CloudsA cloud is a visible mass of condensed water droplets or ice crystals suspended in the atmosphere above Earth's (or another planetary body's) surface. The condensing water vapor forms small droplets of water (typically 0.01 mm) or ice crystals that, when surrounded with billions of other droplets or crystals, are visible as clouds. Clouds reflect all visible wavelengths of light equally and are thus white, but they can appear grey or even black if they are so thick or dense that sunlight cannot pass through. Clouds on other planets often consist of material other than water, depending on local atmospheric conditions (what gases are present, and the temperature). |
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