UoB Benjamin Meaker Visiting Professor Tom Pashby, University of Chicago, USA

Tom Pashby profile picture

Geometry, Time and Knowledge in Physics 

4 June - 1 July 2018


Thomas Pashby’s interests are in the philosophy of physics, history and philosophy of science, metaphysics, and epistemology.  He is particularly interested in questions about the nature of time, matter and light in modern physics. His recent work focuses on the representation of time in quantum theory, the Dirac Equation of the electron, projective geometry, and Russell’s structural realism. His current research aims to answer the questions:  How did Dirac use geometrical reasoning to find his electron equation?  Can the historical challenge to scientific realism be overcome by understanding the special role that light plays in the epistemology of physics?  What roles do time and tense play in our understanding of quantum systems, and what does this teach us about quantum reality?

Pashby is an Assistant Professor of Philosophy at the University of Chicago, where he is also a core faculty member of the Stevanovich Institute on the Formation of Knowledge. Before that, he was a Provost’s Postdoctoral Scholar in the Humanities at the University of Southern California.  He earned his PhD in History and Philosophy of Science from the University of Pittsburgh in 2014, writing his dissertation “Time and the Foundations of Quantum Mechanics” under the supervision of John Earman and John Norton.  He is pleased to return to the University of Bristol, where he completed an MSci in Physics and Philosophy in 2005.


This project addresses a crucial question in the philosophy of science: How do we arrive at physical knowledge? The approach taken here looks to the way that light mediates our knowledge of the physical world, and the way that geometry provides our understanding of light and visual experience, and—in relativity theory—time.  Beginning with Euclid, geometry played a unique role in providing a mathematical understanding of light; with the advent of relativity theory, the geometry of lightrays came to play an essential role in our understanding of space and time. We can trace the origins of this novel geometrical understanding of spacetime in terms of light back to the foundational role played by projective geometry in nineteenth century investigations of non-Euclidean geometries.  Knowledge of projective geometry, though relatively rare today, provided formative mathematical experiences for two very different British academics interested in physics: Bertrand Russell and Paul Dirac.  Giving an account of the role of geometrical understanding in the work of these two figures provides a basis for answers to key questions in recent philosophy of science: How can we be realists about physics in the face of repeated radical transformations of physical theory? What do we know when we know physical structure? What roles do physical and geometrical understanding play in the discovery of new physics?  How can the local nature of temporal passage in relativity theory be made consistent with the non-locality of quantum physics? 

During his stay in Bristol Dr Pashby will be hosted by Professor James Ladyman (Philosophy) and will be giving the following lectures/seminars:

Time in Quantum Physics
21 June 2018, 11.00 AM - 5.00 PM
Verdon Smith Room, Royal Fort House

This Research Workshop will bring together the Bristol philosophy and foundations of physics community as well as members of the UK philosophy of physics community. Talks will include Bristol staff in Physics and Philosophy as well as Pashby.  This topic, a major research interest of his, fits closely with active interests of Popescu and Short in the Physics dept., as well as Thébault.

How Dirac Found His Electron Equation
28 June 2018, 5pm,  Mott Lecture Theatre, Physics

This public lecture, open to all, celebrates the occasion of the 90th anniversary of the Dirac Equation. Paul A. M. Dirac (1902-1984) was a Nobel prize-winning physicist and a University of Bristol alumnus as well as a Bristol native, born and bred. Like Isaac Newton, Dirac was the Lucasian Professor of Mathematics at the University of Cambridge, but his education up to the master’s level took place within yards of the physics department at Bristol. Dirac was the first physicist since Michael Faraday to be memorialised within Westminster Abbey; the Dirac Equation is the only equation to appear within its hallowed walls.

Followed by a drinks reception.

Shedding Light on Structural Continuity
Details to be confirmed.

This Master-Class will be led by Dr Pashby. It will take the form of a graduate student seminar for MSci/MA students in Philosophy of Physics and Science. There are currently 10-12 students who could be expected to attend. The master-class will be an opportunity for Bristol students to be exposed to an internationally renowned scholar with unique expertise. It is also expected that students from other UK institutions will be interested in attending.