Stewart Van Nostrand, age 14, of Grand Forks, N.D., for his question:
WHO DEVELOPED RADAR?
Radar is an electronic device that can "see" great distances despite fog, rain, clouds and darkness. It can accurately locate missiles, aircraft, ships, cities, rainstorms and even mountains.
Physicists and mathematicians made many of the most important discoveries leading to radio and radar in the late 1800s and the early 1900s. Four men made especially important contributions: Heinrich Hertz, Guglielmo Marconi, Karl Ferdinand Braun and Lee DeForest.
Hertz discovered radio waves in the 1880s and showed that they could be focused into a beam and be reflected from objects. In the 1890s, Marconi developed the first radio sending equipment. Braun invented a cathode ray oscilloscope in 1897. In 1907, DeForest invented the radio amplifier tube.
Scientists at the Naval Research Laboratory did a great deal of the early work in the United States on radar. In 1922, A.H. Taylor and L.C. Young detected reflections from a boat on the Potomac River while studying short wave radio. Young and L.A. Hyland observed similar reflections from aircraft in 1930.
These scientists used a system of continuous radio waves called the "best method." This method did not give the range of an object, but it could detect aircraft 50 miles away.
In 1934, Young proposed using pulses of radio waves, the method most widely used today. R.M. Page, a navy scientist, developed a radio of this type and observed echoes from aircraft in December, 1934
By 1916, pulse radar with a range of 25 miles had been developed and by 1938, a pulse radio had tracked an aircraft 100 miles.
This kind of radar was installed on 20 warships and military installations many months before the Japanese attacked Pearl Harbor on Dec. 7, 1941. Unfortunately, proper use of the equipment hadn't been perfected.
An army radar unit in the Hawaiian Islands detected the Japanese air fleet approaching Pearl Harbor on that December Sunday morning, but thought the blips were caused by American bombers.
The British became active in radar early in 1935 when the Air Ministry asked physicist Robert Watson Watt to work on anti aircraft weapons. He and a a group of scientists working with him developed a pulse radar capable of detecting aircraft at ranges up to 17 miles.
The British also developed Ground Control Interception radar and Airborne Interception radar for night fighter planes. During the Battle of Britain, these radars enabled a small force of British fighter planes and anti aircraft artillery to fight off massive German air attacks.
German scientists were also working on radar by 1935 and had good wartime radio for early warning, for anti aircraft gun control and for ships. But the Germans did not develop microwave radars and so failed to obtain accuracy. The Allied scientists scored a big achievement by developing receivers, high power transmitters and antennas to operate with microwaves. Microwaves made it possible to develop narrow beamed, highly accurate radars with small antennas for aircraft, ships and mobile ground stations.