Which term describes heat transfer through space without a physical medium?

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

Answer: (C)

Heat transfer through space without a physical medium happens through radiation. This means energy moves as electromagnetic waves, so it can travel across the vacuum between objects. A classic example is the Sun warming Earth—the energy travels through space without air or any solid to carry it.

Conduction requires direct contact and the vibration or movement of particles within a material to pass energy along, so it cannot occur across a vacuum. Convection needs a moving fluid, like air or water, to transfer heat, which also isn’t possible in empty space. The term conversion isn’t a standard mode of heat transfer; energy can change form, but it doesn’t describe how heat moves through space without a medium.