Radiation: Heat Through Empty Space

Here's a puzzle: the Sun heats the Earth. But space is a vacuum — there's literally nothing between us. No air for convection. No material for conduction. So how does the heat get here?

Radiation. Electromagnetic waves — light, infrared, ultraviolet — that travel through empty space at the speed of light.

Every warm object emits radiation. You're emitting infrared radiation right now (that's how thermal cameras see you). The hotter something is, the more radiation it emits. The Sun is so hot it emits visible light.

When radiation hits something, it can be absorbed (converted to heat), reflected (bounced away), or transmitted (passed through). Dark colors absorb more radiation than light colors — that's why black cars get hotter in the sun and why you wear white in summer.