Microwave ovens heat food by agitating certain molecules with non-ionizing light

Fascinating evolution of the oven

From ancient wood-fired ovens in Rome and Egypt to modern microwaves, the oven’s evolution has shaped how we cook. Early ovens focused on heat retention, but breakthroughs like the gas stove in 1834, and the electric stove in 1892, brought precision. Then, in 1967, the microwave redefined convenience.

The history of many kitchen appliances involves unexpected discoveries and applications, including wartime radar turned hamster defroster and replacing an 'ice king' with heat-stealing boxes.

How to cook food with lasers

Creative Machines Lab at Columbia Engineering have developed a system of software-controlled lasers to cook food with precision, retain moisture with the final-cooked product, brown food within its original packaging, and create an entirely new meal creation process for a consumer. Watch this three-minute video to see for yourself.

Watch an animation of what happens inside cookies as they bake in an oven

As temperatures rise and butter melts, trapped water expands, spreading the dough, which remains held together by a network of proteins. Maillard reactions produce browning on the surface beyond 310 degrees Fahrenheit (154 degrees Celsius), while caramelization can be triggered by baking past 356 degrees Fahrenheit (180 degrees Celsius).

Infrared light is most often associated with thermal radiation and cooking food

Although extensively used in remote controls for electronics, where LED lights send signals wirelessly, infrared cameras allow for night vision and thermography—imaging of heat patterns in the body to non-invasively reveal blood flow for supplementary diagnostics. Infrared radiation also provides heat in toasters, saunas, and other technologies.

Learn how air fryers cook food without the use of oils

While deep or pan frying involves oil transferring thermal energy to the food, air fryers warm food through constant airflow, which prevents the formation of a boundary layer of cold air around the food, though air is a worse conductor of heat.

Radio waves are used in broadcasting, weather radar, telecommunications, and GPS

Its ability to bend around obstacles and reflect off the ionosphere—an electrified layer of Earth's upper atmosphere—allows this type of light to travel long distances without damaging living things due to its low energy. MRI scanners, WiFi, and Bluetooth technologies are also applications of this form of light.

How geometry and uneven charge distribution make some molecules greenhouse gases

Molecules vibrate and rotate with different frequencies based on their elemental composition and shape, which can produce uneven distributions of electrons, as seen in carbon dioxide and water. The resulting unbalanced electric field can interact with electromagnetic waves of the same frequency, causing the molecule to absorb the radiation.

The importance of volatile aroma compounds in the flavor quality of food

Processes such as air movement and heating cause food to lose aroma molecules, which studies have shown play a major role in our sense of taste. While losing these molecules to the environment leaves fewer to be processed during consumption to intensify flavor, it can also produce previously nonexistent aroma compounds or release previously trapped ones, altering or enhancing the food's flavor.

Some materials can absorb low-energy light and emit high-energy radiation

Through anti-Stokes cooling, incoming energy is combined with vibrations in a material's crystal lattice to produce a net reduction in its temperature. Using this effect, lasers can be directed at microchip hot spots to help keep data centers cool.

What makes food crispy, and how science can be used to maximize this property

The fracturing texture experienced when biting into vegetable tempura, fried chicken, pastry crusts, and other foods comes from having a dehydrated, porous surface. When frying food in hot oil, trapped water vaporizes and escapes, creating tunnels and pores in the food as it dehydrates. Breading, particularly with the large, irregular shapes of panko, and leaveners can help create more air spaces.

Water vapor is used to manage heat in high-end smartphones

While smartphones have traditionally been cooled using a highly conductive plate that dissipates heat from the chip, vapor chambers offer a higher heat-removal capacity. This technology has been utilized in laptops for decades to absorb heat by cycling a fluid between liquid and gaseous phases.

Barbecue relies on a unique scientific equation

Barbecue's distinct flavor starts with an interaction between the heat source and food, which creates a Maillard Reaction—better known to diners as those crunchy, caramelized bits on the outside.

High-frequency sound waves have been used to brew espresso with room-temperature water and about one-fourth the energy of a traditional espresso machine, which relies on hot water and pressure.

Microreactors are 100 to 1,000 times smaller than traditional nuclear reactors but still generate thermal energy for heating or electricity by splitting atomic nuclei.

You have never made physical contact with anything in your life because electrons in the outer layer of atoms on the surface of objects repel one another.

Washing dishware before putting it in a dishwasher may reduce the appliance's effectiveness because it dynamically adjusts wash time and temperature based on a sensor that detects dirtiness.

Microchip fabricators create light by heating tin droplets to over 220,000 Kelvin

Every second, lasers strike 50,000 droplets moving at 250 kilometers (155 miles) per hour, vaporizing the tin in supernova-like miniature explosions that produce ultraviolet light. Knowing this light will spread via diffraction as it passes through a filter during manufacturing, designers reverse-engineer the filter design based on the required final microchip pattern.

The weakest form of light that is dangerous to humans is ultraviolet

Unlike radio waves, microwave, infrared, and visible light, UV light can produce chemical changes, such as curing adhesives and resins, causing substances to fluoresce, and destroying the genetic material of microorganisms. This makes UV light useful for sterilization, forensics, and quickly drying nail polish.

Everything with a temperature above absolute zero emits light at nearly all wavelengths

Thermal radiation results from random motions of particles that make up an object, which only theoretically cease at 0 Kelvin, or -273.15 degrees Celsius. The greatest intensity of thermal radiation, also known as blackbody radiation, is emitted at a characteristic wavelength corresponding to the object's surface temperature.

Interacting sound waves can create regions where the pressure from each wave combines, allowing objects to levitate in place against gravity or be manipulated for touch-free construction.

Atmospheric greenhouse gases trap thermal energy and make Earth habitable

The moon and Earth are at the same distance from the sun, but the moon experiences large fluctuations in surface temperature because it lacks an atmosphere to insulate it. Gases such as water vapor, ozone, carbon dioxide, and methane can intercept about 90% of the infrared radiation emitted by Earth's surface.

What is a heat dome?

The world is seeing regular heat waves with multiple causes, including so-called "heat domes," a term rising in use in recent years. A heat dome occurs when the atmosphere traps hot ocean air like a lid or cap, creating stifling conditions and resulting in extended periods of heat. See an illustration of this phenomenon and read how it works with this brief explainer.

Heat slowly moves through Earth's mantle like softened wax

Energy trapped during Earth's formation and released via the radioactivity of elements is carried by convection currents towards the surface, while cooler, denser material sinks. The planet's core is almost as hot as the sun's surface.

Lasers can be used to reduce the motion of atoms because particles of light—photons—can collide with particles of matter, as billiard balls do, to slow them down.

Through sonoluminescence, concentrated sound waves can produce short, high-intensity flashes of light by rapidly collapsing microscopic bubbles to temperatures up to twice that of the sun's surface.

Stimulating electrons to emit identical photons produces lasers

This effect was predicted by Albert Einstein in 1917, and requires all excited electrons in a material to exist in the same excited metastable state within their atoms. Pumping all atoms through the same mechanism, such as electricity or flash lamps, can create this environment.

When struck, objects vibrate at unique rates called resonant frequencies, which makes tapping wood sound different from tapping metal, but providing objects with sound at their resonant frequency can cause them to shatter.

How the sun heats the Earth

We all know it: Without the sun's heat, the Earth would be uninhabitable. So how does it work? The sun fuses roughly 600 million tons of hydrogen every second, the energy from which bursts out into space—including toward our planet. Our atmosphere...

Convection flows in Earth’s mantle drive the movement of tectonic plates

These processes transfer heat from Earth’s core to the surface via rising magma plumes, while cooler, denser rock falls into the mantle at rates similar to human fingernail growth. These rates are determined by combining seismic data with computer simulations to model Earth’s interior.

Rather than measuring the rising and falling of the sun or pendulum swings, optical clocks track the passage of time using the extremely consistent vibrations of atoms.

The frequency of visible light is significantly greater than that of microwaves used in cesium atomic clocks. This makes optical clocks about 100 times more accurate, losing at most one second across the entire age of the universe.

Nanotechnology refers to the study of objects measuring 1 to 100 billionths of a meter, which has produced materials with unique properties by manipulating the arrangement of atoms.

Spontaneous combustion involves an object igniting on its own

Even without matches, sparks, or external flames, exothermic chemical or biological reactions can increase the internal temperature of objects to the point where they reach a threshold temperature that can cause them to catch fire. Running batteries and fermenting bacteria within compressed materials can build this heat and cause combustion.

How helium enables MRI machines to look inside organisms

By cooling the machine's magnets with liquid helium to extremely low temperatures, they can generate and maintain powerful magnetic fields that align the hydrogen atoms in living things to point toward a patient's head or feet. A radio pulse nudges these atoms, which realign and induce a measurable signal in nearby electrical coils. These signals are captured in slices and then stacked into a 3D reconstruction.

Pellet grills evenly distribute heat across a grill

Using ignited wooden pellets and fans to evenly distribute the heat across the cooking surface, pellet grills give food deep flavor and grant cooks more control, offering a newfangled take on barbecue.

In 1880, Jacques and Pierre Curie discovered that electricity could be produced by striking certain materials—the piezoelectric effect—a phenomenon that is seen in barbecue lighters.

By igniting flammable gas in a tube filled with holes and playing music into it, the fire will take the shape of the sound waves, enabling the visualization of audio.

Breaking down the ionosphere, which reflects radio waves from Earth's surface

Made up of ionized regions within the mesosphere and thermosphere, the ionosphere contains charged particles produced when solar radiation knocks electrons free from atoms and molecules in the atmosphere. Before satellites, radio operators would bounce signals off these regions to wrap around the planet and extend the range of transmissions.

Discover the chemistry behind smoking foods, including the types of smoking and the source of smoking flavors and colors.

Acrylamide forms naturally during high-heat cooking through the Maillard reaction

While studies have shown it can damage DNA and potentially cause cancer in mice, humans absorb and metabolize acrylamide at different rates, introducing uncertainty in the research's applicability to humans. Some international health agencies have nonetheless recommended avoiding darker roasts when cooking starchy foods.

Wireless charging uses a magnetic field to move charged particles in a battery

Based on the concept of electromagnetic induction, when a compatible device is placed on a charging pad with correct alignment, the alternating current flowing through the pad creates a changing magnetic field. This magnetic field induces a current in the device, recharging the battery without a connecting wire.

Wind is the movement of air caused by the sun's uneven heating of Earth

The tilt, curvature, and variations in Earth's surface composition across the globe cause different regions to receive different amounts of solar radiation. As the Earth spins and tries to achieve thermal equilibrium, air masses move and interact, creating wind.

Particle beams can be used to alter the surface properties of artificial joints

Surface hardening and embedding specific elements or coatings can improve the biocompatibility and bone tissue integration of these implants. Particle accelerators are significant sources of the radioisotopes needed in medical diagnostics, and microwave linear accelerators are used in the majority of cancer irradiation treatments.

In Raman spectroscopy, molecules use some of the energy from incoming light to shift into a more energetic vibration and scatter the remaining light, which scientists can use to confirm the molecule's presence.

The history of molecular gastronomy, from thickening yolks with alcohol to making art with food

Before understanding why they worked, humans used scientific principles, including designing solutions and analyzing outcomes, to develop preservation methods like curing meat and fermenting vegetables. By the 20th century, the application of industrialized food preparation to smaller kitchens set the stage for the subdiscipline of food science.

Electricity can flow indefinitely along a ring of superconducting material, which provides zero resistance to the movement of charges due to quantum effects.

If two strands of conducting materials are connected at two junctions, electricity can be generated if one junction is heated while the other is cooled—a phenomenon known as the Seebeck effect.

Certain objects are magnetic because their electrons' magnetic moment—an intrinsic quantum property—align within the object in specific patterns.

Scientific applications of bubbles include logic gates, laser production, and medical imaging

Microbubbles of nonreactive gas can be administered to improve the reflection of sound waves and the resulting imaging during an ultrasound. Bouncing light waves within a bubble can stimulate emission of light from a trapped chemical, just as occurs within a laser, and bubbles can act as valves that control the flow and reaction rates in microfluidic systems.

View an animation of how certain chemicals fluoresce—that is, emit visible light after having absorbed higher-energy light, such as ultraviolet radiation.