Which heat transfer mechanism can occur through a vacuum?

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

Answer: (A)

Only radiation can transfer heat across a vacuum. Radiation moves energy via electromagnetic waves and doesn’t need matter to propagate, so it can travel through empty space. In contrast, conduction requires particles to collide and transfer energy, and convection needs a fluid to circulate heat; both need a material medium, which isn’t present in a vacuum. Absorption is about a surface taking in radiant energy, which can change temperature, but it isn’t the transport method itself. A familiar example is the Sun warming Earth: sunlight travels through the vacuum of space and delivers heat by radiation.