Video narration
What keeps Earth running while its surface and weather keep changing? Picture a puddle after rain. Sunlight warms it, water rises into the air, forms clouds, and returns as rain. That is the water cycle: water moving between parts of Earth, not disappearing. This small loop belongs to a connected system. Sunlight powers weather and helps plants grow. Heat from deep inside Earth slowly reshapes the planet, while gravity keeps air and oceans close. Here's the key: energy flows through Earth; matter is reused in cycles. Water, for example, moves through air, land, and living things. Energy doesn't circle in the same way: sunlight arrives, powers change, then leaves as heat. These links happen at different speeds; this is only a simple picture of a much bigger system. So what keeps Earth changing? Sunlight and inner heat drive change, gravity holds the system together, and matter keeps cycling.