The sun, Hal decided, was the cause of a great deal of trouble. As he studied, he found that the sun by shining brightly in the morning heated up the earth and the air above it. Then the warm air expanded and took up moisture. In the afternoon, when the sun began to go down, the air cooled and descended towards earth. And that was where troubles generated. In the cooling, particles of air moisture condensed, then electricity accumulated--then next, like as not, a thunderstorm burst.