German inventor who patented a ship detection device in 1904
Plate 081
1935–1940
Britain, with parallel work elsewhere
No photograph is shown for this exhibition. The museum displays an image only where it can show the object honestly.
About this date
Robert Watson-Watt and colleagues demonstrated radio detection of an aircraft in February 1935. Similar systems were developed independently in Germany, the United States, France and Japan.
About credit
Several nations developed radar at the same time. The cavity magnetron, handed to the United States in 1940, made compact radar possible.
Chapter II
The world before
Life before Radar
Aircraft were detected by sight and sound locators, with little warning in cloud or at night.
II
The human achievement
How it came about
Britain built a chain of coastal radar stations before the war. In 1940 it helped Fighter Command direct limited aircraft in the Battle of Britain. Airborne radar soon followed.
III
Understanding the invention
How it works
Radar, explained in two steps.
01
Step 01 of 02
Echo timing
Radio waves travel at the speed of light; the time for the echo to return gives distance.
Echo timing
Scanning
IV
The transformation
What changed for humanity
War
Air defence and naval warfare were transformed.
Peacetime
Air traffic control, weather radar and speed cameras.
Radar gave early warning of aircraft, helped defeat air attack in the Second World War, and now guides air traffic, weather forecasting and ships.
V
Before and after
Life before and after Radar
Before
Listening with large sound mirrors.
After
Reading a radar screen.
On larger screens, drag the divider (or use the arrow keys) to give more room to the world before or after.
VI
Its legacy
What came after
MHI 081
Radar
Beyond the collection
Microwave ovens
Percy Spencer noticed a magnetron melted a chocolate bar in his pocket in 1945.
Beyond the collection
GPS and satellites
Related radio technology.
VII
Human stories
The people and the moments
The chocolate bar
Percy Spencer of Raytheon is reported to have noticed the melted chocolate while working near a magnetron, leading to the microwave oven.
Where accounts differ, this museum follows the documented record and says so.