This chapter covers the revolutionary advancements due to probably the most brilliant scientist who ever lived: Isaac Newton (lived 1641--1727). His greatest contributions were in all branches of physics. Kepler's discoveries about elliptical orbits and the planets' non-uniform speeds made it impossible to maintain the idea of planetary motion as a natural one requiring no explanation. Newton had to answer some basic questions: What keeps the planets in their elliptical orbits? On our spinning Earth what prevents objects from flying away when they are thrown in the air? What keeps you from being hurled off the spinning Earth? Newton's answer was that a fundamental force called ``gravity'' operating between all objects made them move the way they do.
Newton developed some basic rules governing the motion of all objects. He used these laws and Kepler's laws to derive his unifying Law of Gravity. I will first discuss his three laws of motion and then discuss gravity. Finally, several applications in astronomy will be given. This chapter uses several math concepts that are reviewed in the mathematics review appendix. If your math skills are rusty, study the mathematics review appendix and don't hesitate to ask your astronomy instructor for help. The vocabulary terms are in boldface.
I include images of world atlases from different time periods in this chapter and the previous one as another way to illustrate the advances in our understanding of our world and the universe. Links to the sites from which the photographs came are embedded in the images. Select the picture to go to the site (will display in another window).
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last updated: 28 May 2001