What Would Happen If You Microwaved A Microwave?
This is What Would Happen If, a close examination of mundane hypothetical situations. Each week, we look at something that you could do but probably never would, and take it to its logical endpoint. This week: What would happen if you microwaved another microwave?
The microwave oven: A mysterious box of cooking potential. You open the door, you put some food in and then seconds later it is bubbling and scalding hot. We don't literally think it's magic, but still: It also causes forks to spark and marshmallows to blow up like balloons. If it wasn't a little mystifying we'd just call it the "Hot Box" or something.
So, what might happen if one were to place a microwave inside of a larger microwave and hit the start button? The answer is incredible, but it's going to take a few steps in order to fully explain it.
First, we need to understand how a microwave does its thing: It heats food without a heat source. It seems complex, but the answer is right there in the name "microwave oven." Using something called a magnetron, a microwave fills its cooking chamber with microwaves. Inside sits the food, which contains water molecules. By their very nature, water molecules are slightly negatively charged, so when the microwave passes through the food, the water molecule will try to align with the direction of the microwave.
Now here's where the magic happens. Most conventional microwaves operate at a frequency of 2,450 MHz, which causes the water molecules to oscillate some 2.45 billion times per second. This movement translates into heat, and heat translates into a rising internal temperature, which translates into, well, cooking. All because the microwaves caused the water molecules to move back and forth.
This brings us to putting metal objects in a microwave. Anyone who's accidentally microwaved a fork or metal-flecked plate probably already knows what happens, but let's dive into how metal and microwaves translate into a light show. Unlike food, microwaves cannot penetrate metal; they merely reflect off of it. This isn't necessarily a bad thing — microwavable dinners use a type of packaging called a susceptor to take advantage of this reaction, creating a nice hot surface within the microwave to make things brown and crispy.
Where things start to go wrong is if there is no food inside to absorb those bouncing microwaves. If you microwave a fork, the microwaves will continue to reflect off of the surfaces inside, agitating the electrons in the fork, raising the electrical potential of the air and leading to arcing between some of the curved surfaces of the fork. This is why sparks fly and things catch on fire. It's also why you shouldn't run an empty microwave. With nowhere to land, the microwaves will eventually cause arcing between the surfaces of the cooking chamber and potentially damage the electronics of the appliance.
With that understanding in place, let's go back to our microwave within a microwave. Practically speaking, we're putting a big metal box inside of a bigger metal box. You hit the start button. Microwave radiation will flood into the cooking chamber, and reflect off the metal surfaces of the microwave inside. Because all microwaves sport a Faraday cage to keep the radiation inside the chamber, the bigger microwave's, ah, microwave radiation won't make it into the smaller microwave. However, all the parts outside the cage, like the controls or electronics, aren't protected. As the microwaves reflect again and again and again, there'll be some arcing between metal surfaces, and inside the smaller microwave's electronics. This will cause any plastic or combustible material inside to combust, setting the smaller microwave aflame. If left to run long enough, you'll risk damaging the bigger microwave as well.
Sure, it's not the dividing-by-zero catastrophic event you want to happen, but it's still a great way to ruin two perfectly good microwaves. If you want to have fun with microwave radiation, it's probably best to stick to the marshmallows.
