Heat transfer can occur through three main mechanisms: conduction, convection, and radiation. Among these, radiation is the mechanism by which heat can travel through a vacuum or empty space without the need for a medium.
In conduction, heat transfer occurs through direct physical contact between particles or molecules. When a molecule gains energy, it collides with neighboring molecules, transferring heat energy from one molecule to another. This process requires a medium, such as a solid, liquid, or gas, to transfer the heat.
Convection, on the other hand, involves the transfer of heat through the movement of fluid particles. In this process, warmer fluid particles become less dense and rise while cooler particles sink, creating a circulation pattern. Convection requires the presence of a medium, such as a liquid or gas, for heat transfer to occur.
Radiation, however, is a different mechanism altogether. It is the transfer of heat energy through electromagnetic waves. These waves can travel through a vacuum, which means they can propagate through empty space without requiring a medium. Infrared radiation is an example of the electromagnetic waves that carry heat energy. When an object is at a temperature greater than absolute zero, it emits infrared radiation, and this radiation can be absorbed by other objects, thus transferring heat energy.
To summarize, heat transfer through conduction and convection requires a medium, while radiation allows heat to travel through empty space without the need for a medium.