Why is space cold if the sun is hot?

Answer: No air to hold heat

Darkness equals coldness — Wrong. Darkness doesn't cause cold. Space is cold because vacuum lacks matter to absorb and retain thermal energy from radiation.

Stars don't radiate heat — Wrong. Stars radiate energy (light and heat). Space is cold because vacuum has no particles to absorb, store, or conduct that heat.

No air to hold heat ✓ — Correct! Temperature measures molecular kinetic energy. Space is nearly a vacuum—almost no molecules. Without matter, heat can't be conducted or convected (requires particles). Objects in space gain heat only through radiation (sunlight absorption). Sunlit side of ISS: +121°C; shadowed side: -157°C. No atmosphere to trap and distribute heat. Spacecraft need thermal management—insulation and radiators!