Albedo measures how much light a surface bounces back instead of soaking in as heat. A dark surface like black soil has low albedo. It absorbs most sunlight and warms the air above it quickly. A lighter surface like sand reflects more light and heats up more slowly. When you place different ground surfaces in sealed jars in direct sunlight, you can measure this difference. The surface that absorbs the most light causes the fastest temperature rise inside its jar.