Heinrich Hertz
Hertz observes wireless electromagnetic propagation in Karlsruhe
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Original prompt & settings (JSON) ↗A spark too small to see in normal light crossed a hairline gap in a wire ring metres away — and even the anniversary is unsettled: reputable accounts give three different November dates.
November 1886: a spark answers a spark
In November 1886, in a lecture hall of the Technische Hochschule at Karlsruhe, Heinrich Hertz discharged a spark-gap transmitter and watched a second, tiny spark appear at the same moment in a nearby slotted wire ring. Nothing connected the two.
It was early experimental evidence that an electromagnetic disturbance had crossed open space. The transmitter and receiver stood a few metres apart, in the main building on Kaiserstraße — not in a purpose-built laboratory.
Which November day?
The Karlsruhe Institute of Technology commemorates the event on 11 November, but other reputable accounts identify 1 or 13 November. The German Historical Museum and a scholarly IEEE chronology built from Hertz's memoirs, letters and diaries identify 13 November as the start of the relevant work, while an Oxford anecdotal history gives 1 November.
The exact day is therefore not secure.
The beginning of a program, not its proof
What Hertz had that November was a workable method for generating and detecting rapid electrical disturbances. Reading the receiver spark as a finished one-day proof of Maxwell's theory erases everything that followed.
The wave interpretation still required experimental testing, and the measurements were not tidy: his 1888 work initially produced a serious conflict with theory, including differing inferred velocities in wires and in air. His more conclusive demonstrations of finite propagation, standing waves, reflection and wave behaviour came in 1887–1888.
Sources
Researched 23 Aug 2026 6 sources 3 audit passes Date disputed
How this was checked
Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →
Date disputed. Sources disagree; the research places it at ~1886-11.
What the sources leave uncertain
- KIT commemorates 11 November 1886, but the German Historical Museum and a scholarly IEEE chronology based on Hertz’s memoirs, letters and diaries identify 13 November as the beginning of the relevant work. An Oxford anecdotal history instead gives 1 November. The exact day is therefore not secure.
- The label “verification of electromagnetic waves” compresses a research sequence. Historians of science commonly place Hertz’s decisive wave experiments in 1887–1888, even though the receiver-spark observation began the program in November 1886.