April is the traditional month for spring cleaning: opening doors wide for the first time in months, polishing things till they gleam, possibly beating on rugs with some kind of stick or club? In honor of this season of good housekeeping, we've asked Jeopardy! mastermind Ken Jennings to help us out with a little mental spring cleaning. He'll be dusting away some persistent around-the-house myths and spraying the sweet-smelling Lysol of Truth over all your remaining brain clutter.
The Debunker: Do Microwave Ovens Cook from the "Inside Out"?
Is there a more misunderstood appliance than the humble microwave oven? My generation was the first to grow up with microwaves in the kitchen, so we heard all the craziest craziness from worried parents. Eating microwaved food might cause cancer. (Not true.) Don't look in the microwave while it's running. (Not true.) You can't put metal in the microwave. (Not true, but you do have to be careful about its shape, thickness, etc.) Don't run the microwave empty. (True, but only a problem on older models.)
Many of these concerns have evaporated over time, but I still regularly hear the claim that microwaves, unlike other cooking methods, heat food from the inside out. That's not true—but it sometimes seems like it is, depending on the food. Here's the deal: microwave ovens are essentially just metal boxes containing a magnetron, a device for producing short little radio waves. These waves produce an alternating electric field, and when they hit dipoles (molecules with a positive charge on one end and a negative charge on the other), that alternating field makes the dipoles spin. Wiggling molecules = heat = your bag of popcorn pops.
The most common dipoles in food are fats, sugar, and especially water. Lots of commonly microwaved foods are more liquid in the middle, so the inside of your burrito gets blazingly hot faster. (That's why Hot Pockets come in those aluminum-lined "crisping sleeves." The metal radiates enough heat to make sure the crust cooks at the same speed as the gooey middle.) But if you're cooking something of uniform consistency and wetness, the energy will penetrate the outside first, just like in an oven. This potentially uneven heating—even with that ingenious rotating tray!—is why you should always let your microwaved office lunch sit for a minute before digging in, to let any hot or cold spots diffuse away. No matter how long you wait, though, Chinese leftovers are still going to taste like Chinese leftovers.
Quick Quiz: Some have blamed the decline of Hot Pockets sales on what comedian, who lampooned the brand in his 2005 special Beyond the Pale?
Ken Jennings is the author of six books, most recently his Junior Genius Guides, Because I Said So!, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at ken-jennings.com or on Twitter as @KenJennings.