Bob Gray
Bob Gray | |
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| Known for | Weber electrodynamics, unipolar induction, the "field approach" to Weber's force law |
| Scientific career | |
| Fields | Physics, Electrodynamics |
Bob Gray (also published as Robert W. Gray) is a researcher in classical electrodynamics who works on Weber's electrodynamics — the pre-Maxwellian, action-at-a-distance force law of Wilhelm Eduard Weber — and on its application to the long-standing puzzle of unipolar induction. He is associated with the John Chappell Natural Philosophy Society (CNPS), where he has presented his work in the society's online seminar series, and his research belongs to the small international community that treats Weber's force law as a live alternative to standard Maxwell–Lorentz field theory rather than as a historical curiosity.
Biography
Little biographical detail about Gray has been published. He is known within the CNPS and the wider Weber electrodynamics community through his written introductions to Weber's theory, published under the name Robert W. Gray, and through his December 2022 CNPS presentation on unipolar induction.
Scientific contributions
Weber electrodynamics and the "field approach"
Gray has written an introduction to Weber electrodynamics that sets out what he calls the field approach to the theory. In this treatment, all of Weber electrodynamics is derived from Weber's electrodynamic potential energy function for a system of two or more discrete charged bodies: Weber extended Coulomb's static force law into the dynamic regime by making the interaction depend on the relative radial velocity and relative radial acceleration of the two charges, rather than by introducing independent field entities.
The central philosophical claim of the field approach is that the Coulomb field is the only real, physical field. Any other "field" appearing in the equations — magnetic field, induced electric field — is on this view a mathematical bookkeeping function derived from the motion of charge, not an independently existing physical thing. Gray presents this position in a notation deliberately close to that of Maxwell electrodynamics, so that the two frameworks can be compared term by term, and he gives differential equations for Weber electrodynamics in that notation.
A distinctive feature of Gray's exposition is that he develops Weber's force equation through four successive levels of approximation, beginning with the most fundamental case of discrete charged bodies and working up through progressively coarser descriptions to the case of a conducting wire forming a closed current loop. This layered presentation makes visible where the familiar textbook results of Maxwell theory are recovered as limiting cases, and — more importantly for the dissident argument — where the two theories can be expected to disagree, since it is precisely in the discrete-charge and open-circuit regimes that Weber's law and Maxwell's are not equivalent.
Unipolar induction
Gray's CNPS talk addresses unipolar induction, the phenomenon in which a current is generated when a conductor and a magnet are in relative rotational motion. This is the effect behind the Faraday disc, or homopolar generator, and it has been argued about since Faraday's own time under the name Faraday's paradox: the puzzle of whether the magnetic field rotates with a spinning magnet, and of why rotating the magnet, the disc, or both gives the results it does. Because the standard flux rule gives ambiguous guidance in the rotational case, unipolar induction has long been a favoured test bed for critics of orthodox electrodynamics.
In his presentation Gray develops a mathematical model of a unipolar system with the aim of resolving the paradox and clearing up what he regards as persistent misconceptions about the effect. He goes further than a purely theoretical treatment by proposing a fundamental experiment intended to discriminate empirically between the predictions of Weber's theory, those of F. J. Müller's account of unipolar induction, and those of other competing models. The proposal of a decisive experiment is characteristic of the dissident programme in this area: rather than treating the question as settled by textbook authority, Gray argues that the rival formulations make different predictions and can therefore be separated in the laboratory.
CNPS talks
He has presented in the CNPS online seminar series:
- "Weber Electrodynamics and Unipolar Induction with Bob Gray" (4 December 2022) — developing a mathematical model for a unipolar system to resolve the paradox and clarify misconceptions, and proposing a fundamental experiment that can distinguish between Weber, Müller, and others.
Works
- Robert W. Gray, "An Introduction To Weber Electrodynamics, Part 1" (2019) — introduces the "field approach" to Weber electrodynamics, with comparisons to Maxwell electrodynamics.
- A Field Approach To Weber Electrodynamics: A Short Introduction (2019, ISBN 978-1-0859-4792-3). The Amazon listing for this title carries no named author, but its content corresponds to Gray's field-approach introduction.
External links
- Weber Electrodynamics and Unipolar Induction with Bob Gray — CNPS livestream, 4 December 2022
- An Introduction To Weber Electrodynamics, Part 1 on ResearchGate