Did you know the microwave oven was invented on accident?

Accidental Ascertainments will be a new mini-series that shines a light on numerous scientific discoveries that were made completely on accident! Science isn't perfect, but even when things don't go exactly according to plan, great things can happen when one learns from their mistakes!

These days, just about everyone has a microwave sitting on their kitchen counter that they take for granted every day.

In fact, upwards of 90% of American households contain at least one. Before the mid-20^th century, though, if you wanted to eat hot leftovers, you used the only oven you had, which doesn't always work so well for quickly and evenly heating food that's already been cooked. Microwave ovens are so good at evenly heating, the same technology is also used in numerous industrial processes involving ceramics, polymers, and more.

War has always been a driving force for the advancement of technology. Some discoveries are made in search of new defensive or offensive capabilities, and some are simply byproducts of situational variables lining up while an observer is paying attention.

The microwave falls under the latter category...

It all started on a run-of-the-mill day, in a radar lab in Massachusetts, USA...

The year was 1945, and self-educated engineer and physicist Percy Spencer was building Magnetrons, an essential component of military radar systems. Spencer was a master of magnetrons, even developing a more efficient method of manufacturing the device, putting him in high regard among the US Navy, and Allied countries.

After finishing some tests and getting ready for his lunch break, he noticed the candy bar in his pocket was melting... This piqued his interest, and like any curious scientist, he decided to investigate.

He placed an egg under the magnetron tube. After a moment or two, the egg exploded all over his face! Spencer had a eureka moment, and the next day, cooked the very first microwave popcorn to share with his co-workers in celebration of his latest discovery.

But what exactly did he observe?

What unnoticed heat source was melting the candy bar, and making the egg explode?

Spencer wasn't the first to notice that active radar systems gave off heat, but being the expert he was, he knew there was something more to it..

Magnetrons produce a rotating flow of electrons with a magnetic field. These electrons are emitted as vibrating microwaves, which are perfect for use in RAdio Detection And Ranging, or, RADAR.

These microwaves are polar, meaning they act as a magnet themselves, attracting any other polar molecules the come in contact with.

Want to know of a really common polar molecule? Water.

So, as these microwaves propagate through space, every single water molecule they encounter tries to line up with the polarity of the wave like a magnet. Remember, though, that the microwave is vibrating, so the water molecule has to constantly flip back and forth in order to line up with the wave...

^Source

All that rotation causes a lot of friction, thus heating the every part of the affected material that contains water, or any other polar molecule, like many metals...

It's stupid that I have to do this, but before I move on I must say...

DO NOT PUT METAL OBJECTS IN YOUR MICROWAVE!

Now that that's out of the way, I will say; the danger from putting metal in a microwave oven is much more about the shape, rather than the material...

Metals are already full of electrons, and when they're exposed to microwaves, those electrons get excited, creating an electric current, and turning the object into a sort of heating element. In smooth objects, the electrons are able to spread out, but in objects with sharp points, like a fork, the electrons will bunch up at the edges, and arc from one to the other.

This discovery led to the ability to go from cold, hard pizza in the fridge, to bubbling, lava-hot cheese, in just a matter of moments, simply by putting in a box that will force all the water inside to shake harder than your weird friend Becky on the dance floor, all thanks to a brilliant scientist who carried candy bars in his pocket.

References:

• https://www.popularmechanics.com/technology/gadgets/a19567/how-the-microwave-was-invented-by-accident/
• https://www.nap.edu/read/2266/chapter/7#105
• https://en.wikipedia.org/wiki/Microwave_oven

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