英语翻译What makes it rain?Rain falls from clouds for the same r

英语翻译
What makes it rain?Rain falls from clouds for the same reason as anything falls to the Earth.The Earth's gravity pulls it.But every cloud is made of water droplets(微滴) or ice crystals(结晶).Why doesn't rain or snow fall continuously from all clouds?The droplets or ice crystals in clouds are very small.The effect of gravity on them is tiny.
Droplets and ice crystals act somewhat like dust in the air which is made visible(可见的) in the rays of sunlight.To the careless observer,dust seems to act in a totally disorderly(混乱的) way moving about freely without fixed direction.But in fact dust particles are much larger than water droplets and they finally fall.
The cloud droplet of ordinary size is only 1/2500 inch in diameter(直径).It is so small that it would take sixteen hours to fall half a mile in perfectly still air,and it does not fall out of moving air at all.Only when the droplet grows to a diameter of 1/125 inch or larger can it fall from the cloud.The ordinary raindrop has a million times as much water as a tiny cloud droplet.The growth of a cloud droplet to a size large enough to fall out is the cause of rain.