How do you find a bomber at night, a storm cell in the clouds, or the surface of a planet you cannot see? You send out a radio pulse and time its echo. Every microsecond of waiting means 150 meters of distance. This book explains that simple idea and follows it from Heinrich Hertz's lecture hall in the 1880s to the satellites that map Earth. Inside, you'll find: How the machine works. Why an echo from twice as far comes back sixteen times weaker, and how a change in pitch reveals a target's speed. The fence of steel masts. How Britain's Chain Home stations gave fighter pilots about twenty minutes of warning in 1940, and why that mattered more than extra aircraft. The warning nobody believed. At Opana Point on December 7, 1941, two privates tracked incoming planes 132 miles out, close to an hour before the first bombs fell. The copper block that changed the war. The cavity magnetron, a British invention that crossed the Atlantic in 1940 and launched an MIT laboratory of nearly 3,900 people. Hide and seek. Strips of foil over Hamburg, a Moon mistaken for a missile attack, and a stealth jet shot down in 1999. Radar at home. The melted snack bar that, as the story goes, led to the microwave oven, tornado warnings that grew from under 5 minutes to 13, and some 44,000 flights a day kept apart over the United States. Written in plain English with more than 200 diagrams, charts, maps and illustrations, this book is for anyone who has ever wondered how a machine can see in the dark. It never looks. It listens.
