“I (critically) think, therefore I am”: Thomson’s atomic model and the ineffectiveness of physics education

INTRODUCTION In 1904, Thomson proposed an accurate atomic model (Thomson, 1904), with a precise geometrical structure, intended as a heuristic device and aimed to explain the stability and unity of atomic phenomena, both from a chemical and electrical point of view. Therefore, the plum pudding image - commonly used in textbooks (Walker, 2017; Amaldi, 2020; Halliday, 2021; Cutnell, 2022) and familiar to teachers and students, but never used by Thomson - is due to a deep conceptual misunderstanding or perhaps to a teasing of the model. A WIDESPREAD LACK OF CRITICAL THINKING In physics courses, Thomson’s model is presented after electrostatic issues and described as a spherical distribution of positive charge with electrons randomly arranged in it (as the plums in an alleged “plum pudding”); nevertheless, the awareness that such a configuration cannot be in stable conditions unexpectedly does not arise, showing a widespread failure in using electrostatic knowledge previously acquired in a different context. Moreover, it is known that accelerated charges emit and therefore a stable planetary model cannot be possible. Thomson's model - which supposes electrons in motion, to obtain stable configurations - clearly shows the inaccuracy of this absolute statement: the problem is not the emission, but rather its amount (since collisions can provide a way to regain small energy losses). It is therefore necessary to become aware that, without calculations, the merely qualitative aspects can be misleading. Students and teachers do not usually question themselves how a model proposed by a great physicist - as Thomson was, having won the Nobel Prize in 1906 - could only be an inconsistent qualitative pattern, rather than a rigorous mathematical structure, capable of both explaining phenomena and making predictions. This lack of critical thinking compromises the foundations of physics education, and asks for careful considerations about the real effectiveness of actual physics courses in schools and universities. In this work that we are presenting, we will deal with this theme, which is not an isolated case, since also in other situations (like while dealing with the photoelectric effect and the Compton effect) coherency problems at an elementary level appear, showing the inefficacy of physics education in creating the mental conceptual structures required to critically analyse what is usually taught and learned. REFERENCES Amaldi, U. (2020). Il nuovo Amaldi per i licei scientifici blu (Vol.3). Bologna: Zanichelli. Cutnell, J. D., Johnson, K. W., & Young, D. (2022). Physics: International Adaptation (12th ed.). Hoboken, NJ: Wiley. Halliday, D., & Resnick, R. (2021). Fundamentals of Physics (12th ed.). Hoboken, NJ: Wiley. Thomson, J. J. (1904) On the Structure of the Atom. Philosophical Magazine, 7(39), 237-265. Walker, J. S. (2017). Physics (5th ed.). Bellingham, WA: Western Washington University

“The elegance of quantum mechanics”: An at-distance proposal for secondary school students

INTRODUCTION: THE STATE OF THE ART AND OPEN PROBLEMS Quantum Mechanics has been the focus of physics education research since the 90s and, nowadays, researchers no longer express doubts on the fact that it is fundamental for the culture and the awareness of the individual citizen and of the whole society (Redish, 2000; Besson, 2017). From surveys on teacher training (Stefanel, 2008; Fera, 2011; Giliberti, 2014; Krijtenburg-Lewerissa, 2017), it emerged that most teachers - mainly with a degree in mathematics - often do not have a coherent framework of modern physics in general, and of quantum physics in particular. Furthermore, the didactic path presented in textbooks is limited to a pseudo-historical presentation, which provides a hyper-simplified explanation of the fundamental concepts, in an attempt to bypass the problems associated with students’ lack of adequate mathematical tools, leading to deep misconceptions. OUR COURSE: “THE ELEGANCE OF QUANTUM MECHANICS” In this presentation we describe the work of designing, testing, and evaluating the effectiveness of a course entitled, “The elegance of quantum mechanics”, presented in Academy Year 2021/22. The activity - done online - was offered to teachers and students of the last three years of high school (120 participants overall), from October 2021 to January 2022, through weekly appointments of one and a half hours each. Lessons were integrated with slides, questions with Kahoot! and graphic examples with GeoGebra (https://www.geogebra.org/m/aqf2dgn3). Course effectiveness was assessed by collecting and analyzing different types of data deriving from an anonymous satisfaction survey, 9 Google Forms (given after each of the first nine lessons, with a total of 38 open questions and 24 exercises; for example: https://forms.gle/Nr2umPc53FCCi3KZ9), and 19 individual interviews, aimed at investigating strengths and criticalities. This analysis allowed us to identify the reasoning that students commonly use in facing some conceptual issues of quantum mechanics. The following will be discussed: strengths of the activity, regarding the mathematical aspects, the use of GeoGebra and Kahoot!; criticalities, especially in dealing with spaces with more than 3 dimensions, with the concept of self-adjoint operator, and concerning the confusion between states and operators; materials (https://pls.fisica.unimi.it/materiali/). A new course, implemented with the improvements mentioned above, is expected to start in October 2022. REFERENCES Besson, U. (2017). Didattica della fisica. Rome: Carocci Editore. Fera, G., Challapalli, S. R., Michelini, M., Santi, L., Stefanel, A., & Vercellati, A. (2011). Formare gli insegnanti all’innovazione didattica e all’orientamento, Connessi! Scenari di Innovazione nella Formazione e nella Comunicazione, 411-420. Giliberti, M. (2014). Theories as Crucial Aspects in Quantum Physics Education. Frontiers of Fundamental Physics and Physics Education Research. Springer Proceedings in Physics, vol 145. Springer, Cham. https://doi.org/10.1007/978-3-319-00297-2_51 Krijtenburg-Lewerissa, K., Pol, H.J., Brinkman, A., & Van Joolingen, W. R. (2017). Insights into teaching quantum mechanics in secondary and lower undergraduate education. Physical Review Physics Education Research, 13(1). Redish, E. F. (2000). Who needs to learn physics in the 21st century and why? Plenary lecture, GIREP Conference 2000. Stefanel, A. (2008). Impostazioni e percorsi per l’insegnamento della meccanica quantistica nella scuola secondaria. Giornale di Fisica 49, 15-53

From the Earth to the Sun: the quest for the Astronomical Unit by means of the 1761 and 1769 Venus transits.

In the mid-eighteenth century, the primary and most urgent astronomical problem was to determine the exact value of the Earth-Sun distance (the so-called Astronomical Unit, A.U.). With that value in hand, thanks to Kepler’s third law, all the planet distances would have been easily derived and, as a consequence the entire solar system real dimension would have been determined too. The most promising methods for measuring the A.U., due to Halley and Delisle, were taking advantage of a rare phaenomenon: Venus transit over the Sun. It would have been sufficient that two observers, located in the two Earth hemispheres, had taken accurate measures of the transit to derive from the solar parallax and hence the A.U. The phaenomenon is rare but occurs always in close pairs and thus the attention of the whole scientific community was engaged twice in the eighteenth century: in 1761 and in 1769. While the European powers were fighting in the Seven Years War and in the subsequent struggles for colonial hegemony, 250 astronomers and scholars from different nations, animated by a common purpose in the spirit of Enlightenment, gave life to a joint venture, never attempted before, leaving for the farthest and most inaccessible locations of the known world, such as Siberia, the island of Newfoundland and the mysterious Australia, to observe Venus transit. Along with the astronomical results, those expeditions also improved geographical knowledges, discovered new lands, gave an impulse to the production of scientific instruments, resulted in collection of natural samples and, above all, constituted the first international and collaborative project in the whole history of science. At the crucial point, some astronomers faced a desolately cloudy sky, one passed out from his emotions, others had not even reached their destination, and someone never returned home. This is their story