We listen to the radio in the car, in the shower, in the morning before work or school. Radio was developed in 1901, and by the 1920s most homes were already tuned in.

Radio waves also had more scientific potential. It was war, however, that lead scientists from radios to microwaves.

In England, in 1935 — four years before the start of the Second World War — a Scottish scientist named Robert Watson Watt was asked if radio waves would work as “death rays”. Radio waves as a weapon! The military went so far as to tie a sheep to a post and bombard it with radio waves to see whether radio waves could kill it.

The answer was no; there simply wasn’t enough power in a radio wave to kill anything. The sheep would live, or at least radio waves wouldn’t end its life.

Radio waves, however, did have another property. They were bouncy. Radio waves could bounce off airplanes and end up right back where they started. If you built a radio detector next to your radio transmitter, you might be able to “see” airplanes coming by listening for the bouncing radio waves.

This idea came to be called radar, which stands for radio detection and ranging. With the war quickly approaching, England and Germany both started creating and developing their own radar systems. But there was a problem.

Any light wave (whether it is light you can see or invisible radio waves) can be described by its wavelength. Wavelength tells you just how long any one wave is. The radio waves used in early radar had long wavelengths. These waves could be anywhere from a few metres to a hundred metres long.

The reason early radar used long wavelengths is quite simple: long-wavelength waves are easier to make. But the longer the wavelength, the worse it is for radar. Long wavelengths tend to wrap around their targets, and send back fuzzy images. For instance, with the long wavelengths it was impossible to tell if an approaching formation was one plane, several planes, or even a flock of geese.

As the war began, the British recognized that they needed a better way to fend off air attacks. They needed shorter wavelength radar that could bounce off targets and return a sharper image. These waves should be about 10 centimetres long. Such waves were well known to science; they were called microwaves. That’s right. We’re getting closer. Remember, patience, Grasshopper …