Experiment #48 · Scientific experiment

Hertz's Electromagnetic Waves

Maxwell's prediction realised in the laboratory

Heinrich Hertz · 1887 · Electromagnetism

First published: H. Hertz, "Über elektrodynamische Wellen im Luftraume und deren Reflexion", *Annalen der Physik* 270 (1888): 609–623.

A spark gap on one side of a Karlsruhe laboratory induces sparks in a tuned loop on the other. Maxwell's waves are real, and they travel at the speed of light.

Maxwell's 1865 equations had predicted that electromagnetic disturbances should propagate as waves at the speed of light. Hertz built a transmitter (a spark gap driven by an induction coil) and a receiver (a small loop with its own spark gap, tuned for resonance) and demonstrated that electromagnetic radiation: (i) is transmitted across empty space; (ii) exhibits reflection, refraction, polarisation, and standing-wave patterns; (iii) travels at the speed of light. The result confirmed Maxwell's unification of electricity, magnetism, and optics — light *is* an electromagnetic wave — and opened the era of radio, television, and wireless communication. Hertz's modest remark that the discovery was "of no use whatsoever" has become a standard cautionary tale.

Formulation

Spark-gap transmitter generates oscillating EM field; tuned receiver loop with secondary spark gap registers induced EMF when nearby. Measured wavelength × frequency = c. Verified: reflection from metal sheets, refraction by pitch prisms, polarisation by wire grids.

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Dimensions Engaged

✦

Space

Confirms Space · Ontological Status as a propagating medium for electromagnetic disturbance — the field is real, fills space, and supports wave propagation at finite speed.

⚡

Energy

Demonstrates Energy · Dispersibility through radiation: energy emitted at the source propagates outward and is absorbed elsewhere, with no material medium required.

⧖

Time

Confirms that electromagnetic effects propagate at finite speed (c), not instantaneously — a precursor to relativity's elevation of c to a fundamental constant.

Responses — How Schools Engage

Affirms / takes the bait 5

Naturalism

A canonical empirical confirmation: a precise theoretical prediction realised in the laboratory. Maxwell's unification of electromagnetism and optics becomes established physics.

Realism

Electromagnetic waves are real physical entities propagating through real space at a real speed. Scientific realism vindicated.

Structuralism

The unification of electricity, magnetism, and optics is a triumph of structural physics: distinct phenomena reveal a common underlying structure described by a single set of differential equations.

Logical Positivism

A model of hypothetico-deductive confirmation: Maxwell's equations predict waves at c; Hertz detects them at c. The empirical content of the theory is realised, the metaphysical glosses optional.

Process Philosophy

A wave is a pattern of change, not a thing; the experiment exemplifies the priority of process over substance in modern physics.

Reframes the question 1

Relationalism

EM waves propagate through what 19th-century physics called "aether"; Hertz's detection seemed to confirm a substantival medium. The Michelson–Morley null result and relativity later forced a relational reinterpretation.