Category: 3. Orbits & Gravity

For Further Exploration Articles Brahe and Kepler Christianson, G. “The Celestial Palace of Tycho Brahe.” Scientific American (February 1961): 118. Gingerich, O. “Johannes Kepler and the Rudolphine Tables.” Sky & Telescope (December 1971): 328. Brief article on Kepler’s work. Wilson, C. “How Did Kepler Discover His First Two Laws?” Scientific American (March 1972): 92. Newton Christianson, G. “Newton’s Principia: A Retrospective.” Sky &…

Learning Objectives By the end of this section, you will be able to: Until now, we have considered the Sun and a planet (or a planet and one of its moons) as nothing more than a pair of bodies revolving around each other. In fact, all the planets exert gravitational forces upon one another as…

Learning Objectives By the end of this section, you will be able to: Newton’s universal law of gravitation and Kepler’s laws describe the motions of Earth satellites and interplanetary spacecraft as well as the planets. Sputnik, the first artificial Earth satellite, was launched by what was then called the Soviet Union on October 4, 1957. Since…

Learning Objectives By the end of this section, you will be able to: Recall that the path of an object under the influence of gravity through space is called its orbit, whether that object is a spacecraft, planet, star, or galaxy. An orbit, once determined, allows the future positions of the object to be calculated.…

Learning Objectives By the end of this section, you will be able to: Newton’s laws of motion show that objects at rest will stay at rest and those in motion will continue moving uniformly in a straight line unless acted upon by a force. Thus, it is the straight line that defines the most natural state of…

Learning Objectives By the end of this section, you will be able to: It was the genius of Isaac Newton that found a conceptual framework that completely explained the observations and rules assembled by Galileo, Brahe, Kepler, and others. Newton was born in Lincolnshire, England, in the year after Galileo’s death (Figure 3.6). Against the advice of…

Learning Objectives By the end of this section, you will be able to: At about the time that Galileo was beginning his experiments with falling bodies, the efforts of two other scientists dramatically advanced our understanding of the motions of the planets. These two astronomers were the observer Tycho Brahe and the mathematician Johannes Kepler. Together, they…

How would you find a new planet at the outskirts of our solar system that is too dim to be seen with the unaided eye and is so far away that it moves very slowly among the stars? This was the problem confronting astronomers during the nineteenth century as they tried to pin down a…