Science & Tech

How Do Microwaves Work?

Written by Jonathan Hogeback

Fact-checked by The Editors of Encyclopaedia Britannica

Using microwave oven — © Rostislav Sedlacek/Fotolia

Microwave ovens were life altering from the moment they began humming and heating in homes of the 1970s. The sprinter to the conventional oven’s cross-country runner, microwaves quickened the process of cooking and reheating meals, saving time and increasing the potential for leisure over work. The mechanics of the microwave were, from the very start, mysterious. It seems to be a magical metal box that spins and heats food by invisible means rather than heating the air and everything around it by conduction from a flame (as was the norm). Microwave users also came to accept the odd rules of the technology: no metal, no meltable plastics, and stir to cook evenly. So what is the magic behind the microwave?

Microwave ovens cook foods by injecting them with, surprise, microwaves—a form of energy. These electromagnetic waves are invisible to the human eye and fall between radio waves, which are longer in wavelength, and infrared waves, which are shorter. Inside the guts of a microwave, a device called a magnetron channels electrical energy from a power outlet to a heated filament, creating a flow of electrons that in turn transmits microwaves into the cooking chamber through an antenna. Microwaves bounce around in the chamber and cook food through radiation heating—exciting molecules within an object—by becoming lodged in water, sugars, and fats. Because the microwaves can travel only so far into an object before losing momentum, the outsides of thicker foods become heated by microwaves, and the insides are heated subsequently by the conductive transfer of heat from the outsides.

So how do the common microwave rules make sense with these mechanics? Certain types of plastics are able to absorb microwaves like foods do, making them prone to melting, dissolving, and therefore contaminating the food cooked on or in them. Metal reflects microwaves and therefore interferes with the movement of the waves inside the ovens. And stirring food, at least that which can be stirred, helps to spread the heat, ensuring that the inside is cooked as well as the outside.

Science & Tech

Do Camels Store Water in Their Humps?

Written by Nora Gonzalez

Fact-checked by The Editors of Encyclopaedia Britannica

Camel at Khor Rori, Oman; mammal. — iStockphoto/Thinkstock

Camels have long been known for their ability to go weeks at a time without needing to drink water—an ability that makes them particularly useful pack animals for people traveling across arid environments and that earned them the nickname “ships of the desert.” Camels are also known for their prominent humps (either one or two humps, depending on the species), which leads many people to believe that these are used to store water for access at a later time. However, camels’ humps actually store fatty tissue, not water, which is used as a source of nourishment when food is scarce.

Demystified: Do camels store water in their humps? No. They store fat that camels can use for nourishment. By concentrating fatty tissue in humps on their backs, camels' bodies are less insulated, which helps regulate their body temperature. — What do camels store in their humps?Learn more about camels and their humps.
Encyclopædia Britannica, Inc.

So why do camels store fat in these humps instead of having it spread equally throughout their bodies, like other mammals? Camels typically live in the desert, where food sources can be hard to come by. When a camel is unable to access food for a long period of time, its body is able to metabolize the fat in the humps for nutrition. The humps can deflate and droop if the camel has gone a particularly long time without food, but they will sit upright again once the camel is able to refuel. The camel’s humps also help the animal regulate its body temperature, an important feature in the desert, where temperatures can be extremely high during the day and drop drastically at night. By concentrating fatty tissue in humps on their backs, camels are able to minimize heat insulation throughout the rest of their body during the day when the temperature is high, and their body temperature rises. Then, at night, the extra heat dissipates through the rest of the camel’s body so that their body temperature is not too low when the temperature is cooler.

Although the humps do not store water, camels are still incredibly efficient in the amount of water they use per day, which is why they are able to go nearly a week without drinking. This is partly due to the unique shape of their blood cells, which are oval. Oval-shaped blood cells allow camels to consume large amounts of water (up to 30 gallons in one sitting!) since the cells are more elastic and can change shape more easily. This shape also allows their blood to flow more easily when water is scarce, which is common in a desert.

A camel’s humps are incredibly important for the animal’s survival in a tough environment like a desert. Without its humps, a camel would be more likely to overheat and sweat—but it’s still the oval-shaped blood cells that help the camel retain so much water, not the humps.