What type of heat transfer occurs in a vacuum?

In a vacuum, heat transfer occurs primarily through radiation. This is because radiation involves the transfer of energy via electromagnetic waves, which can travel through empty space without the need for a medium like air or a solid material. Convection requires a fluid medium to facilitate the movement of heat through the bulk movement of that fluid, while conduction relies on direct contact between materials to transfer heat through molecular interaction. In the absence of any matter, such as in a vacuum, neither convection nor conduction can take place, making radiation the sole mechanism available for heat transfer in such an environment. This allows heat to be transferred from one body to another, even if they are separated by a vacuum, which is fundamentally how heat from the sun reaches the Earth.