In 1880, William Herschel tripped over an astounding discovery. He asked a simple question. Sunlight warmed the skin. Do the different colors of the rainbow carry different amounts of heat? He set up a prism to cast a large rainbow on a wall (this is tricky because the angles must be right and the pesky Earth just keeps on rotating). He placed a thermometer in several different bands of color, and a control thermometer just off from the red end of the spectrum where no light fell at all. To his amazement, the control thermometer recorded a rising temperature and the others nothing. He had discovered infrared light and that the rainbow is not just what meets the eye. This opened the door to the entire electromagnetic radiation (EMR) spectrum. By WWII, they had a full theory of light from Maxwell, and radio was all the rage.
The book begins in the 1930's. Radio was not the concern, impending war was, and the first crude radar units were built. Radar is the invention of the title. Radar saved Briton. It is said that the A-Bomb ended the war, but radar won it.
As dry as this book might sound, it is quite engrossing. I must admit I went rapidly through the last 120 pages or so that covered the cold war and other events leading up to our modern world because I am already reasonably familiar with them (it is mostly computer related). My interest in this subject dovetails nicely with my interests in technology, WWII, and the history of science. Science and war go back a long way, and there is nothing like a good war to accelerate both basic science and technology.
A primer is perhaps useful. Light is an ambiguous term. We use it to mean the light that we can see, and any form of light whether it can be seen or not.
The broad forms of light are: Radio; Cell Phone; Microwave; Infrared; Visible; Ultraviolet; X-Rays; and Gamma rays. In wave lengths, these go from miles in the radio spectrum to femtometers and shorter (smaller than the nucleus of an atom). Frequencies are the inverse of wavelength and energy is proportional to frequency. So radio waves are very low frequency, low energy, very long wave length light. Gamma rays are very high frequency, high energy, short wave length light. Radar focused primarily in the microwave band, around the same frequencies used by your microwave oven, with a wavelength of around 2 centimeters. Sort of in the middle.
Generally speaking, the higher the frequency, the lower the wavelength; and the better you can see. To use radar to see an enemy airplane, centimeter wavelengths were the key. One problem is that different materials interact with EMR in different ways at different frequencies. For example, rain plays havoc with 1 cm radars because water absorbs the energy (which is why your microwave works).
In 1940, a group of Brits went to the US to trade secrets. This was known as the Tizzard mission. The US needed the British technology, although they did not know it at the time, and the Brits needed the US's manufacturing capabilities. The Brits brought their super-secret Resonant Cavity Magnetron. This device could create strong emissions of microwave energy at just the right wave lengths. Radar won the war, the magnetron made radar work. The Americans were gob-smacked. The RadLab was created and it produced radars at a dramatically increased pace. Radar was used to detect incoming threats, count them, and get there altitude (all different applications), aim guns, monitor traffic in harbors, guide plans to a safe landing (today we call this ILS for Instrument Landing System), FoF (Friend or Foe) systems and lots more.
Aside: Some FoFs worked by detecting small changes in a planes returns caused by distinctive engine vibrations. Amazingly, analog computers of the day could sniff this out. Cool.
More than a few famous names worked at the RadLab, including Nobel winner I. I. Rabi, Robert Watson Watt (he is related), William Shockley and ploy-math Luis Alvarez. Alvarez would move on to the Manhattan Project, and later in his career he would be known for the asteroid/dinosaur extinction theory.
The development of the bomb took most of the Nobel winners out of the market. This lead to the following amusing conversation:
S1: The bomb guys get all the breaks! They snatch up all the Nobel winners first.
S2: Well, Rabi just won, so we have one too now.
S1: Yeah, but we have only had ours for 3 weeks!
It soon became apparent to the higher-ups, especially Vannevar Bush, that basic science was important, And so scientists suddenly found themselves considerably higher up in the food chain, leading to this: A scientist found himself being frustrated by a military pencil pusher. He (sorry, they are all he's) turned to his tormentor and asked "Who do I see about getting you fired?"
Meanwhile, the Germans were working on their radars in a kind of intellectual, evolutionary game of leapfrog. One project was code named Freya. Freya, Odin's wife in Norse mythology, and the source of Friday (Freya's Day), had a magic necklace that allowed her to see for hundreds of miles in every direction. Only the Nazis would be arrogant enough to use her name on a radar project.
This book is long and full of a lot of detail. It has a good index, lots of notes, and a list of acronyms used. Very helpful. Radar systems were the start of high frequency electronics. Modern computers were a direct result of all that. Radar technology combined with computing power opened up the rest of the EM universe to us. The computer power came from the transistor, invented by Shockley. Early analog computers would contain hundreds of tubes, each tube being a bit. Today, millions of transistors can fit on the head of a pin.
The largest radio telescope in the southern hemisphere is located in Parks Australia in the middle of a sheep paddock. It was built by RadLab alums after the war.
If you enjoy reading about WWII, EMR technology, applied physics and its impact on our lives, this is a book I would recommend. Another, longer, similar book does the same for nuclear physics: The Making of The Atomic Bomb.
It has been suggested that radar advanced applied solid state physics by two decades. The PC, cell phones, the internet, HD TV, smart phones, astronomy, planetary research, NMR machines… a near endless list of things we have already started to take for granted. All delayed by twenty years. You would recognize this world because in people terms, it is practically yesterday.
A recent puff (read: stupid) question for politicians is "If you could, would you go back and kill Hitler as a youth?" Well, if you did, you would have to give up quite a lot today.
Lee Moller is a life-long skeptic and atheist and the author of The God Con.