Wilhelm Eduard Weber
Wilhelm Eduard Weber | |
|---|---|
 | |
| Born | October 24, 1804 Wittenberg, Saxony |
| Died | June 23, 1891 Göttingen, Germany |
| Residence | Göttingen, Germany |
| Nationality | German |
| Known for | Weber electrodynamics, the Weber force law, the absolute system of electrical units, the first electromagnetic telegraph (with Gauss) |
| Scientific career | |
| Fields | Physics, Electrodynamics, geomagnetism |
| Institutions | University of Halle, University of Göttingen, University of Leipzig |
Wilhelm Eduard Weber (1804–1891) was a German physicist who, working closely with Carl Friedrich Gauss at Göttingen, created the absolute system of electrical and magnetic measurement and built the first practical electromagnetic telegraph. He is remembered on this wiki above all for Weber electrodynamics: the fundamental force law of 1846 in which the force between two electric charges depends not only on their separation but on their relative radial velocity and relative radial acceleration. Weber's law is an action-at-a-distance theory that satisfies Newton's third law exactly and requires no independently existing electromagnetic field, and it remains a live research programme among dissident physicists who regard the Maxwell–Lorentz field picture, and the relativity built upon it, as a wrong turn taken before Weber's approach had been properly tested.
Biography
Weber was born in Wittenberg on 24 October 1804, the second of three scientifically gifted brothers; his father Michael Weber was professor of theology at the university there. When the Wittenberg university was dissolved the family moved to Halle, where Wilhelm studied natural philosophy and took his doctorate under Johann Salomo Christoph Schweigger, the inventor of the galvanometer. With his elder brother, the anatomist and physiologist Ernst Heinrich Weber, and his younger brother Eduard Weber, he published work on wave motion and on the mechanics of walking — collaborations that gave him an unusually strong grounding in precision experiment.
In 1831, at the age of twenty-seven and on the personal recommendation of Gauss, Weber was called to the chair of physics at the University of Göttingen. The partnership with Gauss that followed was one of the most productive in nineteenth-century physical science. Together they founded the Magnetischer Verein (Magnetic Union), an international network of observatories making simultaneous, standardised measurements of the Earth's magnetic field; the results appeared in the Resultate aus den Beobachtungen des magnetischen Vereins and in the Atlas des Erdmagnetismus (1840). Out of this work came the decisive methodological innovation of reducing magnetic and, later, electrical quantities to absolute measure — to the mechanical units of length, mass and time — instead of to arbitrary laboratory standards. Modern electrical metrology descends directly from this programme.
In 1833 Gauss and Weber strung a wire some 1,200 metres long over the rooftops of Göttingen, connecting the astronomical observatory with the physics institute, and used induction pulses read on a mirror galvanometer to send coded messages at a few letters per minute. This was the first working electromagnetic telegraph, built years before the commercial systems of Cooke, Wheatstone and Morse.
Weber's Göttingen career was interrupted by politics. In 1837 the new King Ernest Augustus of Hanover revoked the constitution, and Weber was one of seven professors — the Göttingen Seven, who also included the brothers Jacob and Wilhelm Grimm — who signed a public protest. All seven were dismissed in December 1837; three were expelled from the kingdom outright. Weber remained in Göttingen for some years without a post, continuing his research, then held a chair at Leipzig from 1843 until 1849, when the political climate changed and he was reinstated at Göttingen. He served there as director of the astronomical observatory and continued working into old age. He never married, was awarded the Copley Medal in 1859, and died in Göttingen on 23 June 1891. The SI unit of magnetic flux, the weber (Wb), is named after him.
Weber electrodynamics and the Weber force law
The force law
In 1846, in Elektrodynamische Maassbestimmungen über ein allgemeines Grundgesetz der elektrischen Wirkung ("Electrodynamic measurements concerning a general law of electrical action"), Weber proposed a single fundamental law from which electrostatics, Ampère's law of the force between current elements, and Faraday's law of induction could all be derived. His law extends Coulomb's law by making the interaction depend on the motion of the two charges relative to each other:
- F = (q1q2 / r2) [ 1 − (1/2c2)(dr/dt)2 + (r/c2)(d2r/dt2) ]
where r is the instantaneous distance between the charges, dr/dt is the rate at which that distance is changing, and d2r/dt2 is its second derivative. (Weber himself wrote the law with a constant he called c that was defined differently from the modern one; in his notation the bracket read 1 − ṙ2/c2 + 2rr̈/c2, with Weber's c equal to √2 times the speed of light. The two forms are the same physics.)
The law derives from a velocity-dependent potential energy,
- U = (q1q2 / r) [ 1 − (1/2c2)(dr/dt)2 ],
so that energy is conserved. Several features of this construction are what make it attractive to critics of the standard theory:
- It is completely relational. Only the distance between the two charges and its time derivatives appear. No reference frame, no absolute velocity, and no "velocity with respect to the ether" enters anywhere. In this sense Weber's electrodynamics was relativistic in Mach's sense half a century before Einstein, and without any of the kinematic apparatus of special relativity.
- It obeys Newton's third law in the strong form. The force is directed along the line joining the charges and is equal and opposite. Momentum and angular momentum are conserved between the particles themselves, with no need to attribute momentum to a field.
- There is no independent field. Interaction is instantaneous action at a distance. What orthodox theory calls the magnetic field is, on this view, a bookkeeping device summarising the effect of charge motion rather than a physically existing entity.
The constant c and the 1855 measurement
The constant appearing in Weber's law is not put in by hand: it is measurable. In 1855 Weber and Rudolf Kohlrausch determined it by discharging a Leyden jar and comparing the charge measured electrostatically with the same charge measured by its electrodynamic effect. The ratio of the two units of charge came out at approximately 4.39 × 108 m/s — that is, √2 times the independently measured speed of light. Weber interpreted the quantity physically, as the relative velocity at which the velocity-dependent term cancels the electrostatic term. The result was seized upon by Kirchhoff, who in 1857 used it to show that signals travel along a wire at light speed, and later by Maxwell, whose famous inference that light is an electromagnetic wave rests on the Weber–Kohlrausch number. This experiment is discussed on this wiki in The 1855 Weber-Kohlrausch Experiment (The Speed of Light), and the interpretation of the constant in The Meaning of the Constant c in Weber's Electrodynamics by Andre K T Assis.
Weber's planetary atom
A consequence of the force law that Weber himself explored in the 1870s is that at very small separations the acceleration-dependent term reverses the sign of the effective inertia, so that two like charges brought close enough together attract rather than repel. Weber used this to argue for a stable structure of positive and negative particles bound at short range — a planetary model of the atom, complete with a mechanism for nuclear binding, decades before Rutherford and Bohr. Assis has treated this material on this wiki in Webers Planetary Model of the Atom.
Eclipse by Maxwell
Weber's programme was mainstream in continental Europe through the 1850s and 1860s and was taken seriously by Maxwell, who devoted respectful pages of the Treatise to it. It was displaced rather than refuted. Helmholtz's objections concerning energy conservation in certain configurations, the rise of field theory in Britain, and finally the adoption of special relativity left Weber's law an unfashionable subject, and by the twentieth century most textbooks mentioned it, if at all, as a curiosity. Dissident researchers argue that this abandonment was premature: the regimes in which Weber's law and Maxwell's theory actually disagree — open circuits, discrete charges in rapid relative motion, longitudinal forces in conductors, and rotational induction — are precisely the regimes that were never decisively tested.
Modern reception among dissident researchers
Weber electrodynamics has been revived since the 1980s as a serious alternative to Maxwell–Lorentz theory, and this wiki holds a substantial body of work on it.
Paul Wesley developed what is usually called Weber–Wesley electrodynamics, extending Weber's law to cover radiation. In Evidence For Weber-Wesley Electrodynamics (1989) he argues that the theory reproduces all the standard results of Maxwell theory, including electromagnetic radiation, while also predicting a list of effects where he holds the Maxwell theory to fail or not to apply: the force on Ampère's bridge as measured by Moyssides and Pappas, the tension that ruptures current-carrying wires observed by Graneau, the propulsion of the Graneau–Hering submarine and of Hering's mercury pump, the zero self-torque found by Pappas and Vaughan on a Z-shaped antenna, the localised unipolar induction observed by Kennard and Müller, Kaufmann's measurement of e/m without mass change with velocity, a non-radiating hydrogen atom, and the fine-structure splitting of hydrogen levels without relativistic mass increase. Wesley's conclusion — that there is no evidence requiring mass to change with velocity — is a direct challenge to the relativistic orthodoxy. His Weber Electrodynamics with Fields, Waves, and Absolute Space (1987) develops the framework further.
Bob Gray (Robert W. Gray) works on what he calls the field approach to Weber electrodynamics, deriving the whole theory from Weber's potential energy function for systems of discrete charges and presenting it in a notation deliberately close to Maxwell's so that the two can be compared term by term. His central claim is that the Coulomb field is the only physically real field. Gray's particular concern is unipolar induction and Faraday's paradox — the long-disputed question of what happens when a magnet and a conductor are in relative rotation, where the flux rule gives ambiguous guidance. In his December 2022 CNPS presentation he built a mathematical model of a unipolar system intended to resolve the paradox, and went further by proposing a fundamental experiment capable of discriminating experimentally between the predictions of Weber's theory, of F. J. Müller's account, and of rival models. The insistence that the question be settled in the laboratory rather than by textbook authority is characteristic of the dissident approach to this subject.
Andre K T Assis has been the most systematic modern advocate, translating Weber's papers into English and applying the force law well beyond electromagnetism. On this wiki his work appears in Modern Experiments Related to Weber's Electrodynamics (1989), Unipoplar Induction and Weber's Electrodynamics (1994, with Dario S Thober), The Electric Force of a Current: Weber and the Surface Charges of Resistive Conductors Carrying Steady Currents, and Inertial Mass in Mach-Weber-Assis Theory. Assis's Relational Mechanics takes a gravitational analogue of Weber's law and shows that it yields an implementation of Mach's principle in which inertia is produced by the interaction of a body with the distant matter of the universe — see Relational Mechanics and Implementation of Mach's Principle with Weber's Gravitational Force. On this account inertial mass is not intrinsic but relational, which removes the need for absolute space at the root of Newtonian mechanics and offers an alternative to the relativistic account of mass.
Thomas E Phipps proposed a modernised Weber law incorporating a limiting relative speed, recovering Weber's 1846 form as the low-speed limit; see Derivation of a Modernized Weber Force Law (1992) and Toward Modernization of Weber's Force Law. Other treatments on this wiki include Weber-type Laws of Action-at-a-Distance in Modern Physics, Weber Electrodynamics Extended to Include Radiation, Weber's Equation and the Scalar Potential, Induced EMF by Weber's Force, Virial Theorem for Weber's Law, Weber-Ritz & Faraday-Maxwell Formulae: Induction Experiment Test, and Inertial Mass: a Changing Entity? Weber vs. Einstein, Weber Plus Einstein or None?. Laurence Hecht has examined the historical record of the collaboration in The Significance of the 1845 Gauss-Weber Correspondence.
Discussed in CNPS talks
Weber's electrodynamics has been the subject of presentations in the CNPS online seminar series:
- "Weber Electrodynamics and Unipolar Induction with Bob Gray" (4 December 2022) — Bob Gray develops a mathematical model for a unipolar system to resolve Faraday's paradox and clarify misconceptions, and proposes a fundamental experiment that can distinguish between Weber, Müller, and others.
Abstracts
- 1846 - "Determinations of Electrodynamic Measure: Concerning a Universal Law of Electrical Action" (Read in full)
Works
- Wellenlehre auf Experimente gegründet (with Ernst Heinrich Weber, 1825) — a treatise on wave motion.
- Resultate aus den Beobachtungen des magnetischen Vereins (with Carl Friedrich Gauss, 1836–1841).
- Atlas des Erdmagnetismus (with Carl Friedrich Gauss, 1840).
- Elektrodynamische Maassbestimmungen über ein allgemeines Grundgesetz der elektrischen Wirkung (1846) — the fundamental force law.
- Über die Einführung absoluter elektrischer Maasse and the later Elektrodynamische Maassbestimmungen series (1852–1878).
- Wilhelm Webers Werke, 6 vols. (Berlin, 1892–1894) — collected works.
External links
- Wilhelm Eduard Weber on Wikipedia
- Andre Koch Torres Assis's page — English translations of Weber's papers and books on Weber electrodynamics
- Wilhelm Eduard Weber at Encyclopædia Britannica