Which method of heat exchange involves no direct contact between objects?

Radiation is the method of heat exchange that involves no direct contact between objects. In this process, heat energy is transferred through electromagnetic waves. This means that even in the absence of a physical medium, heat can still be transferred from a hotter object to a cooler one. A prime example of radiation is how the sun warms the Earth; the heat from the sun travels through the vacuum of space and warms the planet without any matter intervening.

In contrast, convection requires the movement of fluids (liquids or gases) to transfer heat, while conduction depends on direct contact between materials to transfer thermal energy through molecular interaction. Evaporation, although it involves a phase change and can have cooling effects, is not primarily a method of heat exchange but rather the process of liquid turning into vapor and requires a surface interface. Therefore, radiation uniquely qualifies as the method of heat exchange that operates without direct contact.