immediately discover that the concepts of Newton were different. They look confusing not only to the novice but also to a modern scientist. For example, the First Law of Newton we teach today is not the law formulated by Newton. The original was more complex and in a way different; it was not “a special case of absence of force” (Galili & Tseitlin, 2003). If so, why do we need the historical materials at all, beyond the curiosity and cultural appreciation? Seemingly, many scientists and teachers are indeed convinced that they do not (Galili & Hazan, 2001a).
Prominent physics educators had a difficult time to advocate another view. They claim that the HPS materials are more than historical documents interesting to historians. The focus became to prove the relevance of the HPS to the modern learners of science. One perspective of relevance was apparently obvious to many: the HPS materials inform the learner about the features of scientific knowledge and the nature of science as a human activity in which scientists seek the objective truth about the nature and the laws that govern its order and phenomena. This knowledge about science – metaphysical knowledge – may enrich the learners through familiarizing them with the authentic stories about those who made discoveries and moved forward our civilization (Connant, 1957). The materials were left to the student and teacher to be interpreted. This allowed to the opponents to argue that the historical materials are more appropriate for the extracurricular enrichment, not for regular teaching. The aspect of the nature of science was treated similarly, and all together the HPS materials were left out of regular curriculum.
An important change took place with the entrance of constructivism into science education. The latter considers conceptual change to be the way in which people learn and hence to be the goal deserving encouragement by teachers. At the same time, the researchers in students' conceptions reported about the high resemblance often found between students' naïve and alternative conceptions and those shown by scientists in the past (e.g. McCloskey, 1983; Halloun & Hestenes, 1985). This similarity revived the thesis of resemblance between philo- and onto-genesis of knowledge (Piaget & Garcia, 1989). Two these ideas – educational constructivism and genetic epistemology projected to science – created a new perspective on the relevancy of the HPS materials. Drawing on the similarity in conceptual difficulties of scientists from the past and students of today researchers of science education stated the worthiness to consider the specific historical ideas in the class (Monk & Osborne, 1997). They stated that those ideas may promote conceptual change or cause a cognitive resonance in the learners. Similar motivation was recognized by the program of educational reconstruction which requires scientific clarification as well as the knowledge of students' conceptions as a prerequisite in production of teaching materials in science education (Duit et al., 2005). Researchers agreed that appealing to the particular context from the history of science may promote the learner to match the factors required for success in the conceptual change (Posner et al., 1982): dissatisfaction with the knowledge previously held together with plausibility, intelligibility and fruitfulness of the scientific alternative.
This approach was tested by us in a yearlong experiment in which students of the 10th grade (4 classes in different schools) were taught about light and vision in a special course that integrated fragments from the history of optics. Those were arranged in a narrative from the Greek philosophers of nature to the modern physicists. The results were encouraging: at the end of the course, the students of the experimental program showed better content knowledge in comparison to a regular class as well as more mature views on the nature of science (Galili & Hazan, 2000, 2001b).
New approach: Discipline-Culture
We have suggested a new framework of disciplinary knowledge presentation in educational context, which we called discipline-culture approach (Tseitlin & Galili, 2005). Within this framework, there is a clear distinguishing between three types of knowledge elements constituting the fundamental theory in science (Fig. 1). The first type – nucleus – includes the paradigm of the considered theory, its concepts and principles, including the rules of theory application and knowledge production. The second type – body – includes the application of the central paradigm, solved problems, and explained phenomena, working models, the knowledge of instruments and appliances all built by using the principles of particular nucleus. Together the two areas (nucleus and body) represent what is normally considered as disciplinary knowledge. The third type of knowledge elements represents the conceptions that contradict the nucleus, alternative ideas whether from the past or from more advanced theories which surpassed the particular theory, unexplained phenomena, other unresolved problems and the information about shortcomings, incompatibilities and failures of the considered nucleus. All these elements comprise periphery of the considered theory, and all three areas together comprise a discipline-culture. The relation to culture is justified by the fact that the whole body of three types of knowledge include alternative views on the same subject (the nucleus and periphery) and this feature fits to the modern perspective on culture as containing multiple alternative perspectives on the same subject – a pluralistic picture.
Figure 1. Discipline-Culture structure.
For example, the Classical Mechanics, as a discipline-culture, includes the principles and concepts of Newtonian mechanics in its nucleus, whereas the periphery incorporates the principles of Aristotelian physics as well as of Einstein's theory of relativity. Misconceptions with respect to the Newtonian mechanics also belong to its periphery in this inclusive conceptual structure. It is clear that the history of science provide a plenty of knowledge elements for the periphery of any discipline presented in a cultural way.
Furthermore, we may realize that a structure with separated nuclei, partially overlaying bodies of knowledge all together immersed in the periphery (Fig. 2) could represent different fundamental theories in physics and explain the meaning of the principle of correspondence between physical theories. Such diagram may represent, for example, the relationship between Classical Mechanics and Relativistic Mechanics. Their nuclei contradict each other (for example in regarding space and time) and thus are located each in the periphery of the other. These theories may produce non contradictive results (such as at low velocities limit) which belong to the overlaying area shared by the bodies of knowledge.
Figure 2. Discipline-culture structure of two fundamental theories.
Being different in the fundamentals the two theories possess family resemblance (Wittgenstein) as it is manifested in the shared concepts, methodology, principles, mathematical formalism, etc. We thus have arrived at the structure that represents knowledge of a discipline like physics in cultural perspective.
The role of the Philosophy of Science
Discipline-culture approach led us to further refine the presented arrangement of the scientific knowledge with regard to its meaning (Tseitlin & Galili, 2006). We found possible utilization of the semiotic triangle, commonly relating the triad object-concept-sign (Fig. 3a), for presenting the triad Science – the Philosophy of Science –Science Curriculum as cultural phenomena (Fig. 3b). Within this perspective, the role of the Philosophy of Science becomes clear as (1) providing the conceptual meaning to the scientific contents and (2) prescribing the features and contents to the science curriculum. Indeed, any philosophical approach – empiricist, rationalist, constructivist, and so on – originates the correspondent curriculum for science teaching which suggests and develops its own worldview.
Figure 3. (a) Generic semiotic triangle; (b) The semiotic relationship of Science, the Philosophy of Science and Science Curriculum.
The philosophy of science explains both aspects of conceptual meaning of scientific knowledge: epistemological and ontological fundamentals, both too often are not sufficiently emphasized in textbooks. Importantly, the presented view on the role of philosophy may suggest a resource for reliable knowledge and adequate tools of evaluation of different curricula so badly required in the discourse on the nature of science and scientific knowledge, which remains controversial among the education researchers (Matthews, 2009).
Implication to Physics Education: Cultural Content Knowledge
We have learned from the resent history that several projects that tried to introduce the HPS based materials into science education had very modest results (Monk & Osborne, 1997):
… even materials produced for teachers, for example, those produced in the UK … are not used. Attempts to produce restructured courses that put history at the center of the enterprise … have enjoyed only marginal success, as have those that have sought to introduce a more rigorous and current view of the philosophy of science …
The European project HIPST provided us with a unique opportunity to reconsider the framework of using the HPS materials in light of the previous experience in the subject and the mentioned above research results. In particular, we took into account the described model of discipline-culture to serve as a guiding framework for the new teaching contents.
The feasible format of the new materials aimed to contribute to the existing system of science education appeared to be historical excurses which can support the regular course of physics in its particular points (Fig. 4). This is because our intention was to enrich and improve the currently adopted science curriculum and not to replace it.
Figure 4. Schematic presentation of incorporation of historical excurses into the existing curriculum.
The genre of historical excurse, as we termed our units of intervention, intended to present a comprehensive account of certain subject expanded along a significant historical period. The excurse is special in its features. It has a clear focus in several aspects of content knowledge – theoretical, methodological, instrumental or social. This allows excurse to serve as an effective pedagogical tool for the particular subject chosen for its importance. The excurses must remain compact, and as such they can be manipulated by the teacher and adsorbed by the instruction already dense in materials to be covered. They may include a story, a sort of narrative, known as an appealing format for class teaching which stimulates better mastering of the chosen topic. The problem raised was to establish the criteria, guiding principles in choosing the materials for such cases for the great amount available in the history of physics in its various resources.
For this purpose one may use the culture-discipline structure as a guiding framework. We faced the great historical resources having in mind the elements of the curriculum being affiliated to the different areas of the discipline-culture structure. Then we could saw that two basic options exist for in developing historical materials for teaching and learning (not excluding their combination) (Fig. 5).
I. In the first case, the scientific contents address and enrich the knowledge belonging to the nucleus and the body of the considered theory. For example, such historical excurses could present the story of lever, Archimedes' law of buoyancy, Eratosthenes' measurement of the Earth’s radius, discoveries of microscope and telescope, Cavendish's "weighing the Earth"; the story of the Ohm's law and many others. The common in all these cases is that they present the knowledge proved to be correct by the following history of physics. We label such elements of knowledge as Type I knowledge.
II. In contrast, a historical excurse may address the knowledge elements, which were shown to be wrong by the following history of physics. We termed them contents of Type II knowledge. Of course, their selection is not arbitrary, it would be really too much. One should deliberately choose the contents, which contrast the central paradigms of the currently adopted theory considered, those that were its major rivals. Such were, for example, the principles of Aristotle’s mechanics, Pythagoras’ theory of vision, Impetus theory of the medieval physics, and Caloric theory of heat. They all can exemplify the strong debates followed their adoption and refutation. Each of them presents an alternative to the nucleus of the modern theory and challenges certain fundamental theory included in the current physics curriculum. As such, the elements of this type belong to the periphery knowledge of the theory.
Figure 5. Two types of knowledge and the areas of their affiliation within the discipline-culture structure of physical theory.
On the first glance, it might appear that using the knowledge elements of the first type is natural and of those of the second type – problematic. A more deliberate inspection, however, may essentially change this impression.
Indeed, although the Type I contents of historical excurses could be interesting and enriching the knowledge of the learners, conceptually, their contribution is not unique to study the discipline. This is because these materials could be, in principle, replaced with other materials that cover the same subject matter without historical reference. Of course, such teaching would lose the special attractiveness of historical narrative, demonstration of the social aspects of scientific knowledge and the illustrative power of displaying the features of scientific enterprise in the authentic social environment. The cultural literacy of the learners would suffer from such pedagogy. However, speaking pragmatically, as common with regard to science education, teaching without this type of materials is possible, and in fact, it is common on our days, being justified by lacking of time and the need of focus on the disciplinary contents. For example, one may teach about the lever, as well as all other simple machines, without any reference to the rich history of their use and the personalities of Archimedes, Heron, Cavendish and many others. Instead, one may use examples from the everyday life and technology, familiar to the student, as well as modern experiments. Therefore, one may state with warrant that using Type I historical knowledge is not essential for physics teaching.
Considering the elements of knowledge of the second type is more complex. Some science educators furiously deny the use of such claiming their misleading and confusing influence on the students whose perception of ideas is not sufficiently mature and their knowledge is vulnerable. Indeed, the materials based on the Type II knowledge "revive" the obsolete ideas in science, refuted, often with great efforts, and replaced with other theories, sometimes also refuted later in the later course of history. Why confuse the novice learners? Why mount on their way "artificial obstacles", which once served as “barriers to the progress” of science? There is a good answer to this worry, and in fact, more than one. Here are they:
1. Controversy of the scientific knowledge, which is demonstrated by the elements of periphery, presents one of the major features of the conceptual ecology in which the scientific knowledge emerges. It is the existence of controversy that clearly distinguishes the scientific knowledge from other types of knowledge learning of which is often based on indoctrination. Introducing elements of historical debate into the process of teaching, converts learning into inquiry, creates in the learner an adequate image of science and the scientific enterprise. Multiple ideas regarding certain subject testify for the competition between the different conceptions prior to adoption of the current way of understanding. This feature provides scientific knowledge with a special reliability and maturity.
2. It is the conceptual debate that makes science especially attractive to many learners of science. Certain part of young people are motivated to learn science just because they see in it a living body of human knowledge engaged in self correction, basing on reasoning, a fair play of ideas, a "play" in which they can participate not as passive observers and absorbers, but as those who may join the endeavour of inquiry as practitioners who may take a side, argue on the ideas. For this type of learners the periphery knowledge is of more interest than other contents of science curriculum, they find “dry” and boring. Keeping with strict disciplinary presentation we often lose this type of students.
3. As was mentioned by many not once (e.g., Monk & Osborne, 1997; Galili & Hazan, 2000), the similarity between the obsolete conceptions in science and naïve conceptions of students may be used in a remedial strategy of discussing certain idea from the past in order to refute it and thus cause the required conceptual change, or at least, a cognitive resonance in the learner. Candidates for such remedial discussions are recruited from the periphery knowledge. In the following we will illustrate this idea by specific examples of the units we have developed.
4. In fact, certain elements of obsolete scientific knowledge essentially surpass a mere remedy role. Those are the old conceptions which challenge the nucleus of the contemporary theory. Such are, for example, the conceptions of motion by Aristotle and Buridan. The claim is that these conceptions from the periphery may establish a reasonable conceptual variation to the considered element to be learned and by this create a space of learning, necessary for humans’ effective learning (Marton et al., 2004). The way people learn is fundamentally different from loading new information; such process presumes a space of ideas in which human cognition construct knowledge through permanent comparison between plausible possibilities. This way people provide their new knowledge with meaning, make sense of it. This happens whether or not the teacher provides candidates for this process from the history of science. Explicit inclusion of the historical rivals into teaching facilitates this process in the most relevant direction.
All these make the use of certain elements of Type II kind essential for science teaching. They establish importance of the periphery knowledge of the considered theory. This understanding has brought us to the major inference regarding the goals in science education: the requirement to facilitate Cultural Content Knowledge (CCK). One may define CCK as the disciplinary knowledge upgraded by its periphery.
CCK is related not only to education. It is valuable for science researchers, historians and philosophers of science. However, in those areas CCK is not new and was always respected as an important feature of knowledge. It is developed by training and/or through continuous, years-long practice, personal influence of a master and individual learning. However, it is with regard to science education that CCK is often neglected and underestimated. The evidence for that is that teacher training programs normally do not include courses in the HPS. Our study suggests the necessary change of this erroneous practice.
One can relate the CCK to another paradigmatic concept of science education – the Pedagogical Content Knowledge (PCK – Shulman, 1986). One can visualize the impact of CCK reinforcing and expanding the PCK (Fig. 6), providing the latter with new hitherto not used possibilities significant for education.
Figure 6. Symbolic presentation of the impact of CCK on the PCK: CCK increases PCK.
Implication to development of teaching materials
We have described our vision mainly with regard to the disciplinary contents of the historical materials. By all means, there are other aspects important within the holistic scope of educational validity, to name a few: social, instrumental, moral, and other human dimensions. In the following, we illustrate the above presented rationale by addressing several from the historical modules we have comprised within the HIPST project.
Excurse 1. Understanding Classical Mechanics: A Dialogue with Cartesian Theory of Motion
In this historical excurse we visit mechanics just prior to the Newtonian theory of motion. We address the laws of motion suggested by Descartes in his Principles of Philosophy (1644) thoroughly studied by a young student of Cambridge, whose name was Newton, and who later, years ago, disputed with the great philosopher and provided a different worldview in his Mathematical Principles of Natural Philosophy (1687) that became a cornerstone of the Classical Mechanics. The excurse presented Descartes laws and their implications – the rules that govern collisions between hard (elastic) objects. We elaborated the central revolutionary ideas of Descartes regarding motion: motion as a state, instead of motion as a process (in contrast to all previous physics), the law of inertia, the principle of conservation of the quantity of motion, the account of elastic collisions. All these were reconsidered and further developed by Newton.
We analysed in details each of the stated laws and rules by Descartes, and reveal the origin of the fact that his third law of motion and the rules of collisions (all except one) were wrong. This debate deals directly with the contents relevant to the modern curriculum of mechanics at high school. It is pedagogically important to see how the ideas of the quantity of motion as a scalar (instead of vector), essential distinguishing between motion and rest (violating relativity of motion in accordance with the Principle of Relativity of Galileo), violating of the symmetry of interaction between the colliding bodies (the third Newton’s law), leaving alone the argument “by God's nature” (unacceptable today), all brought the great mind of Descartes to the mistaken inferences regarding collisions.
Descartes saw the inadequacy of his statements and explained them by non ideal conditions that impede his claims – his laws, he thought, were valid in the ideal world. Yet, he was wrong, his physics was incorrect, not the conditions. To show this fact (besides our critique provided in parallel to the presented fragments of his Principles), we proceeded to follow the history that included refutation of Descartes’ rules of collision, first empirically, by John Wallis and Christopher Wren, and after then, theoretically, by Christian Huygens, through his ingenious application of Galileo's principle of relativity. We showed the pioneer work of Huygens who involved thought experiment dealing with two observers who account for elastic collision of two balls (e.g., Mach, 1893/1989). Besides the conservation of momentum as vector quantity, Huygens succeeded to deduce the conservation of kinetic energy (vis viva) taking place in elastic collisions, much before these results became a part of a solid formalism in physics.
Not less important inferences were available in this excurse with regard to the nature of scientific method. The students will have a chance to follow the great mind of Descartes who applied the method of rational metaphysical reasoning to physics. Importantly, his results were refuted first by the empirical method of experiments with controlled variables, and then, by providing theoretical account of collisions by Huygens. An authentic picture of the scientific method – as a continuous spiral combining theoretical-empirical and deductive-inductive treatment, instead of the linear logical sequence applied by Descartes, were suggested for discussion in physics class.
Albeit refuted, many claims of Descartes remained important as illustrating the genuine debate in science. Students receive a chance to observe the consolidation of conceptual fundamentals of the classical mechanics and grasp its principles belonging to the nucleus of this fundamental theory. The conceptual learning to be reached here is due to the Type II elements of knowledge from the periphery of mechanics.
Excurse 2. The Pre-Newtonian Theory of Motion: the Theory of Impetus
The theory of impetus was a great success of the medieval science in the progress of physical science from the time of Aristotle. It was in the debate with impetus that the concepts of modern mechanics were developed by Galileo, Descartes and Newton. It is often that this theory in particular, as well as other great accomplishments of the mediaeval science of mechanics, in general, are neglected in modern education. The considered excurse tries to correct this shortcoming. It presents and discusses the development of the central paradigm of mechanics – the account of motion (the nucleus of mechanics). Impetus – the "charge of motion" – replaced the external mover, as required by Aristotle to support the violent motion, with the internal change of the body causing it to leave the state of rest. Natural motion (free falling) was considered by the scholars in terms of appearance and growth of impetus from the support previously prevented falling. Impetus was a direct predecessor of the modern concept of momentum. The excurse includes both the triumph of impetus over the Aristotelian paradigm, at the time of Buridan, Oreseme and other medieval scholars, as well as the following refutation through recognition of “indifference” of the body to the uniform linear motion established by Galileo.
The conceptual content of this excurse should resonate with the deeply rooted misconceptions of force-motion relationship ("motion implies force") numerously reported in the research on students' knowledge of mechanics (e.g., McCloskey, 1983b; Halloun & Hestenes, 1985; Galili & Bar, 1992). In light of these empirical results, one may realize the high relevance of overcoming the concept of impetus for the meaningful learning of classical mechanics. In fact rejection of impetus idea is prerequisite of understanding the rest-motion equivalence as the claim of the nucleus of classical mechanics which leads to the principle of relativity of Galileo. This important goal may be easily missed if students do not spend some time in the debate with the competitive concept of impetus in their study of mechanics.
Excurse 3. The Story of Optical Image
This excurse illustrates the ontological progress in physics with regard to understanding the concepts of optical image and light ray. It reconstructed the development of physical ideas from several Hellenic theories (Pythagorean active vision, Atomists' eidola theory of passive vision, Plato's hybrid understanding, Aristotle's theory of image transfer through the tension in the medium between the object and observer’s eye), to the Hellenistic theory of Euclidean rays of vision, and the medieval theory of Alhazen (11th c), and eventually to the theory of Kepler (17th c), currently taught in physics classes within the Geometrical Optics (e.g., Lindberg 1976). In parallel, the history of light ray was described following the evolution of ray from being the central concept in theories of light and vision (in the Hellenistic and Medieval physics) to a merely auxiliary formal concept in Newtonian optics and the wave theory of Huygens.
Addressing these contents proved to be potent for remedy of a big cluster of students' misconceptions revealed in students' knowledge as it resulted the common instruction. The latter often neglects deliberate elaboration of the concepts of image and ray. The elicited schemes of knowledge developed by students with regard to light and vision showed similarity to the conceptions of scientists in the past – Type II knowledge of optics. This similarity suggests addressing such theories as holistic image transfer (Atomists) and mapping of the object by means of single rays to its image (Alhazen) for remedial influence on students' misconceptions (Galili & Hazan, 2000). We also observed the positive impact of these historical materials on students' views on the nature of science (Galili & Hazan, 2001b).
Excurse 4. The Story of Weight and Gravitational force – marriage and divorce.
The widespread myth of teaching physics "without philosophy" can be tackled by the excurse in the history of the weight concept. Here, the essential requirement of the operational definition for physical concepts by the constructivist epistemology next to the theoretical definition of those concepts (e.g. Margenau, 1950) may bring to realizing the need of change in the way one teaches the concept of weight. At the same time, the introduction of the operational definition of weight matches the efforts of educational constructivism to treat the common confusion of students regarding weight and gravitational force.
Displaying the history of physics may be elucidative. The excurse follows from the pre-Newtonian holistic understanding of weight as the heaviness of objects and the cause of falling to the Newtonian treatment which split between weight-gravitation and inertial mass. He defined weight as the gravitational force (theoretical definition). Further development of physics in brought further split, this time – between the gravitational force and weight. The latter split drew on the operational definition of weight as the result of weighing and the correspondent theoretical definition as the force exerted by the body on it support (Galili, 2001). The split between gravitation and weight followed the adoption by physics the principle of equivalence of Einstein (Fig. 7).
Figure 7. Conceptual evolution of the weight related concepts in physics history.
All together this conceptual history looks as removing the conceptual degeneracy as following the progress in physics.
By revealing and discussing the historical development of these fundamental concepts the excurse can provide remedy to various schemes of students’ knowledge (misconceptions) in the middle and high schools (e.g. Galili and Kaplan, 1996, Stein et al., 2009). The special benefit of this excurse, however, is bringing to the fore the operational constraint of the modern physics, and this way prepare further learning of the relativistic and quantum mechanics. This process leads to mature views of explaining the reliability of the scientific knowledge which is greater than it was in the past, just because it is based on the modern epistemology. Being non trivial this knowledge is easier to construct through comparison with the historical alternatives, that is by addressing the previous understanding of the same (the periphery).
Conclusions and Implications
We have presented the approach to teaching science aimed at construction of the Cultural Content Knowledge and argued for its importance for the meaningful learning of physics and the quality of constructed knowledge. We have elaborated why and how the history and philosophy of science may play essential role in the educational process seeking genuine understanding of the scientific contents, their hierarchical structure and scientific epistemology. This approach may guide the production of new teaching materials for a culturally rich curriculum. For that, we need deliberate selection of historical materials which reveal the fundamental steps in the conceptual pass to the scientific concepts as we know them now. This implies the need to present Type II knowledge elements, while emphasizing the debate regarding the conceptions to be developed by students.
The discipline-culture approach helps to organize knowledge by introducing the conceptual hierarchy to the curriculum and thus providing the “big picture” of physics knowledge which is equally needed by those who will proceed to practice physics knowledge and by those who seek general literacy in science. The impact of the historical excurses with regard to the central concepts, to be checked by research, should be the transfer of the structure of students' knowledge from the knowledge in pieces (diSessa, 1993), or scheme-facets clusters (Galili & Hazan, 2000), to the structure corresponding to the cultural knowledge of science: nucleus-body-periphery.
The HPS based learning materials by their nature may significantly improve students' image of scientific knowledge and their views on the scientific method (epistemology). They will help to create the authentic image of science and scientific knowledge as objective and accumulated in the process of collective intellectual effort of people through revealing the diachronic and synchronic scientific discourse. This understanding may help to remove competitive ideas traditionally placing doubt on the objective and cumulative nature of science.
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This article is based on a paper presented at the European Science Education Research Association 2009 Conference, Istanbul, Turkey.
 We base on our experience.