“Microwave ovens cook food from the inside out”

The notion that microwave ovens cook food from the inside out (Review) is a widespread misconception, likely born from the seemingly magical way these appliances heat food without a visible flame or heating element. The rapid, often uneven, heating observed in microwave ovens can lead people to assume the energy is targeting the core of the food directly, a stark contrast to the external heating of traditional ovens or stovetops. This invisible process contributes to the myth that microwaves defy conventional heat transfer.

Scientifically, microwave energy does not penetrate food to its very center. Instead, microwaves typically penetrate food to a depth of about 1 to 1.5 centimeters. This means that the outer layers of the food are the first to absorb the microwave energy and begin to heat up. The heat then travels to the interior of the food through the slower process of thermal conduction, much like how heat moves through food in a conventional oven once the surface is hot. The speed of this conduction depends on the food's composition.

People commonly believe this myth because they often experience the center of their food being hot after microwaving, while the outside might feel less intensely hot or the plate remains cool. This sensation can be misleading, as the central warmth is a result of the outer, microwave-heated layers efficiently conducting their heat inwards. Furthermore, the quick cooking time compared to conventional methods might reinforce the idea of a unique, internal heating mechanism, rather than understanding it as a rapid and somewhat superficial energy absorption followed by conduction.