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Invention

Radar

Also Known As Radio Detection and Ranging RADAR is itself an acronym; this is its own full expansion.
Electrical Engineering

Radar (radio detection and ranging) measures the distance, angle and velocity of a distant object by transmitting radio waves and timing the echo reflected back, giving an operator a way to detect aircraft, ships and weather beyond the range of human sight, in darkness, fog or cloud. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/

Facts
Patent or First-Use Date
1904-04-30 1
Filing date of the refiled application; an earlier application dated 21 November 1903 had been rejected. The German patent DE165546 itself was not granted/published until 21 November 1905, a year and a half after this filing, distinct from both this filing date and the 1935 Watson-Watt Daventry Experiment already recorded as this entity's year fact.
Significance
Radar gave the side that had it a decisive early-warning advantage: Britain's Chain Home radar network, built from the Daventry Experiment's success, is a documented factor in the Royal Air Force's ability to intercept incoming raids during the 1940 Battle of Britain. 2
Disputed
Year
1935 2
German engineer Christian Hulsmeyer patented a radio-echo ship-detection device as early as 1904, decades before radar became a working military technology, and Britain's 1935 Daventry Experiment was only one of several near-simultaneous, independently developed pulsed-radar programs in the 1930s, alongside parallel work in Germany, France, the United States and the Soviet Union; crediting any single nation or individual as radar's sole inventor understates how many independent teams reached a working system within a few years of each other.
Connections

Associated With

Aerospace Engineering, Fields
Electrical Engineering, Fields
Military Engineering, Fields

In Field

Electrical Engineering, Fields

Held Differently

Christian Hulsmeyer, Engineers

Why this is disputed. Hulsmeyer's 1904 telemobiloscope was demonstrated successfully in Cologne and in Rotterdam harbor and is the earliest working device that used radio echoes to detect distant objects, but shipping lines declined to adopt it commercially and he abandoned the work by 1905. The operational radar networks that later shaped naval and air warfare descend from Robert Watson-Watt's independent 1935 Daventry Experiment instead.

Source Christian Hulsmeyer (Wikipedia)Wikipedia contributors
Robert Watson-Watt, Engineers

Why this is disputed. Britain's Chain Home network, built from Watson-Watt's 1935 Daventry Experiment, is the direct ancestor of every operational radar system that followed, and popular history credits him as radar's inventor on that basis. German engineer Christian Hulsmeyer had already patented a working radio-echo detection device in 1904, three decades earlier, though his telemobiloscope never became an operational system.

Source Robert Watson-Watt (Wikipedia)Wikipedia contributors

Open Questions

Who should be credited as radar's inventor: Christian Hulsmeyer's 1904 patent, Robert Watson-Watt's 1935 Daventry Experiment, or one of the other near-simultaneous 1930s national radar programs in Germany, France, the United States or the Soviet Union?, Open Questions
Source Radar (Wikipedia)Wikipedia contributors
In the Other Atlases
  • Also in War and Military Atlas: Radar, the same subject.
Sources
1. Hulsmeyer Telemobiloscope Patent DE165546 (Google Patents)
Google Patents / Kaiserliches Patentamtbibliographic panel
Quote, bibliographic panel
Priority date 1904-04-30; Publication date 1905-11-21.
View the Source
2. Radar (Wikipedia)
Wikipedia contributors, Wikimedia FoundationLead section
Quote, Lead section
Radar is a system that uses radio waves to determine the distance (ranging), direction (azimuth and elevation angles), and radial velocity of objects relative to the site.
View the Source
Robert Watson-Watt (Wikipedia)
Wikipedia contributors, Wikimedia FoundationInvented By: Robert Watson-Watt, RADAR section
Quote, Invented By: Robert Watson-Watt, RADAR section
provided the vital advance information that helped the Royal Air Force in the Battle of Britain
View the Source
Christian Hulsmeyer (Wikipedia)
Wikipedia contributors, Wikimedia FoundationInvented By: Christian Hulsmeyer, The Telemobiloscope section
Quote, Invented By: Christian Hulsmeyer, The Telemobiloscope section
the principle of the inventor is correct
View the Source
Open Questions (1 open question)
Who should be credited as radar's inventor: Christian Hulsmeyer's 1904 patent, Robert Watson-Watt's 1935 Daventry Experiment, or one of the other near-simultaneous 1930s national radar programs in Germany, France, the United States or the Soviet Union?

At least five countries reached a working radio-echo detection system independently within a few decades of each other, so the question is which milestone, a working principle, a working military system, or an operational network, defines "invention."

What would resolve this A settled convention for what counts as the invention of a multi-national simultaneous-discovery technology, comparable to how the field already treats the telegraph and telephone priority disputes, would resolve this the same way.
History of technologyWikipedia contributors, Radar (Wikipedia)
Dissenting Readings (1 dissenting reading)
Year

British popular history generally credits Robert Watson-Watt and the 1935 Daventry Experiment as radar's invention, because it led directly to the operational Chain Home network. German historiography points to earlier work by Christian Hulsmeyer, whose 1904 Telemobiloscope patent used radio-wave reflection to detect ships and predates Watson-Watt by three decades, and to parallel 1930s pulsed-radar development at Germany's Gesellschaft fur Elektroakustische und Mechanische Apparate under Rudolf Kuhnhold. French, American and Soviet teams each also built independent working radar systems within a few years of Daventry. Framing radar as one nation's or one engineer's invention understates that it was arrived at independently, in roughly the same decade, by researchers in at least five countries working from the same underlying radio-reflection principle Hulsmeyer had already demonstrated.

A dissenting reading, from an independent laneWikipedia contributors, Radar (Wikipedia), Wikimedia Foundation
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