Today’s Wonder of the Day was inspired by BOB from AUSTIN, TX. BOB Wonders, “ How do microwaves make heat? ” Thanks for WONDERing with us, BOB!

When your tummy is rumbling, there's one kitchen appliance that can quickly stop the grumbling. From reheating leftover pizza to popping up some light and fluffy popcorn, there's one device that gets the job done in a jiffy. What are we talking about? The microwave oven, of course!

You know the drill. You put your leftovers on a microwave-safe plate, pop it into the microwave, hit a few buttons, and like magic, it's warm and ready to eat. And all this takes place in a few seconds rather than the minutes or hours that the stove and oven can take.

Who was the genius who invented this wonderful creation? As a matter of fact, his name was Percy Spencer and his invention was an accident! Spencer worked for a company named Raytheon, developing microwave radar transmitters during World War II.

One day in 1945, he noticed that a candy bar he had in his pocket was starting to melt. The microwaves from the radar set he was working on were cooking the candy bar in his pocket!

With a little experimentation, Spencer figured out that the microwaves could be concentrated to heat food. He created the first working microwave oven, and the first food he cooked in it was popcorn.

Microwave ovens use microwaves, which are radio waves at a frequency of approximately 2,500 megahertz, to heat food. Microwaves are absorbed by water, fats and sugars and are immediately converted to heat. The microwaves penetrate food quickly, so they cook food evenly and quickly.

Microwaves are not absorbed by most plastics, glass or ceramics, so they are perfect for heating food without heating everything else around the food. This enables microwave ovens to use less energy than other cooking appliances.

Raytheon filed a patent for Spencer's microwave cooking process on October 8, 1945. In 1947, Raytheon produced the first commercial microwave oven and called it the “Radarange." Would you believe it was almost six feet tall and weighed about 750 pounds? It's true!

It was also expensive. The first Radarange was $5,000, which would be equal to over $52,000 today. It would be many years before microwave ovens could be produced and sold inexpensively.

Today, millions of kitchens contain a microwave oven. You'll also find them in just about every restaurant kitchen and quite a few convenience stores, too. Whether you're heating up water for coffee, reheating leftovers for lunch or popping a bag of microwave popcorn for a late-night snack, the microwave oven does these things quicker than any other appliance. And that's why it's so popular!