Which type of heat loss occurs without physical contact with other objects?

Heat loss that occurs without physical contact with other objects is known as radiation. This process involves the transfer of heat energy through electromagnetic waves. For instance, the warmth from the sun reaching the earth is a classic example of radiative heat transfer. In this case, heat can move through empty space, nor does it require any medium, such as air or water, to facilitate the transfer.

In contrast, conduction involves direct contact between materials where heat is transferred from the hotter object to the cooler one. Convection requires a fluid medium, like air or water, to carry heat away from a surface. Evaporation involves the conversion of liquid to vapor, which can also result in heat loss, but it is not related to direct thermal transfer through radiation. Thus, radiation is the only method here that allows for heat loss without any physical contact.