Which heat transfer mode can occur in a vacuum?

• A. Conduction
• B. Convection
• C. Radiation
• D. Evaporation

Answer: (C)

When there’s a vacuum, there are no particles to collide or flow, so conduction and convection can’t transfer heat. The only way heat can move across empty space is by radiation, which uses electromagnetic waves to carry energy from one body to another. This explains why the Sun’s warmth reaches Earth through space even though there’s no air in between. Evaporation isn’t a heat transfer mode itself—it’s a phase-change process that can occur with enough energy input, but it doesn’t enable heat to travel through a vacuum the way radiation does.