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is that he is the source of our light and heat, and almost of our life itself. The second reason is because he is in a sense the father of us all. The Earth and planets are "chips of the old block" in the ordinary phrase. One of the regular photographs of the Sun taken at Greenwich. They are parts of the Sun detached from him in the manner we illustrated in the last lecture in talking of satellites. You remember that they were detached as the rate of spin increased. Now I want you to realize that the Sun rotates. You know how we showed in the first lecture that the Earth was rotating, and last Saturday we showed that Jupiter and the other