Which title best reflects the main idea of the passage? The Sun transfers energy in the form of heat to Earth through radiation. The ground gets warmer as heat flows from one ground particle (such as soil particles or rocks) to another. The ground heats up the air above it through conduction when the particles of air absorb heat from the particles of the ground. Heat also flows from the ground to the air through radiation. The warmed mass of air becomes less dense and rises. As it rises, it loses heat to the environment, so it cools and becomes more dense. The cool, dense air sinks and takes the place of the warm, less dense air. This convection process transfers heat from Earth’s surface to the atmosphere and moves heat around Earth.