Grades K–2 · Materials & Matter
Why can a stone stay warm after the Sun goes down?
A stone in sunlight can grow warm. Light brings energy from the Sun to the stone. The stone takes in some of that energy, so its temperature rises. It does not need a flame hidden inside it.
When the Sun goes down, the stone can still be warmer than the air around it. It passes energy to its cooler surroundings and slowly cools. Its warmth does not disappear the instant the light stops.
The yellow arrows point toward the stone by day; the orange arrows point away at night.
A thick stone can hold more warmth than a small piece of the same stone at the same temperature. But both eventually cool if their surroundings stay cooler. Wind, shade and the kind of stone can change how quickly this happens. The warm stone is a small reminder that energy collected earlier can be released later.
About this explanation
The stone is assumed warmer than its surroundings at sunset; not every stone follows the same cooling rate.
Starting knowledge: Follow familiar changes in water, sunlight and rocks using pictures.
Sources
- U.S. Department of Energy — ZEB Technologies: Passive Design Techniques