 In April 1940, "Popular Science" showed an example of a radar unit using the Watson-Watt patent in an article on air defence.Also, in late 1941 "Popular Mechanics" had an article in which a U.S. scientist speculated about the British early warning system on the English east coast and came close to what it was and how it worked.Watson-Watt was sent to the U.S. in 1941 to advise on air defense after Japan's attack on Pearl Harbor.