The primary force that drives the water cycle is solar energy. The sun heats up water in oceans, rivers, and lakes, causing it to evaporate and transform into vapor. This vapor rises into the atmosphere, cools down, and condenses to form clouds. Eventually, the accumulated water in clouds falls back to Earth as precipitation in the form of rain, snow, or hail. This cyclical process is essential for regulating the climate, distributing fresh water, and maintaining ecosystems across the globe.