Heinrich Hertz Created 2026-10-14 Updated 2026-11-05
Heinrich Hertz made electromagnetic waves experimentally accessible using electrical oscillators and a receiving loop with a small spark gap. The receiver's sparks supplied a local readout whose dependence on orientation, position and reflecting surfaces could be investigated. The resulting interference and polarization tests connected the apparatus with a wave description of the field. His collected papers also discuss limitations of early propagation measurements and specify the geometry and controls used to interpret the observations.[ref]
Electric Waves: Being Researches on the Propagation of Electric Action with Finite Velocity through Space by Heinrich Hertz. 1893 collected translation, Introduction pp. 9–12; papers VII–VIII, pp. 107–109 and 125–127
Homepage: www.dhm.de/lemo/biografie/heinrich-hertz
Portrait of Heinrich Hertz
. Photograph identified on the portrait record. Source.
In his 1888 reflection experiments, Heinrich Hertz excited a straight conductor with a central spark gap driven by an induction coil. The receiver was a wire circle of radius with an adjustable small spark gap; tiny sparks were observed in darkness. There was no connecting transmission wire. [ref]
Electric Waves: Being Researches on the Propagation of Electric Action with Finite Velocity through Space by Heinrich Hertz. Hertz, Electric Waves (1893 translation), VII, pp. 108–109; VIII, pp. 125–127
He removed hanging metal fixtures, installed a by zinc reflecting sheet, and moved and rotated the receiver. Spark strength alternated with position and gap orientation, supporting specular reflection and wave interference. He checked observations from farther away because the observer's body perturbed the response. Changing oscillator dimensions changed the spatial pattern. [ref]
Electric Waves: Being Researches on the Propagation of Electric Action with Finite Velocity through Space by Heinrich Hertz. Hertz, Electric Waves, VIII, pp. 125–127 and 135–136: preparations and controls
These tests supported propagating electromagnetic waves, rather than mere detection of nearby induction. They did not establish unlimited reception distance. His wire-versus-air wave interference experiment addressed finite velocity; he later judged its quantitative velocity comparison doubtful because of room effects. [ref]
Electric Waves: Being Researches on the Propagation of Electric Action with Finite Velocity through Space by Heinrich Hertz. Hertz, Electric Waves, VII, pp. 107–108; Introduction, pp. 9–12: retrospective limitations
The physical inference combines transmission with a spatially structured response to a reflected disturbance. In an ideal monochromatic incident-and-reflected model, standing wave nodes are separated by ; combining a reliable wavelength with independently known frequency gives phase velocity . A spark is a threshold event, however: its presence or length is not a calibrated wave intensity or a direct arrival-time measurement. The actual loop also responds to its orientation and finite size, so the simple standing-wave model is an explanation of the test's logic, rather than a reconstruction of Hertz's measured points. Poynting theorem explains how source energy can reach and drive the receiver's discharge.