Year of Invention: 1916
What Is It? A system that uses sound waves transmitted through the water to
detect underwater objects.
Who Invented It? Paul Langevin (in Portsmouth, England)
Sonar saved hundreds of ships and tens of thousands of lives from attacks by German submarines during World War I and many times that number during World War II. After the wars, active sonar systems made long-range submarine navigation possible. Sonar has made ocean transportation safe and has provided a way for fishing fleets to actively seek out and find schools of fish to catch.
Whales have used active sonar for tens of millions of years to guide their underwater path. They broadcast sprays of low-frequency sound waves and read the returning echoes to create a mental image of the water in front of them.
As World War I started, German submarine fleets prowled the North Atlantic like packs of wolves preying on British and French shipping. Surface ships couldn’t spot the subs until it was too late.
Sonar was developed because of a desperate need in World War I. The German sub fleet sank thousands of tons of British cargo during the early years of the war. There seemed to be no way for the British Navy to stop them.
The problem reached its climax when a German sub torpedoed the passenger ship Lusitania in the spring of 1915 off the coast of Ireland. The Lusitania sank in 18 minutes, and 1,198 civilian passengers drowned or froze before help arrived.
In response, the British War Department created the Board of Invention and Research. One of the groups within that organization was the Section on Submarine Detection and Telegraphy. That section was given a massive budget and ordered to get results NOW.