<|im_start|>user
Why are some rain clouds darker than others?<|im_end|>
<|im_start|>assistant
Some rain clouds are darker than others because they contain more water droplets. These water droplets reflect less sunlight back into space than a blanket of white clouds containing fewer water droplets. As a result, the dark clouds absorb more sunlight, which warms them up. They also warm up because they are higher in the atmosphere and the air is colder there.<|im_end|>
