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Earth. He drew a sketch indicating the path that the body would take, which he thought would be a sort of spiral. In Figure 8.3, which is drawn from the point of view of an observer rotating with the Earth, the path of fall of an object dropped from the top of a tower at A is indicated by the dashed line, and we can see that the body strikes the Earth at D, which is ahead of the bottom of the tower, B.

Newton's reply had been hasty, and his spiral path was a serious mistake. By drawing the path continuing through the Earth, he had converted the problem into one of orbital motion about the centre of attraction, and Hooke was quick to realize this. He wrote to Newton correcting the error and stating that he believed the correct path for such an orbit would resemble an ellipse, and he referred to his own theory of circular motions made up of a direct tangential motion and an attractive one toward a centre. Newton's next reply was that of an irritated man; nevertheless, he acknowledged his error and went on to demonstrate to Hooke that he did have the expertise to handle orbital motion correctly, but at the same time he said that he did not consider the matter particularly important. Hooke did not give up. He wrote two further letters in which he stated that he

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