Why does the bowl get hotter than the food in the microwave?
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From the brains behind Brains On, this is the Moment of Um. Moment of Um comes to you from APM Studios. I'm Anna Wegel. Um.

We all go through really weird and challenging moments in our lives, right? Maybe it's studying for a test that feels really hard, or navigating your first year in a new school, or learning how to eat pizza with a mouthful of brand new braces. One of my biggest challenges in life right now is making four separate dinners for everyone in my family every night. And really five dinners, if you count my dog.

I wish I had all the time in the world to prepare everyone's perfect meal. And trust me, I'm dreaming of the day when my one-year-old and my three-year-old can eat the exact same meal as me. And I do believe that day is coming. But that day is not now.

So in the few minutes I have to get everyone's meals ready, I'm chopping, I'm pureeing, I'm slicing, I'm dicing, I'm thawing, I'm boiling, I'm air frying, and I'm microwaving what feels like dozens of tiny portions to suit everyone's needs.

My microwave is a lifesaver, truly. It heats things up much, much faster than the oven. But the thing I'll just never understand is why, why, why when I pull food out of the microwave sometimes, the bowl is flaming hot, but the food is ice cold. How is that even possible? My buddy Josiah was wondering the same thing, so I found someone who knows a lot about this.

Microwaves are sort of amazing because microwaves are meant to cook food using radio waves, which is kind of awesome. My name is Matthew Katz and I run Ceramic Materials Workshop and we are a group that studies and teaches about the science behind ceramics.

So inside your microwave, we're making waves and that will excite certain materials. And the most common one that they excite is water. The water inside the food starts to shake. And when it shakes, it gets hot. Just like when you run around outside and you get really hot from all that exercise, a microwave is doing the same thing to the water molecules in our food.

which are things that are made out of clay or glass, they should be ignored by a microwave. That's why a lot of people's microwave have a glass tray at the bottom, you know, that will rotate your food around.

There are some types of ceramics that will absorb water and that water gets inside the ceramic and that will then vibrate and then make the ceramic hot. And so it really becomes a question of whether the ceramic is what we call vitrified.

Vitrified comes from the Latin word vitrium, which means to become glass. And when you make something out of clay, if you fire it hot enough, it actually does become a type of glass. And regular glass, like your drinking glasses, your window glasses, can't absorb water. And a well-fired thing made out of clay won't absorb water either.

There are some objects made out of clay that aren't fired hot enough. If you've got like a cool mug with like great shapes and colors and decoration, oftentimes they'll fire those to a colder temperature. And so it doesn't fully become glass. So when you use it every day and you wash it, because you hopefully are washing your mug every day, that sometimes in that washing, it'll absorb water through the exposed parts of the clay.

Um, uh, fascinating. Microwaves work by sending invisible waves of energy into our food. Those energy waves make the microscopic drops of water inside the food start shaking and vibrating, which heats the food up.

So why do our bowls and plates get hot in the microwave sometimes then? Well, some dishes absorb little water droplets when we wash them. And when we pop the dishes in the microwave, those water droplets wiggle around and get hot, which makes our dishes get hot too. Hey, did you know, legend has it, that the microwave was invented by accident?

An inventor named Percy Spencer was working on a special machine that makes energy waves when he noticed the candy bar he had in his pocket melted. He realized it was energy waves from the machine making heat and zap! The rest was history.

If you like this episode, take a second to subscribe to Moment of Mum wherever you listen to podcasts. And if you want to hear more about the accidental invention of the microwave, check out the Forever Ago History podcast where we have a whole episode all about this super nifty appliance. Want to see our shows come to life? Head to YouTube where we've got awesome animated Brains On episodes. Search Brains On Universe on YouTube and subscribe.

If you have a question, we'd love to help you answer it. Drop us a line by going to brainson.org slash contact. See you next time and the next day and every weekday. Until then. Food's almost ready, family.

Hey friends, Molly, Sanden, and Mark here with some very big news. Drumroll please.

We're hitting the road in search of adventure, fresh air, and you. That's right. We're going to be live at the Boulder Theater in Boulder, Colorado on Sunday, April 27th. Our science-themed live stage show takes the audience on an adventure through the brain, complete with magic tricks, dance moves, out-of-body experiences, mystery sounds, and a game show. Molly, you almost left out the most important part. Yeah, Molly, don't forget the big party. Oh,

Oh, right. After the shows, we're throwing a brain-tastic bash. Join us afterward for a VIP party where we'll play games, guess mystery sounds, pose for photos, and give as many high fives as humanly possible. Snag a spot by purchasing a VIP pass when you buy your show ticket. Oh, that reminds me. I've got to start training. These hands aren't going to high five by themselves. Five and five. Good idea.

And remember, spots are limited, so grab your tickets today at brainson.org slash events.