Histories and Philosophies of Physics
- 10:30–11:00 Kristian Camilleri – The Fluctuating Fortunes of David Bohm's Theory
- 11:00–11:30 Sophie Ritson – Something from Nothing: 'Non-discovery' and Transformations in High Energy Experimental Physics at the Large Hadron Collider
- 11:30–12:00 Kevin Orrman-Rossiter – A tale of two particles: the discovery of neutral antiparticles
- 12:00–12:30 Anant Tanna – A new concept of why a mover experiences less time
University of Melbourne
The Fluctuating Fortunes of David Bohm’s Theory
The last three decades has witnessed a resurgence of interest in alternative interpretation of quantum mechanics. After a long period during which the ‘Copenhagen orthodoxy’ went virtually unchallenged, we now find a number of competing interpretations vying for ascendancy. Perhaps nowhere is this better illustrated than in the case of David Bohm’s hidden variables theory, which he first proposed in a now-famous two-part paper in 1952. After being ignored for the better part of three decades, it only began to attract renewed attention in the 1980s. Today the de Broglie-Bohm theory, as it is often called, enjoys widespread support, and remains an active area of ongoing research. In 1993, Peter Holland wrote the first textbook on the theory, which signified a major turning point. But how did this turn around in the fortunes of the Bohm’s theory come about? Who was responsible, what were their motivations, and what made the difference? Drawing on historical sources, private correspondence, and interviews with several of the key protagonists, this paper attempts to address these questions. I show that interest in the theory was reignited at Birkbeck College by new generation of younger PhD students and postdoctoral researchers, who made calculations with the theory using computer visualizations. Interestingly, Bohm, who was at Birkbeck at the time, played little role in this development, having largely abandoned his theory some twenty years earlier. This provides a fascinating case study in how a theory’s fortunes can depend crucially on wider intellectual, social and technological contexts.
Kristian Camilleri is a Senior Lecturer in History and Philosophy of Science Program in the School of Historical and Philosophical Studies, having taught there since 2007. After studying physics as an undergraduate at the University of Melbourne, but in his first year he discovered history and philosophy of science, and never looked back. After completing his Bachelor of Science, he completed a PhD in HPS at Melbourne University. Since then, Kristian has established himself as one of a leading scholar in the history and philosophy of modern physics, and has published extensively on the history of quantum mechanics. He has also written on the role of metaphors in science and the epistemology of thought experiments. Kristian coordinates and teaches a range of subjects at undergraduate level in the HPS program. He has also supervised several Masters and PhD theses. He is currently working on a book project with the working title, Quantum Mechanics and its Discontents: The Making of a Scientific Orthodoxy.
University of Melbourne
Something from Nothing: ‘Non-discovery’ and Transformations in High Energy Experimental Physics at the Large Hadron Collider
After a discovery claim is established, the world is reported to be different; by contrast, when something is lost which was never had, seemingly nothing has changed. This paper explores how the negative results at the Large Hadron Collider (LHC) are transforming the epistemic strategies of experimental particle physicists in the ATLAS and CMS experiments. Prior to the start of data collection, many in the high energy physics community strongly expected that evidence for supersymmetry would be observed at the LHC. I will show that whilst the negative results have not transformed the ontology of particle physics, the violated expectations have resulted in transformations in epistemic strategies away from targeted searches for evidence of supersymmetry (and other beyond standard model physics) to attempts to find evidence for “ugly” results and ‘unconceived alternatives’. Epistemic strategies that aim at ‘unconceived alternatives’ are apparent in the shift toward ‘model independent searches’ and standard model measurements, such as the attempts to measure the self-coupling of the Higgs boson. These attempts are in part motivated by the possibility that the measured result will disconfirm the value predicted by the standard model, thereby providing a path to unconceived and alternative new physics. The current situation in particle physics makes for an opportunity to examine the creativity of the highly collaborative experimental particle physics community, where the transformation in epistemic strategies indicates direct attempts to find evidence for ‘unconceived alternatives’, or for disconfirming and “ugly” experimental results, that could provide fundamentally novel concepts.
Dr Ritson’s research focuses on the epistemology of contemporary scientific practices, with an emphasis on changing modes of research, scientific methodology, and science and values. In examining contemporary practices, Ritson seeks to develop a deeper understanding of the changing conditions and contexts of knowledge in 21st century science. Ritson completed the first study of the string theory controversy and showed that the string theory controversy has novel aspects which highlight how contemporary science continues to evolve. Those novel aspects formed the subject of Ritson’s research and included: non-empirical methodologies and appraisal; a negotiation of the boundary between science and non-science where the dominant group is forced to defend its authority; and a potentially new form of peer review. Ritson has also examined novelty and creativity in high-energy experimental particle physics at the Large Hadron Collider (LHC) at CERN in Switzerland. Ritson recently introduced a notion of novelty as disruption and showed that the positive appraisal of disconfirmation and disruption, in the current epistemic context of high-energy physics, is based on forward looking assessments of future fertility. Ritson has also explored creativity as a condition for knowledge formation in massive collaborative experiments and the role of machine learning.
University of Melbourne
A tale of two particles: the discovery of neutral antiparticles
With the discovery of the positron and the antiproton in 1932 and 1955 respectively the concept of antiparticles was established as a particle of equal mass, opposite charge, and undergoing mutual annihilation with its normal matter equivalent. In this paper I explore how scientists associated this antiparticle concept to neutral particles – specifically the neutron and neutrino. Producing the antineutron in 1956 is shown to be more conceptually complex than the experiments resulting in the antiproton observation a year earlier. Observation of the antineutron at the Bevatron involved ‘charge exchange’ collisions – interactions where charge is transferred between nucleons and antinucleons. The annihilation of an antineutron was not observed until 1958. The identification of the antineutrino was a temporally extended ‘discovery’ event, beginning with speculative ideas from Pauli in 1930, and ‘concluding’ with the identification of free neutrinos in 1956 by Cowan and Reines. That these ‘neutrinos’, as well as the neutrino involved in the well-established nuclear process β-decay, to be identified as ‘antineutrinos’ required the introduction of new conservation laws, the conservation of lepton and hadron numbers. With these two ‘discoveries’ the concept of matter particles having antiparticle equivalents had undergone a considerable development. These discoveries, along with the associated positron and antiproton, highlight the genesis and development of the existence of scientific objects – antiparticles in this example – and necessary and sufficient conditions that qualified the discovery of these objects. While the conditions are the same; mass, opposite charge and annihilation with ordinary matter particles, their respective discoveries exhibit quite disparate events. I conclude by discussing whether these specific events support arguments for a discovery process, or merely allow for a taxonomy of discovery.
Kevin Orrman-Rossiter is a part-time PhD student in the School of Historical and Philosophical Studies at the University of Melbourne. His PhD is “A biography of the positron and its antimatter siblings” which in part stems from his original training and professional life as a physicist. Although always interested in the historical and philosophical underpinnings of science, Kevin enrolled in an undergraduate history and philosophy of science degree in 2014 because he also perceived that the public (and government) perception of science was shifting dramatically, and he wanted to have an informed perspective and participation in the debate. His background and interests result in a broad, some may say diffuse, interest in the history and philosophy of modern physics particularly: the concept of antimatter, the development of the space sciences and the Nobel prizes as a system of reward and recognition.
A new concept of why a mover experiences less time
Special relativity demonstrates that a faster relative mover records less time passing than a slower mover. However, both movers measure their own proper time. The desire to understand why less time elapses for a mover, while they perceive time “normally”, can be addressed with the idea that their time is not slower but that they (and their clock) experience less time occurring. The question is then: What mechanism occurs to allow the above? Such a mechanism is the same for any velocity, but at higher velocity occurs more and results in less time elapsing for the faster mover. Consider space to be comprised of quanta of space (“containers”). A system of particles (a clock) occupies a set of containers. Within a container a system can evolve, and hence experience time (the clock can tick). Moving in space requires particles to transfer from container to container. During the transfer process the system does not evolve, such that the information describing the system (the state of the clock) is preserved into the next container. Once in the subsequent container, the system can evolve/experience time. At higher velocities the system traverses containers in less time, undergoing the transfer process more often. A larger proportion of the faster mover’s existence is spent in the transfer process where the system does not evolve and time cannot be experienced. Consequently, the faster clock has less opportunity to evolve as a system than the slower clock, and measures less time passing. In the rest frame of either clock the observer experiences and measures their own proper time as they too are a system of particles that does not evolve during the transfer process.
Anant Tanna is a physicist and communicator currently developing an online ed-tech system for distance and in-classroom science education. His PhD is in astrophysics, a field in which he worked on supernova remnants, HDR radio imaging of peculiar AGN, and a large/deep survey for promordial neutral hydrogen at high redshift. His communication interests include astronomy and physics outreach in addition to teaching. In his spare time he enjoys music, travelling, and pondering the nature of space, time, the Universe and life.