Short Wave - Micro Wave: The Science Of Microwave Ovens + Listener Mail

Episode Date: July 17, 2020

Introducing Micro Waves: low-calorie episodes featuring bite-sized science, mail from our listeners, and...maybe other stuff in the future? We'll figure it out. Write to us at [e-mail]. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

Maddie Safaya here with our trusty shortwave reporter Emily Kwong. What's up, Kwong Song? Hey, Safaya. Are you excited, ma'am? Aren't I always, ma'am? So today we are introducing a new occasional type of episode we are calling a microwave. Each microwave, we will explain a little science nugget. Just a tiny little brain snack.

And then maybe read some listener mail, too. Today's inaugural microwave topic is microwave ovens. And yeah, we know that isn't super creative. But this is a daily show, y'all, and we're tired. And we're stuck inside, inspired by what's most around us. So after the break, we'll tell you a bunch of stuff about the science behind your favorite kitchen appliance. Honestly, I don't really think we needed the sound again, you know? I don't know.

It sounds like dinner to me. Okay, Kwong, so how often do you use your microwave? Oh, I'm sorry, I can't hear you. I'm heating up a burrito. What do you want? How often would you say you think about how it actually works? Actually never. Why are you asking me this question? Listen, there's no shame. Not a lot of people think about how their microwaves actually work. But you know who does? Who?

Ramoswamy and a thyserin. I'm a food scientist and a food engineer. Ramoswami works at Penn State University. He's a big-time food engineer. And honestly, Kwong, I felt a little weird, calling him just to ask him how a microwave works. It's not the weirdest thing you've ever done. It's still a little weird. But there was nothing to fear as he is a man after my science communication heart.

In addition to doing teaching and research, our outreach responsibility is connecting with the public. So helping people like you is part of our mission. Oh, I love that. I know. Me too. Okay, let's get to it. So basically, this mechanism of heating is different than conventional heating. Conventional heating is... So microwave ovens work by shooting energy in the form of waves called microwaves at your food.

And those waves are made by a tube in the oven called a magnetron. One of the most underappreciated transformers. And I forgot any screen time in the movies. Truly, you hadn't even even. heard of him until today. But microwaves are used for like all types of technologies. We use them to send information via communication devices all the time. That energy is the same energy used by your cell phones, but a higher power. Oh. So these waves essentially create inside your little microwave an electromagnetic field. Ramaswami says microwaves interact really well with molecules that

are positively charged on one side and negatively charged on another. Those are called polar molecules. So sort of like those bar magnets we used to play with in high school with one. What do you mean used to? You know what I'm saying? Are you done playing with bar magnets? I have other things to do in my free time. Wow.

Well, wow, wow. Fancy for magnetism, but fine. Okay, so bottom line, the molecules are polarized like magnets, basically. Yeah, basically. And the most dominant polar molecule in food is water. So most of the way microwaves work is by messing with the water molecules in our food? So this is how it goes down. The microwaves oscillate, which means the current inside the oven kind of alternates back and forth.

When it alternates, the charge shift from left to right and as a result of the water molecule starts to rotate clockwise and anti-clockwise, millions of times. And that super fast flipping of the water molecules back and forth creates friction between the molecules. And friction, of course. Creates heat. You got a quang, okay.

It's like a little molecule dance floor. That's right. So each vibrating, dancing water molecule acts as like this little localized heater throughout the food. Okay, but my most pressing microwave question is why does food

stay cold in the middle because it's not like water molecules are only on the outside of food, you know? Yeah, right. No. So of course it depends on the makeup of the food you're heating. And one thing that contributes to uneven heating is the presence of salt. So, you know, like super salty foods like soup don't actually heat as evenly as foods that have barely any salt in them. Like I'm sure you've noticed that when you're out there souping, right?

Sure. Sure. All the time. Okay. So that's partially because these little. salt ions on the surface or along the sides of the bowl absorb a lot of that initial microwave energy and heat up really fast. But that means that there's not kind of enough energy left over to penetrate all the way into the middle. It's why when you look at the microwave and you're like,

what's up, soup? And you look in there and you see like the surface is boiling and then you dip your little spoon in there and it's all a lie. Soup still cold. It happens. So what are you supposed to do about that. Yeah, well, it's pretty complicated. You just stir it. Oh, Jesus. You just stir the soup halfway through, Kwan. That's it. Okay. We got it. But really, Ramoswami says, besides, you know, like safety, that's actually why a lot of food suggests that you let the food sit in the microwave for a minute after it's done, which helps that heat kind of even out a bit. Oh, wait. Most important question from my childhood, is this safe if I look directly into the microwave as I wait for my burrito to be done? You absolutely may look in the microwave quang as long as your little

microwave isn't broken and has passed all its little like microwave baby checkups and it's all perfectly safe. I mean, in Ramoswami's words, the only danger is that the microwave dropped on your foot. I love food scientists. I know. I know. Okay. Before we go, each microwave will also share some listener mail. Yes, you can write us at shortwave at mpr.org. A couple weeks back, Craig wrote us. Subject line, Appreciation from the Desert. Hi, Maddie. I really enjoy your podcast, and it helps me start each day while I make

coffee on my tailgate. I think this fact has served as additional positive reinforcement because I tend to associate your daily episodes with my daily dose of caffeine, and I'd be a fan either way. I'm fine with that. I'm a field biologist working primarily with desert tortoises and the common ravens who prey on them in the Mojave Desert. We work mostly in the middle of nowhere by ourselves, so we are kind of always in some state of social isolation. However, this season has been particularly difficult not being able to see coworkers or my family, and your podcast has really meant a lot to me.

I love that. That's really nice. P.S. Here are a couple pictures of a little tortoise who refused to leave the shade of my tire. The other day, he was kind of grumpy when I explained to him I needed to drive away. Craig sounds really nice. I mean, aren't we all a grumpy little tortoise under a tire right now, Kwong? You know? And don't we all need a little Craig to be nice to us? I agree.

Okay. All right. So here's one more that we'll read that I really love. This is about our recent episode on helium, where we played with some balloons. And yeah, I bit into one and suck the helium out because I'm a human being. And it reads, hi, I enjoyed the helium episode until the very end. Teeth should be used for smiling and eating. not as tools to pop a balloon, etc.

Teeth, wait, wait, this is the best part. Teeth are jewels, not tools. Signed, Brenda Burkell, DMD, aka a dentist. A dentist! This is because you called your teeth nature scissors, isn't it? I said what I said, Brenda. Okay, well, we appreciate you, Brenda, and everyone, this has been our first ever microwave episode.

If you have a question for us or suggestions for future microwave, email us at shortwave at npr.org. This episode was produced by Brent Bachman, edited by Viet Le, and fact-checked by the tortoise under Craig's Tire. JK, it was checked by Yo-Wei Shaw. Thanks, Yo-Wei. I'm Maddie Safaya. And I'm Emily Kwong. Thanks for listening to Shortwave from NPR.