How does radiation occur in the context of heat transfer?

Radiation as a mode of heat transfer involves the emission and absorption of energy in the form of electromagnetic waves. This process does not require any medium, such as air or a solid material, to transfer heat; it can occur through the vacuum of space. All objects emit thermal radiation if their temperature is above absolute zero, and the energy emitted is influenced by the object's temperature and surface characteristics.

This contrasts with conduction, which relies on direct contact between solid materials to transfer heat, and convection, which requires the movement of fluids to transfer heat. In conduction, heat moves from the hotter part of the material to the cooler part, while in convection, warmer fluid rises and cooler fluid sinks, creating currents that transfer heat. Direct contact of surfaces implies a physical interaction, which is different from radiation's non-contact nature. Thus, the key aspect of radiation is its capability to transfer energy through electromagnetic waves, making it distinct from other forms of heat transfer.