Which type of heat transfer can occur in a vacuum?

Radiation is the only type of heat transfer that can occur in a vacuum. This is because radiation involves the transfer of energy through electromagnetic waves, such as light and infrared radiation, which do not require a medium (such as air or water) to travel through. In contrast, convection and conduction both necessitate the presence of matter: convection requires the movement of fluid (liquid or gas) to transfer heat, while conduction requires direct contact between materials for heat to flow. Since a vacuum is devoid of matter, it cannot facilitate convection or conduction; therefore, radiation becomes the sole mechanism of heat transfer in such an environment.