An accidental events often can cause a scientists thought flash. This is 1666 years late summer a warm evening, in England, Lincoln state ur thorpe, one with a book under his arm of the young man walked into his mother's garden, sitting under a tree, and began to his reading his book. When he turned the pages, the top of his head in the branches have something shook up. One of history's most famous apple fell down, hit the 23-year-old Newton's head happen to be in that day, Newton is thinking hard with a question: what is the strength to keep the moon around the earth in the running track, and make the planet orbits the sun to keep in its orbit? Why this only struck him in the head with apple will fall to the ground? It was from thinking the problem began, he found the answer--his theory. : apple fell and a planet around day will the universe dominated by the same? He is correct. And then there is a remarkable work "the mathematical principles of natural philosophy"
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