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# Microwave Math That Einstein Would Have Loved

New physics tricks for the most underestimated of kitchen appliances

Image: Ryan Matthew Smith/Modernist Cuisine LLC

You can find a microwave oven in nearly any American kitchen—indeed, it is the one truly modern cooking tool that is commonly at hand—yet these versatile gadgets are woefully underestimated. Few see any culinary action more sophisticated than reheating leftovers or popping popcorn. That is a shame because a microwave oven, when used properly, can cook certain kinds of food perfectly, every time. You can even use it to calculate a fundamental physical constant of the universe. Try that with a gas burner.

To get the most out of your microwave, it helps to understand that it cooks with light waves, much like a grill does, except that the light waves are almost five inches (12.2 centimeters) from peak to peak—a good bit longer in wavelength than the infrared rays that coals put out. The microwaves are tuned to a frequency (2.45 gigahertz, usually) to which molecules of water and, to a lesser extent, fat resonate.

The water and oil in the exterior inch or so of food soaks up the microwave energy and turns it into heat; the surrounding air, dishes and walls of the oven do not. The rays do not penetrate far, so trying to cook a whole roast in a microwave is a recipe for disaster. But a thin fish is another story. The cooks in our research kitchen found a fantastic way to make tilapia in the microwave. Sprinkle some sliced scallions and ginger, with a splash of rice wine, over a whole fish, cover it tightly with plastic wrap and microwave it for six minutes at a power of 600 watts. (Finish it off with a drizzle of hot peanut oil, soy sauce and sesame oil.)

The cooking at 600 W is what throws many chefs. To heat at a given wattage, check the power rating on the back of the oven (800 W is typical) and then multiply that figure by the power setting (which is given either as a percentage or in numbers from one to 10 representing 10 percent steps). A 1,000-W oven, for example, produces 600 W at a power setting of 60 percent (or “6”). To “fry” parsley brushed with oil, cook it at 600 W for about four minutes. To dry strips of marinated beef into jerky, cook at 400 W for five minutes, flipping the strips once a minute.

If you are up for slightly more math, you can perform a kitchen experiment that Albert Einstein would have loved: prove that light really does zip along at almost 300 million meters per second. Cover a cardboard disk from a frozen pizza with slices of Velveeta and microwave it at low power until several melted spots appear. (You don’t want it rotating, so if your oven has a carousel, prop the cardboard above it.) Measure the distance (in meters) between the centers of the spots. That distance is half the wavelength of the light, so if you double it and multiply by 2.45 billion (the frequency in cycles per second), the result is the velocity of the rays bouncing about in your oven.

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Myhrvold is author and Gibbs is editor of Modernist Cuisine: The Art and Science of Cooking (The Cooking Lab, 2011).

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1. 1. Yacko 06:39 AM 11/10/11

"A 1,000-W oven, for example, produces 600 W at a power setting of 60 percent (or “6”)."

Well yes and no. The tube in a microwave is not scalable, so to achieve 600W it is switched on 60% of the time and off 40%. So it's full on or full off and the time domain is sliced, maybe on 12 secs and off 8. This is not quite the same as feathering down to 60% and while it a good kludge, food does not cook exactly as if it is 60%. There are hot spots and liquids tend to overboil and then sit idle in a continuous cycle.

2. 2. Dave X 11:01 AM 11/18/11

So, 4*60=240s at 600W, or 144 kJoule for a ~4oz (or 113gm) tilapia filet. Does that scale, so you could do something like 6 watt/gram for 4 minutes for anything up to an inch thick?

3. 3. Cogitari 11:08 AM 11/18/11

The distribution of energy in a microwave oven is not necessarily uniform (mine definitely is not). So a solid material, like meat, may also not be cooked uniformly. This is a problem if you are expecting the cooking to kill all the germs unless you cook it slowly enough for the heat to spread throughout the solid. Cooking liquids, on the other hand, should not be a problem.

4. 4. promytius 11:30 AM 11/18/11

I'm hungry...

5. 5. swansont 08:17 AM 11/19/11

Um, grills do not cook solely by radiation and while the majority of the radiation is IR, visible light transfers energy as well.

6. 6. rodovre 11:15 AM 11/19/11

And, somewhere deep in the Sciam archives there is a recipe for the "Inverted Norwegian omelet", i.e. a desert frozen on the outside and boiling hot inside. Only science and a microwave oven can do that trick...

7. 7. sciamr308 in reply to Cogitari 03:44 PM 11/19/11

Right on point. The microwave is basically a convenience device and no substitute for cooking dead meat pot roast in the fireplace open-hearth, Franklin wood stove, wood-fired oven, gas or electric range/oven. Microwave for quick coffee, soup, pizza, or mac and cheese heat up.

8. 8. kienhua68 12:34 AM 11/20/11

good bit longer? shorter.

otherwise great.

9. 9. Wayne Williamson in reply to Dave X 06:10 PM 11/20/11

Dave...thanks for putting it in si terminology...

10. 10. hamidsadeghipour 10:20 AM 11/21/11

It is very important to use the Microwave vases or cover suitably, if not you heat the cover or vase.

11. 11. denke42 01:42 AM 11/22/11

The article should at least say "microwave-safe plastic wrap."

Some would lack confidence that the chemicals transferring from the plastic wrap to the food are harmless. They might use glass containers.

12. 12. tireldo 05:35 PM 11/29/11

Several years ago, during a slow night at work, my coworkers and I decided to put a marshmallow PEEP in the microwave to see what would happen. It grew to the size of a scifi monster before it popped. Very cool.

13. 13. scrubjay 11:52 AM 11/30/11

It sounds scrumptious. Will the recommended plastic wrapper also provide a nice seasoning of phthalates and polyvinyl chlorides?

14. 14. scramjet 02:54 PM 12/8/11

I tried the speed of light measurement. It didn't work. I got melt spots about 9 cm apart. Help me out here...

15. 15. UweHempelmann in reply to scramjet 12:37 PM 12/19/11

I think measuring the speed of light in a microwave in the way described is basically wrong and works only by chance if it does. You should check in the French edition: Pour la Science, Juin 2011, "La vitesse de la lumière et four à micro-ondes", J-M Courty and E. Kierlik", p 96 - 97. I think they give a very good review on this topic.

16. 16. lunazzi 06:14 PM 12/22/11

Is entirely wrong, the experiment does not makes a proof of relativity theory, so why Einstein would had care? Besides, people must know if microwaves velocity is the same than light velocity, something we learn at the university. And measuring frequency of the microwave must be done by a direct measurement, I do not know if a sensor is capable of 1.4 GHz response. No direct methods are based on the previous knowledge of c, like a dog biting his tail.

17. 17. bboczeng 08:39 AM 2/5/12

I've admired SA for years until it published this article in its chinese version, claiming it is possible to measure speed of light by simple standing wave physics. This is true for a 1D resonator (which is not the case nor is it possible for this oven). The peak to peak distance you measure must be 1/m (m is integer) times the dimension of that side. This is forced by boundary conditions. The distance reflects not your wavelength, but rather a projection of the real Wave Vector k. Reason many people claim it works simply because resonance modes for commercial Ovens are TE(323), and one side being 36cm. Thus you always measure 36/3=12, accidentally the number of real wavelength. Indeed, in the range of measurement we are talking about, you never get the order of Speed wrong because it's always some 10 s of centimeters. For other people that get a different value, they would cheat themselves into "measurement errors".
The physics and theory/experiment for a 3D microwave oven was well established long ago. The right way of measurement is to know the mode number and all 3 dimensions of your oven. Then do some complicated math. To see , i can give you the full story (if you can read chinese or trust Google Translate) i wrote in my blog. I would be glad to translate it later if SA wants a rebuttal article for this "False" Science rumor that has reached so far and affected so many that are innocent.
URL： http://bboczeng.blogspot.com/2012/02/blog-post.html

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